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Background: We assessed the utility of EndoPAT, a device that measures reactive hyperemia index (RHI) as a clinical screening tool for identifying low coronary flow reserve (CFR). Distinguishing normal from low CFR aids assessment for coronary microvascular dysfunction (CMD) or large vessel coronary artery disease (CAD)., Methods: From June 2014-May 2019, in a convenience sample, we measured RHI in adults undergoing clinically indicated cardiac Rubidium-82 positron emission tomography/computed tomography (PET/CT) at a single center. Exclusion criteria were inability to consent, lack of English proficiency, and physical limitation. We defined low RHI as <1.67 and low CFR as <2.5. Distribution of RHI was skewed so we used its natural logarithm (LnRHI) to calculate Pearson correlation and area under the curve (AUC)., Results: Of 265 patients with PET/CT, we enrolled 131, and 100 had adequate data. Patients had a mean age of 61 years (SD = 12), 46% were female, 29% non-white. Thirty-six patients had low RHI, and 60 had depressed CFR. LnRHI did not distinguish patients with low from normal CFR (AUC = 0.53; 95% Cl, 0.41-0.64) and did not correlate with CFR (r = -0.021, p = 0.83). Low RHI did not distinguish patients with traditional CAD risk factors, presence of calcification, or perfusion defect (p > 0.05). Conversely, mean augmentation index, a measure of arterial stiffness, was higher with low RHI (p = 0.005) but not CFR (p = 0.625). RHI was lower in patients we identified as CMD (low CFR, no perfusion defect and calcium score of 0) (1.88 versus 2.21, p = 0.35) although we were underpowered (n = 12) to meet statistical significance., Conclusions: Peripheral RHI is insufficient as a clinical screening tool for low CFR as measured by cardiac PET/CT. Differences in vascular pathology assessed by each method may explain this finding., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Aims: Recent studies have demonstrated that chronic obstructive pulmonary disease (COPD) is associated with cardiovascular disease (CVD). However, the association between COPD and coronary microcirculatory dysfunction is unknown. We sought to assess whether myocardial perfusion reserve (MPR) is impaired in patients with COPD, even in the absence of regional myocardial ischaemia or infarction, by using quantitative myocardial perfusion cardiovascular magnetic resonance (CMR)., Methods and Results: We recruited 60 subjects with a normal CMR study: 20 individuals with mild-to-moderate COPD; 20 age-matched control smokers, and 20 age-matched control-never smokers. Individuals with established CVD and diabetes mellitus were excluded. Stress-rest myocardial blood flow (MBF) was quantified in 16 myocardial segments by using a Patlak plot method. There were no significant differences in the rest MBF among COPD patients, control smokers, and control-never smokers. However, the mean MPR was significantly lower in COPD patients than in control smokers and control-never smokers (1.76 ± 0.58, 2.57 ± 1.30, and 3.56 ± 1.27, respectively). Univariate associations with MPR were smoking (r = -0.44, P < 0.001), forced expiratory volume in 1 s (FEV1) (r = 0.30, P = 0.02), haematocrit (r = 0.25, P = 0.04), and C-reactive protein (CRP; r = -0.46, P < 0.001). On multivariable analysis, the levels of CRP, FEV1, and renal dysfunction were independent predictors of the impaired MPR. The presence of COPD was associated with a five-fold increased risk of MPR <1.5 (95% confidence interval, 1.4-19.0; P = 0.01)., Conclusions: The MPR, which was independently associated with systemic inflammation and airflow limitation, was impaired in patients with COPD. The presence of COPD was a powerful predictor of impaired MPR in patients without regional myocardial ischaemia or infarction.

