Risk factors fail to explain higher rates of sudden cardiac death in blacks

Even after adjusting for cardiovascular, behavioral and socioeconomic factors, black adults remain twice as likely to die from sudden cardiac death (SCD) as whites, suggests a study published in the Journal of the American College of Cardiology.

“At the end of the day, we just don’t have a full understanding of why patients who are black are more likely to succumb to SCD—a clear problem and knowledge gap on many levels,” lead author Rajat Deo, MD, an associate professor of cardiovascular medicine at the University of Pennsylvania, said in a press release.

“For many in the black community, their first clinical presentation of any cardiovascular issue is a sudden cardiac death event. Of course, we don’t know whether they have ignored symptoms such as chest pain and opted not to seek medical attention, or if this truly is the first indication of cardiovascular disease, perhaps due to a genetic predisposition. Either way, the data are staggering, and represent a pervasive problem in the black community.”  

Deo and colleagues said it’s already been reported that blacks are about twice as likely to experience SCD as whites. However, no previous population-based analyses controlled for environmental and socioeconomic factors, cardiovascular risk factors and behavioral measures such as drinking habits, depressive symptoms and perceived stress.

That’s exactly what the researchers set out to do, using a cohort of 22,507 participants— 41.8 percent black, the rest white—who had no history of clinical cardiovascular disease at baseline. During a median follow-up of 6.1 years, blacks experienced an age-adjusted incidence of SCD at 1.8 per 1,000 person years compared to 0.7 per 1,000 years among whites—a 2.35-fold increase.

After adjusting for the aforementioned factors, the risk of SCD remained 1.97 times higher.

“Although more comprehensive public health efforts toward risk factor modification in black populations will be a critical step to reduce the higher burden of SCD in blacks compared with whites, our data suggest that it may not eliminate the racial disparity,” the authors wrote in JACC. “Therefore, additional research will be needed to understand the factors that underlie these persistent racial differences in SCD risk to prevent the excess of SCD in blacks.”

The authors pointed to autopsy evidence that indicates the underlying pathology of SCD may differ in blacks versus whites. Black SCD patients have shown a lower prevalence of coronary artery disease, despite the black population’s higher reported incidence of hypertension, diabetes and chronic kidney disease. On the other hand, cardiac hypertrophy is more commonly reported among black patients, while coronary plaque rupture shows up more often on autopsies of white patients.

“These divergent findings suggest that cardiovascular risk factor modification may have a lesser impact on the non-atherosclerotic pathologies and mechanisms underlying SCD in blacks,” Deo et al. wrote.

In a related editorial, two researchers from Cedars-Sinai Medical Center in Los Angeles said the study would have been more complete if it included patients with prior history of CVD as well as sudden cardiac arrest (SCA) that was successfully resuscitated. Excluding the SCA cases, they noted, likely resulted in “at least a modest underestimation of what is essentially the same condition.”

Future studies should include these patients and better assess left ventricular function and structure through imaging, the editorialists said. Additional research could also define genetic variants related to African ancestry that may enhance the risk stratification for SCD.

“We agree that black race is likely to play an important role in the pathophysiology of SCD, but more work is needed to define the specific contribution of race to risk,” wrote Sumeet S. Chugh, MD, and Kyndaron Reinier, PhD, MPH. “Especially given the attenuation of risk when coronary artery disease risk factors were considered in this study and exclusion of prevalent CVD at baseline, at this time we are reluctant to conclude that attention to traditional CVD risk factors will have a low impact on SCD risk in blacks.”