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Purpose of Review: This review evaluates the emerging role of the pullback pressure gradient (PPG) as a standardized metric for assessing coronary artery disease (CAD) patterns and its implications for clinical decision-making when managing patients undergoing percutaneous coronary interventions (PCIs). By integrating PPG with existing physiological assessments, this review highlights the potential benefits of PPG in predicting treatment outcomes and refining therapeutic strategies for CAD., Recent Findings: Recent studies, particularly the PPG Global study have demonstrated a strong correlation between PPG values and post-PCI outcomes, revealing that focal disease is associated with improved fractional flow reserve (FFR) and lower rates of adverse events than vessels with diffuse disease (low PPG). Additionally, PPG has been linked to specific atherosclerotic plaque characteristics, indicating its utility in identifying high-risk plaques. The integration of PPG with advanced imaging techniques further enhances the understanding of CAD patterns and their implications for treatment planning., Summary: The PPG represents a significant advancement in the management of CAD, providing a reproducible and objective assessment of coronary artery disease patterns that can inform clinical decision-making. As research continues to explore the relationship among PPG, atherosclerotic characteristics, and patient outcomes, its integration into routine practice is expected to improve the effectiveness of PCI and optimize patient management strategies. Future studies are warranted to establish specific PPG thresholds and further investigate its potential in identifying vulnerable plaques and guiding treatment decisions., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Introduction and Objectives: Several studies have investigated the effectiveness of fractional flow reserve (FFR) guidance in improving clinical outcomes after myocardial revascularization, yielding conflicting results. The aim of this study was to compare clinical outcomes in patients with coronary artery disease following FFR-guided or angiography-guided revascularization., Methods: Both randomized controlled trials (RCTs) and nonrandomized intervention studies were included. Coprimary endpoints were all-cause death, myocardial infarction, and major adverse cardiovascular events (MACE). The study is registered with PROSPERO (CRD42022344765)., Results: A total of 30 studies enrolling 393 588 patients were included. FFR-guided revascularization was associated with significantly lower rates of all-cause death (OR, 0.63; 95%CI, 0.53-0.73), myocardial infarction (OR, 0.70; 95%CI, 0.59-0.84), and MACE (OR, 0.77; 95%CI, 0.70-0.85). When only RCTs were considered, no significant difference between the 2 strategies was observed for any endpoints. However, the use of FFR was associated with reduced rates of revascularizations and treated lesions. Metaregression suggested that the higher the rate of revascularized patients the lower the benefit of FFR guidance on MACE reduction compared with angiography guidance (P=.012). Similarly, higher rates of patients with acute coronary syndromes were associated with a lower benefit of FFR-guided revascularization (P=.039)., Conclusions: FFR-guided revascularization was associated with lower rates of all-cause death, myocardial infarction and MACE compared with angiographic guidance, with RCTs and nonrandomized intervention studies yielding conflicting data. The benefits of FFR-guidance seem to be less evident in studies with high revascularization rates and with a high prevalence of patients with acute coronary syndrome., (Copyright © 2024 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.)

Background: Diffuse coronary artery disease affects the safety and efficacy of percutaneous coronary intervention (PCI). Pathophysiologic coronary artery disease patterns can be quantified using fractional flow reserve (FFR) pullbacks incorporating the pullback pressure gradient (PPG) calculation. This study aimed to establish the capacity of PPG to predict optimal revascularization and procedural outcomes., Methods: This prospective, investigator-initiated, single-arm, multicenter study enrolled patients with at least one epicardial lesion with an FFR ≤0.80 scheduled for PCI. Manual FFR pullbacks were used to calculate PPG. The primary outcome of optimal revascularization was defined as an FFR ≥0.88 after PCI., Results: A total of 993 patients with 1044 vessels were included. The mean FFR was 0.68±0.12, PPG 0.62±0.17, and the post-PCI FFR was 0.87±0.07. PPG was significantly correlated with the change in FFR after PCI (r=0.65 [95% CI, 0.61-0.69]; P <0.001) and demonstrated excellent predictive capacity for optimal revascularization (area under the receiver operating characteristic curve, 0.82 [95% CI, 0.79-0.84]; P <0.001). FFR alone did not predict revascularization outcomes (area under the receiver operating characteristic curve, 0.54 [95% CI, 0.50-0.57]). PPG influenced treatment decisions in 14% of patients, redirecting them from PCI to alternative treatment modalities. Periprocedural myocardial infarction occurred more frequently in patients with low PPG (<0.62) compared with those with focal disease (odds ratio, 1.71 [95% CI, 1.00-2.97])., Conclusions: Pathophysiologic coronary artery disease patterns distinctly affect the safety and effectiveness of PCI. PPG showed an excellent predictive capacity for optimal revascularization and demonstrated added value compared with an FFR measurement., Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04789317., Competing Interests: Dr Collet reports receiving research grants from Biosensors, Coroventis Research, Medis Medical Imaging, Pie Medical Imaging, CathWorks, Boston Scientific, Siemens, HeartFlow, and Abbott Vascular; consultancy fees from HeartFlow, OpSens Medical, Abbott Vascular, and Philips Volcano; and has patents pending on diagnostic methods for coronary artery disease. Dr Munhoz reports a research grant provided by the CardioPath PhD programme and speaker fees from Abbott Vascular. Dr Mizukami reports receiving research grants from Boston Scientific and speaker fees from Abbott Vascular, CathWorks, and Boston Scientific. Dr Matsuo has received consulting fees from Kaneka and Zeon and speaker’s fees from Abbott Medical Japan, Boston Scientific, Philips, and Amgen. Dr Ko has received consulting fees from Canon Medical, Abbott, and Medtronic. Dr Biscaglia received research grants provided by Sahajanand Medical Technologies, Medis Medical Imaging, Eukon Srl, Siemens Healthineers, General Electric Healthcare, and Insight Lifetech. Dr Engstrøm reports speaker and advisory board fees from Abbott, Boston Scientific, and Novo Nordisk. Dr Leone reports receiving consultancy fees from Abbott and honoraria for sponsored symposia from Abbott, Medtronic, and Abiomed. Dr Fearon receives institutional research support from Abbott, Boston Scientific, and Medtronic and has consulting relationships with CathWorks and Siemens and stock options from HeartFlow. Dr Christiansen has received consulting fees from Abbott Medical Denmark A/S. Dr Yong has received minor honoraria from Abbott Vascular and research grants from Abbott Vascular and Philips. Dr Escaned is supported by the Intensification of Research Activity project INT22/00088 from the Spanish Instituto de Salud Carlos III and received speaker and advisory board member fees from Abbott and Philips. Dr Storozhenko reports a grant provided by the EAPCI Fellowship Programme. Dr West is an employee of Abbott Vascular. Dr De Potter is a paid consultant for Biosense Webster and receives grant support (institutional) and consultancy fees (institutional) from Abbott. Dr Berry receives research funding from the British Heart Foundation (grants RE/18/6134217, BHF/FS/17/26/32744, and PG/19/28/34310) and is employed by the University of Glasgow, which holds consultancy and research agreements for his work with Abbott Vascular, AstraZeneca, Boehringer Ingelheim, Coroventis Research, GlaxoSmithKline, HeartFlow, Menarini, Novartis, Servier, Siemens Healthcare, and Valo Health. Dr Collison has received consulting fees from Abbott. Dr Johnson has received consultancy or speaker fees from Abbott Vascular, Boston Scientific, Medtronic, Shockwave, and Terumo, and research grants from Abbott Vascular. Dr Amano reports receiving lecture fees from Astellas Pharma, Astra Zeneca, Bayer, Daiichi Sankyo, and Bristol Myers Squibb. Dr Perera has received research grant support from Abbott Vascular, HeartFlow, and Philips. Dr Jeremias has received consulting fees from Canon Medical, Artrya Medical, and Boston Scientific. Dr Ali reports institutional grant support from Abbott, Abiomed, Acist, Amgen, Boston Scientific, CathWorks, Canon Medical, Conavi, HeartFlow, Inari, Medtronic, the US National Institutes of Health, Nipro, OpSens Medical, Medis, Philips, Shockwave, Siemens, SpectraWAVE, and Teleflex; consulting fees from Abiomed, Astra Zeneca, Boston Scientific, CathWorks, OpSens Medical, Philips, and Shockwave; and equity in Elucid, Lifelink, SpectraWAVE, Shockwave, and VitalConnect. Dr Pijls has received research grants from Abbott and Hexacath; consultancy fees from Abbott, GE, Philips, and HeartFlow; and has equity in General Electric, Philips, and HeartFlow. Dr De Bruyne reports receiving consultancy fees from Boston Scientific and Abbott and research grants from Coroventis Research, Pie Medical Imaging, CathWorks, Boston Scientific, Siemens, HeartFlow, and Abbott Vascular. Dr Johnson received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; has received significant institutional research support from St Jude Medical (CONTRAST [Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology?; URL: https://www.clinicaltrials.gov; Unique identifier: NCT02184117]) and Philips Volcano (DEFINE-FLOW [Combined Pressure and Flow Measurements to Guide Treatment of Coronary Stenoses; URL: https://www.clinicaltrials.gov; Unique identifier: NCT02328820]) for other studies using intracoronary pressure and flow sensors; has an institutional licensing agreement with Boston Scientific for the smart-minimum FFR algorithm (now commercialized under 510[k] K191008); and has patents pending on diagnostic methods for quantifying aortic stenosis and TAVI physiology and on methods to correct pressure tracings from fluid-filled catheters.

