Bioprosthetic Valve Thrombosis vs. Structural Failure
What are the diagnostic features of bioprosthetic valve thrombosis, and can a diagnostic model be created?
Cases of bioprosthetic valve thrombosis at the Mayo Clinic that occurred between 1997 and 2013 were identified from a pathology database. Patients with valve thrombosis were matched 1:2 based on age, sex, and prosthesis position with patients in whom a bioprosthesis was explanted due to structural valve deterioration (SVD). A diagnostic model for bioprosthetic valve thrombosis was formulated using multivariate linear regression and receiver-operating characteristic.
Among 397 consecutive cases of explanted bioprostheses, there were 46 cases (11.6%) of bioprosthetic valve thrombosis (29 aortic, nine mitral, seven tricuspid, one pulmonary; mean age 63 years, 68% male). Thirty cases (65%) occurred >12 months after valve implantation. Among this group, median bioprosthetic valve durability was 24 months compared to 108 months in patients operated for SVD (p < 0.001). Independent predictors of bioprosthetic valve thrombosis were >50% increase in Doppler mean gradient from baseline within 5 years (odds ratio [OR], 12.7), increased cusp thickness (OR, 12.2), abnormal cusp mobility (OR, 6.9), subtherapeutic international normalized ratio (OR, 7.4), and paroxysmal atrial fibrillation (OR, 5.2). The presence of all five diagnostic features was predictive of bioprosthetic valve thrombosis with a sensitivity 76%, specificity of 93%, positive predictive value of 85%, and negative predictive value of 89% (p < 0.001).
The authors concluded that bioprosthetic valve thrombosis is not uncommon, and can occur several years after surgery. They believe that a combination of clinical and echocardiographic features can reliably diagnose bioprosthetic valve thrombosis.
There is increasing awareness of what might be low-grade thrombus associated with bioprosthetic surgical and transcatheter valves early after implantation (see Makkar RR, et al., N Engl J Med 2015;373:2015-24). In contrast, this single-center retrospective review addresses surgical bioprosthetic valve thrombosis. An important message might be that valve thrombosis can and does occur in the setting of bioprostheses. Whether the clinical criteria described in this cohort have diagnostic power in other patient populations will require additional testing.
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