Myocardial flow reserve in patients with a systemic right ventricle after atrial switch repair

OBJECTIVES The purpose of this study was to assess myocardial blood flow (MBF) and flow reserve in systemic right ventricles (RV) in long-term survivors of the Mustard operation. BACKGROUND There is a high prevalence of systemic RV dysfunction and impaired exercise performance in long-term survivors of the Mustard operation. A mismatch between myocardial blood supply and systemic ventricular work demand has been proposed as a potential mechanism. METHODS We assessed MBF at rest and during intravenous adenosine hyperemia in 11 long-term survivors of a Mustard repair (age 18 ± 5 years, median age at repair 0.7 years, follow-up after repair 17 ± 5 years) and 13 healthy control subjects (age 23 ± 7 years), using N-13 ammonia and positron emission tomography imaging. RESULTS There was no difference in basal MBF between the systemic RV of survivors of the Mustard operation and the systemic left ventricle (LV) of healthy control subjects (0.80 ± 0.19 vs. 0.74 ± 0.15 ml/g/min, respectively, P = NS). However, the hyperemic flows were significantly lower in systemic RVs than they were in systemic LVs (2.34 ± 0.0.69 vs. 3.44 ± 0.62 ml/g/min respectively, p < 0.01). As a result, myocardial flow reserve was lower in systemic RVs than it was in systemic LVs (2.93 ± 0.63 vs. 4.74 ± 1.09, respectively, p < 0.01). CONCLUSIONS Myocardial flow reserve is impaired in systemic RVs in survivors of the Mustard operation. This may contribute to systemic ventricular dysfunction in these patients.