During the past 30 years, fractional flow reserve (FFR) has moved from animal models to class IA recommendations in guidelines. However, the FLOWER-MI, RIPCORD-2, FUTURE, and FAME 3 trials in 2021 were "negative"-has FFR exceeded its expiration date? We critically examine these randomized trials in order to draw insights not just about FFR but also about study design and interpretation. Are all randomized trials created equal? No, rather we must focus on discordant decisions between angiography and FFR and highlight clinical endpoints that can be improved by percutaneous coronary intervention instead of medical therapy., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background and Aims: Coronary flow capacity (CFC) is associated with an observed 10-year survival probability for individual patients before and after actual revascularization for comparison to virtual hypothetical ideal complete revascularization., Methods: Stress myocardial perfusion (mL/min/g) and coronary flow reserve (CFR) per pixel were quantified in 6979 coronary artery disease (CAD) subjects using Rb-82 positron emission tomography (PET) for CFC maps of artery-specific size-severity abnormalities expressed as percent left ventricle with prospective follow-up to define survival probability per-decade as fraction of 1.0., Results: Severely reduced CFC in 6979 subjects predicted low survival probability that improved by 42% after revascularization compared with no revascularization for comparable severity (P = .0015). For 283 pre-and-post-procedure PET pairs, severely reduced regional CFC-associated survival probability improved heterogeneously after revascularization (P < .001), more so after bypass surgery than percutaneous coronary interventions (P < .001) but normalized in only 5.7%; non-severe baseline CFC or survival probability did not improve compared with severe CFC (P = .00001). Observed CFC-associated survival probability after actual revascularization was lower than virtual ideal hypothetical complete post-revascularization survival probability due to residual CAD or failed revascularization (P < .001) unrelated to gender or microvascular dysfunction. Severely reduced CFC in 2552 post-revascularization subjects associated with low survival probability also improved after repeat revascularization compared with no repeat procedures (P = .025)., Conclusions: Severely reduced CFC and associated observed survival probability improved after first and repeat revascularization compared with no revascularization for comparable CFC severity. Non-severe CFC showed no benefit. Discordance between observed actual and virtual hypothetical post-revascularization survival probability revealed residual CAD or failed revascularization., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Background: The interplay between coronary hemodynamics and plaque characteristics remains poorly understood., Objectives: The aim of this study was to compare atherosclerotic plaque phenotypes between focal and diffuse coronary artery disease (CAD) defined by coronary hemodynamics., Methods: This multicenter, prospective, single-arm study was conducted in 5 countries. Patients with functionally significant lesions based on an invasive fractional flow reserve ≤0.80 were included. Plaque analysis was performed by using coronary computed tomography angiography and optical coherence tomography. CAD patterns were assessed using motorized fractional flow reserve pullbacks and quantified by pullback pressure gradient (PPG). Focal and diffuse CAD was defined according to the median PPG value., Results: A total of 117 patients (120 vessels) were included. The median PPG was 0.66 (IQR: 0.54-0.75). According to coronary computed tomography angiography analysis, plaque burden was higher in patients with focal CAD (87% ± 8% focal vs 82% ± 10% diffuse; P = 0.003). Calcifications were significantly more prevalent in patients with diffuse CAD (Agatston score per vessel: 51 [IQR: 11-204] focal vs 158 [IQR: 52-341] diffuse; P = 0.024). According to optical coherence tomography analysis, patients with focal CAD had a significantly higher prevalence of circumferential lipid-rich plaque (37% focal vs 4% diffuse; P = 0.001) and thin-cap fibroatheroma (TCFA) (47% focal vs 10% diffuse; P = 0.002). Focal disease defined by PPG predicted the presence of TCFA with an area under the curve of 0.73 (95% CI: 0.58-0.87)., Conclusions: Atherosclerotic plaque phenotypes associate with intracoronary hemodynamics. Focal CAD had a higher plaque burden and was predominantly lipid-rich with a high prevalence of TCFA, whereas calcifications were more prevalent in diffuse CAD. (Precise Percutaneous Coronary Intervention Plan [P3]; NCT03782688)., Competing Interests: Funding and Author Disclosures The study was sponsored by the Cardiac Research Institute Aalst with unrestricted grants from HeartFlow Inc. Dr Mizukami has received consulting fees from Zeon Medical and HeartFlow Inc; and speaker fees from Abbott Vascular. Dr Leipsic is a consultant and has holding stock options in Circle CVI and HeartFlow Inc; has received a research grant from GE; and modest speaker fees from GE and Philips. Drs Sonck and Munhoz have received research grants provided by the Cardiopath Ph.D. program. Dr Nørgaard has received unrestricted institutional research grants from Siemens and HeartFlow Inc. Dr Otake has received research grants from Abbott Vascular; and speaker fees from HeartFlow Inc and Abbott Vascular. Dr Ko has received consulting fees from Canon Medical, Abbott, and Medtronic. Dr Koo has received institutional research grants from HeartFlow Inc. Dr Maeng has received advisory board and lecture fees from AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Boston Scientific, and Novo Nordisk; and research grants from Bayer and Philips Healthcare. Dr Jensen has received unrestricted institutional research grants from Siemens and HeartFlow Inc. Dr Andreini has received research grants from GE Healthcare and Bracco. Dr Shinke has received research grants from Boston Scientific and Abbott Vascular. CT is an employee of HeartFlow Inc. Dr Barbato has received speaker fees from Boston Scientific, Abbott Vascular, and GE. Dr Johnson has received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; significant institutional research support from St. Jude Medical (CONTRAST [Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology?]; NCT02184117) and Philips/Volcano Corporation (DEFINE-FLOW [Combined Pressure and Flow Measurements to Guide Treatment of Coronary Stenoses]; NCT02328820) for studies using intracoronary pressure and flow sensors; has an institutional licensing agreement with Boston Scientific for the smart-minimum FFR algorithm commercialized under 510(k) K191008; and has pending patents on diagnostic methods for quantifying aortic stenosis and transcatheter aortic valve replacement physiology, as well as algorithms to correct pressure tracings from fluid-filled catheters. Dr De Bruyne has received consultancy fees from Boston Scientific and Abbott Vascular; research grants from Coroventis Research, Pie Medical Imaging, CathWorks, Boston Scientific, Siemens, HeartFlow Inc, and Abbott Vascular; and owns equity in Siemens, GE, Philips, HeartFlow Inc, Edwards Life Sciences, Bayer, Sanofi, and Celyad. Dr Collet has received research grants from Biosensor, Coroventis Research, Medis Medical Imaging, Pie Medical Imaging, CathWorks, Boston Scientific, Siemens, HeartFlow Inc, and Abbott Vascular; and consultancy fees from HeartFlow Inc, OpSens, Abbott Vascular, and Philips Volcano. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Introduction: Diffuse disease has been identified as one of the main reasons leading to low post-PCI fractional flow reserve (FFR) and residual angina after PCI. Coronary pressure pullbacks allow for the evaluation of hemodynamic coronary artery disease (CAD) patterns. The pullback pressure gradient (PPG) is a novel metric that quantifies the distribution and magnitude of pressure losses along the coronary artery in a focal-to-diffuse continuum., Aim: The primary objective is to determine the predictive capacity of the PPG for post-PCI FFR., Methods: This prospective, large-scale, controlled, investigator-initiated, multicenter study is enrolling patients with at least 1 lesion in a major epicardial vessel with a distal FFR ≤ 0.80 intended to be treated by PCI. The study will include 982 subjects. A standardized physiological assessment will be performed pre-PCI, including the online calculation of PPG from FFR pullbacks performed manually. PPG quantifies the CAD pattern by combining several parameters from the FFR pullback curve. Post-PCI physiology will be recorded using a standardized protocol with FFR pullbacks. We hypothesize that PPG will predict optimal PCI results (post-PCI FFR ≥ 0.88) with an area under the ROC curve (AUC) ≥ 0.80. Secondary objectives include patient-reported and clinical outcomes in patients with focal vs. diffuse CAD defined by the PPG. Clinical follow-up will be collected for up to 36 months, and an independent clinical event committee will adjudicate events., Results: Recruitment is ongoing and is expected to be completed in the second half of 2023., Conclusion: This international, large-scale, prospective study with pre-specified powered hypotheses will determine the ability of the preprocedural PPG index to predict optimal revascularization assessed by post-PCI FFR. In addition, it will evaluate the impact of PPG on treatment decisions and the predictive performance of PPG for angina relief and clinical outcomes., Competing Interests: Disclosures AML reports receiving consultancy fees from Abbott and honoraria for sponsored symposiums from Abbott, Medtronic and Abiomed. DM report a research grant provided by the Cardiopath PhD program and speaker fees from Abbott Vascular. BDB reports receiving consultancy fees from Boston Scientific and Abbott and research grants from Coroventis Research, Pie Medical Imaging, Cathworks, Boston Scientific, Siemens, HeartFlow Inc. and Abbott Vascular. CC reports receiving research grants from Biosensor, Coroventis Research, Medis Medical Imaging, Pie Medical Imaging, Cathworks, Boston Scientific, Siemens, HeartFlow Inc. and Abbott Vascular; and consultancy fees from Heart Flow Inc, Opsens, Abbott Vascular and Philips Volcano. BK has received consulting fees from Canon Medical, Abbott and Medtronic. AI has received consulting fees from Canon, Artrya Medical and Boston Scientific. TWJ has received consultancy/speaker fees from Abbott Vascular, Boston Scientific, Medtronic, Shockwave, Terumo and research grants from Abbott Vascular. NPJ received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; has received significant institutional research support from St. Jude Medical (CONTRAST, NCT02184117) and Philips Volcano Corporation (DEFINE-FLOW, NCT02328820) for other studies using intracoronary pressure and flow sensors; has an institutional licensing agreement with Boston Scientific for the smart-minimum FFR algorithm (now commercialized under 510(k) K191008); and has patents pending on diagnostic methods for quantifying aortic stenosis and TAVI physiology, and on methods to correct pressure tracings from fluid-filled catheters. SB received research grants provided by Sahajanand Medical Technologies Ltd (SMT), Medis Medical Imaging Systems, Eukon S.r.l., Siemens Healthineers, General Electric (GE) Healthcare, and Insight Lifetech. EHC has received consulting fees from Abbott Medical Denmark A/S. CB receives research funding from the British Heart Foundation (RE/18/6134217, BHF/FS/17/26/32744, PG/19/28/34310). Colin Berry is employed by the University of Glasgow which holds consultancy and research agreements for his work with Abbott Vascular, AstraZeneca, Boehringer Ingelheim, Coroventis, GSK, HeartFlow, Menarini, Novartis, Servier, Siemens Healthcare, and Valo Health. WFF receives institutional research support from Abbot, Boston, and Medtronic and has consulting relationships with CathWorks and Siemens and stock options with HeartFlow. TE reports speakers and advisory board fees from Abbott, Boston and Novo Nordisk. AY has received minor honoraria from Abbott Vascular, and research grants from Abbott Vascular and Philips. DC has received consulting fees from Abbott. TS reports a grant provided by the EAPCI Fellowship Programme., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Low fractional flow reserve (FFR) after percutaneous coronary intervention (PCI) has been associated with adverse clinical outcomes. Hitherto, this assessment has been independent of the epicardial vessel interrogated., Objectives: This study sought to assess the predictive capacity of post-PCI FFR for target vessel failure (TVF) stratified by coronary artery., Methods: We performed a systematic review and individual patient-level data meta-analysis of randomized clinical trials and observational studies with protocol-recommended post-PCI FFR assessment. The difference in post-PCI FFR between left anterior descending (LAD) and non-LAD arteries was assessed using a random-effect models meta-analysis of mean differences. TVF was defined as a composite of cardiac death, target vessel myocardial infarction, and clinically driven target vessel revascularization., Results: Overall, 3,336 vessels (n = 2,760 patients) with post-PCI FFR measurements were included in 9 studies. The weighted mean post-PCI FFR was 0.89 (95% CI: 0.87-0.90) and differed significantly between coronary vessels (LAD = 0.86; 95% CI: 0.85 to 0.88 vs non-LAD = 0.93; 95% CI: 0.91-0.94; P < 0.001). Post-PCI FFR was an independent predictor of TVF, with its risk increasing by 52% for every reduction of 0.10 FFR units, and this was mainly driven by TVR. The predictive capacity for TVF was poor for LAD arteries (AUC: 0.52; 95% CI: 0.47-0.58) and moderate for non-LAD arteries (AUC: 0.66; 95% CI: 0.59-0.73; LAD vs non-LAD arteries, P = 0.005)., Conclusions: The LAD is associated with a lower post-PCI FFR than non-LAD arteries, emphasizing the importance of interpreting post-PCI FFR on a vessel-specific basis. Although a higher post-PCI FFR was associated with improved prognosis, its predictive capacity for events differs between the LAD and non-LAD arteries, being poor in the LAD and moderate in the non-LAD vessels., Competing Interests: Funding Support and Author Disclosures Dr Collet received research grants from Biosensors, HeartFlow Inc, Abbott Vascular, Insight Lifetech, GE Healthcare, Siemens and Shockwave Medical. Dr Johnson has received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; has received significant institutional research support from St. Jude Medical (CONTRAST, NCT02184117) and Philips Volcano (DEFINE-FLOW, NCT02328820) for studies using intracoronary pressure and flow sensors; has an institutional licensing agreement with Boston Scientific for the smart-minimum FFR algorithm commercialized under 510(k) K191008; and has pending patents on diagnostic methods for quantifying aortic stenosis and TAVI physiology and also algorithms to correct pressure tracings from fluid-filled catheters. Dr Mizukami has received consultancy fees from Zeon Medical. Dr Fearon receives institutional research support from Abbott Vascular, Boston Scientific, Medtronic, and Edwards Lifesciences; he has a consulting relationship with CathWorks and Siemens; and he owns minor stock options in HeartFlow. Dr Berry receives research funding from the British Heart Foundation grant (RE/18/6134217); and is employed by the University of Glasgow, which holds consultancy and research agreements for his work with Abbott Vascular, AstraZeneca, Boehringer Ingelheim, Causeway Therapeutics, Coroventis, Genentech, GlaxoSmithKline, HeartFlow, Menarini, Neovasc, Siemens Healthcare, and Valo Health. Dr Sonck is supported by a grant provided by the CardioPath PhD program. Dr Collison has received honoraria/speaker fees from Abbott. Dr Koo has received an institutional research grant from St. Jude Medical (Abbott Vascular) and Philips Volcano. Dr Meneveau has received consultancy and speaker fees from Abbott Vascular, Edwards Lifesciences, Terumo, Boston Scientific, Bayer Healthcare, BMS-Pfizer, Boehringer, and AstraZeneca. Dr Oldroyd is an employee of Biosensors International. Dr Leipsic is a consultant for and holds stock options in Circle CVI and HeartFlow; and has a research grant from GE Healthcare. Dr Taylor is an employee of HeartFlow Inc. Dr Ko has received consultancy fees from Abbott Vascular and Medtronic; and has received research support from Canon Medical. Dr Perera has received research grant support from Abbott Vascular, HeartFlow, and Philips. Dr Leone received consultant fees and honoraria for lectures in sponsored symposia with Abbott Vascular and Bracco Imaging/ACIST Medical. Dr Matsuo has received consultancy fees from Zeon Medical; and has received speaker fees from Abbott Vascular Japan, Philips, and Boston Scientific. Dr Amabile reports consulting/proctoring fees from Abbott Vascular, Boston Scientific, and Shockwave Medical; and has received an institutional research grant from Abbott Vascular and Boston Scientific. Dr Piróth has received consultancy and speaker fees from Abbott Vascular, Opsens, and Boston Scientific. Dr Toth has received consultancy fees and research support from Abbott, Biotronik, Medtronic, and Terumo. Dr Ihdayhid reports receiving consulting honorarium from Abbott Medical, Edwards Lifesciences, Boston Scientific, Artrya Pty Ltd (including equity interest). Dr West is an employee of Abbott Vascular. Dr Munhoz is supported with a PhD grant from CardioPath. Dr Barbato has received speaker fees from Abbott and Boston Scientific. Dr Engstrøm has received consultancy and speaker fees from Abbott Vascular, Novo Nordisk, and Bayer AS. Dr Escaned is supported by the Intensification of Research Activity project INT22/00088 from Spanish Instituto de Salud Carlos III, and served as speaker and advisory board member for Abbott and Philips. Dr Ali has received institutional grant support Abbott, Abiomed, ACIST Medical, Amgen, Boston Scientific, Cathworks, Canon, Conavi, Heartflow, Inari, Medtronic Inc, National Institute of Health, Nipro, Opsens Medical, Medis, Philips, Shockwave, Siemens, Spectrawave, Teleflex; and consulting fees from Abiomed, AstraZeneca, Boston Scientific, Cathworks, Opsens, Philips, Shockwave and equity in Elucid, Lifelink, Spectrawave, Shockwave, VitalConnect. Dr Kern has received speaker fees from Abbott, ACIST Medical, Boston Scientific, Opsens, and Philips. Dr Pijls has received research grants from Abbott and Hexacath and consultancy fees from Abbott, GE, Philips, and HeartFlow and have equity in GE, Philips, and Heartflow. Dr De Bruyne has received institutional consulting fees from Abbott Vascular, Boston Scientific, Siemens, and GE; has received institutional grant support from Abbott Vascular, Boston Scientific, Biotronic, CathWorks, Pie Medical, and HeartFlow; and holds minor equities in Philips, Siemens, GE, Bayer, HeartFlow, Edwards Lifesciences, and Ceyliad. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: The quantitative flow ratio (QFR) identifies functionally ischaemic lesions that may benefit more from percutaneous coronary intervention (PCI) than from medical therapy., Aims: This study investigated the association between QFR and myocardial infarction (MI) as affected by PCI versus medical therapy., Methods: All vessels requiring measurement (reference diameter ≥2.5 mm and existence of at least one stenotic lesion with diameter stenosis of 50-90%) in the FAVOR III China (5,564 vessels) and PANDA-III trials (4,471 vessels) were screened and analysed for offline QFR. The present study reported clinical outcomes on a per-vessel level. Interaction between vessel treatment and QFR as a continuous variable was evaluated for the threshold of 2-year MI estimated by Cox proportional hazards model., Results: Compared with medical therapy at 2 years, PCI reduced the MI risk in vessels with a QFR ≤0.80 (3.0% vs 4.6%) but increased the MI risk in vessels with a QFR>0.80 (3.6% vs 1.2%). Additionally, continuous QFR showed an inverse association with spontaneous MI (hazard ratio [HR] 0.89, 95% confidence interval [CI]: 0.79-0.99; p=0.04) that was reduced by PCI compared to medical therapy (HR 0.26, 95% CI: 0.17-0.40; p<0.0001). The interaction indicated a net benefit for PCI over medical therapy to reduce total MI beginning at QFR ≤0.64., Conclusions: The present study demonstrated a continuous, inverse relationship between the QFR value of a vessel and its subsequent risk for MI, and PCI, compared to medical therapy, reduced this risk beginning at a QFR value of 0.64. These novel findings provide physicians with an angiographic tool for optimising vessel selection for PCI.

