Exercise echocardiography demonstrates biventricular systolic dysfunction and reveals decreased left ventricular contractile reserve in children after tetralogy of Fallot repair

Background: Long-term biventricular systolic performance is a key determinant of clinical outcomes late after tetralogy of Fallot (TOF) repair. A need exists for early indices of both left ventricular (LV) and right ventricular (RV) compromise in this population. Methods: Twenty-nine children (age range, 5-18 years) with repaired TOF and 44 healthy controls were prospectively evaluated. M-mode and tissue Doppler data were obtained for each ventricle and the RV outflow tract at rest and during semisupine bicycle exercise. By making measurements of myocardial acceleration during isovolumic contraction during exercise, at increasing heart rates, LV force-frequency curves were constructed. Patients also underwent cardiac magnetic resonance imaging, cardiopulmonary exercise testing, and measurement of serum neurohormonal markers. Results: Children with repaired TOF had dilated right ventricles (RV end-diastolic volume index = 153 ± 37.3 mL/m²) but normal ejection fractions as measured on magnetic resonance imaging (LV ejection fraction = 59.3 ± 6.2%, RV ejection fraction = 50.2 ± 8.5%) and normal serum neurohormonal markers. Detailed resting echocardiography detected abnormal ventricular function, worst in the right ventricle and RV outflow tract. Exercise exacerbated these findings and provoked significant decline in LV indices. The LV force-frequency curves of patients were attenuated, with an early plateau and inadequate increase of isovolumic contraction. Correlations were seen between peak exercise LV isovolumic contraction and percentage predicted peak oxygen uptake (r = 0.51, P = .02), LV and RV ejection fractions (r = 0.41, P = .03), and RV and LV long-axis fractional shortening (r = 0.44, P = .02). Conclusions: The postsurgical pathophysiology of TOF begins early after repair. At a time when clinically well and while routine indices of heart function remain normal, children with repaired TOF exhibit RV dilatation and subtle, interlinked biventricular abnormalities on resting echocardiography. Exercise echocardiography provides additional information and reveals abnormal LV excitation-contractile coupling that may be linked to impaired exercise capacity.