1993 Volume 38 Issue 4 Pages 257-264
The purpose of this study was to determine the feasibility of estimating myocardial oxygen supply/demand relationship noninvasively for the evaluation of myocardial stress during arm and leg exercises. Seven healthy males performed arm cranking exercise (ARM) and leg cycle exercise (LEG) at each of four constant power outputs (ARM : 5,10,15,20 W, LEG :25,50,75,10O W). Electrocardiogram, phonocardiogram, carotid pulse wave and blood pressure were simultaneously recorded during the exercises. The pressure of cardiac cycle was estimated by substituting systolic blood pressure (SBP) for peak of carotid pulse wave and diastolic blood pressure (DBP) for base line of that, respectively. Potential subendcardial blood flow was also estimated from the Diastolic Pressure Time Index (DPTI) and myocardial oxygen requirments were estimated from the Tension Time Index (TTI) , respectively. The ratio DPTI/TTI, thus, provided an estimate of myocardial oxygen supply/demand relationship. Results indicated that heart rate (HR) and SBP increased more steeply in relation to work rate during ARM than LEG (HR : 1.53vs.0.41bpm・W^<-1>, SBP : 1.64vs.0.368mmHg・<-1>, p<0.01).Consequently,TTI increased linearly with the work rate both durirg ARM and LEG ; this increase was, however, significantly higher for ARM than LEG,i. e., TTI was higher for ARM at maximum work rate (20W) than LEG at minimum work rate (25W) (3020vs.2300mmHg・sec・min<-1>, p<0.01).The rate of decrease of DPTI/TTI per work rate during ARM was also significantly(p<0.05)greater than LEG. These results suggested that arm exercise in comparison to leg exercise is accompanied by not only higher myocardial oxygen demand but also greater myocardial stress caused by an unfavorable shift in the balance of myocardial oxygen supply and demand. Based upon these results, it seems that DPTI, TTI and DPTI/TTI determined by the noninvasive method employed in the present study may provide an effective index to the measurement of myocardial stress in various type of exercise.