HRJ: Sleep-disordered breathing increases risk of deadly arrhythmias
Sleep-disordered breathing (SDB) affects 24 percent of males and 9 percent of females and has been linked to cardiac arrhythmias during sleep. Adding to these data, researchers from the Rambam Medical Center in Israel found that implantable cardioverter-defibrillator (ICD) patients with SDB had a greater onset of life-threatening ventricular arrhythmias during sleep hours.

“Compared with the general population, the prevalence of SDB is particularly high among patients with heart failure and myocardial infarction SDB is associated with increased morbidity and mortality secondary to multiple contributing factors, “Tawfiq Zeidan-Shwiri, MD, of the Rambam Medical Center in Haifa, Israel, and colleagues wrote in the study published in this month's HeartRhythm Journal. “Currently, there are limited data available with regard to the predictors of fatal arrhythmias in patients with an ICD.”

To better understand whether SDB promotes fatal ventricular arrhythmias, Zeidan-Shwiri and colleagues evaluated 45 ICD patients between August 2007 and March 2009, for life-threatening ventricular arrhythmia events. The researchers defined SDB as apnea-hypopnea index >10 events/hour based on an overnight sleep study conducted at a single center. The study’s primary endpoint was appropriate ICD therapy that was defined as antitachycardia pacing of shock for ventricular tachycardia (VT) or ventricular fibrillation (VF) during a one-year follow-up period.

Of the patients, 57.8 percent had SDB. Appropriate ICD therapy was higher in patients with SDB compared to those without, 73 percent versus 47 percent. The rate of ventricular arrhythmias was higher in patients with SDB because of an increase in arrhythmic events occuring between midnight and 6 a.m. However, the rates of ventricular arrhythmia events that occurred during nonsleeping hours were similar.

The researchers reported that patients with SDB were more likely to be older, have a higher body mass index and higher creatinine values. During the study, 62 percent of patients experienced one or more episodes of ventricular arrhythmias and 56 percent were treated appropriately for VT or VF. Patients with SDB experienced more ventricular arrhythmias.

Zeidan-Shwiri and colleagues reported that appropriate ICD therapy occurred in 69 percent of patients with SDB and 39 percent of patients with SDB. “The increase in appropriate ICD therapies among SDB patients occurred predominantly due to an increase in ventricular arrhythmic events from midnight to 6 a.m. (69 percent vs. 32 percent),” the authors wrote.

“The increased risk for life-threatening ventricular arrhythmias was solely due to a striking increase in the incidence of ventricular arrhythmias occurring during the sleep period as opposed to periods of wakefulness,” the authors wrote. “Furthermore, our analysis also suggests that the severity of SDB correlates with the risk of nocturnal arrhythmias.”

The authors wrote that SDB can further trigger life-threatening ventricular arrhythmias during the night; however, noted that because the study only included patients with ICDs, the results may not be generalizable to the entire population.

“These findings provide a rationale for SDB screening in patients with appropriate ICD therapy if device interrogation reveals a predominance of nocturnal onset of arrhythmias,” the authors wrote. Zeidan-Shwiri and colleagues concluded that future studies should be undertaken to understand whether SDB treatments would reduce the risk of appropriate ICD therapy.