CONTRIBUTION OF LEFT-VENTRICULAR DIASTOLIC FUNCTION TO EXERCISE CAPACITY IN NORMAL SUBJECTS

Previous studies have established that most of the heterogeneity in ex ercise capacity seen with sedentariness, aging, or physical training c an be accounted for by individual differences in the maximal rate of t otal body oxygen consumption (VO2max) during dynamic exercise. However , the factors that limit VO2max) in normal subjects remain disputed. T o test the hypothesis that differences in left ventricular diastolic p erformance contribute to the heterogeneity of VO2max seen in healthy s ubjects, 57 normal sedentary volunteers (36 +/- 13 yr, range 20-76 yr) and 9 endurance athletes (37 +/- 8 yr, range 26-51 yr) were studied. Aerobic capacity was estimated as VO2max during a multistage dynamic c ycle exercise protocol, whereas resting left ventricular systolic and diastolic function was assessed by two-dimensional and Doppler echocar diography. The relationship of the left ventricular functional indexes with VO2max was investigated by stepwise multiple regression analysis . VO2max ranged from 25 to 58 ml . kg-1 . min-1 in sedentary subjects and from 44 to 60 ml . kg-1 . min-1 in athletes. With univariate analy sis, significant correlations were observed between VO2max and age (r = -0.60), maximal heart rate (r = 0.48), maximal work load (r = 0.80), left ventricular volumes at both end diastole (r = 0.51) and end syst ole (r = 0.62), peak early transmitral filling velocities (r = 0.80), and the ratio of early to late transmitral filling velocities (r = 0.8 7). Stepwise multiple regression analysis identified three parameters as independent correlates of VO2max of which the most powerful was the ratio of early to late transmitral filling velocities (P < 0.0001), f ollowed by gender (P < 0.0001) and then left ventricular end-systolic volume index (P = 0.0001). These data thus support the contention that left ventricular diastolic performance contributes significantly to t he aerobic capacity of normal subjects.