The colorful term "coronary steal" arose in 1967 to parallel "subclavian steal" coined in an anonymous 1961 editorial. In both instances, the word "steal" described flow reversal in the setting of an interconnected but abnormal vascular network-in one case a left subclavian stenosis proximal to the origin of the vertebral artery and in the other case a coronary fistula. Over time, the term has morphed to include a larger set of pathophysiology without explicit flow reversal but rather with a decrease in stress flow due to other mechanisms. This review aims to shed light on this phenomenon from a clinical and a pathophysiological perspective, detailing the anatomical and physiological conditions that allow so-called steal to appear and offering treatment options for six distinct scenarios., Competing Interests: Conflict of interest All authors declare no conflict of interest for this contribution., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Data on impact of financial hardship on coronary artery disease (CAD) remain incomplete., Methods: Consecutive subjects referred for clinical rest/stress cardiac positron emission tomography (PET) were enrolled. Financial hardship is defined as patients' inability to pay for their out-of-pocket expense for cardiac PET. Abnormal cardiac PET is defined as at least moderate relative perfusion defects at stress involving > 10% of the left ventricle or global coronary flow reserve ≤ 2.0. Patients were followed for major adverse cardiovascular event (MACE) comprised of all-cause mortality, non-fatal myocardial infarction, and late coronary revascularization., Results: We analyzed a total of 4173 patients with mean age 65.6 ± 11.3 years, 72.2% men, and 93.6% reported as having medical insurance. Of these, 504 (12.1%) patients had financial hardship. On multivariable analysis, financial hardship associated with abnormal cardiac PET (odds ratio 1.377, p = 0.004) and MACE (hazard ratio 1.432, p = 0.010) and its association with MACE was mostly through direct effect with small proportion mediated by abnormal cardiac PET or known CAD., Conclusion: Among patients referred for cardiac rest/stress PET, financial hardship independently associates with myocardial perfusion abnormalities and MACE; however, its effect on MACE is largely not mediated by abnormal myocardial perfusion or known CAD suggesting distinct impact of financial hardship beyond traditional risk factors and CAD that deserves attention and intervention to effectively reduced adverse outcomes. Having medical insurance does not consistently protect from financial hardship and a more preventive-oriented restructuring may provide better outcomes at lower cost., (© 2023. The Author(s) under exclusive licence to American Society of Nuclear Cardiology.)

