Cardiac Autonomic Dysfunction Associated With Silent MI Risk in Type 2 Diabetes

Cardiac autonomic dysfunction is significantly associated with an increased risk for incident silent myocardial infarction (SMI) after adjustment for traditional atherosclerotic risk factors among adults with type 2 diabetes, according to a study in the Journal of the American Heart Association.

The results are from a prospective cohort analysis of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study, which enrolled adults with type 2 diabetes in the United States and Canada from January 2001 to October 2005. The current analysis excluded patients with established atherosclerotic cardiovascular disease at baseline.

Cardiac autonomic dysfunction was assessed with heart rate variability (HRV) metrics from a digitalized 12-lead ECG. The ECG recordings were used to obtain 2 HRV time-domain indices: standard deviation of all normal-to-normal R-R intervals (SDNN) and the root mean square of successive differences between normal-to-normal R-R intervals (rMSSD).

The participants were followed prospectively until SMI, death, or study end in June 2009. Incident SMI was defined as a major Q-wave abnormality or minor Q/QS waves in major ST-T abnormalities without clinical cardiovascular disease.

The analysis included 4842 participants (mean age, 62.5 [SD, 5.7] years; 46.6% women; and 60.2% White), and the baseline cardiac autonomic dysfunction prevalence was 18.6%.

After a median follow-up of 4.9 years, 73 participants had an SMI (incidence rate 3.1/1000 person-years; 95% CI, 2.5-3.9). The crude incidence rate of SMI was greater than 1.5-fold higher in patients with cardiac autonomic dysfunction vs those without cardiac autonomic dysfunction.

Cardiac autonomic dysfunction was associated with an increased risk for SMI after multivariable adjustment (hazard ratio [HR], 1.91; 95% CI, 1.14-3.18). The magnitude and significance of the association continued after additional adjustments for medications affecting HRV (HR, 1.92; 95% CI, 1.15-3.20) and retinopathy history (HR, 1.91; 95% CI, 1.14-3.20).

Low HRV was significantly associated with an increased risk for SMI. A 1-SD reduction in SDNN was associated with a 1.29-fold increased SMI risk (HR, 1.29; 95% CI, 1.02-1.65). Individuals who had a low SDNN had a 1.67-fold increased risk for SMI vs those with normal SDNN (HR, 1.67; 95% CI, 1.02-2.72). Low rMSSD was associated with an increased, although nonstatistically significant, risk for SMI (HR, 1.56; 95% CI, 0.94-2.58).

The specificity, sensitivity, and negative and positive predictive values of cardiac autonomic dysfunction for detecting SMI were 81.5%, 30.1%, 98.7%, and 2.4%, respectively.

Among several study limitations, cardiac autonomic dysfunction is assessed using time-domain indices from 10-s ECG recordings only, ECG data are not used for a longer period, and SMI was diagnosed with use of ECGs only. Also, the power to detect the full extent of the association of the cardiac autonomic dysfunction exposures and SMI may have been limited by the relatively small number of events.

“Our findings underscore the potential usefulness of CAN [cardiac autonomic dysfunction] for optimization of the approach to identify asymptomatic coronary heart disease in people with type 2 diabetes,” wrote the investigators.

Disclosure: One of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

This article originally appeared on The Cardiology Advisor