Sleep and Exertional Periodic Breathing in Chronic Heart Failure

Abstract

Background— Sleep and exertional periodic breathing are proverbial in chronic heart failure (CHF), and each alone indicates poor prognosis. Whether these conditions are associated and whether excess risk may be attributed to respiratory disorders in general, rather than specifically during sleep or exercise, is unknown. Methods and Results— We studied 133 CHF patients with left ventricular ejection fraction (LVEF) ≤40%. During 1170±631 days of follow-up, 31 patients (23%) died. Nonsurvivors had higher New York Heart Association class, ventilatory response (V̇ e /V̇ co 2 slope), and apnea-hypopnea index (AHI) and lower peak V̇ o 2 (all P <0.01); lower LVEF and prescription of β-blockers, and shorter transmitral deceleration time (all P <0.05). Exertional oscillatory ventilation (EOV), established by cyclic fluctuations in minute ventilation that persisted for ≥60% of exercise duration with an amplitude ≥15% of the average resting value, was significantly more frequent in nonsurvivors (42% versus 15%, P <0.01). Multivariable analysis selected AHI (hazard ratio [HR] 5.66, 95% CI 2.3 to 19.9, P <0.01), peak V̇ o 2 (HR 0.93, 95% CI 0.90 to 0.97, P <0.01), and β-blocker prescription (HR 0.34, 95% CI 0.13 to 0.87, P <0.05) as predictors of cardiac events. The best cutoff for AHI was >30/h. EOV was significantly related to AHI >30/h (χ 2 14.6, P <0.01): 78% of EOV patients showed AHI >30/h. Multivariable analysis, including breathing disorders alone (EOV, AHI >30/h) or in combination (EOV plus AHI >30/h), selected combined disorders as the strongest predictor of events (HR 6.65, 95% CI 2.6 to 17.1, P <0.01). Conclusions— In CHF, EOV is significantly associated with AHI >30/h. Although each breathing disorder alone is linked to total mortality, their combination has a crucial prognostic burden.