Enhanced ventilatory response to exercise in patients with chronic heart failure and central sleep apnea

In patients with chronic heart failure (CHF), central sleep apnea (CSA) and enhanced ventilatory response (VE/VCO2 slope) to exercise are common. Both breathing disorders alone indicate poor prognosis in CHF. Although augmented chemosensitivity to CO2 is thought to be one important underlying mechanism for both breathing disorders, it is unclear whether both breathing disorders are related closely in patients with CHF. We investigated 20 CHF patients with clinically important CSA (apnea-hypopnea-index (AHI), number of episodes per hour >or=15) and 10 CHF patients without CSA. Patients with and without CSA did not differ with respect to exercise capacity (peak VO2, 63.4+/-3.4% versus 60.8+/-4.4% of predicted value; P=0.746) and left ventricular ejection fraction (LVEF, 31+/-2% versus 31+/-3%; P=0.948). The AHI was not correlated with exercise capacity (peak VO2, percent of predicted value; P=0.260) and LVEF (percent, P=0.886). In contrast, the positive correlation of the VE/VCO2 slope, determined by cardiopulmonary exercise testing, with the AHI was highly significant (P