An analysis of the determinants of exercise performance in congestive heart failure.

Twenty-nine patients with chronic congestive heart failure underwent symptom-limited maximal exercise to define the determinants and predictors of exercise capacity in this condition. Clinically, the combination of age, cardiothoracic ratio, and left ventricular displacement was moderately predictive of exercise capacity (R2 = 0.44, p = 0.004). Noninvasive and angiographic measurements of ventricular performance failed to predict maximal exercise duration. Resting systemic and pulmonary arteriolar resistances correlated modestly with maximal effort tolerance (supine: R2 = 0.25, p = 0.02; upright: R2 = 0.38, p = 0.002). At a predetermined level of submaximal exercise, changes in heart rate and pulmonary arteriolar resistance plus the absolute value of systemic arteriolar resistance correlated moderately with exercise duration (R2 = 0.44, p = 0.003). For all parameters examined, exercise capacity was most reliably determined during the transition from submaximal to maximal exercise through the combination of changes in heart rate and stroke volume and the exercise end point value of systemic arteriolar resistance (R2 = 0.87, p = 0.0001). Exercise capacity in chronic cardiac failure appears to be best explained by the patient's ability to increase heart rate and stroke volume beyond a set submaximal stage of exercise. Excessive vascular resistances may further restrain cardiac performance and the delivery of blood to exercising structures during exhaustive exercise.