Cardiac autonomic neuropathy a risk factor for silent myocardial infarction

Individuals with cardiac autonomic neuropathy appear to be at increased risk of incident silent myocardial infarction (SMI), regardless of the presence of traditional atherosclerotic risk factors, according to a study.

The study included 4,842 participants (mean age 62.5 years, 46.6 percent women, 60.2 percent White) with type 2 diabetes from the ACCORD (Action to Control Cardiovascular Risk in Diabetes) study who were free of atherosclerotic cardiovascular disease at baseline.

Cardiac autonomic neuropathy was ascertained using heart rate variability indices, which were calculated from 10‐second resting electrocardiograms. The heart rate variability (HRV) indices included standard deviation of all normal‐to‐normal R‐R intervals and root mean square of successive differences between normal‐to‐normal R‐R intervals. Cardiac autonomic neuropathy was defined as both the standard deviation of all normal‐to‐normal R‐R intervals and root mean square of successive differences between normal‐to‐normal R‐R intervals less than the fifth percentile of the general population.

At baseline, 903 participants (18.6 percent) had cardiac autonomic neuropathy. Participants with low HRV were more likely to have higher body mass index, HbA_1C, duration of diabetes, as well as lower high‐density lipoprotein cholesterol or estimated glomerular filtration rate. Over a median follow‐up of 4.9 years, 73 participants developed SMI, yielding an incidence rate of 3.1 per 1,000 person‐years (95 percent confidence interval [CI], 2.5–3.9).

Multivariable Cox proportional hazards regression showed that low HRV was associated with a higher risk of SMI (low standard deviation of all normal‐to‐normal R‐R intervals: HR, 1.67, 95 percent CI, 1.02–2.72; root mean square of successive differences between normal‐to‐normal R‐R intervals: HR, 1.56, 95 percent CI, 0.94–2.58).

The risk of SMI was 1.9‐fold higher among participants with cardiac autonomic neuropathy (HR, 1.91, 95 percent CI, 1.14–3.20).

The present data highlight the potential usefulness of cardiac autonomic neuropathy for optimizing the approach to identify asymptomatic coronary heart disease in individuals with type 2 diabetes.