Scar From Old MI Common When CAD Revealed at Autopsy After Sudden Death

Liam Davenport

July 15, 2019

Scar from myocardial infarction (MI) that went unrecognized may have been involved in two fifths of cases of out-of-hospital sudden cardiac death (SCD) in people with previously unknown coronary artery disease (CAD) in an autopsy cohort in Finland.

Among 5869 individuals who died from SCD over a 20-year period in the cohort from Finland, 1322 of the 3122 who had not been previously diagnosed with CAD (42.3%) were found on autopsy to have evidence of myocardial scar indicative of old MI.

Ischemic heart disease had gone unrecognized in more than two thirds of persons in whom CAD was noted at autopsy as the cause of SCD.

Those with old MI were more likely to be older and male and to have a greater total heart weight than those without evidence of silent MI. They were also more likely to have experienced SCD during physical activity, note the authors of the study, led by Juha H. Vähätalo, BM, Oulu University Hospital and University of Oulu, Finland. Their report was published July 10 in JAMA Cardiology.

The group obtained pre-SCD electrocardiograms (ECGs) from 187 persons with silent MI and from 251 of the approximately 1000 persons in the overall SCD cohort who had been previously diagnosed with CAD.

Those found to have had silent MI were significantly more likely to show at least one ECG abnormality that might have flagged a history of MI (66.8% vs 55.4%; P = .02). The abnormalities consisted of fragmented QRS intervals or durations ≥110 ms, pathologic Q waves, and T-wave inversion.

Although firm conclusions can't be drawn from such a small sample of ECGs from the overall cohort, the findings provide "motivation" for further studies into how such techniques could be used to recognize and prevent silent MIs and potentially prevent SCD down the line, the group writes.

They add that while "more efficient methods" than ECG might be able to diagnose silent MI in the future, the cost-effectiveness of, for example, cardiac MRI for that purpose "is likely to be unreasonable."

Instead, they propose that ECG screening be reserved for high-risk populations and that MRI and plus myocardial strain analysis by echocardiography be reserved for individuals who warrant further examination.

This sort of approach is already used in individuals with a T-wave inversion in the precordial leads, and "often, these patients have an echocardiogram after that," senior author M. Juhani Junttila, MD, Oulu University Hospital and University, told | Medscape Cardiology.

"The most important thing is to identify these individuals with many risk factors for coronary artery disease, although they don't have any symptoms. And if they have ECG findings, they would undergo some kind of imaging," he said.

Surprisingly High Prevalence

Junttila said he was "surprised" that the prevalence of silent MI in SCD patients was similar to that seen in studies conducted in the 1970s and 1980s, apparently belying the commonly held belief that "cardiovascular diseases are decreasing in society."

In an accompanying commentary, William C. Roberts, MD, Baylor University Medical Center, Dallas, Texas, also notes that the prevalence of silent MI in the analysis was similar to what had been seen in previous studies. Together, the figures suggest that left ventricular scars indicative of healed MI are likely present in 40% to 50% of people who experience SCD.

The current study has "major positives," he writes, including the "huge database" on SCD and autopsy findings on everyone. However, "large numbers do not necessarily guarantee perfect data."

A limitation, he writes, is that the autopsies were performed over 2 decades by different pathologists with likely "variable interests in cardiac disease." Also, left ventricular scars were not well described.

Also, there may have been shortfalls in accuracy in the clinical histories obtained via family and acquaintance questionnaires. There was no definition of dyslipidemia, and "its frequency is strikingly low" in the study, suggesting statins may have been in use.

Two Decades of SCD

The researchers gathered death certificates, medical records, autopsy reports, standardized questionnaires that were completed by next of kin, and police reports from the scene of death to supplement a cohort from the Finnish Genetic Study of Arrhythmic Events (FinGesture).

The case-control study included all individuals with out-of-hospital SCD for whom autopsy was performed in Northern Finland between 1998 and 2017. Autopsies are required by law in Finland for all unexpected deaths, the authors explain.

Of the 5869 individuals from FinGesture, CAD was noted as the underlying cause of death for 4392 (74.8%); SCD was the first known manifestation of the ischemic heart disease in 3122 persons, or about 71% of CAD cases.

Persons with prior silent MI were more likely to die from SCD during physical activity, at 18.2%, vs 12.4% for those without silent MI (P < .001); and they were more likely to die outdoors (20.0% vs 14.9%; P = .001), the report states.

"Surprisingly, SCDs in saunas were more common in individuals without silent MI (78 of 1798 [4.3%]) compared with individuals with silent MI (21 of 1322 [1.6%]; P = .03)," the authors state.

The study was funded by the Sigrid Juselius Foundation, the Finnish Foundation for Cardiovascular Research, the Yrjö Jahnsson Foundation, and the Paavo Nurmi Foundation. Junttila has received grants from Abbot Medical Finland and personal fees from AstraZeneca, Boehringer Ingelheim, Merck Sharp & Dohme, and Pfizer outside the submitted work. The other study authors and Roberts have disclosed no relevant financial relationships.

JAMA Cardiol. Published online July 10, 2019. Abstract, Commentary

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