Silent Myocardial Infarction Among Patients with Sudden Cardiac Death

A new study has revealed that the incidence of silent myocardial infarction (SMI) in patients who suffer from sudden cardiac death (SCD) may be more common than previously thought. 



After evaluating more than 5000 individuals who experienced coronary artery disease-associated SCD without prior knowledge of coronary artery disease and more than 40% of those patients had scarring associated with SMI at autopsy. 



In order to evaluate the prevalence of SMI scars among individuals who experienced SCD through examination of data from then Finnish Genetic Study of Arrhythmic Events, which involved 5869 individuals who experienced SCD between 1998 and 2017.

Data available on individuals in the study included clinical history from medical records, previous electrocardiograms (ECG), and a standard questionnaire that was provided to next of kin. SMI was defined by investigators as a scar detected by macroscopic and microscopic evaluation of myocardium without previously diagnoses coronary artery disease.

Upon analyses, investigators found that 4392 (74.8%) of the individuals had coronary artery disease as an underlying cause of death. Of that group, 71.1% (3122) individuals had no history of coronary artery disease prior to death, with SCD being the first manifestation of underlying heart disease in the patient. 

No information was available on whether coronary artery disease had been diagnosed prior to SCD in 244 individuals and those cases were excluded from the study. An additional 2 individuals were excluded due to incomplete autopsy information.

Patients with SMI were more often men (1102 of 1322 [83.4%] versus 1357 of 1798 [75.5%]; P&thinsp;<&thinsp;.001)and older (66.9 versus 65.5 years) than patients without MI scarring. Investigators noted that heart weight was higher among patients with SMI and, in patients with SMI, SCD occurred more often during physical activity. Additionally, prior ECG was abnormal in 66.8% (125 of 187) of individuals who had SCD after SMI, which is more than 10% than the rate among those without SMI (55.4%, 139 of 251).

In a related commentary, Williams C. Roberts, MD, of Baylor Scott and White Heart and Vascular Institute, applauded the study’s size and breadth of data but also pointed out that the length of the study and other characteristics limit the applicability of the results. &#8232;&#8232;

“Although a number of previous articles have described and compared the frequency of myocardial scars indicating previous healed acute MI in individuals who experienced sudden cardiac death, none included the huge number of patients described by the Finnish group,” Roberts wrote. “Nevertheless, large numbers do not necessarily guarantee perfect data.”&#8232;&#8232;

This study, titled “Association of Silent Myocardial Infarction and Sudden Cardiac Death,” is published in JAMA Cardiology.