During the past 30 years, fractional flow reserve (FFR) has moved from animal models to class IA recommendations in guidelines. However, the FLOWER-MI, RIPCORD-2, FUTURE, and FAME 3 trials in 2021 were "negative"-has FFR exceeded its expiration date? We critically examine these randomized trials in order to draw insights not just about FFR but also about study design and interpretation. Are all randomized trials created equal? No, rather we must focus on discordant decisions between angiography and FFR and highlight clinical endpoints that can be improved by percutaneous coronary intervention instead of medical therapy., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Subendocardial ischemia is commonly diagnosed but not quantified by imaging., Objectives: This study sought to define size and severity of subendocardial and transmural stress perfusion deficits, clinical associations, and outcomes., Methods: Regional rest-stress perfusion in mL/min/g, coronary flow reserve, coronary flow capacity (CFC), relative stress flow, subendocardial stress-to-rest ratio and stress subendocardial-to-subepicardial ratio as percentage of left ventricle were measured by positron emission tomography (PET) with rubidium Rb 82 and dipyridamole stress in serial 6,331 diagnostic PETs with prospective 10-year follow-up for major adverse cardiac events with and without revascularization., Results: Of 6,331 diagnostic PETs, 1,316 (20.7%) had severely reduced CFC with 41.4% having angina or ST-segment depression (STΔ) >1 mm during hyperemic stress, increasing with size. For 5,015 PETs with no severe CFC abnormality, 402 (8%) had angina or STΔ during stress, and 82% had abnormal subendocardial perfusion with 8.7% having angina or STΔ >1 mm during dipyridamole stress. Of 947 cases with stress-induced angina or STΔ >1 mm, 945 (99.8%) had reduced transmural or subendocardial perfusion reflecting sufficient microvascular function to increase coronary blood flow and reduce intracoronary pressure, causing reduced subendocardial perfusion; only 2 (0.2%) had normal subendocardial perfusion, suggesting microvascular disease as the cause of the angina. Over 10-year follow-up (mean 5 years), severely reduced CFC associated with major adverse cardiac events of 44.4% compared to 8.8% for no severe CFC (unadjusted P < 0.00001) and mortality of 15.2% without and 6.9% with revascularization (P < 0.00002) confirmed by multivariable Cox regression modeling. For no severe CFC, mortality was 3% with and without revascularization (P = 0.90)., Conclusions: Reduced subendocardial perfusion on dipyridamole PET without regional stress perfusion defects is common without angina, has low risk of major adverse cardiac events, reflecting asymptomatic nonobstructive diffuse coronary artery disease, or angina without stenosis. Severely reduced CFC causes angina in fewer than one-half of cases but incurs high mortality risk that is significantly reduced after revascularization., Competing Interests: Funding Support and Author Disclosures Research supported by internal funds of the Weatherhead PET Center. Dr Gould has received internal funding from the Weatherhead PET Center and is the applicant for 510(k) U.S. Food and Drug Administration–cleared HeartSee K202679 PET software. Dr Johnson has received internal funding from Weatherhead PET Center for Preventing and Reversing Atherosclerosis and research support from St. Jude Medical (for CONTRAST [Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology] trial; NCT02184117) and Volcano/Philips Corporation (for the DEFINE-FLOW [Combined Pressure and Flow Measurements to Guide Treatment of Coronary Stenoses] trial; NCT02328820). To avoid any conflict of interest, Drs Gould, Nguyen, Johnson, and Kirkeeide waived their rights to the royalties that they were personally eligible to receive from sales of the intellectual property developed by them and licensed by the University of Texas Health Science Center (UTHealth) to third parties. UTHealth approved their request that all derived royalties be redirected to student scholarships or UTHealth’s Weatherhead PET Center research. UTHealth has a financial interest related to intellectual property via its affiliation with the UTHealth’s Weatherhead PET Imaging Center. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Background Coronary artery disease (CAD) patterns play an essential role in the decision-making process about revascularization. The pullback pressure gradient (PPG) quantifies CAD patterns as either focal or diffuse based on fractional flow reserve (FFR) pullbacks. The objective of this study was to evaluate the impact of CAD patterns on acute percutaneous coronary intervention (PCI) results considered surrogates of clinical outcomes. Methods and Results This was a prospective, multicenter study of patients with hemodynamically significant CAD undergoing PCI. Motorized FFR pullbacks and optical coherence tomography (OCT) were performed before and after PCI. Post-PCI FFR >0.90 was considered an optimal result. Focal disease was defined as PPG >0.73 (highest PPG tertile). Overall, 113 patients (116 vessels) were included. Patients with focal disease were younger than those with diffuse CAD (61.4±9.9 versus 65.1±8.7 years, P =0.042). PCI in vessels with high PPG (focal CAD) resulted in higher post-PCI FFR (0.91±0.07 in the focal group versus 0.86±0.05 in the diffuse group, P <0.001) and larger minimal stent area (6.3±2.3 mm 2 in focal versus 5.3±1.8 mm 2 in diffuse CAD, P =0.015) compared withvessels with low PPG (diffuse CAD). The PPG was associated with the change in FFR after PCI ( R 2 =0.51, P <0.001). The PPG significantly improved the capacity to predict optimal PCI results compared with an angiographic assessment of CAD patterns (area under the curve PPG 0.81 [95% CI, 0.73-0.88] versus area under the curve angio 0.51 [95% CI, 0.42-0.60]; P <0.001). Conclusions PCI in vessels with focal disease defined by the PPG resulted in greater improvement in epicardial conductance and larger minimal stent area compared with diffuse disease. PPG, but not angiographically defined CAD patterns, distinguished patients attaining superior procedural outcomes. Registration URL: https://clinicaltrials.gov/ct2/show/NCT03782688.

