Background: Conceptually the right ventricle (RV) is less suitable to support the Fontan circulation than the left (LV). After palliation of hypoplastic left heart syndrome (HLHS) involving aortic reconstruction during the Norwood procedure the RV is exposed to abnormal afterload. We studied ventricular function and ventriculo-arterial coupling in HLHS patients (RV) and Fontan patients with single LV morphology that did (LV+N) and did not (LV-N) undergo Norwood-type aortic reconstruction.
Methods: Eighty patients (55 RV, 8 LV+N, 17 LV- N) were simultaneously studied with the conductance-catheter and echocardiography 4.8 (0.9-22.9)years after Fontan completion.
Results: Ejection fraction (EF) was lowest in the HLHS group (RV 60.9±11.0 vs. LV+N 68.4±10.5 vs. LV-N 69.7±8.0, P=0.003) whereas end systolic elastance (Ees), i.e. ventricular contractility, and end diastolic stiffness (Eed) were highest (Ees: RV 3.38±2.2 vs. LV+N 2.3.±13.8 vs. LV-N 1.92±1.37mmHg/ml, P=0.02; Eed: RV 0.59±0.36 vs. LV+N 0.48±0.29 vs. LV-N 0.32±0.17mmHg/ml, P<0.02). Arterial elastance, a measure of afterload, was highest in HLHS patients and correlated positively with Ees and Eed and inversely with EF in the study cohort. Only long axis function analysis suggested superior ventricular function in HLHS patients whereas all other echocardiographic measures did not reveal any group differences.
Conclusion: Ventricular contractility of the RV of HLHS patients is higher than that of the ventricle of Fontan patients with LV morphology. This likely reflects a physiological response to higher arterial elastance resulting from aortic arch reconstruction. Increased arterial elastance negatively impacts diastolic stiffness, which is higher in the systemic RV than LV.
Keywords: Fontan procedure; Hypoplastic left heart syndrome; Ventricular function.
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