Abstract 12706: Exercise Physiology and Determinants of Exercise Capacity in Patients With Fontan Circulation
BACKGROUND: Precise mechanisms of limitations of cardiac performance and exercise intolerance in patients with Fontan physiology are not fully understood.
OBJECTIVES: We assessed hemodynamics during exercise in patients after Fontan operation to examine determinants of exercise intolerance and inherent limitations of Fontan physiology.
METHODS: The subjects were 18 Fontan patients aged 15to 31 years, 10-22 years after Fontan operation. We determined peak oxygen uptake (VO2) by cardiopulmonary exercise test. In addition, we evaluated vascular endothelial function by using flow-mediated vasodilation (FMD) and skeletal muscle hemodynamics during exercise by using near-infrared spectroscopy(NIR). Cardiac catheterization was performed at rest and during exercise. After baseline measurements of systolic and diastolic ventricular function, patients performed supine bicycle ergometry with his feet, using a stepwise increase of load. Hemodynamic changes in response to exercise were assessed.
RESULTS: During exercise, the mean pulmonary arterial pressure and pulmonary arterial wedge pressure (PAWP) increased from 10 to 18 mmHg and 6 to 10 mmHg, respectively. Cardiac index (2.3 L/min/m2 at baseline) increased to 4.5 L/min/m2 at peak exercise. The percent increase in cardiac index correlated with the peak VO2. The cardiac index at peak exercise negatively correlated with PAWP. FMD and postexercise recovery of oxygenation in working skeletal muscles by NIR had a close relationship with the peakVO2 and cardiac index augmentation . Ventricular systolic and diastolic properties at rest did not correlated with exercise capacity.
CONCLUSIONS: In Fontan patients, PAWP increases during exercise, which does not occur in normal physiology. FMD and postexercise recovery of oxygenation in working skeletal muscles closely correlate with cardiac output during exercise, which link to the exercise capacity, suggesting that dynamic vascular function during exercise plays an important role in limiting exercise capacity in Fontan physiology. Limitted vasodilation during exercise may increase ventricular afterload, resulting in the increase in PAWP, which in turn may limit exercise capacity.
- © 2012 by American Heart Association, Inc.