Leaflet thrombosis (LT) has been claimed as a potential cause of hemodynamic dysfunction or bioprosthetic valve degeneration of transcatheter heart valves. Sparse and contrasting evidence exists, however, regarding LT occurrence, prevention and treatment. MEDLINE, ISI Web of Science and SCOPUS databases were searched for studies published up to January 2020. Only studies reporting data on incidence and outcomes associated to the presence/absence of clinical or subclinical LT, detected or confirmed with a multidetector computed tomography exam were included. The study was designed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) requirements. Two reviewers independently screened articles for fulfillment of inclusion criteria. Data were pooled using a random-effect model. The primary end point was the incidence of LT. Secondary outcomes included: stroke and transient ischemic attacks and mean transvalvular gradients at different time-points in patients with and without LT. Of the initial 200 studies, 22 were finally included with a total of 11,567 patients. LT overall incidence was 8% (95% Confidence Interval [CI]: 5% to 13%, I2 = 96.4%). LT incidence in patients receiving only antiplatelets was 13% (95% CI: 7% to 23%, p <0.0001); patients discharged on oral anticoagulants had a reported incidence of 4% (95% CI: 2% to 8%, p <0.0001). Patients with LT, either clinical or subclinical, were not at increased risk of stroke (OR 1.06, 95% CI: 0.75 to 1.50, p = 0.730, I2 = 0.0%) or transient ischemic attacks (Odds Ratio 1.01, 95% CI: 0.40 to 2.57, p = 0.989, I2 = 0.0%). LT was associated with higher mean transvalvular gradients compared with patients without LT at 30 days post-transcatheter implantation, but not at discharge or at 1 year. LT is a relatively common event that, even when clinically manifest, is not associated with an increased risk of cerebrovascular events. Although patients on anticoagulants appear to be at lower risk of LT, the available evidence does not allow formulation of recommendations for prophylactical anticoagulation nor routine computed tomography after transcatheter aortic valve replacement.
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