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The exercise capacity of patients with chronic heart failure (CHF) is greater when assessed by the treadmill rather than the bicycle ergometer, but the mechanism of this difference has not been clarified. The present study aimed to determine the difference between the hemodynamics of these exercise modes and the mechanism underlying the different peak oxygen uptake (VO2). Patients (n = 18) underwent a bicycle test and treadmill test using individual ramp protocols. Respiratory gas analysis and hemodynamic measurements with an opti-catheter were performed during both exercise tests. The peak VO2 was significantly larger in the treadmill test than the bicycle test (1410+/-292 vs. 1630+/-331 ml/min, p<0.001). Both the peak cardiac output (Q; 10.2+/-2.2 vs. 10.9+/-2.1 L/min, p<0.001) and the peak arteriovenous oxygen difference (a-v 02 diff; 13.9+/-1.5 vs. 15.0+/-1.2 vol%, p<0.001) were also significantly higher in the treadmill test. The relative contribution of Q and a-v O2 diff to the increased peak VO2 was equivalent, which suggests that both Q and a-v O2 diff. Contribute equally to the different peak VO2 responses in CHF.
Kim et al. (Fri,) studied this question.