Value of the Bruce protocol to determine peak exercise oxygen consumption in patients evaluated for cardiac transplantation

Background Peak exercise oxygen consumption (peak Vo(2)) is an important di scriminator of survival in patients with systolic heart failure and is used to select ambulatory patients for transplantation. The major trials assess ing the relationship between peak Vo(2) and survival have used a variety of low-level exercise protocols. It is unknown how peak Vo(2) measured in thi s patient population by the more vigorous Bruce treadmill protocol compares with that obtained on less intense protocols. Methods We studied 15 patients (50 +/- 12 years old) with severe heart fail ure (left ventricular ejection fraction 23.5% +/- 8.6%). Patients randomly performed 3 exercise tests with the Bruce treadmill, modified Naughton trea dmill, and modified bicycle protocols within 14 days. To determine the abil ity of this patient population to perform the Bruce protocol, we also retro spectively analyzed the ability of 84 patients to perform this test on thei r initial evaluations at our center. Results All patients reached the anaerobic threshold (AT) on all 3 protocol s. The Bruce and modified Naughton treadmill protocols resulted in similar peak Vo(2), Percent predicted peak Vo(2), and Vo(2) at AT values (17.7 +/- 3.8 mL/kg/min, 57.2% +/- 21.1% and 15.4 +/- 4.1 mL/kg/min vs 18.0 +/- 4.7 m L/kg/min, 58.1% +/- 22.5% and 15.6 +/- 4.4 mL/kg/min, respectively). Peak V o(2) and Vo(2) at AT on both treadmill protocols were higher than those obt ained with bicycle testing (15.3 +/- 3.1 and 11.8 +/- 3.0 mL/kg/min, P <.05 ). Exercise duration was shorter with the Bruce and bicycle protocols (6.2 +/- 2.2 and 6.7 +/- 2.4 minutes, respectively) compared with the modified N aughton protocol (9.7 +/- 4.3 minutes, both P <.005). In addition, 79 of th e 84 patients (94%) evaluated were able to complete the Bruce protocol and reach AT. Conclusions The Bruce protocol was more time efficient than the modified Na ughton protocol and yielded similar peak Vo(2), percent predicted peak Vo(2 ), and Vo(2) of AT values. Bicycle exercise may underestimate peak Vo(2) va lues. The form of exercise should be considered when assessing peak Vo(2) c riteria for transplant listing.