Characteristics of Chronically Paced Cardiac Functions in the Congenital Complete Atrioventricular Block

Abstract

Characteristics of morphology, cardiac function, and cardiac reserve at late state were evaluated at rest, by changing the pacing rates, and after exercise in patients with ventricular pacemakers for isolated congenital complete atrioventricular block. Heart size was reduced statistically after pacemaker implantation, and concentric myocardial hypertrophy was observed. Cardiac pump functions at rest seemed fairly well compensated by increased ejection fraction, but the cardiac index was still lower than that of the normal heart. Responses of cardiac function towards the changing rates were considered satisfactory, and those variables had statistic correlations with the pacing rates. After exercise, significant increase of cardiac pump function and also statistic acceleration of myocardial function were observed. This fact proved that cardiac reserve was good, although the increased cardiac output after exercise was still insufficient without an increase in heart rate. More physiological pacing modes would be required as currently recommended.

Functional Capacity of Patients with Pacemaker Due to Isolated Congenital Atrioventricular Block

“…The population evaluated comprised individuals without cardiac defects, except CAVB, and represented an excellent model for understanding the effects caused by cardiac dyssynchrony induced by cardiac pacing, considering that, in addition to the normal cardiac anatomy, intraventricular impulse conduction is also normal in most cases. In the present study, we evaluated the primary factors related to poor clinical and functional outcomes, including age at the first PM implantation 27 , pacing mode used 10 , site of RV pacing 11 , 28 , 29 , duration of cardiac pacing 7 , 16 , 30 , 31 , duration of the PM-stimulated QRS complex 12 , 29 , 30 , presence of dyssynchrony on echocardiography 32 , 33 , and the presence of maternal autoantibodies 34 - 36 .…”