Silent but Deadly: 45% of Heart Attacks Lack Symptoms

Silent myocardial infarctions (SMIs), heart attacks that can occur without classic symptoms, account for 45% of heart attacks and can increase the risk of death from coronary heart disease (CHD) by 3 times, according to a new study.

The researchers analyzed 9498 participants, aged 45 to 64 years, who did not have cardiovascular disease at baseline and participated in the Atherosclerosis Risk in Communities (ARIC) study in the United States.
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Participants completed a phone interview and clinic visit at baseline (1987-1989) and made 4 follow-up visits (1990-1992, 1993-1995, 1996-1998, and 2011-2013).

After a median 9-year follow-up, 3.3% of participants had an SMI, and 4.1% had a clinically documented MI (CMI). Although men were more likely to develop an SMI, women were more likely to die from an SMI.

Overall, SMIs increased participants’ risk of all-cause mortality by 34% and of heart disease mortality by 3 times.

In addition, black participants were slightly more likely to develop an SMI than participants who were white, and white participants were more likely to develop a CMI than black participants.

“SMI represents over 45% of incident MIs and is associated with poor prognosis,” the researchers concluded. “Race and sex differences in the incidence and prognostic significance of SMI exist, which may warrant considering SMI in personalized assessment of CHD risk.”

—Amanda Balbi

Reference:

Zhang ZM, Rautaharju PM, Prineas RJ, et al. Race and sex differences in the incidence and prognostic significance of silent myocardial infarction in the Atherosclerosis Risk in Communities (ARIC) study [published online May 16, 2016]. Circulation. doi:10.1161/CIRCULATIONAHA.115.021177.