Exercise Hyperventilation in Chronic Heart Failure is Not Caused by Systemic Lactic Acidosis

BACKGROUND: Patients with heart failure have an abnormally high ventilatory response to exercise associated with gas exchange defects and reduced arterial pCO(2). AIMS: We examined the possibility of lactic acidosis as the stimulus to this increased ventilation that abnormally depresses pCO(2) during exercise in heart failure. METHOD AND RESULTS: We studied 18 patients with chronic heart failure. We measured VE/VCO(2) slope during exercise, arterial blood gases and lactate concentrations during cardiopulmonary exercise testing (rest, peak exercise and one minute after the end of exercise). Neither VE/VCO(2) slope nor arterial pCO(2) were related to arterial lactate concentrations at peak exercise (r = -0.16, p = 0.65 and r = -0.15, p = 0.6). During early recovery, patients with a high VE/VCO(2) slope had a particularly pronounced rise in arterial lactate and hydrogen ion concentrations (r = 0.57, p < 0.05 and r = 0.84, p < 0.0001) and yet their arterial pCO(2) rose rather than fell (r = 0.79, p < 0.001). The rise in arterial pCO(2) correlated with the increase in arterial hydrogen concentration (r = 0.78, p < 0.001) and with arterial pCO(2) at peak exercise (r = -0.76, p < 0.001). CONCLUSIONS: In heart failure VE/VCO(2) slope and low arterial pCO(2) at peak exercise are not related to the degree of systemic lactic acidosis. Lactic acidosis is therefore not a plausible mechanism of exercise induced hyperventilation.