Development of Cardiac Functions in Boys

Abstract

One hundred and thirty-nine boys (6-14 years of age) were studied to determine the relationship between cardiac functions and body size during growth. Heart volume (HV) was obtained by X-ray method. Left ventricle diastolic and systolic demensions were measured by ultra-sound cardiography. Cardiac functions during growth were developed greatly, While cardiac functions as well as body size showed great deviations at equal age group. The individual differences became larger as the subjects grew. Although growth of cardiac functions were not always proportional to growth of body size the correlation between cardiac functions and body size at 10 to 13 years of age were significant (r=0.39-0.88, p<0.001). Increase in stroke volume (SV) and decrease in heart rate (HR) during growth were attributable to increase in end-diastolic volume (EDV) rather than smaller increase in end-systolic volume (ESV). HV, Ieft ventricle volume, cardiac muscle wall thickness, SV, and cardiac output (CO) were correlated significantly (r=0.42-0.78, p<0.001) each other. Heart volume to body surface area (BSA) ratio increased during growth, while cardiac index (CO/BSA) showed steady values.