Coronary Blood Flow in Patients with Hypoplastic Left Heart Syndrome and Total Cavopulmonary Anastomosis at Rest and under Submaximal Exercise

Background: Hypoplastic left heart syndrome (HLHS) is a congenital heart disease characterized by the underdevelopment of the left side of the heart due to severe stenosis or atresia of the mitral and/or aortic valves. Surgical treatment with a staged palliation approach has become the standard of care. In the initial stage (Norwood I), the native proximal aorta is anastomosed to the neo-aorta, receiving retrograde flow to supply the coronary arteries, which still originate at its root. With an increasing number of HLHS patients surviving into early adulthood, the focus has shifted to long-term complications. This study aimed to measure coronary blood flow at rest and during exercise in HLHS patients after TCPC.

Methods: We prospectively examined 20 HLHS patients following TCPC, with a median age of 15.5 years, who underwent CMR testing during routine follow-up. We excluded four patients due to incomplete datasets. We obtained flow measurements of the native and neo-aorta, along with SSFP cine images taken for volumetric evaluation of the systemic right ventricle, using a 1.5-T MR scanner. The CMR examination was conducted both at rest and during exercise (25% of peak VO₂) using a modified and validated leg paddelergometer. None of the patients exhibited antegrade flow in the native aorta. Instead, the native aorta’s net retrograde blood flow entirely supplies the coronary circulation.

Results: The stress test resulted in a 16.3% increase in heart rate, reaching 45.7% of the calculated maximum heart rate. During the physical stress CMR, coronary blood flow increased significantly per heartbeat (p = 0.03) and per minute (p = 0.002) in the native aorta. Additionally, we observed a positive correlation between the native aorta’s cross-sectional area and coronary blood flow measurements under stress (R ² = 0.350), but not at rest (R ² = 0.056). Relative coronary blood flow, in relation to cardiac output, averaged 3.7% (median 3.8%) at rest and 4.1% (median 4.0%) during exercise. However, there was notable variability in relative coronary blood flow during exercise. Seven of the sixteen patients could either not increase or even experience a decrease in relative coronary flow.

Conclusion: Mean coronary blood flow in patients with HLHS is slightly reduced compared with normal values. However, an increase in coronary blood flow is observed during exercise in most patients. The cross-sectional area of the native aorta showed a weak positive correlation with the increase in coronary blood flow during stress.

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Artikel online veröffentlicht:
11. Februar 2025