163 EFFECT OF AGE AND HEART RATE(HR) ON ATRIOVENTRICULAR CONDUCTION (AVC) AND ITS SEGMENTS

Abstract

Findings differ as to the effect of age and HR on normal AVC. Previous studies which included children with normal hearts and patients with severe congenital heart disease, yielded conflicting results. Therefore, we analyzed data of 70 children, 3 days to 18 years, with normal electrocardiograms. Of these 70 children 46 were normal. The others had mild pulmonary stenosis (9), small ventricular septal defect (6), small patent ductus arteriosus (PDA) (3), bicuspid aortic valve(2) and mild aortic stenosis, mild aortic insufficiency, mild pulmonary hypertension and post-operative coarctation with PDA in 1 each. Multiple linear regressions were performed with age and cycle length (CL) as the independent variables and conduction time from high right atrium(HRA) to low right atrium (LRA), LRA to His potential (H), H to ventricle(V), HRA-V, and P-R interval as dependent variables. The significance of the data is shown in the table below. AVC intervals increased with age, mostly due to increase in HRA-LRA and LRA-H. Although CL varied with age it had no effect on the AVC. This data supports the concept of age-dependent increasing parasympathetic influence on the atria and AV node. We conclude that age of the subject must be considered in evaluation of AVC time.