Ischemia with no obstructive coronary artery disease (INOCA) is prevalent in women and is associated with increased risk of developing heart failure with preserved ejection fraction (HFpEF); however, the mechanism(s) contributing to this progression remains unclear. Given that diastolic dysfunction is common in women with INOCA, defining mechanisms related to diastolic dysfunction in INOCA could identify therapeutic targets to prevent HFpEF. Cardiac MRI was performed in 65 women with INOCA and 12 reference controls. Diastolic function was defined by left ventricular early diastolic circumferential strain rate (eCSRd). Contributors to diastolic dysfunction were chosen a priori as coronary vascular dysfunction (myocardial perfusion reserve index [MPRI]), diffuse myocardial fibrosis (extracellular volume [ECV]), and aortic stiffness (aortic pulse wave velocity [aPWV]). Compared to controls, eCSRd was lower in INOCA (1.61 ± 0.33/s vs. 1.36 ± 0.31/s, P = 0.016); however, this difference was not exaggerated when the INOCA group was sub-divided by low and high MPRI (P > 0.05) nor was ECV elevated in INOCA (29.0 ± 1.9% vs. 28.0 ± 3.2%, control vs. INOCA; P = 0.38). However, aPWV was higher in INOCA vs. controls (8.1 ± 3.2 m/s vs. 6.1 ± 1.5 m/s; P = 0.045), and was associated with eCSRd (r = −0.50, P < 0.001). By multivariable linear regression analysis, aPWV was an independent predictor of decreased eCSRd (standardized β = −0.39, P = 0.003), as was having an elevated left ventricular mass index (standardized β = −0.25, P = 0.024) and lower ECV (standardized β = 0.30, P = 0.003). These data provide mechanistic insight into diastolic dysfunction in women with INOCA, identifying aortic stiffness and ventricular remodeling as putative therapeutic targets. • INOCA is prevalent in women and is associated with increased risk of developing HFpEF. • The mechanism(s) contributing to heart failure progression in women with INOCA remains unclear. • Here we show that elevated aotric stiffness is an independent predictor of impaired diastolic function in INOCA. [ABSTRACT FROM AUTHOR]

Background: Quantification of myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) by cardiovascular magnetic resonance (CMR) perfusion requires sampling of the arterial input function (AIF). While variation in the AIF sampling location is known to impact quantification by CMR and positron emission tomography (PET) perfusion, there is no evidence to support the use of a specific location based on their diagnostic accuracy in the detection of coronary artery disease (CAD). This study aimed to evaluate the accuracy of stress MBF and MPR for different AIF sampling locations for the detection of abnormal myocardial perfusion with expert visual assessment as the reference. Methods: Twenty-five patients with suspected or known CAD underwent vasodilator stress-rest perfusion with a dual-sequence technique at 3T. A low-resolution slice was acquired in 3-chamber view to allow AIF sampling at five different locations: left atrium (LA), basal left ventricle (bLV), mid left ventricle (mLV), apical left ventricle (aLV) and aortic root (AoR). MBF and MPR were estimated at the segmental level using Fermi function-constrained deconvolution. Segments were scored as having normal or abnormal perfusion by visual assessment and the diagnostic accuracy of stress MBF and MPR for each location was evaluated using receiver operating characteristic curve analysis. Results: In both normal (300 out of 400, 75 %) and abnormal segments, rest MBF, stress MBF and MPR were significantly different across AIF sampling locations (p < 0.001). Stress MBF for the AoR (normal: 2.42 (2.15–2.84) mL/g/min; abnormal: 1.71 (1.28–1.98) mL/g/min) had the highest diagnostic accuracy (sensitivity 80 %, specificity 85 %, area under the curve 0.90; p < 0.001 versus stress MBF for all other locations including bLV: normal: 2.78 (2.39–3.14) mL/g/min; abnormal: 2.22 (1.83–2.48) mL/g/min; sensitivity 91 %, specificity 63 %, area under the curve 0.81) and performed better than MPR for the LV locations (p < 0.01). MPR for the AoR (normal: 2.43 (1.95–3.14); abnormal: 1.58 (1.34–1.90)) was not superior to MPR for the bLV (normal: 2.59 (2.04–3.20); abnormal: 1.69 (1.36–2.14); p = 0.717). Conclusions: The AIF sampling location has a significant impact on MBF and MPR estimates by CMR perfusion, with AoR-based stress MBF comparing favorably to that for the current clinical reference bLV. [ABSTRACT FROM AUTHOR]

