Illicit drug use involved in nearly one in three sudden cardiac deaths in young adults

Sudden cardiac death

Approximately one-third of young adults in Victoria who experienced sudden cardiac deaths outside of a hospital from 2019 to 2021 used illicit drugs prior to their fatal events, a study by researchers at the Baker Heart and Diabetes Institute has found.

The study, published in the journal, Heart Rhythm, found “astonishingly high” levels of illicit drugs than is typical for that population, as well as a greater prevalence of multiple substance use with cannabis the most common illicit drug identified.

Whilst the exact mechanism of sudden cardiac death (SCD) in the context of illicit drug use is unclear, the researchers found that the over-representation of drug use in these young people in the absence of elevated rates of cardiac conditions suggests that it contributes to SCD independent of traditional cardiovascular risk factors.

Sudden cardiac death is a major global health issue that clinicians and researchers are grappling with. It represents 50% of all cardiovascular deaths and occurs unexpectedly in people without prior history of cardiac disease or a known predisposition for it.

Lead investigator, Dr Liz Paratz, said “As clinicians in Melbourne, we frequently see complications of illicit drug use in young people. We noticed a consistent trend of illicit drugs involved in our registry’s young SCD cohort and were very keen to tease this out further. We found the prevalence of illicit drug use in young SCD patients was astonishingly high at almost one in three cases and exceeds reported rates in the young population”.

The analysis of data on substance abuse was revealed through positive toxicology reports and patient histories and recorded in one of the world’s largest and most comprehensive sudden cardiac death registries, the unexplained cardiac death project led by the Baker Institute.

The investigators analysed data from a statewide registry on patients aged 18–50 years who experienced out-of-hospital SCD between April 2019 and April 2021 in Victoria. Toxicology assessment results were available for nearly all patients, 32.5% of which were positive for drug use. Previous estimates of drug use in Australia had ranged from approximately 16.0% overall to 19.0% for those aged 14–49.

The study focused on patients for whom a cardiovascular cause of death was identified and does not include those who died suddenly of illicit drug overdoses (i.e. the illicit drugs were thought to be incidental).

Dr Paratz said these patients were more likely to be male, smokers, and excessive alcohol drinkers, and had a psychiatric diagnosis, lower body mass index, and lower rates of hypertension. Their deaths commonly occurred while they were sedentary or sleeping. While cannabis was the most common illicit drug identified (which maybe associated with an up to five-fold increased risk of heart attack), others included cocaine, amphetamines, heroin, and novel/psychoactive substances; with more than one substance frequently involved.

Dr Paratz said: “We were surprised by the very high rates of illicit drugs prevalent in the toxicological results of this group compared to the overall population. Our findings raise the question: Is substance abuse underestimated or does it lead to a higher rate of cardiovascular pathology that results in SCD? We know that some young people may have a genetic predisposition for sudden death or developing coronary disease, but drug use may interact with this tendency to accelerate poor outcomes.”

An editorial in the journal by Norwegian researchers titled Sudden cardiac death in the young — can illicit drug use explain the unexplained? says we need to better understand how drug use contributes to cardiac disease in adults under 50 — which is critical since it is potentially a reversible risk factor.

“Despite years of research, we still struggle with a high proportion of lacking diagnoses in young SCD. Genetic analyses were thought to help us explain; however, we are still often left with the unexplained,” they said.

/Baker Institute Public Release. View in full here.