Over the past thirty years, there has been a significant decrease in risk of sudden cardiac death after myocardial infarction (heart attack), write researchers in the November 5 issue of JAMA. A. Selcuk Adabag, M.D., M.S. (Veterans Affairs Medical Center, Minneapolis) and colleagues at Mayo Clinic, Rochester, Minn. also find that patients have a relatively higher risk of sudden cardiac death for the first month after a heart attack, but this risk decreases as long as they can stave off heart failure.

"Sudden cardiac death is a devastating complication of myocardial infarction," write the authors. There are still challenges in determining which patients are at risk for the condition as well. Researchers suggest that the current prediction model, based on patient characteristics gathered just after heart attack, is not sufficient in adequately determining risk. There may be improvements in predicting the risk of sudden cardiac death if models take into account the patient's state in the days and weeks following heart attack, with special focus given to heart failure or a condition that can cause chest pain from a narrowed or blocked coronary artery called recurrent ischemia.

To further investigate the relationship between sudden cardiac death and myocardial infarction, Adabag and colleagues analyzed 2,997 Olmsted County, Minn. residents who had a heart attack between 1979 and 2005. The sample was 59% men and about 67 years old, on average. For about 4.7 years (through Feb. 29, 2008), researchers followed the patients using medical records.

During the study period, 1,160 patients died and 24% (282) died from sudden cardiac death. The researchers also computed a 1.2% 30-day cumulative incidence of sudden cardiac death - a figure that is four times greater than expected. This rate remained constant for each year that followed, which is actually lower than the general population rate of sudden cardiac death. After five years, the cumulative incidence of sudden cardiac death was 6.9% among the heart attack patients.

Of the 2,997 patients, 842 patients developed recurrent ischemia, 365 developed heart failure and 873 developed both ischemia and heart failure. There was no association noted between recurrent ischemia and sudden cardiac death. Patients who experienced heart failure during the follow-up period had a 2.5% increase in risk of sudden cardiac death within 30 days of heart attack and in each year after compared with patients who did not experience heart failure during this time.

Adabag and colleague write that, "The risk of sudden cardiac death has declined significantly over time for myocardial infarctions that occurred between 1997 and 2005 compared with between 1979 and 1987." This is a decline of over 40% over the past 25 years - "A decline that predates the widespread use of defibrillators but parallels drastic changes in medical therapy for acute MI, including reperfusion and secondary prevention."

"In the community, the risk of sudden cardiac death is the highest during the first month after myocardial infarction when it markedly exceeds the rate in the general population," conclude the researchers. "Among 30-day survivors, the risk of sudden cardiac death declines rapidly but it is markedly increased by the occurrence of heart failure during follow-up. This underscores the importance of continued surveillance of patients after myocardial infarction and the dynamic nature of risk stratification."

Sudden Death After Myocardial Infarction
A. Selcuk Adabag, MD, MS; Terry M. Therneau, PhD; Bernard J. Gersh, MB, ChB, DPhil; Susan A. Weston, MS; Véronique L. Roger, MD, MPH
JAMA (2008); 300[17]: pp. 2022-2029.
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: Peter M Crosta