Transcatheter aortic valve implantation: preliminary experience in West China Hospital

Transcatheter aortic valve implantation (TAVI) is a promising alternative to surgical aortic valve replacement for patients with symptomatic severe aortic stenosis (AS) who were deemed at a high surgical risk. This novel technique has kept evolving rapidly throughout the world in the past decade, but was not introduced to China until recently. Here we report our clinical experience in TAVI based on the largest cohort of Chinese patients in a single center. A total of 16 patients with severe AS (mean age, 73 years, range from 58 to 87 years; 10 men and 6 women), who were considered unsuitable for surgical valve replacement on account of high perceived operative mortality (mean logistic EuroSCORE, 34.6%), underwent TAVI in West China Hospital between April 2012 and October 2012. All patients were severely symptomatic with a mean (± standard deviation (SD)) aortic-valve gradient of (56.7± 10.4) mmHg (1 mmHg=0.133 kPa) and a mean peak jet velocity of (4.7±0.5) m/s. Eleven patients (68.8%) had a bicuspid aortic valve (BAV), including purely bicuspid valves in eight patients and potentially tricuspid valve with unequal cusps in three patients. The mean preprocedural left ventricular ejection fraction was (58.8 ±10.1)% (range from 40% to 79%), and 75% of patients had New York Heart Association (NYHA) functional class III or IV. Chronic pulmonary disease (56.3%), hypertension (50.0%), coronary artery disease (37.5%), peripheral vascular disease (31.3%) and malignancies (18.8%), were common coexisting clinical conditions which adversely affected 87.5% of the patients. Moreover, multiple (three or more) comorbidities were considerably prevalent in this population with the rate of 37.5%. Prior to TAVI, three-dimensional computed tomography angiography, percutaneous coronary angiography, and transthoracic echocardiography were performed to assess the procedure-related cardiovascular morphology. All patients were evaluated cooperatively by cardiac surgeons, anesthesiologists, echocardiographic cardiologists, and interventional cardiologists. The TAVI procedure was conducted in a hybrid operating room, with the patient under general anesthesia. Transesophageal echocardiography was performed during the procedure to assess the hemodynamic changes, cardiac function, and prosthetic valve position and performance. The Medtronic CoreValve aortic valve prosthesis (Medtronic, USA) was implanted via a transfemoral or transsubclavian approach, depending on the feasibility of the former. Details of the device and procedure have been described elsewhere.1,2 The TAVI procedure was conducted via the transfemoral approach in 15 (93.7%) of the 16 patients (Table 1). The transsubclavian route was employed in one patient (6.3%) due to the inadequacy of femoral arteries. The CoreValve prosthesis was implanted successfully in all cases with the exception of one in which the native aortic valve was calcified too heavily to allow the adequate dilation and deployment of the prosthetic valve. In this patient, the device was retrieved safely without adverse effects. For one (6.3%) patient, an additional prosthesis (valve-in- valve) was implanted due to severe regurgitation of the initial prosthetic aortic valve, thereafter, only trivial regurgitation was observed. Coronary intervention was performed as an integral part of the TAVI procedure in one patient with three-vessel disease diagnosed by preprocedural coronary angiography.Table 1: Procedural and in-hospital outcomes (n=16)Striking improvements in hemodynamic parameters were observed in the 15 patients for whom prosthetic valves were implanted, with the mean aortic-valve gradient reduced significantly to an averaged level of (13.2±7.0) mmHg and the peak jet velocity dropped by 50% to a mean of (2.3±0.6) m/s (Table 2). Individually, the hemodynamic goal of either a mean aortic-valve gradient less than 20 mmHg or a peak jet velocity lower than 3 m/s was achieved without exception. In 13 (86.7%) of the 15 patients, the aortic regurgitation (AR) grade improved or remained unchanged after the procedure. A worsening of AR from trivial to mild or from mild to moderate following TAVI was noted in two patients (13.3%). Significant prosthetic valve AR was present in one patient (6.3%), which, at most, could be classified as moderate. With regard to flow-independent parameters, the minimum indexed effective orifice area was 0.86 cm2/m2 among these patients, thus there was no significant prosthesis-patient mismatch. Overall, the rate of device success was 81.25% using the standardized definition of the Valve Academic Research Consortium-2 (VARC-2) consensus document.3 Unaccomplished implantation, valve-in-valve deployment and moderate prosthetic valve AR accounted for the unachieved device success in the three cases, respectively.Table 2: Echocardiographic characteristicsThere was no intraprocedural or periprocedural (defined as within 72 hours following TAVI) death. Two patients (12.5%) were attacked by ischemic stroke, immediately following TAVI or four days after the procedure, but recovered favorably with no important sequelae at discharge. New or worsened conduction disturbances occurred with a considerable incidence of 68.8%; however, more than 60% of these new arrhythmias were first-degree atrioventricular block (AVB) or isolated bundle branch block. Permanent pacemaker implantation was required in four patients (25.0%) owning to the onset of post-TAVI third-degree AVB. One patient (6.3%) suffered from vascular complication (could also be categorized as minor bleeding according to VARC-2 definition), which manifested as the formation of hematoma in the pelvic cavity and the rectus abdominis, and died of sudden cardiac death 20 days after TAVI. The results are comparable to previous reports in terms of the device success rate and the incidence of major complications, but a distinguishing feature of our study is that patients with a BAV were not disqualified from the TAVI procedure. In fact, the proportion of patients with BAV stenosis was nearly 70%. BAV is frequently associated with large annulus diameter, dilated aortic root and ascending aorta, asymmetrical morphology and distribution of calcification, which are presumed to result in suboptimal seating of prosthetic valve and paravalvular regurgitation.4 Therefore, BAV is considered to be a relative contraindication to TAVI and listed as an exclusion of trials. Subsequently, there is still little evidence or experience with regard to the safety and efficacy of TAVI procedure for this patient population. However, attempts have been made, and the transcatheter approach has been shown to be feasible with acceptable short-term outcomes in selected high-risk patients with symptomatic severe BAV stenosis.4,5 Besides, following characteristics of the CoreValve system theoretically justified the implementation of TAVI in treating BAV stenosis: (1) the availability of the 31-mm prosthetic valve rendered TAVI doable for many patients with a large annulus diameter, which is often the case with BAV; (2) the supra-annular location of the CoreValve leaflets may weaken the negative impacts posed by the deformed native bicuspid valve.4 Nevertheless, patients with AS and BAV would predispose to a rather high procedural risk if they have bulky leaflets and significant aortic incompetence. In conclusion, TAVI shows great promise in treating severe stenosis of tricuspid as well as bicuspid aortic valves in selected Chinese patients unsuitable for surgery. However, the experiences were especially limited in terms of TAVI for patients with severely stenotic BAV. Further investigations with larger sample size and longer follow-up duration are warranted to evaluate the long-term clinical efficacy of TAVI in this patient subset.