AHA.14 Q&A: Putting DAPT findings in perspective

The Dual Antiplatelet Therapy (DAPT) study presented Nov. 16 at the American Heart Association scientific session in Chicago found that continuing DAPT beyond one year reduced the risk of ischemic events in patients treated with drug-eluting stents compared with aspirin alone. But it increased the risk of moderate or severe bleeding.

Robert W. Yeh, MD, an interventional cardiologist at Massachusetts General Hospital (MGH) in Boston and a DAPT study investigator, talked with Cardiovascular Business about the study’s findings and implications. The interview was edited and shortened for this Q&A.

Which patient population benefits from continued treatment?

It is best to refer back to the overall results of the trial. They showed that for the patient population enrolled, those patients who made it through a year who did not have a significant bleeding event or an adverse ischemic event on average benefited significantly in terms of a reduction of thrombosis and major adverse cardiac and cerebrovascular events.

Keep in mind there was an increase in moderate and severe bleeding, predominantly moderate bleeding. For those patients who are at a particularly high risk for bleeding, it would be reasonable to think they would benefit less and be at greater risk for bleeding complications with dual antiplatelet therapy. Those patients at elevated ischemic risk and perhaps less of a bleeding risk would benefit from continued dual antiplatelet therapy.

Identifying who exactly those patients are is one the next steps for us in the trial.

Which patients might be better suited for shorter treatment?

The way the trial was established, patients really had to get through the first 12 months of therapy event-free before being considered for randomization. Patients whose blood counts are dropping even within the first few months of treatment, who are getting a high number of nuisance bleeding events, had a serious hospitalization for bleeding within those first 12 months, those are patients for whom we would not recommend continuing dual antiplatelet therapy. Those are the patients we excluded for randomization.

There are other studies looking at different duration periods, whether it is three months, six months or beyond what you looked at. Did your results inform what they are doing?

It is hard to compare individual studies against one another. They have different protocols, enroll different populations and were conducted in different geographic regions. The one thing we can say for certain is that the DAPT study is the only study that was designed and powered to look at important endpoints: stent thrombosis individually and major adverse cardiac and cerebrovascular events.

As a practicing interventional cardiologist, I know the primary reason we continue DAPT for many of these patients is to avoid stent thrombosis and also myocardial infarctions in the non-stented region. The DAPT study is the only study that was sufficiently powered to answer the question we were interested in.

What did you learn from the three-month post-randomization observation period?

That was an interesting part of the study design. This was an observation period in which after 30 months of treatment in the 30-month arm all patients were to discontinue study drugs and basically patients were treated the same way. We learned that after discontinuation of study drugs, those patients who had been randomized to extended duration dual antiplatelet therapy started to have an increase, an accrual of cardiovascular events. Some of those events were stent thrombosis but usually more of those events were myocardial infarction in the non-stented vessel.

Whether or not you discontinue dual antiplatelet therapy or thienopyridine at 12 months or 30 months, in the immediate several months after discontinuation, patients do have an elevated risk of having cardiovascular events.

Knowing that, what would you do in your practice?

So much of practice has to be individualized to the patient. That being said, in each of my visits with patients we have a discussion about what has been happening with their bleeding risk, if they have been having any of the complications with prolonged dual antiplatelet therapy—bleeding in their stool, urine, nuisance bleeding. For those patients who typically do well on dual antiplatelet therapy the benefit of continuing that treatment certainly outweighs the risk.

On the other hand, those patients who express that they have been having serious bleeding or have an upcoming surgery, etc., who would really benefit from discontinuing therapy, I probably would counsel them that it does make sense to discontinue therapy at this time. But I would be sure to counsel them about the slightly elevated risk that they would incur by doing so.

Dr. Yeh is an interventional cardiologist at the MGH Institute for Heart, Vascular and Stroke Care, where he is co-director of the MGH Chronic Total Occlusion Intervention Program and associate director of the MGH Cardiac Intensive Care Unit.