Visual assessment of coronary stenosis severity using conventional coronary angiography is associated with wide interoperator variability and a weak relationship with hemodynamics. Invasive coronary physiology assessment using fractional flow reserve (FFR) has been shown to be safe and beneficial. Large multicenter randomized trials have demonstrated the superiority of FFR-guided percutaneous coronary intervention in reducing the risk of major cardiac adverse events, number of stents used, and total cost in patients with multivessel coronary disease. FFR requires vasodilatory agents for the microvasculature to induce maximal hyperemia, which carry a slight risk, cost, and effort. Nonhyperemic pressure ratios provide a physiologic metric without vasodilator medications but with more limited clinical outcomes data. The transition from anatomy to physiology for coronary artery disease decision-making represents a cultural sea change in the cardiac catheterization laboratory that requires time and retooling., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background and Objectives: Cancer and coronary artery disease (CAD) often coexist. Compared to quantitative coronary angiography (QCA), fractional flow reserve (FFR) has emerged as a more reliable method of identifying significant coronary stenoses. We aimed to assess the specific management, safety and outcomes of FFR-guided percutaneous coronary intervention (PCI) in cancer patients with stable CAD. Materials and Methods: FFR was used to assess cancer patients that underwent coronary angiography for stable CAD between September 2008 and May 2016, and were found to have ≥50% stenosis by QCA. Patients with lesions with an FFR > 0.75 received medical therapy alone, while those with FFR ≤ 0.75 were revascularized. Procedure-related complications, all-cause mortality, nonfatal myocardial infarction, or urgent revascularizations were analyzed. Results: Fifty-seven patients with stable CAD underwent FFR on 57 lesions. Out of 31 patients with ≥70% stenosis as measured by QCA, 14 (45.1%) had an FFR ≥ 0.75 and lesions were reclassified as moderate and did not receive PCI nor DAPT. Out of 26 patients with <70% stenosis as measured by QCA, 6 (23%) had an FFR < 0.75 and were reclassified as severe and were treated with PCI and associated DAPT. No periprocedural complications, urgent revascularization, acute coronary syndromes, or cardiovascular deaths were noted. There was a 22.8% mortality at 1 year, all cancer related. Patients who received a stent by FFR assessment showed a significant association with decreased risk of all-cause death (HR: 0.37, 95% CI 0.15−0.90, p = 0.03). Conclusions: Further studies are needed to define the optimal therapeutic approach for cancer patients with CAD. Using an FFR cut-off point of 0.75 to guide PCI translates into fewer interventions and can facilitate cancer care. There was an overall reduction in mortality in patients that received a stent, suggesting increased resilience to cancer therapy and progression.

Competing Interests: Funding Support and Author Disclosures Dr Munhoz has received research grants provided by the CardioPath PhD program. Dr Collet has received research grants from Biosensors, HeartFlow, and Abbott Vascular; and has received consultancy fees from HeartFlow, Abbott Vascular, Boston Scientific, Opsens, and Philips/Volcano. Dr Johnson has received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; has received significant institutional research support from St. Jude Medical and Philips/Volcano Corporation; has an institutional licensing agreement with Boston Scientific for the smart-minimum FFR algorithm; and has pending patents on diagnostic methods and algorithms. Dr Matsuo serves as an advisory board member for Zeon Medical; and receives lecture fees from Abbott Vascular Japan, Boston Scientific Japan, and Phillips Japan. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Fractional flow reserve (FFR) pullbacks assess the location and magnitude of pressure drops along the coronary artery. The pullback pressure gradient (PPG) quantifies the FFR pullback curve and provides a numeric expression of focal versus diffuse coronary artery disease. This study aims (1) to validate the PPG using manual FFR pullbacks compared with motorized FFR pullbacks as a reference; and (2) to determine the intra- and interoperator reproducibility of the PPG derived from manual FFR pullbacks. Patients with stable coronary artery disease and an FFR ≤ 0.80 were included. All patients underwent FFR pullback evaluation either with a motorized device or manually, depending on the study cohort. The agreement of the PPG between repeated pullbacks was assessed using the Bland-Altman method. Overall, 116 FFR pullback maneuvers (96 manual and 20 motorized) were analyzed. There was excellent agreement between the PPG derived from manual and motorized pullbacks (mean difference -0.01 ± 0.07, 95% limits of agreement [LOA] -0.14 to 0.12). The intra- and interoperator reproducibility of PPG derived from manual pullbacks were excellent (mean difference <0.01, 95% LOA -0.11 to 0.12, and mean difference <0.01, 95% LOA -0.12 to 0.11, respectively). The duration of the pullback maneuver did not impact the reproducibility of the PPG (r = 0.12, 95% CI: -0.29 to 0.49, p = 0.567). Manual pullbacks allow for an accurate PPG calculation. The inter- and intraoperator reproducibility of PPG derived from manual pullbacks were excellent., (© 2022 Wiley Periodicals LLC.)

Background: In chronic coronary syndromes, guidelines mandate invasive functional guidance of revascularization whenever non-invasive proof of ischemia is missing. ISIS-2 survey aimed to evaluate how the adoption of guideline recommendation on ischemia-guided revascularization has evolved over the last 5-7 years., Methods: In ISIS-2 participants assessed five complete angiograms, presenting only intermediate stenoses without information on non-invasive pre-testing. Fractional flow reserve was known for each stenosis, but remained undisclosed. Participants could determine stenosis significance either by angiography or by requesting an adjunctive invasive diagnostic method (intravascular imaging or functional tests). Primary endpoint was the rate of requesting adjunctive functional assessment. Secondary endpoints were the rate of concordance between angiography-based decisions and know functional severity. ISIS-2 utilized the same web-based platform as ISIS-1 in 2013. (NCT04001452)., Results: 334 participants performed 2059 lesion evaluations: 1202 (59%) decisions were based solely on angiography without expressed need for further evaluation. These decisions were discordant with known functional significance in 39%, mainly with potential of overtreatment. Participants requested invasive functional assessment in 643 (31%) and intravascular imaging in 214 (10%) cases. Compared to ISIS-1 the rate of purely angiography-based decisions has decreased (59% vs 66%; p < 0.001), while invasive functional tests were more frequently requested (31% vs 25%; p < 0.001)., Conclusions: ISIS-2 suggests an evolving pattern in the intention to integrate invasive coronary physiology into the revascularization decisions. However, the disconnect between recommendations and current thinking is still dominant., (Copyright © 2021. Published by Elsevier B.V.)

