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Transcatheter Aortic Valve Thrombosis
Study Questions:
What are the frequency, predictors, and implications of device thrombosis following transcatheter aortic valve replacement (TAVR)?
Methods:
This study examined 405 patients with both cardiac computed tomography (CCT) and echocardiography performed between 1 and 3 months following balloon-expandable TAVR at a single center. TAVR thrombosis was defined as hypo-attenuated leaflet thickening of the prosthesis on CCT. Patients were treated with dual antiplatelet therapy, unless there was a history of atrial fibrillation, in which case warfarin alone or with a platelet inhibitor was used at the discretion of the physician.
Results:
TAVR thrombosis was noted by CCT in 28 of 405 (7%) patients; 23 (6%) cases were subclinical, whereas five (1%) had obstructive thrombosis. The risk of valve thrombosis in patients not receiving warfarin was higher compared to those on warfarin (10.7% vs. 1.8%; relative risk [RR], 6.1; 95% confidence interval [CI], 1.9-19.8). A larger prosthesis was associated with an increased thrombosis risk (p = 0.03). Valve generation or other characteristics were not associated with risk of thrombosis. On multivariable analysis, a 29 mm prosthesis (RR, 2.9; 95% CI, 1.4-5.8) and no post-TAVR warfarin treatment (RR, 5.5; 95% CI, 1.7-17.7) independently predicted prosthesis thrombosis. In the 28 patients with thrombosis, warfarin alone was used in four, warfarin with antiplatelet therapy was used in 17, and three patients already on warfarin were continued on this with a higher target international normalized ratio of 2.5-3.0; no warfarin was used in four patients. Treatment with warfarin resulted in resolution of valve thrombosis in 85% of patients.
Conclusions:
Prosthesis thrombosis following balloon-expandable TAVR was observed in 7% of patients on early follow-up, although only 1% of patients had valve obstruction. Baseline warfarin use or the use of smaller valves was associated with lower rates of valve thrombosis, while initiation of warfarin was associated with a high rate of resolution.
Perspective:
Device thrombosis was common (7%) on early follow-up after balloon-expandable TAVR, although most cases were subclinical at the time of diagnosis. The optimal diagnostic and treatment strategies are still being evaluated for post-TAVR thrombosis, but CCT and echocardiography (transthoracic and potentially transesophageal) appear to have complementary roles for the diagnosis. Warfarin appears to markedly reduce the incidence of valve thrombosis and results in a high rate of resolution once initiated for thrombosis. These results are helpful in understanding this disorder, but diagnostic and treatment strategies need to be fully examined in prospective clinical trials.
Keywords: Atrial Fibrillation, Anticoagulants, Cardiac Surgical Procedures, Diagnostic Imaging, Echocardiography, Heart Valve Diseases, International Normalized Ratio, Platelet Aggregation Inhibitors, Prostheses and Implants, Risk, Thrombosis, Tomography, Transcatheter Aortic Valve Replacement, Warfarin
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