Hemodynamic Exercise Testing

Abstract

Background Peak exercise oxygen consumption (V̇ o 2 ), a noninvasive index of peak exercise cardiac output (CO), is widely used to select candidates for heart transplantation. However, peak exercise V̇ o 2 can be influenced by noncardiac factors such as deconditioning, motivation, or body composition and may yield misleading prognostic information. Direct measurement of the CO response to exercise may avoid this problem and more accurately predict prognosis. Methods and Results Hemodynamic and ventilatory responses to maximal treadmill exercise were measured in 185 ambulatory patients with chronic heart failure who had been referred for cardiac transplantation (mean left ventricular ejection fraction, 22±7%; mean peak V̇ o 2 , 12.9±3.0 mL·min −1 ·kg −1 ). CO response to exercise was normal in 83 patients and reduced in 102. By univariate analysis, patients with normal CO responses had a better 1-year survival rate (95%) than did those with reduced CO responses (72%) ( P <.0001). Survival in patients with peak V̇ o 2 of >14 mL·min −1 ·kg −1 (88%) was not different from that of patients with peak V̇ o 2 of ≤14 mL·min −1 ·kg −1 (79%) ( P =NS). However, survival was worse in patients with peak V̇ o 2 of ≤10 mL·min −1 ·kg −1 (52%) versus those with peak V̇ o 2 of >10 mL·min −1 ·kg −1 (89%) ( P <.0001). By Cox regression analysis, exercise CO response was the strongest independent predictor of survival (risk ratio, 4.3), with peak V̇ o 2 dichotomized at 10 mL·min −1 ·kg −1 (risk ratio, 3.3) as the only other independent predictor. Patients with reduced CO responses and peak V̇ o 2 of ≤10 mL·min −1 ·kg −1 had an extremely poor 1-year survival rate (38%). Conclusions Both CO response to exercise and peak exercise V̇ o 2 provide valuable independent prognostic information in ambulatory patients with heart failure. These variables should be used in combination to select potential heart transplantation candidates.