Transcatheter aortic valve‐in‐valve implantation for procedural related aortic regurgitation

Transcatheter aortic valve replacement (TAVR) is becoming an established treatment for no-option or high-risk patients with severe symptomatic aortic stenosis (AS). However, the TAVR procedure is challenging and demands technical precision and procedural expertise. Post-procedural aortic regurgitation (AR) is one of the major problems with TAVR [1]. Paravalvular leaks are extremely rare in surgical aortic-valve replacement, observed in just few of operative cases (1–2%) [2]. However, AR is a common finding after TAVR [1]. Mild AR after TAVR occurs up to 60% and moderate to severe AR is described up to 17% [3-7]. Significant AR is defined as AR ≥ 2 over a scale of 4. This phenomenon has been described using both the Sapien (Edwards Lifesciences, CA) and the CoreValve (Medtronic, MN) implants. The PARTNER cohort A trial showed a higher rate of moderate or severe paravalvular AR within the TAVR group compared to surgical treated patients at 30-day (12.2% vs. 0.9%) and after one year (6.8% vs. 1.9%) [4]. The FRANCE 2 TAVR registry reported a 16.5% rate of grade moderate or severe AR (Sapien 13.9% and CoreValve 21.5%) [7]. In the German TAVR registry, in-hospital death rates were significantly higher in patients with significant AR than in those with no or mild AR (15.1% vs. 6.7%), as were rates of low cardiac output (20% vs. 4.4%) and respiratory failure (16.5% vs. 7.1%) [6]. Significant AR occurred in 17.2% of the patients. Using multivariate analysis, the presence of moderate to severe post-procedural AR remained a strong independent predictor of in-hospital death (adjusted OR = 2.43). Thus, the overall consensus is that higher amount of AR following TAVR is significantly associated with reduced short- and long-term survival. There are different reasons for occurrence of post-procedural intra-valve or paravalvular AR. This can occur due to: (1) valve under-sizing caused by too small prosthesis implanted within a relatively large aortic annulus leading to incomplete apposition, (2) valve under-expansion within the heavily calcified annulus causing impaired leaflet coaptation and intra-valve leak, (3) prosthesis malfunction due to technical failure (e.g., frozen leaflet), (4) valve malpositioning caused by “too high” or “too low” implantation into the aortic root or left ventricle outflow tract, respectively, and (5) very oval shaped annulus with incomplete prosthesis sealing and/or valve alignment due to deformed prosthetic frame. Valve under-sizing and malpositioning are probably the most common causes of TAVR-related AR. Tremendous malpositioning can cause severe acute AR and immediate hemodynamic collapse. Thus, it mandates emergent life saving treatment using another valve implantation. Significantly low implantation can cause severe paravalvular regurgitation, residual stenosis, mitral insufficiency, conduction abnormality, and in extreme cases, device drop into the left ventricular cavity. Considerably high implantation could result in paravalvular regurgitation, coronary flow obstruction, and device embolization. These complications could lead to clinical instability and occasionally require further interventions, such as implantation of another device or an emergent surgery. Therefore, careful procedural planning and implantation technique is required to ensure precise positioning and avoidance of these problems. Severity of AR can be evaluated by aortic root angiography or using echocardiography with color Doppler. Also, hemodynamic assessment immediately after TAVR can detect the loss of aortic dicrotic notch, a high left ventricular end-diastolic pressure (LVEDP) and a minimal or no separation between the lower than normal diastolic aortic pressure and higher than normal LVEDP. Altogether, those are warning signs of hemodynamic significant AR that is life threatening and mandates urgent corrective treatment. In this context, Giri et al. describe herein the clinical and procedural outcomes of patients treated with the valve-in-valve technique for severe AR after implanting the Sapien device [8]. In their series, among 142 patients undergoing TAVR in University of Pennsylvania medical center, five (3.5%) patients needed the valve-in-valve technique to correct for aortic valve insufficiency. The etiology was bioprosthesis malposition, valve dysfunction, and valve under-sizing on those cases. With placement of the second valve, the first valve dimensions increased to approach the nominal valve size while the second valve size remained less than nominal. Procedural success was obtained in four of the five patients and one patient required cardiopulmonary bypass and died of complication. Of particular note, two of the five patients suffered strokes. Also, one patient had a higher than usual mean gradient across the two superimposed valves. This is an interesting report. Indeed, the treatment options of significant AR after TAVR are dependent upon the mechanism of malfunctioning. In case of valve malposition, implantation of a second prosthesis above or below the original valve as a valve-in-valve procedure can immediately correct the leak problem and restore hemodynamics. Preliminary results of this approach seemed to be encouraging in a previous larger report but the long-term safety and durability of this approach await more confirmatory data [9]. Also, it is yet unknown whether the clinical outcome of the valve-in-valve approach is comparable between the balloon expandable and the self-expandable valves. In case of paravalvular AR due to incomplete prosthesis apposition, a post-dilatation can be performed within the implanted valve. In cases with hemodynamic instability and AR of mild to moderate degree, conservative management could be the elected strategy as some leaks would probably improve spontaneously over time [10, 11]. In selected cases, implantation of a plug can be performed for the treatment of paravalvular AR. Finally, emergent open-heart surgery for valve replacement should be considered in some cases although the TAVR patients are by definition poor surgical candidates with prohibitive risks for surgical treatment. The current report highlights the needs for precise valve sizing and/or positioning compared to the native aortic valve annulus. Failure to achieve an accurate valve sizing or placement would result in exaggerated AR. Also, whether balloon expandable or a self-expandableTAVR device is used, well controlled, properly sized, and precise valve positioning in the correct annular plane is mandatory to assure procedural success with minimal or no residual AR. Recent literature supports the use of multi-slice CT (MSCT) perimeter and cross-sectional area parameters over echocardiography as the recommended methods for optimal valve sizing and reduced paravalvular leaks [12-14]. The use of live guidance systems such as the Paieon C-THV technology (Paieon Medical, Park Afek, Israel) and rotational 3D cineangiography imaging could be of great potential in facilitating the proper positioning of the TAVR device online [15]. In summary, TAVR adoption is increasing worldwide. AR is a common finding after TAVR and when severe, it seems to be associated with poor prognosis. Post-TAVR severe AR is life threatening and demands proper and immediate management. Careful procedural planning using echocardiography and particularly MSCT imaging is mandatory for correct valve sizing. In case of inappropriate valve sizing or positioning causing severe AR, urgent valve-in-valve implantation technique is a life saving bailout treatment. The long-term safety and efficacy of this ad-hoc therapeutic strategy should be further explored. Finally, when performing TAVR, always have an additional valve on site, just in case.