Patients with chronic heart failure (CHF) complain of breathlessness and fatigue. Their exercise limitation can be assessed by incremental exercise testing with metabolic gas exchange to derive peak oxygen consumption (pV˙o₂). The slope of the relation between ventilation (V˙e) and carbon dioxide production (V˙co₂), V˙e/V˙co₂ can characterise the ventilatory response to exercise. CHF patients have a reduced pV˙o₂ and an increased V˙e/V˙co₂ slope.¹ Thus, for a given V˙co₂, the ventilatory response is greater. These two measures are inversely related in patients, but not controls, and both are related to prognosis.

The form of exercise undertaken, stationary cycle or treadmill, varies between exercise laboratories. Treadmill based protocols achieve higher values of pV˙o₂ and anaerobic threshold than those using a cycle. The effects of the different exercise modes on the V˙e/V˙co₂ slope and the symptoms of breathlessness are unknown. The aim of the present study was to explore the effect of cycle and treadmill exercise on ventilation and symptoms.

METHODS

Eleven patients with CHF and 11 age matched controls were studied. The patients all had New York Heart Association (NYHA) functional class II symptoms, an ejection fraction < 40% on echocardiography, and all had been stable for the preceding three months on optimal doses of angiotensin converting enzyme inhibitors and β blockers. Patients with other conditions restricting exercise testing were excluded. The controls were individuals of a similar age chosen at random from the lists …