Background: A significant number of women with angina and no obstructive coronary artery disease (CAD; <50% stenosis) have coronary microvascular dysfunction (CMD) which carries an adverse cardiovascular prognosis. Coronary microvascular function can be evaluated by transthoracic Doppler echocardiography (TTDE) as a coronary flow velocity reserve (CFVR) and by static CT myocardial perfusion (CTP) as a myocardial perfusion reserve (MPR). Whether these methods are correlated is not known. We assessed the correlation between CFVR and MPR and investigated whether women with angina, CMD and no obstructive CAD have reduced MPR compared with asymptomatic women. Methods: Static CTP with adenosine‐induced vasodilation and TTDE of the left anterior descending artery with dipyridamole‐induced vasodilation were successfully performed and analysed in 99 women with stable angina and no obstructive CAD and 33 asymptomatic women with no obstructive CAD. CMD was defined as CFVR < 2. Results: Correlation between rate‐pressure product corrected MPR and CFVR was weak but significant (r =.23; p =.007). MPR was highest among asymptomatic women with normal CFVR (median [interquartile range; IQR] 158 [145–181] %). Symptomatic women with normal CFVR had reduced MPR (148 [134–162] %; age‐adjusted p <.001); however, the lowest MPR was found in symptomatic women with CMD (140 [129–164] %; age‐adjusted p <.001), independent of cardiovascular risk factors and haemodynamic parameters (p =.017). Conclusion: Women with angina, CMD and no obstructive CAD had markedly diminished MPR compared with asymptomatic women. Correlation between CFVR and MPR was weak, suggesting that CTP and TTDE are not interchangeable for detection of CMD. [ABSTRACT FROM AUTHOR]

Background: We measured myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) by a dynamic low-dose CZT-SPECT protocol in patients with suspected or known coronary artery disease (CAD) and investigated the capability of dynamic data in predicting obstructive CAD. A total of 173 patients with suspected or known CAD underwent dynamic CZT-SPECT after the injection of 155 MBq and 370 MBq of 99mTc-sestamibi for rest and stress imaging, respectively. Standard rest and stress imaging were performed at the end of each dynamic scan. A total perfusion defect (TPD) < 5% were considered normal. Obstructive CAD was defined as ≥ 70% stenosis at coronary angiography. Results: Global MPR was lower (p < 0.05) in patients with abnormal compared with those with normal MPI (2.40 ± 0.7 vs. 2.70 ± 0.8). A weak, albeit significant correlation between TPD and MPR (r = − 0.179, p < 0.05) was found. In 91 patients with available angiographic data, hyperemic MBF (2.59 ± 1.2 vs. 3.24 ± 1.1 ml/min/g) and MPR (1.96 ± 0.7 vs. 2.74 ± 0.9) were lower (both p < 0.05) in patients with obstructive CAD (n = 21) compared with those without (n = 70). At univariable analysis, TPD, hyperemic MBF, and MPR were significant predictors of obstructive CAD, whereas only MPR was independent predictor at multivariable analysis (p < 0.05). At per vessels analysis, regional hyperemic MBF (2.59 ± 1.2 vs. 3.24 ± 1.1 ml/min/g) and regional MPR (1.96 ± 0.7 vs. 2.74 ± 0.9) were lower in the 31 vessels with obstructive CAD compared with 242 vessels without (both p < 0.05). Conclusions: In patients with suspected or known CAD, MPR assessed by low-dose dynamic CZT-SPECT showed a good correlation with myocardial perfusion imaging findings and it could be useful to predict obstructive CAD. [ABSTRACT FROM AUTHOR]

