Thrombosis of aortic valve leaflets raises concern of increased stroke risk

By John Murphy, MDLinx
Published January 21, 2016

Key Takeaways

Patients with aortic stenosis who undergo bioprosthetic valve replacement may be at greater risk for thrombosis of the valve leaflet (flap), which could lead to embolic stroke, according to an investigation published online October 5, 2015 in the New England Journal of Medicine.

The FDA issued a statement that “bioprosthetic aortic valves remain reasonably safe and effective,” but the agency will continue to evaluate their performance. 

Investigators also reported in their study that anticoagulant medications, such as warfarin, quickly resolve thrombosis and restore leaflet motion in the bioprosthetic valves.

“We are not recommending that all patients with these devices be on blood thinners, but clearly further studies need to be done to define best medication regimens,” said lead investigator of the study Raj Makkar, MD, Director of the Interventional Cardiology and Cardiac Catheterization Laboratory at Cedars-Sinai Medical Center, in Los Angeles, CA.

Dr. Makkar began the study when he noted that a patient who had a stroke after transcatheter aortic valve replacement (TAVR) showed thrombosis and reduced motion of the aortic valve leaflet on computed tomography (CT).

“We wanted to find out if patients undergoing a tissue valve procedure are susceptible to blood clots on the leaflets and study the clinical consequences of the same,” Dr. Makkar said. “We also wanted to understand whether our aortic valve patients were more susceptible to having blood clots and whether those clots could indicate that the patient might experience a neurological complication,” such as transient ischemic attack.

Dr. Makkar and colleagues reviewed data from 55 patients in the PORTICO IDE clinical trial of TAVR and from two single-center registries—RESOLVE and SAVORY—that included 132 patients undergoing either TAVR or surgical aortic-valve bioprosthesis implantation.

After analyzing the data, the investigators observed reduced leaflet motion on CT in 40% of patients (22 of 55) in the clinical trial, and in 13% of patients (17 of 132) in the two registries. They also found that therapeutic anticoagulation with warfarin decreased the incidence of reduced leaflet motion to zero.

“These observations suggest that the observed reduced leaflet motion is due to thrombosis,” the investigators concluded. “Normalization of leaflet motion with anticoagulation also suggests that thrombus formation is the primary event leading to reduced leaflet motion rather than reduced leaflet motion leading to the formation of an overlying thrombus.”

Regardless, these findings raise the concern that patients undergoing bioprosthetic aortic valve replacement could be at greater risk for leaflet thrombosis and, consequently, embolic stroke, the investigators noted.

However, they added, this finding of a higher incidence of stroke is preliminary and inconclusive. Only 6 neurologic events occurred among all patients (3 strokes and 3 transient ischemic attacks), “and all strokes occurred within 1 day after the TAVR procedure and before four-dimensional CT was performed. It is more likely that these first-day strokes were related to the procedural aspects of TAVR rather than to leaflet thrombosis,” the researchers wrote.

Still, further research is needed to answer the many questions raised by this study, the investigators cautioned.

On a similar note, the FDA issued a statement that reduced leaflet motion in the bioprosthetic aortic valves is “of unknown clinical significance,” but that the agency “believes that the benefits of using these devices for the currently approved indications continue to outweigh the risks.”

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