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The article discusses the use of [15O]H2O PET/CT myocardial perfusion imaging to diagnose coronary artery disease, with a case study of a 74-year-old male who presented with symptoms of peripheral edema and orthopnea. While the patient's myocardial perfusion was normal, the imaging revealed subsegmental perfusion defects in the lower and middle lobes of the right lung, leading to a suspicion of pulmonary embolisms. The study highlights the importance of recognizing perfusion defects during PET/CT imaging as potential indicators of pulmonary embolism, even though PET/CT is not a primary diagnostic tool for this condition. [Extracted from the article]

Aims Myocardial external efficiency (MEE) is the ratio of cardiac work in relation with energy expenditure. We studied MEE in patients with different aetiologies and stages of heart failure (HF) to discover the role and causes of deranged MEE. In addition, we explored the impact of patient characteristics such as sex, body mass index (BMI), and age on myocardial energetics. Methods and results Cardiac energetic profiles were assessed with 11C-acetate positron emission tomography (PET) and left ventricular ejection fraction (LVEF) was acquired with echocardiography. MEE was studied in 121 participants: healthy controls (n  = 20); HF patients with reduced (HFrEF; n  = 25) and mildly reduced (HFmrEF; n  = 23) LVEF; and patients with asymptomatic (AS-asymp; n  = 38) and symptomatic (AS-symp; n  = 15) aortic stenosis (AS). Reduced MEE coincided with symptoms of HF irrespective of aetiology and declined in tandem with deteriorating LVEF. Patients with AS-symp and HFmrEF had reduced MEE as compared with controls (22.2 ± 4.9%, P  = 0.041 and 20.0 ± 4.2%, P  < 0.001 vs. 26.1 ± 5.8% in controls) and a further decline was observed in patients with HFrEF (14.7 ± 6.3%, P  < 0.001). Disproportionate left ventricular hypertrophy was a major cause of reduced MEE. Female sex (P  < 0.001), a lower BMI (P  = 0.001), and advanced age (P  = 0.03) were associated with a lower MEE. Conclusion MEE was reduced in patients with HFrEF, HFmrEF, and HF due to pressure overload and MEE may therefore constitute a treatment target in HF. Patients with LVH, advanced age, female sex, and low BMI had more pronounced reduction in MEE and personalized treatment within these patient subgroups could be relevant. [ABSTRACT FROM AUTHOR]

Aims: The present study tested the hypothesis that metformin treatment may increase myocardial efficiency (stroke work/myocardial oxygen consumption) in insulin‐resistant patients with heart failure and reduced ejection fraction (HFrEF) without diabetes. Methods and results: Thirty‐six HFrEF patients (ejection fraction 37 ± 8%; median age 66 years) were randomised to metformin (n = 19) or placebo (n = 17) for 3 months in addition to standard heart failure therapy. The primary endpoint was change in myocardial efficiency expressed as the work metabolic index (WMI), assessed by 11C‐acetate positron emission tomography and transthoracic echocardiography. Compared with placebo, metformin treatment (1450 ± 550 mg/day) increased WMI [absolute mean difference, 1.0 mmHg·mL·m‐2·106; 95% confidence interval (CI) 0.1 to 1.8; P = 0.03], equivalent to a 20% relative efficiency increase. Patients with above‐median plasma metformin levels displayed greater WMI increase (25% vs. –4%; P = 0.02). Metformin reduced myocardial oxygen consumption (–1.6 mL O2·100 g‐1·min‐1; P = 0.014). Cardiac stroke work was preserved (–2 J; 95% CI –11 to 7; P = 0.69). Metformin reduced body weight (–2.2 kg; 95% CI –3.6 to –0.8; P = 0.003) and glycated haemoglobin levels (–0.2%; 95% CI –0.3 to 0.0; P = 0.02). Changes in resting and exercise ejection fraction, global longitudinal strain, and exercise capacity did not differ between groups. Conclusion: Metformin treatment in non‐diabetic HFrEF patients improved myocardial efficiency by reducing myocardial oxygen consumption. Measurement of circulating metformin levels differentiated responders from non‐responders. These energy‐sparing effects of metformin encourage further large‐scale investigations in heart failure patients without diabetes. [ABSTRACT FROM AUTHOR]

