Decrease in risk of community sudden cardiac death over the last 30 years

Although several large clinical trials have recently examined the risk of sudden cardiac death after myocardial infarction (MI), community-based data reflecting the contemporary risk of sudden cardiac death after MI are lacking. Adabag et al. determined to evaluate the risk of sudden cardiac death after MI and the impact of recurrent ischemia and heart failure on sudden cardiac death.

The authors analysed data from a population-based surveillance study of 2997 residents (mean [SD] age, 67 [14] years; 59% were men) experiencing an MI in Minnesota, between 1979 and 2005, and followed up through February 29, 2008.  The main outcome measure was sudden cardiac death (defined as out-of-hospital death due to coronary disease); and observed survival free of sudden cardiac death compared with that expected in the surrounding area.

Median follow-up was 4.7 years, during which 1160 deaths occurred – 282 were due to sudden cardiac death (24%). The 30-day cumulative incidence of sudden cardiac death was 1.2% (95% confidence interval [CI], 0.8%-1.6%). Thereafter the rate of sudden cardiac death remained constant at 1.2% per year, yielding a 5-year cumulative incidence of 6.9% (95% CI, 5.9%-7.9%). The 30-day incidence of sudden cardiac death was 4-fold higher than expected (standardized mortality ratio, 4.2; 95% CI, 2.9-5.8), but the risk of sudden cardiac death declined significantly over time (hazard ratio [HR], 0.62 [95% CI, 0.44-0.88] for MIs that occurred between 1997 and 2005 compared with between 1979 and 1987; P = .03). The recurrent events of ischaemia (n = 842), heart failure (n = 365), or both (n = 873) occurred in 2080 patients. After adjustment for baseline characteristics, recurrent ischaemia was not associated with sudden cardiac death (HR, 1.26 [95% CI, 0.96-1.65]; P = .09), although heart failure markedly increased the risk of sudden cardiac death (HR, 4.20 [95% CI, 3.10-5.69]; P < .001).

Much of modern cardiac care is directed towards the acute phase of the disease; this study reminds us of the importance of long-term follow up in patients who have had a myocardial infarction.  Although the risk of sudden cardiac death following MI in community practice has declined significantly over the past 30 years, patients suffering from subsequent heart failure – but not those with recurrent ischaemia – have an increased risk of sudden cardiac death.  Although not a new finding, the study once again reminds us that the increased mortality risk of MI patients is highest in the early stage following the infarct.

Adabag AS, Therneau TM, Gersh BJ, et al. Sudden death after myocardial infarction. JAMA 2008; 300:2022-2029.

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