Subclinical leaflet thrombosis of bioprosthetic aortic valves is characterized by hypoattenuated leaflet thickening (HALT) and reduced leaflet motion of the bioprosthetic valve leaflets noted on 4-dimensional computed tomography (CT). The early reports on subclinical leaflet thrombosis noted this finding to be present in up to 10% to 15% of patients after transcatheter aortic valve replacement (TAVR), more frequently in transcatheter compared with surgical bioprosthetic valves.[2–4] This finding was routinely missed on transthoracic echocardiograms because of the relatively normal aortic valve gradients.[1,2] A few studies also noted an association between subclinical leaflet thrombosis and neurological events (strokes or transient ischemic attacks).[1,2] Anticoagulation was noted to be effective in the prevention of subclinical leaflet thrombosis in both randomized trials and registries1,2,6 and in the treatment of subclinical leaflet thrombosis in registries.[1,2,4] After these initial reports, the US Food and Drug Administration mandated incorporation of CT substudies into the low-risk TAVR trials to understand the natural history of subclinical leaflet thrombosis. At the same time, several industry-sponsored randomized trials were initiated to evaluate the impact of routine anticoagulation after TAVR on clinical outcomes and subclinical leaflet thrombosis. Although many questions concerning subclinical leaflet thrombosis have been answered in randomized clinical trials, several questions remain unanswered.