Relationship of exercise capacity to resting left ventricular performance and basal plasma norepinephrine levels in patients with congestive heart failure

Abstract

Seventeen patients with chronic congestive heart failure (CHF) were studied to assess the relationship of resting left ventricular function, as measured by noninvasive and invasive methods, to maximal exercise capacity, as measured by peak total body oxygen consumption (VO2). Supine basal plasma norepinephrine (NE) was also measured to evaluate its relationship to the severity of heart failure and to determine whether it may be a better predictor of exercise capacity in patients with CHF than the more commonly employed noninvasive and invasive tests of left ventricular function. Fourteen of the 17 patients underwent upright bicycle exercise (average peak VO2 10.60 +/- 1.40 ml/kg/min, +/- SEM) to their symptomatic maximum. There was no significant correlation between peak VO2 and the noninvasive measurements of left ventricular performance obtained at rest, including cardiothoracic ratio, left ventricular internal dimension by M-mode echo, percent shortening of the minor axis by M-mode echo, and radionuclide ejection fraction. Hemodynamic measurements were performed in 16 patients. The hemodynamic measurements at rest also failed to correlate with exercise capacity. The supine basal plasma NE, which was elevated in these 17 patients (612 +/- 100 pg/ml), had an inverse relationship with stroke work index (r - -0.70, p less than 0.01) and stroke index (r = -0.83, p less than 0.001) and a positive correlation with right atrial pressure (r = 0.81, p less than 0.001). Although both noninvasive and invasive measurements at rest failed to correlate significantly with peak VO2 during exercise, the plasma NE had a significant inverse correlation with peak exercise VO2 (r = -0.50, p less than 0.05). The basal supine plasma NE is therefore elevated in patients with CHF, is a marker for the severity of CHF as measured by hemodynamics performed at rest, and is a better predictor of exercise capacity than standard noninvasive and invasive tests performed at rest.