Abstract 13950: Dynamic Myocardial Systolic and Diastolic Response to Exercise in Patients After the Fontan Operation

Abstract

Background: Exercise capacity is one of the predictors of morbidity and mortality in patients after the Fontan circulation. The influence of myocardial systolic and diastolic functional reserve on exercise performance has not been well established in this population. This study aimed at studying the myocardial response to exercise in Fontan patients using exercise echocardiography. Methods: Twenty-three Fontan patients with baseline ejection fraction >55% and 23 age and gender matched controls were included. A stepwise exercise stress echocardiography protocol was used. Tissue Doppler imaging (TDI) systolic (s’), and early diastolic (e’) velocities and myocardial acceleration during isovolumic contraction (IVA) were measured in the free wall of the dominant ventricle and interventricular septum and in the left ventricular free wall and septum of controls. Measurement was taken at rest and at incremental heart rate (HR). Changes in tissue Doppler velocities versus heart rate were studies and compared between patients and controls. Results: Resting HR was not significantly different between patients and controls but peak HR was lower in the Fontan group vs controls ( p <0.001). At rest patients had significantly lower lateral and septal e’ and s’ compared to controls (lateral s’: 6.35±1.05 vs. 14.41± 1.88 cm/s; lateral e’: 9.38±1.71 vs.20.66±2.55 cm/s; septal s’: 5.30±2.46 vs. 11.58±2.26 cm/s; septal e’: 10.45±2.46 vs. 17.80±1.58 cm/s P <0.001) except for IVA. At peak exercise, all variables were significantly lower in the patient group. During exercise, the slopes of lateral and septal s’ and IVA were significantly different between patients and controls except for e’. Conclusion: Our data suggest that patients with Fontan physiology have blunted systolic contractile response to exercise. Surprisingly our data suggest that the dynamic early diastolic myocardial reserve is preserved which suggest that early myocardial relaxation is not a limiting factor.