Background: The literature reports no randomized trial in chronic coronary artery disease (CAD) of a comprehensive management strategy integrating intense lifestyle management, maximal medical treatment to specific goals and high precision quantitative cardiac positron emission tomography (PET) for identifying high mortality risk patients needing essential invasive procedures. We hypothesize that this comprehensive strategy achieves greater risk factor reduction, lower major adverse cardiovascular events and fewer invasive procedures than standard practice., Methods: The CENTURY Study (NCT00756379) is a randomized-controlled-trial study in patients with stable or at high risk for CAD. Patients are randomized to standard of care (Standard group) or intense comprehensive lifestyle-medical treatment to targets and PET guided interventions (Comprehensive group). Comprehensive Group patients are regularly consulted by the CENTURY team implementing diet/lifestyle/exercise program and medical treatment to target risk modification. Cardiac PET at baseline, 24-, and 60-months quantify the physiologic severity of CAD and guide interventions in the Comprehensive group while patients and referring physicians of the Standard group are blinded to PET results. The primary end-point is the CENTURY risk score reduction during 5 years follow-up. The secondary endpoint is a composite of death, non-fatal myocardial infarction, stroke, and coronary revascularization., Conclusions: The CENTURY Study is the first study in stable CAD to test the incremental benefit of a comprehensive strategy integrating intense lifestyle modification, medical treatment to specific goals, and high-precision quantitative myocardial perfusion imaging to guide revascularization. A total of 1028 patients have been randomized, and the 5 years follow-up will conclude in 2022., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objectives: Performing percutaneous coronary intervention (PCI) for fractional flow reserve (FFR) positive coronary lesions improves clinical outcomes and is recommended by international guidelines. It has been hypothesized that lesions with a positive FFR but a preserved coronary flow reserve (CFR) are less likely to be flow limiting and might best be treated medically. We investigated the association of CFR in FFR-positive lesions with clinical outcomes when treated medically, as well as the treatment effect of PCI vs medical therapy in FFR-positive lesions and a preserved CFR., Methods: We performed a substudy of the randomized, multicenter Compare-Acute trial, in which stabilized ST-segment elevation myocardial infarction (STEMI) patients with non-culprit lesions were randomized to either FFR-guided PCI or medical therapy. Based on baseline and hyperemic pressure gradients, we computed physiologic limits of CFR, the so-called pressure-bounded CFR (pb-CFR), and classified lesions as low (<2) or preserved (≥2). The primary endpoint was 12-month major adverse cardiac and cerebrovascular event (MACCE) rate, defined as a composite of death from any cause, non-fatal myocardial infarction, revascularization, or cerebrovascular events., Results: A total of 980 lesions from 885 patients were included in this substudy. In lesions with FFR ≤0.80, a total of 249 patients had a pb-CFR <2 and 29 patients had a preserved CFR (pb-CFR ≥2). The rate of MACCE at 1 year was not significantly different between patients with FFR ≤0.80 and pb-CFR <2 vs patients with FFR ≤0.80 and pb-CFR ≥2 (25% vs 17%, respectively; P=.39). Because of randomization, baseline characteristics were well balanced between patients with FFR ≤0.80 and pb-CFR ≥2 treated by either by PCI or medical therapy. Importantly, in patients with FFR ≤0.80 and pb-CFR ≥2, MACCE occurred more frequently in patients treated medically vs patients treated by PCI (44% vs 0%, respectively; P=.01)., Conclusions: Preserved or low pb-CFR did not alter clinical outcomes in patients with a positive FFR. Patients with FFR-positive coronary lesions but a preserved CFR had more clinical events when treated medically vs those treated with PCI.

Objectives: This study sought to determine the relationship between the severity of reduced quantitative perfusion parameters and mortality with and without revascularization., Background: The physiological mechanisms for differential mortality risk of coronary flow reserve (CFR) and coronary flow capacity (CFC) before and after revascularization are unknown., Methods: Global and regional rest-stress (ml/min/g), CFR, their regional per-pixel combination as CFC, and relative stress in ml/min/g were measured as percent of LV in all serial routine 5,274 diagnostic PET scans with systematic follow-up over 10 years (mean 4.2 ± 2.5 years) for all-cause mortality with and without revascularization., Results: Severely reduced CFR of 1.0 to 1.5 and stress perfusion ≤1.0 cc/min/g incurred increasing size-dependent risks that were additive because regional severely reduced CFC (CFCsevere) was associated with the highest major adverse cardiac event rate of 80% (p < 0.0001 vs. either alone) and a mortality risk of 14% (vs. 2.3% for no CFCsevere; p = 0.001). Small regions of CFCsevere ≤0.5% predicted high risk (p < 0.0001 vs. no CFCsevere) related to a wave front of border zones at risk around the small most severe center. By receiver-operating characteristic analysis, relative stress topogram maps of stress (ml/min/g) as a fraction of LV defined these border zones at risk or for mildly reduced CFC (area under the curve [AUC]: 0.69) with a reduced relative tomographic subendocardial-to-subepicardial ratio. CFCsevere incurred the highest mortality risk that was reduced by revascularization (p = 0.005 vs. no revascularization) for artery-specific stenosis not defined by global CFR or stress perfusion alone., Conclusions: CFC is associated with the size-dependent highest mortality risk resulting from the additive risk of CFR and stress (ml/min/g) that is significantly reduced after revascularization, a finding not seen for global CFR. Small regions of CFCsevere ≤0.5% of LV also carry a high risk because of the surrounding border zones at risk defined by relative stress perfusion and a reduced relative subendocardial-to-subepicardial ratio., Competing Interests: Funding Support and Author Disclosures This work was supported by internal funds of the Weatherhead PET Center. Dr. Gould has received internal funding from the Weatherhead PET Center; and is the 510(k) applicant for Food and Drug Administration–cleared HeartSee K171303 PET software (to avoid any conflict of interest. Dr. Gould assigned any royalties arising from PET software to the University of Texas for research or student scholarships). Dr. Johnson has received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; and has received research support from St. Jude Medical (for NCT02184117) and Volcano/Philips Corporation (for NCT02328820). All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Can imaging provide sufficient risk stratification to warrant revascularization of a stable plaque with negative fractional flow reserve (FFR)? Prophylactic stenting could at best be applied selectively since the composite group of FFR-negative lesions has a death or myocardial infarction rate of approximately 1%/year or less but modern stents have a rate of 2% to 3.5%/year. Because vulnerable features exist in a minority of lesions, at least 9,000 patients must be screened in order to enroll a cohort with sufficient risk. While several ongoing randomized trials are testing the concept of plaque sealing in FFR-negative lesions, preventive stenting depends on such a small effect that sample sizes to validate or refute its benefit become prohibitive. Since FFR provides a quantitative, straightforward, and reproducible metric of plaque vulnerability and burden without the need for or expense of additional catheter devices, intracoronary imaging cannot meaningfully guide prophylactic stenting when faced with a negative FFR., Competing Interests: Funding Support and Author Disclosures Dr. Pijls has received institutional grant support from Hexacath and Abbott; serves as a consultant for Abbott, Opsens, and GE Health; and possesses equity in Philips, GE, ASML, and Heartflow. Drs. Gould and Johnson have received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis. Drs. Pijls, Gould, and Johnson have a patent pending on diagnostic methods for quantifying aortic stenosis and TAVI physiology. Dr. Gould is the 510(k) applicant for CFR Quant (K113754) and HeartSee (K143664 and K171303), software packages for cardiac positron emission tomography image processing, analysis, and absolute flow quantification. Dr. Johnson has an institutional licensing and consulting agreement with Boston Scientific for the smart minimum fractional flow reserve algorithm; and has received significant institutional research support from St. Jude Medical (CONTRAST, NCT02184117) and Volcano/Philips (DEFINE-FLOW, NCT02328820) for studies using intracoronary pressure and flow sensors. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

With the increasing prevalence of aortic stenosis (AS) due to a growing elderly population, a proper understanding of its physiology is paramount to guide therapy and define severity. A better understanding of the microvasculature in AS could improve clinical care by predicting left ventricular remodeling or anticipate the interplay between epicardial stenosis and myocardial dysfunction. In this review, we combine five decades of literature regarding microvascular, coronary, and aortic valve physiology with emerging insights from newly developed invasive tools for quantifying microcirculatory function. Furthermore, we describe the coupling between microcirculation and epicardial stenosis, which is currently under investigation in several randomized trials enrolling subjects with concomitant AS and coronary disease. To clarify the physiology explained previously, we present two instructive cases with invasive pressure measurements quantifying coexisting valve and coronary stenoses. Finally, we pose open clinical and research questions whose answers would further expand our knowledge of microvascular dysfunction in AS. These trials were registered with NCT03042104, NCT03094143, and NCT02436655., Competing Interests: JMZ reports no support or industry relationships. PALT, NHJP, RLK, KLG, and NPJ have a patent pending on diagnostic methods for quantifying aortic stenosis and TAVI physiology. PALT reports no additional support or industry relationships. NHPJ receives institutional grant support from Abbott, serves as a consultant for Abbott and Opsens, and possesses equity in Philips, GE, ASML, and Heartflow. BDB has received institutional research grants and consulting fees from Abbott Vascular (formerly St. Jude Medical), Boston Scientific, and Opsens. BDB, RLK, KLG, and NPJ have a patent pending on correcting pressure signals from fluid-filled catheters. RLK reports no additional support or industry relationships. KLG is the 510(k) applicant for CFR Quant (K113754) and HeartSee (K143664 and K171303), software packages for cardiac positron emission tomography image processing, analysis, and absolute flow quantification. NPJ receives internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis, has an institutional licensing and consulting agreement with Boston Scientific for the smart minimum FFR algorithm (commercialized under 510(k) K191008), and has received significant institutional research support from St. Jude Medical (CONTRAST, NCT02184117) and Philips Volcano Corporation (DEFINE-FLOW, NCT02328820), studies using intracoronary pressure and flow sensors., (Copyright © 2020 Jo M. Zelis et al.)

Fractional flow reserve is the current invasive gold standard for assessing the ischemic potential of an angiographically intermediate coronary stenosis. Procedural cost and time, the need for coronary vessel instrumentation, and the need to administer adenosine to achieve maximal hyperemia remain integral components of invasive fractional flow reserve. The number of new alternatives to fractional flow reserve has proliferated over the last ten years using techniques ranging from alternative pressure wire metrics to anatomic simulation via angiography or intravascular imaging. This review article provides a critical description of the currently available or under-development alternatives to fractional flow reserve with a special focus on the available evidence, pros, and cons for each with a view towards their clinical application in the near future for the functional assessment of coronary artery disease.

