Early thrombosis risk in patients with biologic valves in the aortic position

ObjectivePatients who require aortic valve replacement are increasingly receiving biologic valves to avoid long-term anticoagulation. The thromboembolic risk of bioprosthetic valves is reportedly low. The study objective was to review the incidence of early valve thrombosis requiring reoperation in patients who received a bioprosthetic valve in the aortic position.MethodsWe reviewed all adult patients who had a biologic valve implanted in the aortic position at Mayo Clinic between January 1993 and July 2009. Records were reviewed for all cases of reoperation that occurred less than 2 years postoperatively. Incidences of valve thrombosis were calculated including 95% Poisson confidence intervals.ResultsDuring the study interval, 4568 patients received biologic valves for aortic valve replacement. We identified 8 patients who underwent reoperation to replace the aortic prosthesis because of thrombus that resulted in functional aortic stenosis. The median age of patients at the time of reoperation was 77 years (range, 52–86), and the median time to reoperation was 398 days (range, 106–626). All patients with valve thrombosis received a stented porcine valve: St Jude Biocor (St Jude Medical, Inc, St Paul, Minn) in 4 patients, Medtronic Mosaic (Medtronic Inc, Minneapolis, Minn) in 2 patients, and Medtronic Hancock (Medtronic Inc) in 2 patients. The calculated incidence of valve thrombosis was 1.26% (confidence interval, 0.56–1.96) for the Biocor valve, 0.37% (confidence interval, 0.19–0.56) for the Mosaic valve, and 0.84% (confidence interval, 0.42–1.25) for the Hancock valve (P = .34). There were no cases of valve thrombosis in patients who received a pericardial valve (5923 patient-years) or stentless valve (172 patient-years).ConclusionsThe incidence of early thrombosis of porcine aortic bioprostheses requiring reoperation was not insignificant. Potential causes and mechanisms for such thrombosis are unknown. Recognition of this unanticipated problem and reoperation resulted in a satisfactory outcome for patients