DE-MRI shows asymptomatic patients are undergoing small, silent heart attacks.
With the prevalence of diabetes on the rise, the complications due to prolonged uncontrolled glycemic levels are becoming of major healthcare concern, specifically, the development of coronary artery disease (CAD). Not all patients present with symptoms of CAD, but coronary computed tomography angiography has been able to determine that up to 70% of patients with diabetes who are asymptomatic, have evidence of CAD. What could this mean in terms of risk for cardiac events? Previous studies have used delayed-enhancement MRI (DE-MRI) to identify the presence of unrecognized myocardial infarction (MI) in symptomatic patients with diabetes, in association with increased risk of cardiac events.
This study wanted to use previous findings using DE-MRI, but in asymptomatic patients with diabetes, to measure the prognostic impact of unrecognized MI. The researchers first gathered asymptomatic patients with diabetes without a history of cardiac disease. They split into two prespecified cohorts with diabetes: the first, high-risk group, with 50 patients having type 1 diabetes and advanced nephropathy; the second, average-risk group, with 70 patients having type 2 diabetes without known decreased renal function. A third group was added to reduce observer bias, including 24 healthy volunteers. The primary endpoint was looking at the composite of all-cause mortality and clinical MI. As a secondary endpoint, they looked at the composite of cardiac mortality and MI. A follow-up occurred 46 months later. To further reduce observer bias, all MRI images were randomized into a single group before analysis.
From the total patient population, unrecognized MI was found in 19%, with an increased amount in the high-risk group, 28%, versus the average-risk group, 13%. The study noted that the infarct size was small and of the left ventricle. A logistic regression analysis was performed, determining that the only baseline variable to be a predictor or unrecognized MI was diabetes type. Within six months of the MRI, a combined 35 patients from both groups had a coronary angiography performed to measure the extent of CAD. Significant CAD was defined as > 70% stenosis, which was presented in 12 of 29 high-risk patients and 5 of 6 from the average-risk. During follow-up, six patients had to undergo coronary revascularization.
Kaplan-Meier survival curves were used to determine event-free survival, with significant data representing distinctly reduced event-free survival in patients with unrecognized MI compared to those without unrecognized MI (P < 0.0001). This was seen in both cohorts. Researchers then used another approach to analyze the data, Cox regression models. They determined, again, the only significant predictor of the primary endpoint listed was unrecognized MI by DE-MRI (P < 0.0001).
The authors concluded that there was a significant prevalence in the total study population who presented with an unrecognized MI (19%). Consequently, this small infarct leads to an 8-fold higher risk for adverse outcomes. While the high-risk group had almost double the rate of adverse events as the average-risk group, this doesn’t mean that cardiovascular risk is the same across both groups, but it shows there is a difference in the prevalence of the cardiac disease. As this topic is further researched, the aggressive preventative strategy is under consideration to be used in everyone with diabetes, but trials have yet to demonstrate benefit from both aggressive glycemic and blood pressure control in regards to cardiovascular events.
The authors noted that not all patients with diabetes are candidates for risk stratification as performed due to safety concerns in patients with insufficient renal function. They also discussed that due to the lack of larger sample size, this could affect the precision of their data, and future studies should be performed in larger groups. They also felt not all potential variables may have been collected; again, something to be looked at in future studies. Overall, in asymptomatic patients with diabetes and without cardiac disease, the presence of unrecognized MI showed an increased risk of death and clinical MI.
- 70% of patients with diabetes who are asymptomatic, have evidence of CAD.
- Imaging of the heart is showing that asymptomatic patients with diabetes, without a history of cardiovascular disease, are undergoing small, silent heart attacks.
- This study can’t prove the clinical significance for the use of set preventive guidelines, but can be used as the hypothesis for future trials.
Elliott, Michael, et al. Prevalence and Prognosis of Unrecognized Myocardial Infarction in Asymptomatic Patients With Diabetes: A two-Center Study With Up to 5 Years of Follow-up. Diabetes Care. 2019 April 22.
Emma Kammerer, L|E|C|O|M Bradenton School of Pharmacy, PharmD Candidate
See more on diabetes and heart disease in our Cardiology center.