Evaluation of Diastolic and Systolic Cardiac Function in Beta Blocked Pediatric Patients using Exercise Echocardiography

Abstract

PURPOSE: To evaluate the effect of beta blockade on diastolic and systolic cardiac function during exercise in pediatric patients. METHODS: We evaluated 20 normal controls (N, 14 females, mean age 14.8 yrs) and 11 patients with congenital prolonged QT treated with beta blockers (BB, 7 females, mean age 13.4 yrs) using the James cycle ergometer protocol with echocardiography and tissue Doppler. RESULTS: There were no significant differences in N and BB height (1.61 vs 1.55 meters) or weight (59.8 vs 55.6 kilograms). The working capacity was significantly decreased in BB compared to N (789 vs 1153 watts, P<0.05). Aerobic capacity (VO2), resting and maximal heart rate (HR), cardiac output index (CI), and systolic tissue velocity (SaLAT) were significantly decreased in BB compared to N. Diastolic filling time (DFT) and systolic ejection time (SyET) were significantly prolonged in BB compared to N. The DFT and SyET proportions to the entire cardiac cycle, myocardial relaxation (Em) and index of ventricular filling pressure (E/Em) were not significantly different in BB compared to N.Table: Caption not availableCONCLUSION: This group of pediatric patients treated with beta blockade showed decreased aerobic and working capacity associated with impaired cardiac output and systolic tissue velocity. Indices of myocardial relaxation (Em) and ventricular filling (E/Em) were unchanged compare to normals. This suggests that beta blockade impacts cardiac output by impairing the augmentation of systolic function which occurs normally with exercise-induced sympathetic stimulation.