Discussion:
Bioprosthetic valve thrombosis (BPVT) has been described previously as a rare entity in the literature. Nevertheless, with developing 4D imaging technologies, detection of subclinical thrombosis, which was previously considered degenerative, is increasing. Clinically relevant thrombosis is believed to be less prevalent. BPVT appears to be more common in Transcatheter heart valves (THV) than in surgically implanted heart valves1, possibly as a result of leaflets manipulation and crimping of pericardial leaflet tissues during transcatheter procedures, which may predispose the valve to a superimposed clot2. In a large registry of 306 patients who underwent tricuspid valve in valve procedure, eight patients had clinical thrombosis detected by TEE. At three years, the cumulative incidence of thrombosis was reported to be 0.03 percent. Three of these events in this study occurred several days following the procedure, and two of these three patients were discharged without anticoagulation.3 In another multicenter registry for transcatheter mitral heart valves, clinical thrombosis was detected in ten out of four hundred and eleven patients. The cumulative incidence of thrombosis was considerably higher in those who did not receive anticoagulation following the procedure (6.6 percent VS 1.6 percent).4 Despite the lack of consensus, these studies outline the potential benefit of anticoagulation over DAPT for THV, especially in high-risk patients with a history of clot formation and the tricuspid valve position, which is assumed to be more thrombogenic than left-sided valve position. In 26 case series with THV thrombosis, the most common echocardiographic features consistent with the diagnosis of BPVT were increased transvalvular gradients and leaflet thickness (77 percent). In contrast, thrombotic mass was found in only 23% of cases.5 Egbe et al. have proposed a practical predictive model for surgical BPVT with high sensitivity and specificity. This model incorporated five variables, each has a single score: 1. 50% increase in transvalvular gradient, 2. increased cusp thickness>2 mm, 3. abnormal cusp mobility, 4. paroxysmal AF, 5. subtherapeutic INR.6,7 Respecting similar echo findings in both surgical and transcatheter bioprosthetic valves, this model could be implemented for THVs. Applying this model to our patient yielded a score of four with 94% specificity for BPVT.
Anticoagulation is the first step in managing thrombotic bioprosthetic valves in patients who do not have contraindications, according to the 2020 ACC/AHA guideline for managing valvular heart disease1. Most documented cases demonstrated a great response to this treatment with significant improvement in leaflet mobility, thickness, and gradients8-10. There is no consensus to decide on thrombolysis or perform high-risk surgery for those with ongoing symptoms and/or hemodynamic deterioration, such as this case. Thrombolysis is a promising treatment for Mechanical tricuspid valve thrombosis. In a therapeutic outcome study for tricuspid mechanical valve thrombosis, 41 patients received fibrinolytic therapy without intracranial or gastrointestinal bleeding and two episodes of retroperitoneal bleeding. The success rate was 84%11. The other study compared five thrombolytic regimens for treatment of prosthetic valve thrombosis, including 10 cases of the mechanical tricuspid valve, reported an 85% overall success rate for ultra-slow infusion of alteplase and the lowest complication rate compared to the other regimens. No complication was reported in patients with the tricuspid position of heart valve12. There are no published articles describing the use of fibrinolysis in bioprosthetic valves, and we found only one case report of thrombolytic therapy for transcatheter heart valve thrombosis. Akhras et al. demonstrated a case of transcatheter mitral valve thrombosis early after the procedure and significant improvement of gradients and sPAP eight hours after alteplase infusion at a rate of 10mg/hr13. Given the high likelihood of success for thrombolysis in tricuspid prosthetic valve thrombosis, the heart team preferred trying fibrinolysis to high-risk 4do surgery. Ultra-slow infusion of alteplase 1 mg/hr for 25 hr was chosen since it has been described in the literature as an efficient regimen with a low complication rate 12,14. Although the safety and efficacy of thrombolysis and the best regimen in these situations warrant further investigations, this treatment was shown to be safe and effective without any complication and could be considered in similar cases.