Transcatheter aortic valve replacement: Role of anesthesiologists.

According to American College of Cardiology/American Heart Association (ACC/AHA) 2014 guidelines,[1] aortic valve replacement (AVR) is a Class I indication for severe symptomatic aortic valve stenosis (AS). Even then, one-third of the patients were not referred or rejected for surgical AVR due to multiple comorbidities, advanced age, left ventricular dysfunction, chronic renal disease, and frailty. Transcatheter AVR (TAVR) has effectively filled this gap allowing a minimally invasive treatment option for sick and elderly patients with severe AS. The technique and technology have made rapid progress, surpassing the volumes of surgical AVR in many centers.

TAVR with the SAPIEN valve (Edwards Life sciences, Irvine, California, USA) was shown to be superior[2] to medical treatment in the Placement of Aortic Transcatheter Valve (PARTNER) B trial, which found a reduction in mortality through 5 years of follow-up in patients deemed inoperable (93.6% vs. 71.8%; P < 0.0001). Comparable results were obtained in extreme risk patients treated with the Medtronic CoreValve (Medtronic, Minneapolis, Minnesota) transcatheter heart valve.[3] In patients with severe AS at high surgical risk included in the PARTNER 1A cohort, TAVR using the balloon expandable SAPIEN prosthesis showed similar safety and efficacy compared with surgical AVR during long-term follow-up (67.8% vs. 62.4% overall mortality; P = 0.76).[2] On the basis of these data, TAVR was recommended as the therapy of choice for inoperable patients with symptomatic severe AS with a life expectancy longer than 1 year (Class I, B) and an alternative to surgical AVR in patients considered at increased surgical risk (Class IIa, B) in ACC/AHA 2014 guidelines and European guidelines. However, in the 2017 focused update, TAVR was given Class I indication in high-risk patients similar to surgical AVR and those with intermediate risk getting a Class IIA recommendation-based PARTNER II trial, which showed noninferiority of TAVR in intermediate-risk patients.[4] Inoperable patients carry a 50% composite risk of mortality and morbidity, and high-risk patients carry Society of Thoracic Surgery (STS) PROM score of 8–15%. All high- risk and intermediate-risk patients require a heart team to assess the suitability of TAVR [Figure 1].

Figure 1

Algorithm for the management of severe aortic valve stenosis. For intermediate-risk and high-risk patients for TAVR; decision is made by a heart team (2). SAVR: Surgical Aortic Valve Replacement, TAVR: Transcatheter Aortic Valve Replacement

Vascular complications, acute kidney injury, paravalvular leak, and increased requirement of pacemakers remain a major concern for TAVR.[5] Transesophageal echocardiography (TEE) helps in the proper sizing of the prosthesis, for accurate guiding of valve deployment as well as detection and quantification of paravalvular leak. The three major mechanisms of paravalvular leak are suboptimal placement of prosthesis with incomplete sealing of the annulus, incomplete apposition of valve stent frame due to extensive calcification, and undersizing of the prosthesis. Even mild paravalvular leak has a negative impact on survival. In a large data, mild paravalvular leak was reported in 38% of patients and moderate to severe in 9.1% of patients after TAVR.[5] Valve Academic Research Consortium defines mild, moderate, and severe paravalvular leak as <10% between 10% and 29% and >30% as an extent of prosthetic frame circumference.[6] Significant paravalvular leaks in hypertrophic, poorly complaint left ventricle are very poorly tolerated. Aortic root angiography may not be able to differentiate paravalvular with intravalvular regurgitation. TEE is more appropriate for identifying and quantifying paravalvular leak.

If significant paravalvular leak occurs after deployment, further balloon dilation of prosthesis can be considered under TEE guidance. Excessive overdilation increases the risk of annular rupture. Significant residual paravalvular leak may require redeployment, valve-in-valve deployment, percutaneous device closure, and sometimes may require emergency surgery. TEE is thus a very valuable tool in assessing and guiding TAVR and quantification of paravalvular leak, limiting the volume of contrast injected, thus reducing the potential of acute kidney injury. However, recent studies and registries have shown decreased rates of paravalvular regurgitation. This is attributed to improved case selection, improved periprocedure techniques, and increased procedural experience and better technology. Newer valves such as Edwards SAPIEN 3 have a sealing skirt and more accurate mechanism of valve positioning to reduce the rate of paravalvular leaks.

Case selection and procedural experience seem to be the most important variable, in reducing the incidence of paravalvular leak and shortening the procedure time. Hence, in very experienced centers (like reported in this article),[7] only conscious sedation is used for performing TAVR while general anesthesia with TEE was reserved for patients who are at the highest risk and more technically difficult TAVRs. In the future, newer technology using small vascular access sheaths, expanding off-label[8] indications, and with the reduction in the valve cost should see an exponential increase in the number of TAVRs performed in India. However, it may be prudent to start the TAVR program using general anesthesia and TEE guidance till sufficient procedure experience is gained. After sufficient experience, there could be two subsets of patients; where one group may be suitable for conscious sedation and day care procedure while another group with high periprocedural risk may be suitable for TAVR using general anesthesia and TEE guidance. Anesthesiologists will have important roles to play in the decision-making process in Heart Team meeting, periprocedural echocardiography guidance for the TAVR deployment and managing these complex cases inside the hybrid OR and postoperative intensive care unit.