In patients with cyanotic congenital heart disease (CCHD), a right-to-left shunt results in systemic hypoxemia. Systemic hypoxemia incites a compensatory erythrocytosis, which increases whole blood viscosity. We considered that these changes might adversely influence myocardial perfusion in CCHD patients. Basal and hyperemic (intravenous dipyridamole) perfusion measurements were obtained with [13N]ammonia positron emission tomographic imaging in left (LV) and right (RV) ventricular and septal myocardium in 14 adults with CCHD [age: 34.1 yr (SD 6.5)]; hematocrit: 62.2% (SD 4.8)] and 10 healthy controls [age: 34.1 yr (SD 6.5)]. In patients, basal perfusion measurements were higher in LV [0.77 (SD 0.24) vs. 0.55 ml·min−1·g−1 (SD 0.09), P < 0.02], septum [0.71 (SD 0.16) vs. 0.49 ml·min−1·g−1 (SD 0.09), P < 0.001], and RV [0.77 (SD 0.30) vs. 0.38 ml·min−1·g−1 (SD 0.09), P < 0.001]. However, basal measurements normalized for the rate-pressure product were similar to those of controls. Calculated oxygen delivery relative to rate-pressure product was higher in the patients [2.2 (SD 0.8) vs. 1.6 (SD 0.4) × 10−5 ml O2·min−1·g tissue−1·(beats·mmHg)−1 in the LV, P < 0.05, and 2.0 (SD 0.7) vs. 1.4 (SD 0.3) × 10−5 ml O2·min−1·g tissue−1·(beats·mmHg)−1 in the septum, P < 0.01]. Hyperemic perfusion measurements in CCHD patients did not differ from controls [LV, 1.67 (SD 0.60) vs. 1.95 ml·min−1·g−1 (SD 0.46); septum, 1.44 (SD 0.56) vs. 1.98 ml·min−1·g−1 (SD 0.69); RV, 1.56 (SD 0.56) vs. 1.65 ml·min−1·g−1 (SD 0.64), P = not significant], and coronary vascular resistances were comparable [LV, 55 (SD 25) vs. 48 mmHg·ml−1·g·min (SD 16); septum, 67 (SD 35) vs. 50 mmHg·ml−1·g·min (SD 21); RV, 59 (SD 26) vs. 61 mmHg·ml−1·g·min (SD 27), P = not significant]. These findings suggest that adult CCHD patients have remodeling of the coronary circulation to compensate for the rheologic changes attending chronic hypoxemia.
Quantification of MRI measured myocardial perfusion reserve in healthy humans: A comparison with positron emission tomography
