Hemodynamic studies in children with congenital atrioventricular block

Abstract Eleven children with isolated congenital complete atrioventricular (A-V) block, 3 weeks to 21 years of age, underwent cardiac catheterization, including electrical pacing and isoproterenol infusion studies. The resting ventricular rates of the infants ranged from 60 to 90/min; those of the rest 40 to 55/min. The resting intracardiac pressures were normal or minimally increased. Mean cardiac index was low normal (3.3 liters/min per m 2 ± 0.8 SD), but stroke index was abnormally high (65.6 ml/m 2 ± 12.1 SD). Electrical pacing of the right ventricle to rates of 60 to 120 beats/min resulted in increased cardiac index (+26 percent), left ventricular minute work (+31 percent) and left ventricular stroke output impedance (+63 percent), but reduced stroke index (−32 percent), left ventricular stroke work (−37 percent), and tension-time index per beat (−36 percent). No significant changes in systemic vascular resistance, left ventricular ejection rate or output/tension-time ratio were observed. Isoproterenol infusion resulted in greater rise in cardiac index (+65 percent), left ventricular ejection rate (+57 percent) and output/tension-time ratio (+45 percent), no change in stroke index, and reduced systemic vascular resistance (−39 percent). The hemodynamic improvement due to isoproterenol infusion reflects the agent's combined inotropic, chronotropic and peripheral vasodilatory effects. The overall hemodynamic findings in children with congenital A-V block are better than in adults with acquired block. It is suggested that intrinsic myocardial disease may be a significant feature in symptomatic subjects with this disease.