1 Introduction

One of the most common types of valvular heart disease in the elderly population is aortic stenosis (AS). As the ageing population increases, the prevalence of life-threatening,severe AS will rise.[1] In the US population over 75 year old,12.4% suffer from AS. The current practice regarding severe symptomatic AS is surgical aortic valve replacement(SAVR), but the treatment options has evolved noticeably.[2,3] Transcatheter aortic valve replacement (TAVR) has emerged as a new alternative approach in patients at high surgical risk. Comparison of the two methods is essential for selecting the ideal therapy in each patient. In the current review, we provide all the most recent data regarding the efficacy and safety of TAVR over SAVR, as well as important issues regarding complications’ pattern and incidence of the two techniques.[3]

2 Historical background

The first transcatheter aortic stent valve in animals was described in 1992, by Andersen, et al.[4] presenting the results of the implantation in pigs. It is notable that the first transcatheter aortic stent valve was implanted in humans, in 2002, using the transeptal approach and femoral vein access due to the bulky characteristics of the first device.[5] In 2005,due to the technology progression, novel techniques and tools led to change the way we approach the patient from the femoral vein to the transfemoral artery position, making the technique easier for the doctor and the patient as well.[6]TAVR, in general, is indicated for high risk patients, using the appropriate risk scores, who suffered from severe symptomatic AS. Currently, FDA expanded the approval for the TAVR technique, for special device, for people with symptomatic AS who are considered to be not only high risk but intermediate as well. The two procedures are completely different since SAVR remains a well standardized technique for most of the patients, but TAVR tends to be the approach for most of them during the following years. The current commercially used valves and the most important characteristics of them are listed in Table 1.

3 Major trials comparing TAVR versus SAVR

3.1 TAVR in high risk patients

The first large trial which compared the TAVR versus standard treatment in high-risk inoperable patients was the PARTNER 1B study.[7] The trial showed superior outcomes from TAVR versus conservative treatment for death from any cause and death from cardiovascular causes. This was a revolutionary step which changed the way physicians approached inoperable patients with severe symptomatic AS.The next step was the PARTNER 1A trial, where 699 high-risk patients with severe AS were randomly assigned to undergo either TAVR with a balloon-expandable bovine pericardial valve (both either transfemoral or the transapical approach) or SAVR.[8] The authors concluded that in highrisk patients with severe AS, the two procedures were associated with similar rates of death from any cause at 1 year.At 30 days, major vascular complications (11.0% vs. 3.2%,P ＜ 0.001) and rates of stroke (8.3% vs. 4.3%, P ＜ 0.05)were more frequent with TAVR over SAVR. The results were consistent even in the 2-year follow up with mortality rates 33.9% for TAVR vs. 35.0% for SAVR (P = 0.78).Importantly, TAVR was associated with an increased late mortality with a hazard ratio of 2.11 (95% CI: 1.43-3.1; P ＜0.001) due to more mechanical complications of the valve such as paravalvular leak, which was more common in the TAVR group (6.9% for TAVR vs. 0.9% for SAVR, P ＜0.001, at 2-year follow-up).[8]

A meta-analysis of five randomized trials and 31 observational studies including 16,638 patients showed no mortality difference of TAVR as compared with SAVR but potential benefit in low-to-intermediate risk patients undergoing transfemoral TAVR over SAVR (OR: 0.67; 95% CI:).[9] It was confirmed that the incidence of periprocedural myocardial infarction, major bleeding, acute kidney injury or new onset atrial fibrillation was lower with TAVR and the risk of pacemaker implantation, vascular complications, and paravalvular leak increased lower with SAVR.[9]

3.2 TAVR in intermediate risk patients

An Italian observational, multicenter, “real-world” study,in a low-intermediate risk population, revealed comparable mortality, major adverse cardiac and cardiovascular events(MACCE) and rates of rehospitalization between SAVR and TAVR in a propensity-matched population of 1300 patient.[10]

In the PARTNER 2A randomized trial, TAVR was compared with SAVR in 2032 intermediate-risk patients. The primary endpoint of all-cause mortality or disabling stroke at two years was to be similar for both groups (Pnoninferiority =0.001). TAVR resulted in higher rate of major vascular complications and more paravalvular regurgitation; while surgical replacement resulted in higher rates of acute kidney injury, severe bleeding and new-onset atrial fibrillation.[11]

The latest Surgical Replacement and Transcatheter Aortic Valve Implantation (SURTAVI) trial was a multinational,randomized, clinical trial which included 1746 patients at intermediate surgical risk, of whom 1660 underwent TAVR or surgical operation.[12] The incidence of primary endpoint,a composite of death from any cause or disabling stroke at 24 months was 12.6% and 14% in the two groups, respectively. Complications followed the same pattern shown in PARTNER 1A and 2A trials[8,11] and the aforementioned meta-analysis.[9] Based on the results of the SURTAVI trial and summarizing all the data regarding the intermediate risk patients, a new IIa indication was given for the TAVR procedure according to the 2017 AHA/ACC focused update of the 2014 AHA/ACC Guideline for the management of patients with valvular heart disease.[13]

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