Undiagnosed sleep-disordered breathing is common but does not predict mortality in chronic heart failure patients with ICDs

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Wolfram Grimm, Department of Cardiology, Philipps-University, Marburg, Baldingerstraβe, Germany, and others reported in EP Europace that while undiagnosed sleep-disordered breathing is common in patients with implantable cardioverter defibrillators (ICDs) and chronic heart failure, it does not independently predict appropriate ICD therapy or mortality.

Grimm et al wrote that previous studies have produced conflicting results regarding the presence of sleep apnoea being a predictor of appropriate ICD therapy in chronic heart failure patients and that the association between sleep-disordered breathing and mortality in ICD patients is not known. They stated: “Therefore, we performed a prospective observational study in ICD patients to determine whether screening for sleep-disordered breathing is helpful to predict appropriate ICD therapy and mortality.”

In the prospective observational study, the investigators conducted overnight sleep studies in 150 patients who were receiving an ICD and in 54 patients who were receiving a generator replacement for their existing ICD. Grimm et al used overnight cardiorespiratory polysomnography (Somnocheck R&K, Weinmann) in 82 patients and used in-hospital unattended overnight cardiorespiratory polygraphs (with Embletta, ResMed) in the remaining 122 patients. The primary endpoints were appropriate ICD therapies for ventricular tachycardia or ventricular fibrillation and all-cause mortality. Patients were followed-up for 38 months (from time of diagnostic sleep study) and reviewed every six months or as soon as possible after a spontaneous ICD shock.

Of the 204 patients examined, 70 did not have a sleep disorder, 105 had central sleep apnoea, and 29 had obstructive sleep apnoea. Of those patients with sleep apnoea, 37 had a mild form of the condition, 41 had a moderate form, and 56 had a severe form. Grimm et al reported that, during follow-up, 80 patients received one or more appropriate ICD therapies. They added that age, left ventricular end diastolic diameter, secondary prevention ICD indication, and the use of diuretics and absence of aldosterone antagonists were all independently associated with appropriate ICD therapy in a multivariate analysis. However, they wrote: “Both sleep apnoea classification and sleep apnoea severity did not show a significant association with appropriate ICD therapy.”

According to the authors, in a univariate analysis, central sleep apnoea was more common in patients who died during follow-up compared with survivors (59% vs. 49%, respectively; p=0.057). But, just as they were not found to be independent predictors of appropriate therapy, sleep apnoea classification and sleep apnoea severity were not found to be significantly associated with total mortality in a multivariate analysis.

Grimm commented: “Our findings support the hypothesis that central sleep apnoea is merely a marker but not an independent risk factor for an adverse prognosis in patients with heart failure. This may, in part, explain why a previous large prospective study using continuous positive airway pressure to treat severe central sleep apnoea in patients with chronic heart failure failed to show a survival benefit for the central sleep apnoea therapy. Whether newer forms of ventilation therapy like adaptive servoventilation are more beneficial in heart failure patients with central sleep apnoea is currently under investigation in the SERVE-HF trial.”

They concluded that while undiagnosed sleep-disordered breathing, especially central sleep apnoea, was common in patients with ICDs, “The presence and severity of previously unknown sleep apnoea in ICD recipients, however, does not appear to be an independent predictor of appropriate ICD therapy or mortality during follow-up.”

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