Purpose: Cardiac imaging with positron emission tomography/computed tomography (PET/CT) allows measurement of coronary artery calcium (CAC), stress-induced myocardial ischemia and myocardial perfusion reserve (MPR). We evaluated the prognostic role of the combined assessment of regional CAC score, ischemic total perfusion defect (ITPD) and MPR in predicting lesion-related outcome in patients with suspected coronary artery disease (CAD). Methods: We studied 206 patients with suspected CAD referred to 82Rb PET/CT cardiac imaging and available coronary angiographic data. The outcome end points were cardiac death, target vessel-related myocardial infarction or coronary revascularization. Results: Compared to vessels without event, those with event showed higher CAC score and ITPD, and lower hyperemic myocardial blood flow and MPR (all p < 0.001). At Cox regression multivariable analysis, significant CAD (≥50% stenosis) (p < 0.001), CAC score ≥ 300 (p < 0.01) and MPR <2 (p < 0.01) were independent predictors of events. The decision trees analysis for the identification of events produced five terminal nodes. The initial split was on CAC score values. For vessels with CAC <300 and MPR ≥2, no further split was performed, while vessels with CAC <300 and MPR <2 were further stratified by ITPD. For vessels with CAC ≥300 a further stratification was performed only by MPR. The worst prognosis was observed in vessels with CAC ≥300 and MPR <2 and in vessels with CAC <300, MPR <2 and ITPD ≥5%. Conclusion: The combination of CAC score and MPR is useful to predict the lesion-related outcome in the presence of significant CAD. [ABSTRACT FROM AUTHOR]

Aims We evaluated the relationship between epicardial adipose tissue (EAT) and coronary vascular function assessed by rubidium-82 (82Rb) positron emission tomography/computed tomography (PET/CT) in patients with suspected coronary artery disease (CAD). Methods and results The study population included 270 patients with suspected CAD and normal myocardial perfusion at stress–rest 82Rb PET/CT. Coronary artery calcium (CAC) score and EAT volume were measured. Absolute myocardial blood flow (MBF) was computed in mL/min/ from the dynamic rest and stress imaging. Myocardial perfusion reserve (MPR) was defined as the ratio of hyperaemic to baseline MBF and it was considered reduced when <2. MPR was normal in 177 (65%) patients and reduced in 93 (35%). Patients with impaired MPR were older (P  <   0.001) and had higher CAC score values (P  =   0.033), EAT thickness (P  =   0.009), and EAT volume (P  <   0.001). At univariable logistic regression analysis, age, heart rate reserve (HRR), CAC score, EAT thickness, and EAT volume resulted significant predictors of reduced MPR, but only age (P  =   0.002), HRR (P  =   0.021), and EAT volume (P  =   0.043) were independently associated with reduced MPR, at multivariable analysis. In patients with CAC score 0 (n  =   114), a significant relation between EAT volume and MPR (P  =   0.014) was observed, while the relationship was not significant (P  =   0.21) in patients with CAC score >0 (n  =   156). Conclusion In patients with suspected CAD and normal myocardial perfusion, EAT volume predicts hyperaemic MBF and reduced MPR, confirming that visceral pericardium fat may influence coronary vascular function. Thus, EAT evaluation has a potential role in the early identification of coronary vascular dysfunction. [ABSTRACT FROM AUTHOR]

Summary: Purpose: Combined coronary CT angiography and CT perfusion (CTP) is a novel, non‐invasive, 'one‐stop' diagnostic tool to rule out ischaemia in patients suspected for coronary artery disease (CAD). However, the normal myocardial perfusion pattern by static CTP in humans is poorly described. We aimed to investigate global and regional myocardial perfusion during rest and adenosine‐induced hyperaemia in asymptomatic women without history of coronary heart disease (CHD). Methods: Using a 320‐row CT scanner with a static protocol, semi‐quantitative assessment of rest and stress CTP was performed in 34 asymptomatic middle‐aged women without obstructive CAD (<50% stenosis) or history of CHD, and with normal exercise stress test and left ventricular (LV) function. Using a 16‐segment model, we assessed global and regional values of LV myocardial perfusion reserve (MPR) and transmural perfusion ratio (TPR). Results: Mean±SD age was 56 ± 13 years. Resting and hyperaemic myocardial perfusion was heterogeneously distributed throughout the LV myocardium. During hyperaemia, global MPR increased by median (IQR) 158% (144–176) with the highest increase in the right coronary artery territory (171%; P<0.02). Rest and stress segmental TPR values ranged between 0.93‐1.26 and 0.99‐1.13, respectively, with the lowest values detected in the inferoseptal segments. No differences in perfusion parameters were found between participants with normal epicardial arteries and participants with non‐significant epicardial atheromatosis (all P>0.05). Global perfusion parameters were not associated with age or menopausal status (all P>0.05). Conclusions: This descriptive study presents data on global and regional myocardial perfusion in a cohort of healthy middle‐aged women. [ABSTRACT FROM AUTHOR]

