carbon-11-acetate and Hypertension--Pulmonary

The right ventricle (RV) has a high capacity to adapt to pressure or volume overload before failing. However, the mechanisms of RV adaptation, in particular RV energetics, in patients with pulmonary hypertension (PH) are still not well understood. We aimed to evaluate RV energetics including RV oxidative metabolism, power and efficiency to adapt to increasing pressure overload in patients with PH using (11)C-acetate PET.. In this prospective study, 27 patients with WHO functional class II/III PH (mean pulmonary arterial pressure 39.8 ± 13.5 mmHg) and 9 healthy individuals underwent (11)C-acetate PET. (11)C-acetate PET was used to simultaneously measure oxidative metabolism (k mono) for the left ventricle (LV) and RV. LV and RV efficiency were also calculated.. The RV ejection fraction in PH patients was lower than in controls (p = 0.0054). There was no statistically significant difference in LV k mono (p = 0.09). In contrast, PH patients showed higher RV k mono than did controls (0.050 ± 0.009 min(-1) vs. 0.030 ± 0.006 min(-1), p < 0.0001). PH patients exhibited significantly increased RV power (p < 0.001) and hence increased RV efficiency compared to controls (0.40 ± 0.14 vs. 0.017 ± 0.12 mmHg·mL·min/g, p = 0.001).. The RV oxidative metabolic rate was increased in patients with PH. Patients with WHO functional class II/III PH also had increased RV power and efficiency. These findings may indicate a myocardial energetics adaptation response to increasing pulmonary arterial pressure.

Topics: Acetates; Adult; Aged; Carbon; Case-Control Studies; Female; Heart Ventricles; Humans; Hypertension, Pulmonary; Male; Middle Aged; Oxygen Consumption; Positron-Emission Tomography; Radiopharmaceuticals; Stroke Volume; Ventricular Function, Right

Idiopathic pulmonary arterial hypertension (IPAH) results in increased right ventricular (RV) workload and oxygen demand. It has been shown that myocardial oxygen consumption (MVO2) of the hypertrophied right ventricle of IPAH patients can be measured using PET and (15)O-labeled tracers. This method is, however, not very suitable for routine clinical practice. The purpose of the present study was to assess whether MVO2 can also be determined in the right ventricle of IPAH patients from the clearance of (11)C-acetate, a simple method that is in use for MVO2 measurements of the left myocardium.. Seventeen of 26 IPAH patients performed the total PET study. Nine other patients were scanned only for (11)C-acetate. (15)O-H2O, (15)O-O2, and (15)O-CO scans were used to derive RV flow, oxygen extraction fraction, and blood volume, respectively, from which RV MVO2 was calculated. The rate of clearance determined by monoexponential curve fitting (K(mono)) and the efflux rate constant k2 were derived from the (11)C-acetate scan. The RV rate-pressure product was also determined by means of right heart catheterization, as an index of the RV MVO2, and was calculated as the product of systolic pulmonary artery pressure and heart rate.. Both (11)C-acetate clearance rates, K(mono) (R(2) = 0.41, P = 0.006) and k2 (R(2) = 0.45, P = 0.003), correlated with RV MVO2. They also correlated with RV rate-pressure product (K(mono), R(2) = 0.41, P = 0.0005; k2, R(2) = 0.48, P < 0.0001).. (11)C-acetate clearance rates correlated moderately with quantitative RV MVO2 measurements in IPAH. Therefore, (11)C-acetate PET can be used only as an index of RV oxidative metabolism in IPAH patients.

Topics: Acetates; Adult; Aged; Blood Pressure; Carbon; Female; Heart Ventricles; Humans; Hypertension, Pulmonary; Male; Middle Aged; Myocardium; Oxygen; Oxygen Radioisotopes; Positron-Emission Tomography; Pulmonary Artery; Radioactive Tracers