Heightened Stroke Risk After MI Lingers Longer Than Previously Believed

Alexander E. Merkler, MD, an assistant professor of neurology at Weill Cornell Medicine

Alexander E. Merkler, MD

Historically, the medical literature has suggested that for patients who have suffered a myocardial infarction (MI), or heart attack, the risk of stroke is heightened for a period of about 1 month after the MI. Although, a recent study of Medicare claims data has suggested that this may not be the case.

In fact, the new study has shown that this risk window may extend to up to 3 months, much longer than previously believed. Ultimately, findings showed that the risk of ischemic stroke was highest in the first 4 weeks after discharge from the MI hospitalization (hazard ratio [HR], 2.7; 95% CI, 2.3 to 3.2), and remained elevated during weeks 5 to 8 (HR, 2.0; 95% CI, 1.6‐2.4) and weeks 9‐12 (HR, 1.6; 95% CI, 1.3‐2.0).¹

To find out more about the study and its findings, NeurologyLive sat with lead author Alexander E. Merkler, MD, an assistant professor of neurology at Weill Cornell Medicine, to hear his perspective on the data.

NeurologyLive: Could you provide an overview of the study you helped conduct?

Alexander E. Merkler, MD: We did this study to evaluate the relationship between acute myocardial infarction, or MI, and stroke. Traditionally, MI is associated with a heightened risk of stroke for about a month, and that's based on all these old literatures that are small studies and pretty old in nature—from 20 or 30 years ago. We did this study using Medicare claims to see what, in modern times, is the temporal association between MI and stroke.

What we found was that MI is associated with a more prolonged risk of stroke than we previously thought. As I mentioned, traditionally, MI is associated with a risk of stroke for about 1 month, so patients who have an MI are at an elevated risk for stroke for 1 month after the MI. But we found in this study that, actually, the risk of stroke is prolonged for at least 3 months, and that's a big difference because, in all the current stroke classification systems, MI is considered a risk for only 1 month. So, if you have a stroke today and you had a history of MI 3 months ago, or 4 months ago, or 2 months ago, that would not be considered the reason, or the cause, of stroke. That classification is used in modern-day stroke trials and classification systems.

Our findings are that if you have an MI, you're really at increased risk of stroke for at least 3 months, and this could change how we consider stroke ideology in class education systems and may lead to changes in clinical trial selection criteria.

As this is based on Medicare claims data, is the next step to replicate the findings?

It is only in Medicare claims, it's a claims-based study, and so all the patients are over age 66, and while most patients who have a stroke are around that age, anyway, the study definitely lacks certain information regarding granularity of detail. We didn't have stroke mechanism, we didn't have the size of the heart attack, we didn't have the location of the heart attack, and so I think one of the follow-up studies should be sort of subgroups that are at even higher risk. This would help provide information both for patients and for clinicians to say, “OK, you had a heart attack in this part of the heart.” There may be some subgroups of patients who are at more or less risk to have a stroke than others.

Have there been in questions that have consistently arisen from your peers?

The main question is in part a primary and a secondary prevention one. I'm looking at it from the secondary prevention perspective, meaning the patient has had a stroke already—how do we best prevent a future stroke from happening? Knowing that they may be at risk for stroke for 3 months or longer tells us we don't have to go and search for another ideology, it may purely be this MI.

But, one of the big questions is going to be for primary prevention. We know that MI is now a big risk for stroke for several months, how do we best prevent these patients from having a stroke, who are the ones that we need to focus on, and what strategies? Is it a combination of antiplatelet and anticoagulant therapies? Are there other medications that we need to use to avoid having a stroke in these patients? I think that's really important to prevent a stroke from occurring in a primary fashion.

This finding is itself surprising, but was anything else a little unexpected?

We did a subgroup analysis where we looked at patients who had a STEMI [ST-elevation MI] versus an NSTEMI [non-ST-elevation MI], and we found that really the results were identical. Both types of heart attack are equally associated with an increased risk of stroke, it wasn't just that the full STEMI was the only type of MI that was associated with stroke. I thought that was surprising.

What's the one thing you want the clinician community to take away from the findings?

It's a reiteration of the fact that MI is associated, independently, with a risk of stroke for at least 3 months. That really is the primary finding, and it is very different from all the prior literature and the current guidelines and classifications and clinical trial selection criteria. It's a big change, so hopefully, further research will confirm this, or further evaluate it at least, and we'll find some subgroups that might be interesting.

Transcript edited for clarity.

REFERENCE

1. Merkler A, Diaz I, Wu X, et al. Duration of heightened ischemic stroke risk after acute myocardial infarction. Presented at: 143^rd Annual Meeting of the American Neurological Association; October 20-23, 2018; Atlanta, Georgia. Abstract #M122.