Purpose of Review: This review discusses similarities and differences between cardiac positron emission tomography (PET), absolute myocardial blood flow, and flow reserve with invasive fractional flow reserve (FFR)., Recent Findings: Fundamentally, cardiac PET measures absolute myocardial blood flow whereas FFR provides a relative flow reserve. Cardiac PET offers a non-invasive and therefore lower risk alternative, able to image the entire left ventricle regardless of coronary anatomy. While cardiac PET can provide unique information about the subendocardium, FFR pullbacks offer unparalleled spatial resolution. Both diagnostic tests provide a highly repeatable and technically successful index of coronary hemodynamics that accounts for the amount of distal myocardial mass, albeit only indirectly with FFR. The randomized evidence base for FFR and its associated cost effectiveness remains unsurpassed. Cardiac PET and FFR have been intertwined since the very development of FFR over 25 years ago. Recent work has emphasized the ability of both techniques to guide revascularization decisions by high-quality physiology. In the past few years, cardiac PET has expanded its evidence base regarding clinical outcomes, whereas FFR has solidified its position in randomized studies as the invasive reference standard.

Background: Intravenous infusion of adenosine is considered standard practice for fractional flow reserve (FFR) assessment but is associated with adverse side-effects and is time-consuming. Intracoronary bolus injection of adenosine is better tolerated by patients, cheaper, and less time-consuming. However, current literature remains fragmented and modestly sized regarding the equivalence of intracoronary versus intravenous adenosine. We aim to investigate the relationship between intracoronary adenosine and intravenous adenosine to determine FFR., Methods: We performed a lesion-level meta-analysis to compare intracoronary adenosine with intravenous adenosine (140 µg/kg per minute) for FFR assessment. The search was conducted in accordance to the Preferred Reporting for Systematic Reviews and Meta-Analysis statement. Lesion-level data were obtained by contacting the respective authors or by digitization of scatterplots using custom-made software. Intracoronary adenosine dose was defined as; low: <40 µg, intermediate: 40 to 99 µg, and high: ≥100 µg., Results: We collected 1972 FFR measurements (1413 lesions) comparing intracoronary with intravenous adenosine from 16 studies. There was a strong correlation (correlation coefficient =0.915; P <0.001) between intracoronary-FFR and intravenous-FFR. Mean FFR was 0.81±0.11 for intracoronary adenosine and 0.81±0.11 for intravenous adenosine ( P <0.001). We documented a nonclinically relevant mean difference of 0.006 (limits of agreement: -0.066 to 0.078) between the methods. When stratified by the intracoronary adenosine dose, mean differences between intracoronary and intravenous-FFR amounted to 0.004, 0.011, or 0.000 FFR units for low-dose, intermediate-dose, and high-dose intracoronary adenosine, respectively., Conclusions: The present study documents clinically irrelevant differences in FFR values obtained with intracoronary versus intravenous adenosine. Intracoronary adenosine hence confers a practical and patient-friendly alternative for intravenous adenosine for FFR assessment.

Objectives: To identify clinical, angiographic and hemodynamic predictors of discordance between instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR)., Background: The iFR was found to be non-inferior to the gold-standard FFR for guiding coronary revascularization, although it is discordant with FFR in 20% of cases. A better understanding of the causes of discordance may enhance application of these indices., Methods: Both FFR and iFR were measured in the prospective multicenter CONTRAST study. Clinical, angiographic and hemodynamic variables were compared between patients with concordant values of FFR and iFR (cutoff ≤0.80 and ≤0.89, respectively)., Results: Out of the 587 patients included, in 466 patients (79.4%) FFR and iFR agreed: both negative, n = 244 (41.6%), or positive, n = 222 (37.8%). Compared with FFR, iFR was negative discordant (FFR+/iFR-) in 69 (11.8%) patients and positive discordant (FFR-/iFR+) in 52 (8.9%) patients. On multivariate regression, stenosis location (left main or proximal left anterior descending) (OR: 3.30[1.68;6.47]), more severe stenosis (OR: 1.77[1.35;2.30]), younger age (OR: 0.93[0.90;0.97]), and slower heart rate (OR: 0.59[0.42;0.75]) were predictors of a negative discordant iFR. Absence of a beta-blocker (OR: 0.41[0.22;0.78]), older age (OR: 1.04[1.00;1.07]), and less severe stenosis (OR: 0.69[0.53;0.89]) were predictors of a positive discordant iFR., Conclusions: During iFR acquisition, stenosis location, stenosis degree, heart rate, age and use of beta blockers influence concordance with FFR and should be taken into account when interpreting iFR., (© 2019 Wiley Periodicals, Inc.)

Aims: The instantaneous wave-free ratio (iFR) and whole-cycle Pd/Pa investigate coronary physiology during non-hyperaemic conditions. To test for unique physiologic properties of the wave-free period when making resting coronary pressure measurements, we compared post hoc a diastolic pressure ratio (dPR) and Pd/Pa against iFR for numerical similarity and test/retest repeatability., Methods and Results: Eight hundred and ninety-three lesions from 833 subjects were included from the VERIFY 2 and CONTRAST studies. Diastolic pressure ratio and a linear transform of Pd/Pa were compared against iFR for diagnostic performance. Mean difference between dPR and iFR [Δ = -0.006 ± 0.011, r2 = 0.993, area under receiver operating characteristic (ROC) curve (AUC) = 0.997] mirrored the difference of two iFR measurements repeated immediately (Δ = <0.001 ± 0.004, r2 = 0.998, AUC = 1.00). Minor variations in the definition of dPR changed its value by <1-2% over a broad range of the cardiac cycle. A linear transform of Pd/Pa showed very good diagnostic performance (Δ = -0.012 ± 0.031, r2 = 0.927, AUC = 0.979). Post hoc iFR values were validated against real-time iFR values and matched almost exactly (average Δ = <0.001 ± 0.004, 99.6% within ±0.01)., Conclusions: Our dPR offers numerical equivalency to iFR. Despite different technical approaches for identifying the relevant period of diastole, the agreement between dPR and iFR and the insensitivity of dPR to minor variations in its definition further confirm numerical equivalency among resting metrics., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2019. For permissions, please email: journals.permissions@oup.com.)

Because randomized coronary revascularization trials in stable coronary artery disease (CAD) have shown no reduced myocardial infarction (MI) or mortality, the threshold of quantitative myocardial perfusion severity was analyzed for association with reduced death, MI, or stroke after revascularization within 90 d after PET. Methods: In a prospective long-term cohort of stable CAD, regional, artery-specific, quantitative myocardial perfusion by PET, coronary revascularization within 90 d after PET, and all-cause death, MI, and stroke (DMS) at 9-y follow-up (mean ± SD, 3.0 ± 2.3 y) were analyzed by multivariate Cox regression models and propensity analysis. Results: For 3,774 sequential rest-stress PET scans, regional, artery-specific, severely reduced coronary flow capacity (CFC) (coronary flow reserve ≤ 1.27 and stress perfusion ≤ 0.83 cc/min/g) associated with 60% increased hazard ratio for major adverse cardiovascular events and 30% increased hazard of DMS that was significantly reduced by 54% associated with revascularization within 90 d after PET ( P = 0.0369), compared with moderate or mild CFC, coronary flow reserve, other PET metrics or medical treatment alone. Depending on severity threshold for statistical certainty, up to 19% of this clinical cohort had CFC severity associated with reduced DMS after revascularization. Conclusion: CFC by PET provides objective, regional, artery-specific, size-severity physiologic quantification of CAD severity associated with high risk of DMS that is significantly reduced after revascularization within 90 d after PET, an association not seen for moderate to mild perfusion abnormalities or medical treatment alone., (© 2019 by the Society of Nuclear Medicine and Molecular Imaging.)

Aims: To assess the effect of fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) with contemporary drug-eluting stents on the composite of cardiac death or myocardial infarction (MI) vs. medical therapy in patients with stable coronary lesions., Methods and Results: We performed a systematic review and meta-analysis of individual patient data (IPD) of the three available randomized trials of contemporary FFR-guided PCI vs. medical therapy for patients with stable coronary lesions: FAME 2 (NCT01132495), DANAMI-3-PRIMULTI (NCT01960933), and Compare-Acute (NCT01399736). FAME 2 enrolled patients with stable coronary artery disease (CAD), while the other two focused on non-culprit lesions in stabilized patients after acute coronary syndrome. A total of 2400 subjects were recruited from 54 sites world-wide with 1056 randomly assigned to FFR-guided PCI and 1344 to medical therapy. The pre-specified primary outcome was a composite of cardiac death or MI. We included data from extended follow-ups for FAME 2 (up to 5.5 years follow-up) and DANAMI-3-PRIMULTI (up to 4.7 years follow-up). After a median follow-up of 35 months (interquartile range 12-60 months), a reduction in the composite of cardiac death or MI was observed with FFR-guided PCI as compared with medical therapy (hazard ratio 0.72, 95% confidence interval 0.54-0.96; P = 0.02). The difference between groups was driven by MI., Conclusion: In this IPD meta-analysis of the three available randomized controlled trials to date, FFR-guided PCI resulted in a reduction of the composite of cardiac death or MI compared with medical therapy, which was driven by a decreased risk of MI.