Purpose: We evaluated the feasibility of dynamic stress 201Tl/rest 99mTc-tetrofosmin SPECT imaging using a cardiac camera equipped with cadmium-zinc-telluride detectors for the quantification of myocardial perfusion reserve (MPR).Methods: Subjects with stable known or suspected coronary artery disease (CAD) who had undergone or were scheduled to undergo fractional flow reserve (FFR) measurement were prospectively enrolled. Dynamic stress 201Tl/rest 99mTc-tetrofosmin SPECT imaging was performed using a dedicated multiple pinhole SPECT camera with cadmium-zinc-telluride detectors. MPR was derived using Corridor4DM software.Results: A total of 34 subjects were enrolled (25 men and 9 women; mean age 60.4 years). FFR was measured in 65 coronary arteries with intermediate lesions. The average global MPR was 2.58 ± 1.03. Global MPR was associated with the extent of CAD (P = 0.028) and global summed stress score (r = −0.60, P < 0.001). Regional MPR showed a significant correlation with diameter stenosis (r = −0.57, P < 0.001), minimum lumen diameter (r = 0.50, P < 0.001), summed stress score (r = −0.52, P < 0.001) and FFR (r = 0.52, P < 0.001). The area under the receiver operating characteristic curve of MPR for the diagnosis of functionally significant stenosis (FFR ≤0.8) was 0.79 (P < 0.001). The sensitivity and specificity of regional MPR were 67% and 83%, respectively, using a cut-off value of 2.0.Conclusion: Dynamic stress 201Tl/rest 99mTc-tetrofosmin SPECT imaging and quantification of MPR is feasible in patients with stable CAD. The preliminary results of this study in a small number of patients require confirmation in a larger cohort to determine their implications for bolstering the role of SPECT imaging in the diagnosis and risk prediction of CAD. [ABSTRACT FROM AUTHOR]

Background: Preliminary semi-quantitative cardiovascular magnetic resonance (CMR) perfusion studies have demonstrated reduced myocardial perfusion reserve (MPR) in patients with angina and risk factors for microvascular disease (MVD), however fully quantitative CMR has not been studied. The purpose of this study is to evaluate whether fully quantitative CMR identifies reduced MPR in this population, and to investigate the relationship between epicardial atherosclerosis, left ventricular hypertrophy (LVH), extracellular volume (ECV), and perfusion. Methods: Forty-six patients with typical angina and risk factors for MVD (females, or males with diabetes or metabolic syndrome) who had no obstructive coronary artery disease by coronary angiography and 20 healthy control subjects underwent regadenoson stress CMR perfusion imaging using a dual-sequence quantitative spiral pulse sequence to quantify MPR. Subjects also underwent T1 mapping to quantify ECV, and computed tomographic (CT) coronary calcium scoring to assess atherosclerosis burden. Results: In patients with risk factors for MVD, both MPR (2.21 [1.95,2.69] vs. 2.93 [2.763.19], p < 0.001) and stress myocardial perfusion (2.65 ± 0.62 ml/min/g, vs. 3.17 ± 0.49 ml/min/g p < 0.002) were reduced as compared to controls. These differences remained after adjusting for age, left ventricular (LV) mass, body mass index (BMI), and gender. There were no differences in native T1 or ECV between subjects and controls. Conclusions: Stress myocardial perfusion and MPR as measured by fully quantitative CMR perfusion imaging are reduced in subjects with risk factors for MVD with no obstructive CAD as compared to healthy controls. Neither myocardial hypertrophy nor fibrosis accounts for these differences. [ABSTRACT FROM AUTHOR]

