Rationale: Cardiopulmonary exercise testing (CPX) has become an integral tool for assessing the clinical status and prognosis of patients with heart failure (HF). These tests are typically terminated due to patient request, with general fatigue and dyspnea being two of the most commonly reported reasons for termination.

Objectives: The present investigation examines differences in CPX variables and prognosis according to the reason for patient-initiated test termination.

Methods: One hundred HF patients (74 males/ 26 females, mean age: 53.6 +/-14.9 years, resting left ventricular ejection fraction: 25.5 +/-12.0%) underwent CPX where the minute ventilation/carbon dioxide production (VE/VCO₂) slope, peak oxygen consumption (Vo₂) and peak respiratory exchange ratio (RER) were determined. Subjects were tracked for cardiac events (death, transplant, hospitalization) following CPX.

Results: Dyspnea and general fatigue were the primary reason for test termination in 55 and 45 patients, respectively. The following unpaired t test results are reported dyspnea vs general fatigue subgroups. Age (55.1 +/-15.7 vs 52.4 +/-14.3 years) and left ventricular ejection fraction (25.8 +/-12.8 vs 25.3 +/-11.4%) were not significantly different between groups (P <= .30). Peak Vo₂ (15.1 +/-5.3 vs 17.9 +/-5.8 mLO₂ kg^-1 min^-1) and peak RER (1.07 +/-0.09 vs 1.10 +/-0.10) were significantly lower while the VE/Vco₂ slope (39.1 +/-13.5 vs 33.7 +/-8.7) was significantly higher in the dyspnea subgroup (P < .05). There were 19 cardiac-related events (1 death, 2 transplants, and 16 hospitalizations) during the 2-year tracking period (18.7% annual event rate). Patients terminating exercise secondary to dyspnea were at a significantly higher risk for adverse events (hazard ratio: 5.6, 95% confidence interval: 1.8-16.8, P = .002). Event-free survival for the general fatigue and dyspnea subgroup was 92.7% and 66.8%, respectively (log-rank: 11.7, P = .0006).

Conclusion: These results indicate that HF patients who terminate an exercise test secondary to dyspnea have worse prognosis and poorer CPX markers, including a lower peak Vo₂ and higher VE/VCo₂ slope compared to patients who terminate secondary to general fatigue. Exercise-limiting dyspnea should therefore be considered an important factor during exercise testing in patients with HF.