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.