Differences in tracer characteristics may influence the interpretation of positron emission tomography myocardial perfusion imaging (MPI). We compare the reading of MPIs with a low-extraction retention tracer (82Rb) and a high-extraction non-retention tracer (15O-water) in a selected cohort of patients with known coronary artery disease (CAD). Thirty-nine patients with known CAD referred to 82Rb MPI due to angina underwent rest and stress imaging with both tracers and experienced MPI readers provided blinded consensus reads of all studies. In addition, a comparison of regional and global quantitative measures of perfusion was performed. The results showed 74 % agreement in the reading of 82Rb and 15O-water MPI for regional reversible ischemia and global disease, and 82 % agreement for regional irreversible ischemia. The 15O-water MPI identified more cases of global disease (n = 12 (15O-water) vs n = 4 (82Rb), p = 0.03), whereas differences in reversible ischemia (n = 22 vs n = 16, p = 0.11) and, irreversible ischemia (n = 8 vs n = 11, p = 0.45) were not significant. The correlation between myocardial blood flow measured using the two tracers was similar to previous studies (R2 = 0.78) with wide limits of agreement (−0.93 to 0.84 ml/g/min). Agreement between consensus readings of 82Rb and 15O-water MPI was good in patients with known CAD. In this limited size study, no significant differences in the identification of reversible and irreversible ischemia found, whereas 15O-water MPI had a higher positive rate for suspected global disease. [Display omitted] [ABSTRACT FROM AUTHOR]

Aims Left ventricular filling pressure (preload) can be assessed by pulmonary capillary wedge pressure (PCWP) during pulmonary arterial catheterization (PAC). An emerging method [pulse indexed contour cardiac output (PICCO)] can estimate preload by global end-diastolic volume (GEDV) and congestion as extravascular lung water (EVLW) content. However, no reliable quantitative non-invasive methods are available. Hence, in a porcine model of pulmonary congestion, we evaluated EVLW and GEDV by positron emission tomography (PET). The method was applied in 35 heart failure (HF) patients and 9 healthy volunteers. Methods and results Eight pigs were studied. Pulmonary congestion was induced by a combination of beta-blockers, angiotensin-2 agonist and saline infusion. PAC, PICCO, computerized tomography, and 15O-H2O-PET were performed. EVLW increased from 521 ± 76 to 973 ± 325 mL (P  < 0.001) and GEDV from 1068 ± 170 to 1254 ± 85 mL (P  < 0.001). 15O-H2O-PET measures of EVLW increased from 566 ± 151 to 797 ± 231 mL (P  < 0.001) and GEDV from 364 ± 60 to 524 ± 92 mL (P  < 0.001). Both EVLW and GEDV measured with PICCO and 15O-H2O-PET correlated (r 2 = 0.40, P  < 0.001; r 2 = 0.40, P  < 0.001, respectively). EVLW correlated with Hounsfield units (HU; PICCO: r 2 = 0.36, P  < 0.001, PET: r 2 = 0.46, P  < 0.001) and GEDV with PCWP (PICCO: r 2 = 0.20, P  = 0.01, PET: r 2 = 0.29, P  = 0.002). In human subjects, measurements were indexed (I) for body surface area. Neither EVLWI nor HU differed between chronic stable HF patients and healthy volunteers (P  = 0.11, P  = 0.29) whereas GEDVI was increased in HF patients (336 ± 66 mL/m2 vs. 276 ± 44 mL/m2, P  = 0.01). Conclusion The present study demonstrates that 15O-H2O-PET can assess pulmonary congestion and preload quantitatively. Hence, prognostic information from 15O-H2O-PET examinations should be evaluated in clinical trials. [ABSTRACT FROM AUTHOR]

Background: The glucagon-like peptide-1 analog liraglutide increases heart rate and may be associated with more cardiac events in chronic heart failure (CHF) patients. We studied whether this could be ascribed to effects on myocardial glucose uptake (MGU), myocardial blood flow (MBF) and MBF reserve (MFR).Methods and Results: CHF patients with left ventricular ejection fraction ≤45% and without type 2 diabetes were randomized to liraglutide (N = 18) 1.8 mg once daily or placebo (N = 18) for 24 weeks in a double-blinded design. Changes in MGU during an oral glucose tolerance test (OGTT) and changes in MBF and MFR from baseline to follow-up were measured quantitatively by 18F-FDG and 15O-H2O positron emission tomography. Compared with placebo, liraglutide reduced weight (P = 0.03), HbA1c (P = 0.03) and the 2-hour glucose value during the OGTT (P = 0.004). Despite this, changes in MGU (P = 0.98), MBF (P = 0.76) and MFR (P = 0.89) from baseline to follow-up did not differ between groups. Furthermore, there was no association between the level of insulin resistance at baseline and changes in MGU in patients treated with liraglutide.Conclusion: Liraglutide did not affect MGU, MBF, or MFR in non-diabetic CHF patients. Any potential increase in cardiac events in these patients seems not to involve changes in MGU, MBF, or MFR.Trial Registration: Trial registry: http://www.ClinicalTrials.org . Identifier: NCT01472640. Url: https://clinicaltrials.gov/ct2/show/NCT01472640?term=NCT01472640&rank=1. [ABSTRACT FROM AUTHOR]

