Objectives: This study sought to evaluate regional myocardial flow reserve in long-term survivors of repair of anomalous left coronary artery from pulmonary artery (ALCAPA) and to relate the flow abnormalities to the patients' exercise performance.
Background: Patients with ALCAPA usually present during infancy with severe ischemic cardiomyopathy. The left ventricular function recovers after surgical repair. However, the extent of recovery of myocardial blood flow (MBF) and its potential physiologic significance in long-term survivors are unknown.
Methods: We evaluated MBF (ml/g per min) at baseline and during maximal coronary vasodilation by adenosine in 11 patients after ALCAPA repair (median age 17 years, range 7 to 22) using nitrogen-13 ammonia and dynamic positron emission tomographic imaging. Patients also underwent an incremental exercise test with metabolic monitoring. In each patient, MBF was quantified in the three major vascular territories: the left anterior descending and left circumflex coronary artery territories and the right coronary artery (control region) territory.
Results: Basal MBF was mildly reduced in the left coronary territories versus the control region (0.79 +/- 0.14 vs. 0.85 +/- 0.19, p = 0.05). During hyperemia, flow in the left coronary territories was significantly lower than that in the control region (2.1 +/- 0.5 vs. 2.6 +/- 0.5, p < 0.001). As a result, myocardial flow reserve was lower in the left coronary territories than in the control region (2.6 +/- 0.7 vs. 3.2 +/- 0.7, p < 0.001). Exercise performance was impaired in patients when compared with age-matched control subjects. Maximal oxygen consumption correlated linearly with maximal hyperemic flows in the left coronary artery territories (r = 0.73, p = 0.03).
Conclusions: Long-term survivors of ALCAPA repair demonstrate regional impairment of myocardial flow reserve. This may contribute to impaired exercise performance by limiting cardiac output reserve.