Sub-clinical valve thrombosis in the setting of bioprosthetic aortic valves

Bioprosthetic aortic valves have played a critical role in improving both quality of life and prognosis in patients with severe aortic valve disease. Implanted either surgically (SAVR) or percutaneously (TAVI), they provide restoration of valve function without the need for anticoagulation as required with mechanical valves.  This study was the result of clinical evaluation of a patient with a stroke soon after TAVI.  This evaluation included CT imaging of the bioprosthetic valve which revealed restricted leaflet mobility and prompted further inquiry.  Using data from a TAVI randomized trial and 2 registries of patients with both TAVI and SAVR, the authors went on to evaluate 187 patients who underwent CT and echocardiographic imaging during the first 12 months after bioprosthetic valve implantation in the aortic position.  The authors found reduced leaflet motion was not uncommon with 40% of patients in the clinical trial and 13% in the two registries having findings of moderate to severe restriction in 1 or more valve leaflets.  Although the cause of restricted motion could not be determined definitively, imaging suggested thrombus at the base of the valve leaflets that impaired normal leaflet excursion.  The possibility that thrombus was the causal factors was further suggested by the lack of impaired leaflet motion in any patient who was anticoagulated with warfarin.  In addition, among patients with restricted leaflet motion, restoration of leaflet motion was found in 100% of patients who were subsequently started on warfarin as compared with 10% of patients not anticoagulated (P<0.001).  Interestingly, abnormalities in leaflet motion could not be seen on standard transthoracic echo imaging and there was no evidence of an increased gradient across valves with restricted leaflet motion by CT or TEE.  The clinical consequences of this finding remain unclear with no increase in stroke or TIA patients with restricted leaflet motion, although the sample size was small.

Conclusion

Using advanced imaging techniques, reduced motion of bioprosthetic aortic valves was commonly observed and suggestive of subclinical valve thrombosis.  The clinical consequences of this finding remain uncertain and further study is warranted to ascertain optimal imaging approaches and management of this finding.

Summarized by Hussain Contractor and Steven M. Bradley

Makkar RR, Fontana G, Jilaihawi H, Chakravarty T, Kofoed KF, de Backer O, Asch FM, Ruiz CE, Olsen NT, Trento A, Friedman J, Berman D, Cheng W, Kashif M, Jelnin V, Kliger CA, Guo H, Pichard AD, Weissman NJ, Kapadia S, Manasse E, Bhatt DL, Leon MB, Søndergaard L. Possible Subclinical Leaflet Thrombosis in Bioprosthetic Aortic Valves. N Engl J Med. 2015 Oct 5. [Epub ahead of print]

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