Effects of simulated altitude-induced hypoxia on exercise capacity in patients with chronic heart failure

PURPOSE: Patients with stable heart failure often wish to spend time at alt itudes above those of their residence. However, it is not known whether the y can safely tolerate ascent to high altitudes or what its effects on work capacity may be. SUBJECTS AND METHODS: We studied 14 normal subjects and 38 patients with cl inically stable heart failure, 12 of whom had normal workload [peak exercis e oxygen consumption (VO2) greater than 20 mL/min/kg], 14 of whom had sligh tly diminished workload (peak VO2 20 to 15 mL/min/kg), and 12 of whom had m arkedly diminished workload (peak VO2 less than 15 mL/min/kg) at baseline. All performed cardiopulmonary exercise tests with inspired oxygen fractions equal to those at 92, 1,000, 1,500, 2,000, and 3,000 m, and maximum achiev ed work rates (mean +/- SD) were measured. RESULTS: All subjects completed the trial; no test was interrupted because of arrhythmia, angina, or ischemia. Maximum work rate decreased in parallel with increasing simulated altitude. The percentage decrease was greater fo r patients with heart failure and was most marked among those with the lowe st workload at baseline. Maximum achieved work rate declined by 3% +/- 4% p er 1,000 m in normal subjects, by 5% +/- 3% (P <0.01) in patients with hear t failure with normal workload, by 5% +/- 4% (P <0.01) in patients with sli ghtly diminished workload, and by 11% +/- 5% (P <0.01 vs normal subjects an d us the other patients with heart failure) in patients with markedly reduc ed workload. CONCLUSION: Patients with stable heart failure who ascend to higher altitud es should expect to have a reduction in maximum physical activity in propor tion to their exercise capacity at sea level. Am J Med. 2000;109:450-455. ( C) 2000 by Excerpta Medica, Inc.