SEATTLE – A marked increase in the risk of sudden cardiac death among people with HIV correlates with a significantly higher burden of myocardial fibrosis, according to an autopsy study presented at the Conference on Retroviruses and Opportunistic Infections.
M. Alexander Otto/MDedge News
Dr. Zian Tseng
Fibrosis is a known trigger for fatal arrhythmias, so the take home is that fibrosis should be considered as a criteria for defibrillator implantation in HIV patients, said lead investigator Zian Tseng, MD, a cardiologist, cardiac electrophysiologist, and professor of medicine at the University of California, San Francisco.
The finding also speaks to a larger issue. The main criterion right now for implantation is an ejection fraction below 35%, but “there are a lot of people who die suddenly with normal ejection fractions,” and not just people with HIV, he said.
Many of those deaths might be prevented if fibrosis is added to implantation criteria. All that’s needed for assessment is a cardiac MRI, Dr. Tseng said.
The approach would be particularly fruitful for HIV patients, but cardiac fibrosis “isn’t just an” HIV problem, he said.
The conclusions have their roots in an investigation to determine the true incidence of sudden cardiac death (SCD) in the general public. SCD is commonly listed on death certificates, but it’s a presumed diagnosis, based on the best guesses of paramedics and clinicians. Autopsy is the only way to know for sure if a death was truly due to a sudden cardiac arrhythmia, or even related to the heart,
To clear the wheat from the chaff, Dr. Tseng and his colleagues performed autopsies on 525 out-of-hospital SCD cases among adults in San Francisco from 2011-2016; to qualify, the cases had to meet World Health Organization SCD criteria, meaning unexpected death within 1 hour of symptom onset, or, in unwitnessed cases, within 24 hours of when the person was last seen alive and well.
Cases were considered sudden arrhythmic death – and, therefore, true SCD – if no extracardiac causes of death or acute heart failure were found on autopsy. Overall, 40% of deaths attributed to SCD “were not sudden or unexpected, and nearly half of presumed SCDs were not arrhythmic.” The findings had “implications for ... mortality data, clinical trials, and cohort studies,” Dr. Tseng and his team concluded (Circulation. 2018 Jun 19;137[25]:2689-2700).
They next turned their attention to HIV. It’s known that the virus increases the risk of strokes, heart attacks, and heart failure; the researchers wanted to see if it did the same for SCD. The HIV results were presented at CROI.
Forty-seven presumed SCD cases with HIV met inclusion criteria during the study period. Based on the earlier findings and epidemiological data, people with HIV had more than an 80% higher risk of SCD and an almost 60% higher risk of confirmed arrhythmic death than did the general public. Similar to the general population, only about half of presumed SCD cases were confirmed on autopsy. About one-third of what turned out to be non-cardiac HIV deaths were due to occult overdose, versus 13.5% in the general population, which points to the increased need for drug screening and treatment in HIV.
Beyond that, though, the team found that the burden of myocardial fibrosis in HIV “was profound,” far surpassing what was found in SCD deaths in the general population. After adjustment for age, gender, and heart disease, “sudden cardiac deaths with HIV had 60% higher interstitial fibrosis by myocardial trichrome staining. Cardiac fibrosis, a known substrate for fatal arrhythmias in the general population, may underlie the mechanism by which HIV increases the risk” of sudden death in HIV, Dr. Tseng said.
It could be that the virus enters heart cells and sets off an inflammatory cardiomyopathy, or perhaps it’s related to chronic inflammation caused by the virus. Whatever the case, infection seems to have an “independent effect” on increasing fibrosis among people with HIV, he said.
Intriguingly, a large epidemiologic study in United States veterans, also presented at CROI, found a higher risk of SCD among HIV patients, but only if their infections were active over an extended period of time, as indicated by sustained high viral loads and low CD4 cell counts. Dr. Tseng was involved in that work, as well, but noted that the number of HIV SCD cases in the San Francisco study was too small to draw meaningful conclusions regarding the relationship between disease control and cardiac fibrosis.
Cardiac defibrillators can prevent arrhythmic death, so, at least for now, he said that the autopsy study findings mean that criteria for implantation should be broadened to include extensive cardiac fibrosis.
The work was funded by the National Institutes of Health. Dr. Tseng didn’t have any disclosures.
SOURCE: Tseng ZH et al. CROI 2019 abstract 32