Cardiac arrest deaths often misinterpreted, autopsy study finds
About 40 percent of deaths attributed to sudden cardiac arrest (SCA) aren’t really from “sudden” or heart-related causes, according to an autopsy study conducted in the San Francisco area.
Researchers prospectively monitored all deaths in the county over a 37-month period and identified 541 out-of-hospital cardiac arrest cases that met World Health Organization (WHO) definitions for sudden cardiac death (SCD). These criteria included sudden unexpected death either within one hour of symptom onset if witnessed, or within 24 hours of having been seen alive and symptom free if the event is unwitnessed.
Sixteen families didn’t allow autopsies to be performed for religious reasons so the researchers examined 525 cadavers for their analysis, which was published online June 18 in Circulation.
Among their findings:
- 40 percent of deaths were found to have nonsudden, noncardiac causes.
- 55.8 percent of SCDs were attributed to arrhythmias, which were the first manifestation of heart disease in more than half (57 percent) of autopsy-defined sudden arrhythmic deaths.
- Top causes of presumed SCDs included coronary artery disease (32 percent), drug overdose (13.5 percent), cardiomyopathy (10 percent), cardiac hypertrophy (8 percent) and neurological (5.5 percent).
- 98 percent of sudden arrhythmic deaths had structural disease at autopsy.
“Because approximately half of deaths attributed to OHCA and WHO-defined SCDs were found to be nonarrhythmic after postmortem examination, it is difficult to identify SCDs with a high degree of accuracy by using conventional methods; therefore, one may consider deaths meeting WHO criteria as sudden deaths rather than as sudden cardiac deaths,” wrote lead researcher Zian H. Tseng, MD, an electrophysiologist the University of California, San Francisco, and colleagues. “Although comprehensive autopsies are not practical in most clinical trials and population, observational, or molecular association studies, understanding the limits of current criteria used to define SCD is important for interpreting the results.”
The findings highlight that drug overdoses may be underestimated and instead attributed to SCD when no evidence of drug use is present at the scene. Nonforensic autopsies are rarely performed, leaving the presumption of cause of death up to emergency medical service records and noninvasive assessment by a coroner or medical examiner. However, extensive autopsies are required to rule out noncardiac and nonarrhythmic conditions that may have caused the death, Tseng et al. noted.
“Cardiac arrests defined by paramedic criteria and sudden cardiac deaths defined by conventional or retrospective methods, as in most cohort studies or clinical trials, have limited accuracy for actual arrhythmic deaths,” they wrote. “These data reflect the decreasing prevalence of coronary disease and increasing prevalence of nonischemic causes; therefore, further inroads into reducing the overall burden of sudden death requires investigation and earlier recognition of nonischemic and nonarrhythmic causes.”
In a related editorial, Robert J. Myerburg, MD, pointed out the inclusion criteria may have actually underestimated the “true incidence” of sudden cardiac arrhythmia leading to SCD. Even when the specifics and limitations of the study design are taken into account, Myerburg said the work of Tseng et al. is a noteworthy contribution to the literature on SCD.
“The conclusion that 40 percent of events appearing to be SCDs were not sudden or unexpected is sobering and requires our attention as we classify SADs in the design and execution of future studies on this important topic,” wrote Myerburg, with the University of Miami Miller School of Medicine. “The converse perception, that the cumulative numbers still contain a large representation of events that are indeed cardiac-based SCDs, and that there may be some undercounting, should not be lost as a result of the principles elucidated in this study.”
Daniel joined TriMed’s Chicago editorial team in 2017 as a Cardiovascular Business writer. He previously worked as a writer for daily newspapers in North Dakota and Indiana.