Age-related reduction of systemic arterial compliance induces excessive myocardial oxygen consumption during sub-maximal exercise

Abstract

Reduction of systemic arterial compliance (SAC) with aging increases left ventricular afterload. The present study was designed to examine whether age-related reduction of SAC is related to excessive myocardial oxygen consumption during sub-maximal aerobic exercise. We studied elderly (60-69 years; n=25) and senior (70-82 years; n=25) subjects. We measured SAC immediately before the start of the ramp-fashion exercise (ie., at the end of the 20 W warm-up exercise) and the double product (DP: systolic blood pressure × heart rate) during the ramp-fashion exercise (20-50 W). SAC was significantly lower in senior subjects (0.76±0.25 ml mmHg-1 m-2) compared with elderly subjects (0.95±0.22 ml mmHg-1 m-2). DP was higher in senior subjects (20 W: 14.3±3.1; 30 W: 15.9±4.2; 40 W: 17.7±4.9; 50 W: 20.6±5.6 [x 103 mmHg bpm]) than in elderly subjects (12.8±3.0, 14.0±3.5, 15.1±4.0, 17.1±4.3 [x 103 mmHg bpm]). In total subjects, SAC correlated significantly with DP (r=-0.64, r=-0.64, r=-0.64, r=-0.64). In senior subjects, SAC was related significantly to DP (r=-0.83, r=-0.78, r=-0.76, r=-0.74). In elderly subjects, SAC tended to correlate with DP although its relationships were not statistically significant (r=-0.34, r=-0.36, r=-0.33, r=-0.31). Correlation coefficients at each respective exercise intensity were significantly higher in senior subjects compared with elderly subjects. These results suggest that the age-related reduction of SAC is related to excessive myocardial cardial oxygen consumption during sub-maximal aerobic exercise in older humans, but this relation does not become significant until the SAC reduction becomes pronounced.