Decreased Systemic Arterial Compliance in the Elderly Increases Myocardial Oxygen Uptake

Abstract

0587 A decrease in systemic arterial compliance (SAC) with aging increases left ventricular afterload, and consequently, may increase myocardial oxygen demand in the elderly. PURPOSE: The purpose of this study was to investigate the relationship between systemic arterial compliance and myocardial oxygen uptake at the sub-maximal intensity of an aerobic exercise in young and elderly people. METHODS: Subjects were 100 elderly people (65 ± 7 yrs) and 36 young people (22 ± 3 yrs). All subjects were apparently healthy, and were not taking medications for hypertension, hyperlipidemia and/or diabetes. After the steady state warm-up exercise (20 watt, 4 minutes), subjects performed a ramp-fashion exercise {10 watt/min, 3 minutes (20–50 watt)}. For the estimation of SAC by using area method (Liu et al., Am J Physiol, 1986), finger arterial pressure waveform was recorded by using volume clamp method, and the waveform was transformed by using transfer function into brachial arterial waveform (Otsuki et al., International Journal of Sport and Health Science, 2003). Stroke volume (SV), which is necessary to the calculation of SAC, was obtained by using Modelflow method from the same arterial waveform. During the exercise, double product (DP) was calculated every 20 seconds from heart rate calculated by the R-R intervals and systolic blood pressure measured by using Korotkoff sound and R-wave. Log-liner regression analysis was performed between SAC and DP at 20 watt exercise (DP20) and 50 watt exercise (DP50). RESULTS: SAC in the elderly subjects was significantly lower than that in the young subjects (0.93 ± 0.26 vs 1.27 ± 0.20 ml·mmHg−1·m−2, mean ± SD). SAC was significantly related to the DP20 and DP50 in the total subjects (r = −0.51, r = −0.57, respectively) and in the elderly subjects (r = −0.49, r = −0.52, respectively), but not in the young subjects (r = −0.11, r = −0.10, respectively). CONCLUSIONS: These results suggest that systemic arterial compliance is decreased with aging, and that the decreased systemic arterial compliance in the elderly increases myocardial oxygen uptake even in a sub-maximal aerobic exercise. This work was supported by 1) grants-in-aid for scientific research and Special Coordination Funds of the Ministry of Education, Culture, Sports, Science and Technology, the Japanese Government and 2) Special Coordination Funds of the Ministry of Education, Culture, Sports, Science and Technology, the Japanese Government.