[Effects of age, weight and heart rate on cardiac function at rest in normal subjects].

The effects of age, body weight, and heart rate on cardiac function and left ventricular (LV) volumes at rest were determined for 203 normal subjects, aged 10 to 75 years, using a multiple linear regression model. LV volume was calculated by the formula: volume = 7 X dimension3/(2.4 + dimension). There were age-related increases in ejection fraction, mean velocity of circumferential shortening (mVcf), fractional shortening (FS), stroke volume (SV), and cardiac output (CO). Weight-related increases in SV and CO were observed. Heart rate-related increases in mVcf and CO were also observed. LV volumes at end-systole and at the end of the rapid filling, and slow filling phases decreased with age and increased with weight. However, end-diastolic volume increased with weight, independently of age. The change in LV volume during the rapid filling phase increased with weight; that during the slow filling phase was independent of age, weight, or heart rate. The change in LV volume during the atrial contraction phase increased with age and weight. The ratio of the change in LV volume during atrial contraction to end-diastolic volume was age-related, but independent of weight and heart rate [(an increase in LV volume during atrial contraction)/(end-diastolic volume) = 0.0032 X age (years) + 0.00042 X weight (Kg) + 0.034 X RR interval (sec)]; (r = 0.67, p less than 0.001). The velocity of change in LV volume during the rapid filling phase decreased and that during atrial contraction increased with age.(ABSTRACT TRUNCATED AT 250 WORDS)