Coronary circulatory function with increasing obesity: A complex U-turn.

AIMS: The aim of this investigation was to explore and characterize alterations in coronary circulatory function in function of increasing body weight with medically controlled cardiovascular risk factors and, thus, "metabolically" unhealthy obesity. MATERIALS AND METHODS: We prospectively enrolled 106 patients with suspected CAD but with normal stress-rest myocardial perfusion on 13 N-ammonia PET/CT and with medically controlled or no cardiovascular risk factors. 13 N-ammonia PET/CT concurrently determined myocardial blood flow (MBF) during pharmacologically induced hyperaemia and at rest. Based on body mass index (BMI), patients were grouped into normal weight (BMI: 20.0-24.9 kg/m2 , n = 22), overweight (BMI: 25.0-29.9 kg/m2 , n = 27), obese (BMI: 30.0-39.9 kg/m2 , n = 31), and morbidly obese (BMI ≥ 40kg/m2 , n = 26). RESULTS: Resting MBF was comparable among groups (1.09 ± 0.18 vs. 1.00 ± 0.15 vs. 0.96 ± 0.18 vs.. 1.06 ± 0.31 ml/g/min; p = .279 by ANOVA). Compared to normal weight individuals, the hyperaemic MBF progressively decreased in in overweight and obese groups, respectively (2.54 ± 0.48 vs. 2.02 ± 0.27 and 1.75 ± 0.39 ml/g/min; p < .0001), while it increased again in the group of morbidly obese individuals comparable to normal weight (2.44 ± 0.41 vs. 2.54 ± 0.48 ml/g/min, p = .192). The BMI of the study population correlated with the hyperaemic MBF in a quadratic or U-turn fashion (r = .34, SEE = 0.46; p ≤ .002). CONCLUSIONS: The U-turn of hyperaemic MBF from obesity to morbid obesity is likely to reflect contrasting effects of abdominal versus subcutaneous adipose tissue on coronary circulatory function indicative of two different disease entities, but needing further investigations.

Cardiovascular magnetic resonance with an MR compatible pacemaker.

Magnetic resonance imaging (MRI) within FDA guidelines for the MRI-conditional pacemaker precludes placing the heart at the center of the magnet's bore. This in effect appears to preclude cardiovascular MR. In this manuscript, we describe a protocol for cardiovascular MR of patients with a Revo pacemaker system while operating within FDA guidelines, and the first US case of cardiovascular MR in a patient with a Revo MRI-conditional pacing system despite position constraints.

PET-determined prevalence of coronary microvascular dysfunction and different types in a cardio-metabolic risk population.

Background: The aim was to investigate the prevalence of "classical" (predominantly related to alterations in hyperemic MBFs) and "endogen" (predominantly related to alterations in resting MBF) normal coronary microvascular function (nCMF) or coronary microvascular dysfunction (CMD) in a clinical population without flow-limiting obstructive CAD. Methods: We prospectively enrolled 239 symptomatic patients with normal pharmacologically-stress and rest myocardial perfusion on 13N-ammonia PET/CT. 13N-ammonia PET/CT concurrently assessed myocardial flow reserve (MFR = MBF stress/MBF rest). Normal nCMF was defined by a MFR of ≥ 2.0, while an abnormal MFR of < 2.0 signified CMD. In addition, patients were subgrouped into classical and endogen type of nCMF and CMD, respectively. Results: In the whole study population, CMD was present in 54% (130/239). The classical type was more prevalent than the endogen type of CMD (65% vs 35%, p ≤ 0.008). The classical type of CMD was paralleled by a high prevalence of diabetes mellitus, metabolic syndrome, and obesity, while the endogen type of CMD was accompanied by a higher prevalence of arterial hypertension, obesity, and/or morbid obesity. Further, the classical type of nCMF was more frequently observed that the endogen type (74% vs. 26%, p ≤ 0.007). The endogen type of nCMF was related to lower heart rate and/or arterial blood pressures. Conclusions: In this contemporary clinical study population, slightly more than half of symptomatic patients had CMD with predominance of the classical type. These observations emphasize the need for standardized reporting of CMD to gear individualized and/or intensified medical treatment to improve symptoms and/or clinical outcome in these patients.

18F-FDG PET in Myocardial Viability Assessment: A Practical and Time-Efficient Protocol.

We assessed image quality using a practical and time-efficient protocol for intravenous glucose loading and insulin injection before administration of 18F-FDG for PET myocardial viability evaluation in patients with ischemic cardiomyopathy (ICM), with and without type 2 diabetes mellitus. Methods: The metabolic preparation period (MPP) or optimal cardiac 18F-FDG uptake was determined from the time of intravenous infusion of 12.5 or 25 g of 50% dextrose to the time of 18F-FDG injection. Cardiac 18F-FDG image quality was evaluated according to a 5-point scoring system (from 5, excellent, to 1, nondiagnostic) by 2 independent observers. In cases of disagreement, consensus was achieved in a joint reading. Fifteen patients with ICM who underwent oral glucose loading and intravenous insulin administration served as a reference for MPP comparisons. Results: Fifty-nine consecutive patients (age, 63 ± 10 y; 48 men and 11 women) underwent rest 99mTc-tetrofosmin SPECT/CT and 18F-FDG PET/CT for the evaluation of myocardial viability. 18F-FDG image quality was scored as excellent in 42%, very good in 36%, good in 17%, fair in 3%, and nondiagnostic in 2%. When diabetic and nondiabetic patients were compared, the quality scores were excellent in 29% versus 76%, very good in 41% versus 18%, good in 24% versus 6%, fair in 4% versus 0%, and nondiagnostic in 2% versus 0%. The mean (±SD) quality score was 4.12 ± 0.95, and overall it was better in nondiabetic than in diabetic patients (4.71 ± 0.59 vs. 3.88 ± 0.96; P < 0.0001). Notably, the average MPP was significantly less with intravenous glucose loading than with oral glucose loading (51 ± 15 min vs. 132 ± 29 min; P < 0.0001), paralleled by higher insulin doses (6.3 ± 2.2 U vs. 2.0 ± 1.69 U; P < 0.001). Conclusion: Using a practical and time-efficient protocol for intravenous glucose loading and insulin administration before 18F-FDG injection reduces the MPP by 61% as compared with an oral glucose challenge and affords good-to-excellent image quality in 95% of ICM patients.