Background Quantitative assessment of myocardial flow reserve (MFR) by single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is challenging but may facilitate evaluation of multi-vessel coronary artery disease (CAD). Methods We enrolled 153 patients with suspected or known CAD, referred for pharmacological stress MPI. They underwent a 99m Tc-perfusion stress/rest SPECT with an ultrafast cadmium-zinc-telluride (CZT) camera. Dynamic data were acquired and time-activity curves fitted to a 1-tissue compartment analysis with input function. K1 was assigned for stress and rest data. The MFR index (MFR i ) was calculated as K1 stress/K1 at-rest. The findings were validated by invasive coronary angiography in 69 consecutive patients. Results The global MFR i was 1.46 (1.16–1.76), 1.33 (1.12–1.54), and 1.18 (1.01–1.35), for 1-vessel disease (VD), 2-VD, and 3-VD, respectively. In the 3-VD, global MFR i was lower than that in 0-VD (1.63 [1.22–2.04], P < 0.0001) and 1-VD (P = 0.003). Multivariate logistic regression analysis for 3-VD showed significant associations with smoking history (odds ratio [OR]: 4.4 [0.4–8.4]), left ventricular ejection fraction (OR: 61.6 [57.5–66.0]), and global MFR i (OR: 119.6 [111.5–127.7], P = 0.002). A cut-off value of 1.3 yielded 93.3% sensitivity and 75.9% specificity for diagnosing 3-VD. Fractional flow reserve positively correlated with regional MFR i (r = 0.62, P = 0.008), and the SYNTAX score correlated negatively with global MFR i (r = 0.567, P = 0.0003). Conclusion We developed and validated a clinically available method for MFR quantification by dynamic 99m Tc-perfusion SPECT utilizing a CZT camera, which improves the detectability of multi-vessel CAD. [ABSTRACT FROM AUTHOR]

Aims Myocardial perfusion reserve (MPR) is defined as the maximal possible increase in myocardial blood flow (MBF) above baseline conditions. Global MBF can be measured non-invasively by means of coronary sinus flow velocity encoded cine (VENC) cardiovascular magnetic resonance (CMR). We aimed to explore the relationship between global MBF/MPR and the extent and severity of coronary artery disease (CAD) in patients referred for CAD work-up by adenosine-stress CMR. Methods and results Fifty-eight patients with suspected obstructive CAD underwent both adenosine-stress CMR and invasive coronary angiography. In addition to standard cine- and late gadolinium enhancement (LGE)-imaging, first-pass myocardial perfusion imaging (MPI) and coronary sinus flow measurements (VENC) were performed at rest and during peak stress (after 140 mg/kg/min adenosine), respectively. Nineteen young patients with a very low CAD pre-test probability and normal adenosine-stress CMR formed the control group. Fifty-nine percent (n=34) of the study group showed segmental, adenosine-induced myocardial perfusion defects compared to none of the control group (P<0.001). Global MPR was lower in the study group compared to the control group: 2.3 (1.5-3.1) vs. 3.1 (2.0-4.3), P=0.016. The SYNTAX score was higher in the study group patients with an impaired MPR (<2) compared to those with a preserved MPR (3.0 vs. 16.0, P=0.01)--mainly due to higher prevalence of proximal epicardial stenoses (60% vs. 27%, P=0.02) and multi-vessel disease (56% vs. 24%, P=0.017). The diagnostic yield of stress CMR for the diagnosis of CAD (>50% stenosis) increased from 65 to 88% when global MPR assessment was considered in addition to MPI (P=0.025). Conclusions Global MBF and MPR values correlate with the anatomical extent and complexity of CAD and increase the diagnostic yield of non-invasive stress CMR in the work-up of CAD. CMR-based MBF and MPR measurements may play a future role in the evaluation of the total ischaemic burden--particularly in patients with multi-vessel disease. [ABSTRACT FROM AUTHOR]

