Abstract 14160: Rest and Reserve Functions in Fontan Patients With Right Ventricular Morphology are Worse Than Those With Left Ventricular Morphology

Introduction: Fontan patients with right ventricular morphology (RV-F) are associated with worse outcome and exercise capacity compared with those with left ventricular morphology (LV-F). Diminished cardiac reserve is one of major mechanisms of impaired exercise capacity in heart failure patients. However, it remains unclear whether and how rest and reserve functions differ between RV-F and LV-F. Hypothesis: We assessed the hypothesis that rest and reserve functions in RV-F may be worse than those in LV-F. Methods: This study included 28 RV-F and 17 LV-F (6.0 vs 6.2 years. p=N.S.). Ventricular pressure-area relationships were determined during cardiac catheterization, both before and after β-adrenergic stimulation with dobutamine (5 microg/kg/min) and increased heart rates by atrial pacing. Results: There were no significant differences in heart rate, central venous pressure, and pulmonary vascular resistance between RV-F and LV-F. End-systolic pressure in RV-F was lower than that in LV-F (89 vs 97mmHg), while end-systolic and end-diastolic volume in RV-F were larger than those in LV-F. Consistently, contractile function in RV-F was worse than that in LV-F (20.1±10.5 vs 30.8±19.7 mmHg/cm2 хm2 in Ees index; and 978±237 vs 1186±297 mmHg/s in dp/dt max). The worse contractile function in RV-F was persisted after dobutamine (24.9 vs 45.1 mmHg/cm2 хm2 in Ees index; and 1721 vs 2241 mmHg/s in dp/dt max). Furthermore, the response of Ees index to faster heart rate in RV-F was blunted, which was in striking contrast to positive chronotropic response in LV-F (Figure). Conclusions: Compared with LV-F, RV-F has worse systolic function at rest and markedly attenuated chronotropic reserve in systolic function, which can be responsible for worse outcome in RV-F. Given the lack of definitive therapy for Fontan failure, development of medical therapy to improve rest and reserve function should be pursued for better prognosis in Fontan patients.