In the largest dataset of its kind, researchers found that 12 percent of patients undergoing aortic valve replacement developed subclinical leaflet thrombosis that reduced valve motion, according to an observational study presented March 19 at ACC.17.

In the study, 931 patients had high–resolution CT scanning after transcatheter or surgical aortic valve implantation. The CT–detected valve–associated clots were found to increase the risk of transient ischemic attacks, but were not associated with increased risk of death, heart attack or stroke.

The researchers analyzed CT scans and other health records from 850 patients enrolled in two single–center medical registries, known as RESOLVE (which included patients treated at Cedars–Sinai Heart Institute) and SAVORY (which included patients treated at Rigshospitalet hospital in Copenhagen). The patients had undergone CT scans an average of three months after transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR).

Analysis of the CT scans revealed subclinical leaflet thrombosis in 13.6 percent of TAVR patients and 3.8 percent of SAVR patients for a rate of 12.1 percent among all patients combined. In addition, a total of 14.8 percent of patients on antiplatelet therapy had thromboses compared with 4 percent among patients taking warfarin and 3 percent among patients taking non–vitamin K antagonist anticoagulants (NOACs). There was no significant difference in risk observed among those taking warfarin versus NOACs.

"We need to further study whether routine anticoagulation may be useful for this patient population," said Raj Makkar, MD, FACC, the study's lead author. "Dual antiplatelet therapy was not effective in preventing and treating subclinical leaflet thrombosis, and it does have a small risk of bleeding, particularly in older patients. There is an impetus to study the risks and benefits of dual antiplatelet therapy further in randomized clinical trials."

Analysis of a small group of patients (58) who underwent a second CT scan showed subclinical leaflet thrombosis resolved over time in the vast majority of patients who were started on oral anticoagulant therapy after the first CT scan and that thromboses resolved in only a small portion of patients who were not started on anticoagulants.

The results of this observational study do not directly assess cause and effect. Makkar noted that further study is needed, but added that the study findings "can help optimize the use of different blood thinning medications in patients undergoing aortic valve replacement, which might potentially result in further improvements in valve hemodynamics and clinical outcomes."