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Previously identified peak times for sudden cardiac arrest may not be valid
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Contradictory to previous findings on the circadian and septadian variation of sudden cardiac arrest, a morning or Monday peak may not exist, according to a study published in Heart Rhythm.
“For several decades, studies of cardiac arrest have shown a consistent finding: These events are most common in the early morning hours of the day and most likely to occur on Mondays as opposed to other days of the week,” Sumeet S. Chugh, MD, FHRS, medical director of the Heart Rhythm Center at Smidt Heart Institute at Cedars-Sinai Medical Center, told Cardiology Today. “Our findings indicate that, today, this may no longer be true. Unexpectedly, the peak during the day and the peak during the week no longer exists. Sudden cardiac arrests appear to occur with the same consistency during the hours of the day or days of the week.”
To evaluate circadian and septadian variation of sudden cardiac arrest in the general population, researchers analyzed data from the Oregon Sudden Unexpected Death Study, which is an ongoing, prospective community-based study that monitors out-of-hospital sudden cardiac arrest in the Portland, Oregon, metropolitan area. Included in the analysis were 1,535 cases of sudden cardiac arrest — witnessed by bystanders or Emergency Medical Services personnel — that occurred between February 2002 and January 2014 in adults (mean age, 67 years; 69% men; 48.2% with CAD; 7.1% with sleep apnea).
Researchers categorized the time of sudden cardiac arrest into 2-hour increments starting at midnight and into four 6-hour time groups, including early morning, morning, afternoon and evening. A statistical analysis was conducted, testing the distribution of sudden cardiac arrest among the 6-hour, 2-hour and day of the week groups. In addition, researchers performed subgroup analyses by age, sex, and presence of CAD or sleep apnea.
No morning peak
Researchers found no morning (6 a.m. to noon) peak, with 13.9% of sudden cardiac arrests occurring in the early morning, 27.6% in the morning, 31.6% in the afternoon and 26.9% in the evening (P < .0001).
The results of the subgroup analyses for age, sex and CAD also demonstrated the pattern of early-morning nadir and no peak.
For the presence or absence of sleep apnea, a difference in pattern emerged with researchers observing an early-morning nadir and lack of peak in those with no history of sleep apnea and no significant circadian differences or nadir in those with a history of sleep apnea.
No Monday peak
When considering the days of the week, researchers observed no peak on Mondays and a nadir on Sunday (accounting for 11.3% of sudden cardiac arrest events during the week; P = .004).
“In recent years, there have been some alterations in our behavior or the care that we receive that have eliminated these diurnal and weekly peaks of sudden cardiac arrest occurrence,” Chugh said. “However, sudden cardiac arrest remains a major public health problem, responsible for at least 1,000 lives lost in the United States on a daily basis (more than 350,000 lives annually). If we are going to make a real impact on prevention of sudden cardiac death, we need to [continue] to study this most unexpected finding.” – by Melissa J. Webb
For more information:
Sumeet S. Chugh, MD, FHRS, can be reached at sumeet.chugh@cshs.org.
Disclosures: The authors report no relevant financial disclosures.
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