Hemodynamic exercise testing - A valuable tool in the selection of cardiac transplantation candidates

Background Peak exercise oxygen consumption (V over dot O-2), a noninvasive index of peak exercise cardiac output (CO), is widely used to select candidates for heart transplantation. However, peak exercise V over dot 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 V over dot O-2. 12.9+/-3.0 mL . min(-1) . kg(-1). CO response to exercise was normal in 83 patients and reduced in V over dot O-2. 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 V over dot O-2 of >14 mL . min(-1) . kg(-1) (88%) was not different from that of patients with V over dot O-2 of less than or equal to 14 mL . min(-1) . kg(-1) (79%) (P=NS). However, survival was worse in patients with peak V over dot O-2 of less than or equal to 10 mL . min(-1) . kg(-1) (52%) versus those with peak V over dot O2 >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 V over dot 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 V over dot O-2 of less than or equal to 10 mL . min(-1) . kg(-1) had an extremely poor 1-year survival rate (38%). Conclusions Both CO response to exercise and peak exercise V over dot 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.