Background: Currently, invasive physiologic assessment such as fractional flow reserve is widely used worldwide with different adoption rates around the globe. Patient characteristics and physician preferences often differ in the Asia-Pacific (APAC) region with respect to treatment strategy, techniques, lesion complexity, access to coronary physiology and imaging devices, as well as patient management. Thus, there is a need to construct a consensus document on recommendations for use of physiology-guided percutaneous coronary intervention (PCI) in APAC populations. This document serves as an overview of recommendations describing the best practices for APAC populations to achieve more consistent and optimal clinical outcomes., Methods and Results: A comprehensive multiple-choice questionnaire was provided to 20 interven- tional cardiologists from 10 countries in the APAC region. Clinical evidence, tips and techniques, and clinical situations for the use of physiology-guided PCI in APAC were reviewed and used to propose key recommendations. There are suggestions to continue to develop evidence for lesion and patient types that will benefit from physiology, develop directions for future research in health economics and local data, develop appropriate use criteria in different countries, and emphasize the importance of education of all stakeholders. A consensus recommendation to enhance the penetration of invasive physiology-based therapy was to adopt the 5E approach: Evidence, Education, Expand hardware, Economics and Expert consensus., Conclusions: This consensus document and recommendations support interventional fellows and cardiologists, hospital administrators, patients, and medical device companies to build confidence and encourage wider implementation of invasive coronary physiology-guided therapy in the APAC region.

Objectives: The goal of this study was to investigate sex differences in adenosine-free coronary pressure indexes., Background: Several adenosine-free coronary pressure wire indexes have been proposed to assess the functional significance of coronary artery lesions; however, there is a theoretical concern that sex differences may affect diagnostic performance because of differences in resting flow and distal myocardial mass., Methods: In this CONTRAST (Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology?) substudy, contrast fractional flow reserve (cFFR), obtained during contrast-induced submaximal hyperemia, the instantaneous wave-free ratio (iFR), and distal/proximal coronary pressure ratio (Pd/Pa) were compared with fractional flow reserve (FFR) in 547 men and 216 women. Using FFR ≤0.8 as a reference, the diagnostic performance of each index was compared., Results: Men and women had similar diameter stenosis (p = 0.78), but women were less likely to have FFR ≤0.80 than men (42.5% vs. 51.5%, p = 0.04). Sensitivity was similar among cFFR, iFR, and Pd/Pa when comparing women and men, respectively (cFFR, 77.5% vs. 75.3%; p = 0.69; iFR, 84.9% vs. 79.4%; p = 0.30; Pd/Pa, 78.8% vs. 77.3%; p = 0.78). cFFR was more specific than iFR or Pd/Pa regardless of sex (cFFR, 94.3% vs. 95.8%; p = 0.56; iFR, 75.6% vs. 80.1%; p = 0.38; Pd/Pa, 80.6% vs. 78.7%; p = 0.69). By receiver-operating characteristic curve analysis, cFFR provided better diagnostic accuracy than resting indexes irrespective of sex (p ≤ 0.0001)., Conclusions: Despite the theoretical concern, the diagnostic sensitivity and specificity of cFFR, iFR, and Pd/Pa did not differ between the sexes. Irrespective of sex, cFFR provides the best diagnostic performance., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Fractional flow reserve (FFR)-guided coronary artery bypass graft (CABG) surgery has been associated with lower number of graft anastomoses, lower rate of on-pump surgery, and higher graft patency rate as compared with angiography-guided CABG surgery. However, no clinical benefit has been reported to date., Methods and Results: Consecutive patients (n=627) treated by CABG between 2006 and 2010 were retrospectively included. In 198 patients, at least 1 stenosis was grafted according to FFR (FFR-guided group), whereas in 429 patients all stenoses were grafted based on angiography (angiography-guided group). The 2 coprimary end points were overall death or myocardial infarction and major adverse cardiovascular events (composite of overall death, myocardial infarction, and target vessel revascularization) up to 6-year follow-up. In the FFR-guided group, patients were significantly younger (66 [57-73] versus 70 [63-76]; P <0.001), more often male (82% versus 72%; P =0.008), and less often diabetic (21% versus 30%; P =0.023). Clinical follow-up (median, 85 [66-104] months) was analyzed in 396 patients after 1:1 propensity-score matching for these 3 variables. The rate of overall death or myocardial infarction was significantly lower in the FFR-guided (n=31 [16%] versus n=49 [25%]; hazard ratio, 0.59 [95% confidence interval, 0.38-0.93]; P =0.020) as compared with the angiography-guided group. Major adverse cardiovascular events rate was also numerically lower in the FFR-guided than in the angiography-guided group (n=42 [21%] versus n=52 [26%]; hazard ratio, 0.77 [95% confidence interval, 0.51-1.16]; P =0.21)., Conclusions: FFR-guided CABG is associated with a significant reduction in the rate of overall death or myocardial infarction at 6-year follow-up as compared with angiography-guided CABG., (© 2018 American Heart Association, Inc.)

Objective: We propose a novel technique called pressure-bounded coronary flow reserve (pb-CFR) and demonstrate its application to the randomized DEFER trial., Background: Intracoronary flow reserve assessment remains underutilized relative to pressure measurements partly due to less robust tools., Methods: While rest and hyperemic intracoronary pressure measurements cannot quantify CFR exactly, they do provide upper and lower bounds. We validated pb-CFR invasively against traditional CFR, then applied it to high fractional flow reserve (FFR ≥ 0.75) lesions in DEFER randomized to revascularization or medical therapy., Results: pb-CFR showed an 84.4% accuracy to predict invasive CFR < 2 or CFR ≥ 2 in 107 lesions. In its proof of concept application to DEFER lesions with FFR ≥ 0.75, the 28 with pb-CFR < 2 compared to 28 with pb-CFR ≥ 2 had a non-significant reduction in freedom from angina (61% vs. 71% at 5 years, P = 0.57) and a non-significantly higher rate of major adverse cardiac events (MACE, 25% vs. 15%, P = 0.34). Lesions with FFR ≥ 0.75 but pb-CFR < 2 showed no difference in freedom from angina (61% vs. 50%, P = 0.54) or MACE (25% vs. 38%, P = 0.27) between the 28 randomized to medical therapy and the 16 randomized to revascularization., Conclusions: pb-CFR offers a new method for studying FFR/CFR discordances using regular pressure wire measurements. As an example application, DEFER suggested that low pb-CFR with high FFR may be a risk marker for more angina and worse outcomes, but that this risk cannot be modified by revascularization. © 2017 Wiley Periodicals, Inc., (© 2017 Wiley Periodicals, Inc.)

Objectives: The aim of this study was to compare site-reported measurements of fractional flow reserve (FFR) with FFR analysis by an independent core laboratory (CL)., Background: FFR is an index of coronary stenosis severity that has been validated in multiple trials and is widely used in clinical practice. However, the incidence of suboptimal FFR measurements is unknown., Methods: Patients undergoing FFR assessment within the CONTRAST (Can Contrast Injection Better Approximate FFR Compared to Pure Resting Physiology) study had paired, repeated measurements of multiple physiological metrics per local practice. An independent central physiology CL analyzed blinded pressure tracings off-line in a standardized fashion for comparison., Results: A total of 763 patients were included in the study; 4,946 distal coronary artery pressure/aortic pressure (nonhyperemic) and FFR tracings were analyzed by the CL (mean 6.5 tracings per patient). Pull-back data were available for 616 patients (80.7%), of whom 108 (17.5%) had signal drift, defined as distal coronary artery pressure/aortic pressure (nonhyperemic) <0.97 or >1.03. Among the remaining 4,217 tracings without evidence of signal drift, 222 (5.3%) were noted to have ventricularization of the aortic waveform, and 168 (4.0%) had aortic waveform distortion. Excluding cases with signal drift and waveform distortion, there was excellent agreement between CL-calculated and site-reported FFR, with a mean difference of 0.003 ± 0.02. Predictors of distorted waveforms were smaller guiding catheter size (odds ratio: 6.30; 95% confidence interval: 3.22 to 12.32; p < 0.001) and intracoronary adenosine use (odds ratio: 0.13; 95% confidence interval: 0.05 to 0.33; p < 0.001)., Conclusions: This FFR CL analysis showed that almost 10% of tracings demonstrated waveform artifacts, and an additional 17.5% had signal drift. Among adequate tracings, there was a close correlation between site-reported and CL-analyzed FFR values. Attention to detail is critical for FFR studies to ensure adequate technique and optimal results., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)