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QICC 2016|Yang Yuejin:What is the Future of TAVR in China—Domestic Valve vs. Imported Valve?

Date:2016-11-18 13:39

Since Professor Alain Cribier of France successfully completed the world's first case of aortic valve replacement (TAVR) surgery in 2002, the technology has been in development for more than 10 years, which leads to the accumulation of abundant clinical experience in this field at home and abroad. At the same time, there has been a heated discussion among clinicians about the merits of domestic and imported valves. On September 24th, 2016, Professor Yang Yuejin, from Fuwai Hospital of the Chinese Academy of Medical Sciences, made an excellent speech in the TAVR session of 10th Qian Jiang International Cardiovascular Congress.
General Situation of TAV
ercutaneous aortic valve replacement has been widely used around the world (except Africa and the Middle East) and so far, 250,000 patients have successfully received this surgery. At present, TAVR accounts for 32% for all the valve replacement, about 50% of the valves are SAVR Mech and one third of the valves are TF TAVR and TA TAVR.
CE has approved a variety of valves for clinical use (Figure 1) from 2007 to 2015. While SAPIEN THV and CORE VALVE were used in 2007, SAPIEN 3 and ACURATE NEO were already used in 2014.  And in 2015 EVOLUT R was  developed, showing a rapid progress.

Figure 1: Valve Type Approved By CE From 2007 to 2015

The outflow of MDT Evolut R is slightly shorter, suitable for transportation when compared to CORE VALVE. Secondly, the inflow is sealed to prevent paravalvular leakage. The external skirt of Edwards Sapien 3 is also made to prevent paravalvular leakage(Figure 2)

Figure 2: Design Features of MDT Evolut R and Edwards Sapien 3
Medtronic 2.0 uses the original valve design, manufacturing process and the treatable range for annulus, but adds a porcine pericardial tissue to the external skirt for reinforcement and inflow is improved for the prevention of paravalvular leakage. It also uses 20 Fr delivery systems, including 26/29 mm CLS, which can handle 26 / 29 mm TAV.
Edwards Sapien 3 adopts Axela Sheath 5.5 mm vessel indication, suitable for a variety of valve penetration. The valve can be packaged in advance and it is suitable for most femoral artery. The head of the drive system is significantly shortened and the stent does not need to be pre-installed (has already pre-installed). The pusher has been skived, which needs one hand operation to locate the valve.
Venus A-valve of Venus Medtech is the first independently researched and developed valve product in China. The most significant feature of Venus A-valve is the addition of two markers and 3 hooks, conducive to positioning and preloading. The valve uses a manual system , convenient for location and implantation. 18 Fr and 20 Fr capsule can be adopted. At present, Venus A-valve has completed clinical trial, the mortality rate of which is 4.6% and 8% in a year.
Domestic MicroPort VitaFlow Valve uses a self-expanding Nitinol valve frame and is divided into inflow, mid and outflow portion. The bovine pericardial leaflets have received anti-calcification treatment. The lower dress design is made to prevent perivalvular leakage. The different sizes include 21,24,27 and 30, with the conventional size 18F and the large valve size 20F  and manual and electronic handle for selection. 
Therapeutic Status of TAVR
PARTNER trials found that while all-cause mortality rate of 5-year-control group of PARTNER Cohort B was 93.6%, that of TAVR group fell to 71.8%. In comparison, the 5-year mortality rate of SAVR and TAVR in Cohort A were 69.3% and 69.8%, with no statistic difference (P = 0.76) (Figure 3).

Figure 3: PARTNER Cohort A and Cohort B
ACC 2014 released CoreValve US high-risk patients with TAVR and surgical trial results (Figure 4). The mortality rate of 30-day surgical group was19.1% and TAVR group was 14.2%, with no statistic difference. The 1-year mortality rate in surgery group was 19.1% and the rate in TAVR group fell to 14.2%, with no statistic difference (P=0.04).

Figure 4: CoreValve Surgery and TAVR Effects Analysis
PARTNER 2A test results published at ACC2016 annual meeting showed that TAVR is non-inferior to SAVR. PARTNER 2A was the first large-scale randomly controlled and non-inferiority trial which compared intermediate risk patients with TAVR and SAVR. A total of 2032 intermediate risk patients were enrolled in the trial, which was performed by cardiologists and surgeons together. The TAVR group used Edwards' second-generation valve SAPIEN XT, of which 76% of the patients used the femoral artery path. The trial endpoint was a 2-year all-cause death and disabling stroke. Secondary end point included vascular complications, pericardial leakage, bleeding, acute renal failure during hospitalization and other symptoms. Two groups of patients were in good ration in terms of age, gender and STS score. PARTNER 2A results showed that in patient population, the primary end points of response rate were 19.3% and 21.1% in 2 years in TAVR group and the surgical treatment group (HR=0.89;95%CI 0.73~1.09;P=0.001). In terms of patients, end points of response rate were 18.9% and 21% respectively (HR = 0.87; 95% CI 0.71-1.07; P <0.001). In the femoral artery group, the primary end point rate of TAVR was lower (HR = 0.79; 95% CI 0.62 ~ 1), but there was no difference between the two treatment methods in the thoracic approach group.
The trial also found that while the patients in TAVR group had greater aortic valve area, lower risk of acute kidney injury, serious bleeding and rate of new atrial fibrillation, the surgical treatment group had lower incidence rate of major vascular complication and aortic regurgitation. The main conclusion of the trial was that the effect of middle-to-high risk patients with TAVR is not inferior to those with surgical treatment. And in femoral approach subgroup, TAVR was even superior to surgical treatment.

Figure 5: PARTNER 2A Trial Result Analysis
Future Prospect of TAVR 
At present, TAVR still leads to several problems like vascular complications, stroke, paravalvular leakage and implantation of a pacemaker, so its long-term effects should be further studied. The future target is that TAVR should be the procedure of choice for all the severe AS patients, with all-cause mortality rate <3%, major stroke rate  <2%, vascular complications rate <5%, pacemaker rate <10%, moderate to severe regurgitation rate < 5%.
In the future, improvements should be made in such aspects as valve, frame, delivery system and deployment method. The valve mainly should focus on the tissue components and processing (including pericardium, thickness, anti-calcification, etc), construction and location, durability considerations and other novel features (including 3D single-leaflet construction, low-stress sealing and other technologies); in terms of structure, a variety of materials can be chosen and the composition of “stent-like” geometry with mesh or solid patterns and shape variations is the best choice. The delivery system should mainly consider profile (OD/ID) throughout full length to achieve the desired effect that both cardiac apex and femoral artery can adopt. The deployment method should mainly consider balloon expansion, self-expanding, and other designs and recycle features. Perivalvular leakage reduction should mainly concentrate on frame and positioning, sub-annular fixation, external skirts and coating, and other novel features.
 
Conclusion: What is the Future?
Whether domestic or imported, the ideal valve must be able to meet clinical needs. The ideal system size is ≤ 18 and ≤16 better. The outer diameter can be used for all the valves and >90%~95% via femoral artery. Recyclability is important in clinical applications as well.  The ideal TAVR should also prevent the occurrence of PVL and its life cycle needs to satisfy the clinical requirements and prevent serious complications at the same time.
 
 
This article is reproduced from the magazine Clinic

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