Background: Myocardial efficiency measured by 11C-acetate positron emission tomography (PET) has successfully been used in clinical research to quantify mechanoenergetic coupling. The objective of this study was to establish the repeatability of myocardial external efficiency (MEE) and work metabolic index (WMI) by non-invasive concepts.Methods and Results: Ten healthy volunteers (63 ± 4 years) were examined twice, one week apart, using 11C-acetate PET, cardiovascular magnetic resonance (CMR), and echocardiography. Myocardial oxygen consumption from PET was combined with stroke work data from CMR, echocardiography, or PET to obtain MEE and WMI for each modality. Repeatability was estimated as the coefficient of variation (CV) between test and retest. MEECMR, MEEEcho, and MEEPET values were 21.9 ± 2.7%, 16.4 ± 3.7%, and 23.8 ± 4.9%, respectively, P < .001. WMICMR, WMIEcho, and WMIPET values were 4.42 ± 0.90, 4.07 ± 0.63, and 4.58 ± 1.13 mmHg × mL/m2 × 106, respectively, P = .45. Repeatability for MEECMR was superior compared with MEEEcho but did not differ significantly compared with MEEPET (6.3% vs 12.9% and 9.4%, P = .04 and .25). CV values for WMICMR, WMIEcho, and WMIPET were 10.0%, 14.8%, and 12.0%, respectively, (P = .53).Conclusions: Non-invasive measurements of MEE using 11C-acetate PET are highly repeatable. A PET-only approach did not differ significantly from CMR/PET and might facilitate further clinical research due to lower costs and broader applicability. [ABSTRACT FROM AUTHOR]

Background: In type 2 diabetes, a decrease in myocardial glucose uptake (MGU) may lower glucose oxidation and contribute to progression of chronic heart failure (CHF). However, it is unsettled whether CHF patients with prediabetes have abnormal MGU and myocardial blood flow (MBF) during normal physiological conditions.Methods and Results: We studied 35 patients with CHF and reduced left ventricular ejections fraction (34 ± 9%) without overt T2D (mean HbA1c: 40 ± 4 mmol/mol) using echocardiography and quantitative measurements of MGU by 18F-FDG-PET and perfusion by 15O-H2O-PET. An oral glucose tolerance test (OGTT) was performed during the FDG-PET, which identified 17 patients with abnormal and 18 patients with normal glucometabolic response. Global MGU was higher in patients with normal OGTT response (0.31 ± 0.09 µmol/g/min) compared with patients with abnormal OGTT response (0.25 ± 0.09 µmol/g/min) (P = 0.05). MBF (P = 0.22) and myocardial flow reserve (MFR) (P = 0.83) were similar in the study groups. The reduced MGU in prediabetic patients was attributable to reduced MGU in viable myocardium with normal MFR (P < 0.001).Conclusion: CHF patients with prediabetes have reduced MGU in segments with preserved MFR as compared to CHF patients with normal glucose tolerance. Whether reversal of these myocardial abnormalities can improve outcome needs to be investigated in large-scale studies. [ABSTRACT FROM AUTHOR]

Background: Noninvasive estimation of myocardial external efficiency (MEE) requires measurements of left ventricular (LV) oxygen consumption with [(11)C]acetate PET in addition to LV stroke volume and mass with cardiovascular magnetic resonance (CMR). Measuring LV geometry directly from ECG-gated [(11)C]acetate PET might enable MEE evaluation from a single PET scan. Therefore, we sought to establish the accuracy of measuring LV volumes, mass, and MEE directly from ECG-gated [(11)C]acetate PET.Methods: Thirty-five subjects with aortic valve stenosis underwent ECG-gated [(11)C]acetate PET and CMR. List mode PET data were rebinned into 16-bin ECG-gated uptake images before measuring LV volumes and mass using commercial software and compared to CMR. Dynamic datasets were used for calculation of mean LV oxygen consumption and MEE.Results: LV mass, volumes, and ejection fraction measured by CMR and PET correlated strongly (r = 0.86-0.92, P < .001 for all), but were underestimated by PET (P < .001 for all except ESV P = .79). PET-based MEE, corrected for bias, correlated fairly with PET/CMR-based MEE (r = 0.60, P < .001, bias -3 ± 21%, P = .56). PET-based MEE bias was strongly associated with LV wall thickness.Conclusions: Although analysis-related improvements in accuracy are recommended, LV geometry estimated from ECG-gated [(11)C]acetate PET correlate excellently with CMR and can indeed be used to evaluate MEE. [ABSTRACT FROM AUTHOR]