Page 34 - Journal of Structural Heart Disease Volume 3, Issue 2

Case Report
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Discussion
Although there is an increasing number of reports of successful transcatheter deployment of biological valves in the tricuspid position, this is not yet stan- dard of care. In 2011, a study of 15 patients from eight medical centers reported successful deployment in 12 patients without complication [10]. A more re- cent study of 10 patients, including ve with Ebstein’s anomaly, reported only one complication of valve mi- gration post-deployment [11]. The largest experience to date is a multi-center database of TVIV implants detailing the outcomes and 1-year follow-up of 156 patients with TVIV, which demonstrated no proce- dural mortality and excellent short- to medium-term outcomes [6]. Our two cases involved speci c com- plexities of the procedure and post-implantation out- come, demonstrating our approach to their manage- ment.
Among these patients, it is important to identify the primary diagnosis because Ebstein’s anomaly is associated with complex hemodynamics. Patients with Ebstein’s anomaly often su er from RV dysfunc- tion and restrictive diastolic function and may have undergone numerous surgical repairs and replace- ments. Moreover, they are at increased risk for both atrial and ventricular arrhythmias [12]. As the mor- bidity and mortality risk associated with surgical TV replacement is often high [5], the excellent short- and intermediate-term outcomes of trans-catheter valve replacement make it a viable alternative.
Surgical TV replacement is most often performed using bioprosthetic valves. There is limited experi- ence with mechanical valves in this position, and there is a concern for a higher risk of valve throm- bosis in the tricuspid position [13]. It has tradition- ally been recognized that the primary mode of bio- prosthetic TV failure is structural deterioration with resultant calci cation and progressive stenosis and regurgitation. However, recent studies show that bioprosthetic valve thrombosis (BPVT) is common and a more underdiagnosed mode of failure than originally thought [14, 15]. The estimated prevalence of BPVT in the tricuspid position is 12%, resulting in early failure of the valve usually occurring within 5 years of implantation. BPVT of a tricuspid biopros- thesis is usually insidious in presentation and re-
sults from an elevation in central venous pressure, which symptomatically is much less dramatic than left-sided valve thrombosis with a resultant eleva- tion in left atrial pressure and pulmonary edema [13, 16]. Pathognomonic signs of BPVT include an acute rise in transvalvular gradient of more than 50% over baseline in the short- to medium-term, paroxys- mal atrial brillation, increased cusp thickness, de- creased cusp mobility, and sub-therapeutic interna- tional normalized ratio [16]. BPVT was highly likely in Case 1, in which there was a sharp increase in valve gradient (>50%) within 8 months after Melody valve placement. The initiation of anticoagulation resulted in a dramatic improvement in valve gradient, which provides additional support for the assertion that this was early BPVT. The use of non-vitamin K antag- onists for anticoagulation following bioprosthetic valve replacement has not been well studied but in this case proved e ective.
Percutaneous valve replacement of native TVs presents with additional challenges due to the lack of secure circumferential sca olding provided by surgical bioprostheses. The native annulus is highly distensible and is not a stable landing zone for balloon-dilated transcatheter valves. In patients with annuloplasty bands or rings of the TV, a transcatheter valve-in-ring approach is feasible. Case 2 demonstrates that such an approach is possible in patients with incomplete an- nuloplasty rings from previous TV repair.
It should be noted that an incomplete ring annu- loplasty does not supply the same level of support as a previously placed bioprosthetic valve. PVL is common and should be expected, especially in the medial open part of the ring. However, this can be readily treated with transcatheter vascular plug/ occluder deployment at the time of valve implanta- tion. PVL can be progressive, as in Case 2, and may require additional vascular plug placement during follow-up.
Additionally, it is important to recognize that the reduced radial support along the open portion of the existing ring could ostensibly lead to deformation of the bioprosthetic valve. Su cient loss of circular shape could prevent the lea ets from coapting as originally designed, potentially resulting in regurgita- tion. However, despite the loss of the circular shape in Case 2, there was minimal intravalvular regurgitation.
Journal of Structural Heart Disease, April 2017
Volume 3, Issue 2:55-61