Characteristics of peak aerobic capacity in symptomatic and asymptomatic subjects with left ventricular dysfunction

Abstract

Expired gas analysis was used to determine the aerobic exercise performance of subjects with depressed left ventricular (LV) systolic function and congestive heart failure (CHF). To determine whether subjects with no or minimal CHF have better aerobic exercise performance than do those with overt CHF, oxygen consumption (VO 2) at anaerobic threshold (AT) and peak exercise was measured in 184 subjects with LV ejection fraction ≤0.35 who participated in the Studies of Left Ventricular Dysfunction. Subjects were divided into those with overt CHF needing treatment (treatment trial; n = 20) and those who had neither overt CHF nor treatment for CHF (prevention trial; n = 164). Treatment trial subjects had a lower LV ejection fraction (0.25 ± 0.07) than did prevention trial ones (0.29 ± 0.05; p = 0.001), but there were no differences in age, gender, body weight, resting heart rate and blood pressure. Treadmill exercise testing was performed after 2 to 3 weeks of placebo (no angiotensin-converting enzyme inhibitor) treatment. Treatment trial subjects exercised for a shorter time (493 ± 160 seconds) and attained a lower peak VO 2 (13 ± 4 ml/kg/min) and VO 2 at AT (11 ± 4 ml/kg/min) than did prevention trial ones (842 ± 277 seconds, and 20 ± 6 and 16 ± 5 ml/kg/min, respectively). Analysis of covariance showed that the differences in peak VO 2 and VO 2 at AT were statistically significant between the 2 trials after adjusting for age, gender, LV ejection fraction and New York Heart Association functional class. In contrast, there was no correlation between the expired gas measurements and LV ejection fraction or New York Heart Association classification after adjusting for other factors. Thus, it is concluded that of subjects with reduced LV ejection fraction, those with no or minimal CHF have higher aerobic exercise performance than do those with overt CHF, and this difference cannot be explained by gender, age, LV ejection fraction or New York Heart Association functional class.