In patients with systolic heart failure (HF), central apneas occur throughout a 24-hour period and are associated with neurohormonal activation, ventricular arrhythmic burden and worse prognosis, according to research publish Sept. 4 in the Journal of the American College of Cardiology.

Michele Emdin, MD, PhD, et al., enrolled 525 patients with systolic HF and impaired left ventricular systolic function receiving stable guideline-recommended treatment. All patients underwent 24-hour continuous polygraphic recording, including electrocardiography, respiration by chest and abdominal inductance plethysmography belts, nasal airflow detection and oxygen saturation (SaO2). The endpoint was death attributable to cardiac cause.

During the 24-hour period, normal breathing increased in the daytime, the obstructive apnea prevalence decreased and the central apnea prevalence remained predominant. The prevalence rates of patients with central apnea at night, during the day and throughout the 24-hour period were 69.1 percent, 57.0 percent and 64.8 percent, respectively, whereas the prevalence rates of patients with obstructive apnea were 14.7 percent, 5.9 percent and 12.7 percent, respectively.

During a median 34-month follow-up, 50 deaths occurred. Episodes of central apnea were associated with neurohormonal activation, ventricular arrhythmic burden and systolic/diastolic dysfunction. Nighttime, daytime, and 24-hour moderate-to-severe central apneas were associated with increased cardiac mortality.

According to the researchers, these findings may at least partially explain why previous therapeutic attempts, such as continuous positive airway pressure or adaptive servoventilation, both targeting "sleep" apnea episodes, have failed: targeting only "sleep" apnea may be insufficient in patients who manifest central apneas all day. On the other hand, this could explain why only adjustment or upgrade of HF therapy treatment have been associated with a prognostic benefit and with decreasing central apnea incidence. These treatments likely act on the pathophysiological triggers of central apnea and over the whole circadian period, thus including the subset at major risk.

In an accompanying editorial comment, John S. Floras, MD, Dphil, FACC, wrote, "although the present data may conflate central apnea, obstructive apnea, and normal breathing pauses plus events during wakefulness and sleep, the concept of a 24- hour central apnea burden with prognostic significance, as presented by Emdin et al., is a hypothesis sufficiently intriguing and so potentially transformational that it merits further independent investigation."