Background: Although a common symptom in patients with severe aortic stenosis (AS) without obstructive coronary artery disease (CAD), little is known about the pathogenesis of exertional angina.Objectives: This study sought to prove that microvascular dysfunction is responsible for chest pain in patients with severe AS and normal epicardial coronary arteries using adenosine-stress cardiac magnetic resonance (CMR) imaging.Methods: Between June 2012 and April 2015, 117 patients with severe AS without obstructive CAD and 20 normal controls were enrolled prospectively. After exclusions, study patients were divided into 2 groups according to presence of exertional chest pain: an angina group (n = 43) and an asymptomatic group (n = 41), and the semiquantitative myocardial perfusion reserve index (MPRI) was calculated.Results: MPRI values were significantly lower in severe AS patients than in normal controls (0.90 ± 0.31 vs. 1.25 ± 0.21; p < 0.001), and were much lower in the angina group than the asymptomatic group (0.74 ± 0.25 vs. 1.08 ± 0.28; p < 0.001). In logistic regression analysis, the only independent predictor for angina was MPRI (odds ratio: 0.003; p < 0.001). Univariate associations with MPRI were identified for diastolic blood pressure, E/e' ratio, left ventricular volume and ejection fraction, cardiac index, presence of late gadolinium enhancement, and left ventricular mass index (LVMI). In multivariate analysis, LVMI was the strongest contributing factor to MPRI (standardization coefficient: -0.428; p < 0.001).Conclusions: Our results suggest that, in patients with severe AS without obstructive CAD, angina is related to impaired coronary microvascular function along with LV hypertrophy detectable by semiquantitative MPRI using adenosine-stress CMR.Clinical Trial Registration: NCT02575768. [ABSTRACT FROM AUTHOR]

A wide variety of imaging modalities is available for the diagnosis of ischemic coronary artery disease (CAD). Myocardial hypo-perfusion is one of the first steps in the ischemic cascade and can be detected before clinical symptoms, ECG alterations or wall motion abnormalities occur. Currently, nuclear medicine techniques (scintigraphy) such as single-photon emission computed tomography using Thalium-201 or TC-99 m sestamibi are most frequently used for the imaging of myocardial perfusion. Positron emission tomography (PET) is the reference standard for myocardial perfusion imaging. These techniques attain a sensitivity and specificity for the detection of myocardial ischemia of, respectively, 83–95 and 53–95%. However, PET is not widely available, which makes it relatively inaccessible. Other disadvantages of myocardial perfusion imaging scintigraphy are: high costs, long-time commitment, radiation exposure, specificity depending on quality control of laboratory and trained readers and low specificity in presence of left bundle branch block. As a result of the fast hardware and software development magnetic resonance imaging (MRI) has become a promising new technique for perfusion imaging. This paper will give an introduction to myocardial perfusion MRI for the detection of ischemic heart disease followed by an overview of the post-processing procedures. [ABSTRACT FROM AUTHOR]

Background: Adenosine is used in stress perfusion cardiac imaging to reveal myocardial ischemia by its vasodilator effects. Caffeine is a competitive antagonist of adenosine. However, previous studies reported inconsistent results about the influence of caffeine on adenosine's vasodilator effect. This study assessed the impact of caffeine on the myocardial perfusion reserve index (MPRI) using adenosine stress cardiovascular magnetic resonance imaging (CMR). Moreover, we sought to evaluate if the splenic switch-off sign might be indicative of prior caffeine consumption. Methods: Semiquantitative perfusion analysis was performed in 25 patients who underwent: 1) caffeine-naïve adenosine stress CMR demonstrating myocardial ischemia and, 2) repeat adenosine stress CMR after intake of caffeine. MPRI (global; remote and ischemic segments), and splenic perfusion ratio (SPR) were assessed and compared between both exams. Results: Global MPRI after caffeine was lower vs. caffeine-naïve conditions (1.09 ± 0.19 vs. 1.24 ± 0.19; p < 0.01). MPRI in remote myocardium decreased by caffeine (1.24 ± 0.19 vs. 1.49 ± 0.19; p < 0.001) whereas MPRI in ischemic segments (0.89 ± 0.18 vs. 0.95 ± 0.23; p = 0.23) was similar, resulting in a lower MPRI ratio (=remote/ischemic segments) after caffeine consumption vs. caffeine-naïve conditions (1.41 ± 0.19 vs. 1.64 ± 0.35, p = 0.01). The SPR was unaffected by caffeine (SPR 0.38 ± 0.19 vs. 0.38 ± 0.18; p = 0.92). Conclusion: Caffeine consumption prior to adenosine stress CMR results in a lower global MPRI, which is driven by the decreased MPRI in remote myocardium and underlines the need of abstinence from caffeine. The splenic switch-off sign is not affected by prior caffeine intake. [ABSTRACT FROM AUTHOR]