Silent Heart Attacks Are Linked to Sudden Cardiac Death

Many individuals who suffer sudden cardiac death (SCD) had previously experienced silent myocardial infarctions (SMIs), according to a study published in JAMA Cardiology.

Researchers performed a case-control study that compared autopsy findings, clinical characteristics, and electrocardiogram (ECG) markers associated with SMI in a consecutive cohort of individuals in the Finnish Genetic Study of Arrhythmic Events study population who were verified to have had SCD. The study consisted of individuals who had autopsy verified SCD in Northern Finland between 1998 and 2017. The researchers included 5,869 individuals (79% male, mean age, 65) who had SCD with CAD and evidence of SMI who were considered as having had cases. Participants those who had SCD with CAD without SMI were considered control participants. Silent MI in this study was defined as scar detected by both macroscopic and microscopic evaluation of myocardium without any previous occurrences of CAD.

The researchers procured clinical history from medical records, previously recorded ECGs, as well as a standardized questionnaire which was administered to the study subject’s next of kin. They hypothesized that SMI would be prevalent in the population who had had SCD with CAD, and it might be discerned or suspected in many individuals from ECG findings prior to death. Analyses of ECG tests were carried out by investigators blinded to the SMI data. Data analysis was completed from October 2018 through November 2018.

In a large autopsy verified sudden cardiac death study, ≈ 40% of ischemic SCD victims had evidence of prior silent myocardial infarction. https://t.co/1mUKaVRYR1

— JAMA Cardiology (@JAMACardio) July 11, 2019

The Silent Killer

According to the results, the cause of SCD was CAD in 4,392 individuals (74.8%), among whom 3,122 had no history of previously diagnosed CAD. Two individuals were excluded owing to incomplete autopsy information. An ECG recorded prior to SCD was available in 438 individuals. The findings detected silent MI in 1,322 individuals (42.4%) who experienced SCD without a clinical history of CAD. Moreover, participants with SMI were older than participants without MI scarring (mean [SD] age, 66.9 [11.1] years; 65.5 [11.6] years; P < .001) and were more often men (1102 of 1322 [83.4%] vs 1357 of 1798 [75.5%]; P < .001). Furthermore, weight was higher in participants with SMI (mean [SD] weight, 483 [109] g vs 438 [106] g; P < .001). In participants with SMI, SCD occurred more often during physical activity (241 of 1322 [18.2%] vs 223 of 1798 [12.4%]; P < .001). A prior ECG was abnormal in 125 of the 187 individuals (66.8%) who had SCD after SMI compared with 139 of 251 (55.4%) of those who had SCD without SMI (P = .02).

The study authors wrote in their conclusion that a “substantial number of individuals who experienced coronary artery disease–associated sudden cardiac death had had prior myocardial infarction without a diagnosis of coronary artery disease; some of these individuals might have been identifiable by premortem electrocardiography.”

This isn’t a huge surprise; none-the-less I find it extremely interesting! #HeartGeek #CardioTwitter #MedTwitter https://t.co/zIycbJ2CDh

— Simon 〽️ark (@simonmarkdaley) July 11, 2019

#Cardiology researchers of #UniOulu found that 42% of individuals who experienced coronary artery disease–associated sudden cardiac death had had prior myocardial infarction without a diagnosis of coronary artery disease. Read article @JAMACardio https://t.co/DpWhfCSHzI

— University of Oulu (@UniOulu) July 11, 2019