Transcatheter aortic valve implantation (TAVI) is an alternative option for patients with severe aortic stenosis (AS) who are classified as high-risk patients or patients not eligible for conventional aortic valve surgery. Quality-of-life (QOL) is a critical measure of effectiveness of TAVI in this patient population. Two major studies paved the way to the increasing clinical use of TAVI.12,13
Many patients with severe aortic stenosis and coexisting conditions are not candidates for surgical replacement of the aortic valve; this motivated Leon et al. to randomly assign 358 patients with severe aortic stenosis, whom surgeons considered not to be suitable candidates for surgery, to standard therapy or transfemoral transcatheter implantation of a balloon-expandable bovine pericardial valve.12 The primary end-point was the rate of death from any cause. Leon et al. found that 1) at 1 year, the rate of death from any cause was 30.7% with TAVI, as compared with 50.7% with standard therapy (hazard ratio with TAVI, 0.55, 95% CI 0.40–0.74, P < 0.001); 2) the rate of the composite end-point of death from any cause or repeat hospitalization was 42.5% with TAVI as compared with 71.6% with standard therapy (hazard ratio 0.46, 95% CI 0.35–0.59, P < 0.001); 3) among survivors at 1 year, the rate of cardiac symptoms (New York Heart Association class III or IV) was lower among patients who had undergone TAVI than among those who had received standard therapy (25.2% versus 58.0%, P < 0.001); 4) at 30 days, TAVI, as compared with standard therapy, was associated with a higher incidence of major strokes (5.0% versus 1.1%, P = 0.06) and major vascular complications (16.2% versus 1.1%, P < 0.001); and 5) in the year after TAVI, there was no deterioration in the functioning of the bioprosthetic valve, as assessed by evidence of stenosis or regurgitation on an echocardiogram. These pivotal findings indicated that in patients with severe aortic stenosis who were not suitable candidates for surgery, TAVI, as compared with standard therapy, significantly reduced the rates of death from any cause, the composite end-point of death from any cause or repeat hospitalization, and cardiac symptoms, despite the higher incidence of major strokes and major vascular events.
Smith et al. addressed these procedures in 699 randomly assigned high-risk patients with severe AS who underwent either transcatheter aortic valve replacement with a balloon-expandable bovine pericardial valve or surgical replacement.13 The primary end-point was death from any cause at 1 year. The authors found that: 1) The rates of death from any cause were 3.4% in the transcatheter group and 6.5% in the surgical group at 30 days (P = 0.07) and 24.2% and 26.8%, respectively, at 1 year (P = 0.44), a reduction of 2.6 percentage points in the transcatheter group; 2) The rates of major stroke were 3.8% in the transcatheter group and 2.1% in the surgical group at 30 days (P = 0.20) and 5.1% and 2.4%, respectively, at 1 year (P = 0.07); 3) At 30 days, major vascular complications were significantly more frequent with transcatheter replacement (11.0% versus 3.2%, P < 0.001), and adverse events that were more frequent after surgical replacement included major bleeding (9.3% versus 19.5%, P < 0.001) and new-onset atrial fibrillation (8.6% versus 16.0%, P = 0.006); 4) More patients undergoing transcatheter replacement had an improvement in symptoms at 30 days, but by 1 year there was not a significant between-group difference. These key observations suggested that in high-risk patients with severe aortic stenosis, transcatheter and surgical procedures for aortic valve replacement were associated with similar rates of survival at 1 year, although there were important differences in periprocedural risks.
The Implantation Techniques (Transfemoral, Transapical, Transaortic)
The first developed TAVI device is the Edwards SAPIEN valve (Edwards Lifesciences, Inc., Irvine, CA, USA). It consists of three bovine pericardial leaflets mounted within a balloon-expandable stainless-steel stent. Current prosthesis sizes include 23 and 26 mm. Current devices require either 22 F or 24 F (transfemoral) or 26 F (transapical) sheath for delivery. The Edwards SAPIEN valve was first implanted via the antegrade transseptal approach to the left atrium and passage through the mitral valve to reach the aortic valve (AV). With this approach there is a high risk of anterior mitral valve leaflet injury, causing severe mitral regurgitation. Transfemoral retrograde approach has been shown to be safer and is now preferred.14–18
Patients are usually placed under general anesthesia with endotracheal intubation, although sedation and analgesia may be sufficient. After crossing the AV, a balloon aortic valvuloplasty (BAV) is performed using standard techniques in order to pre-dilate the stenotic valve. Simultaneous rapid right ventricular pacing using a temporary pacemaker (usually 180 beats/min), decreasing cardiac output, is used to stabilize the balloon during the inflation.19
Because of the large profile of the device, many patients with small or diseased iliofemoral arteries are not eligible for the procedure or are at risk for major vascular complications. An alternative transapical antegrade approach has been proposed; through a left anterolateral minithoracotomy, with the patient under general anesthesia, the pericardium is opened over the apex. Temporary pacing wires are placed on the left ventricle (LV), the LV apex is punctured, and two pledgeted sutures are placed. A stiff wire is passed to the descending aorta, and BAV is performed. The percutaneous valve is then deployed.
As the number of patients screened for TAVI increases, many are found with absolutely no option for peripheral artery access. Therefore, Latsios et al. tested the safety and efficacy of the retrograde, minimally invasive, “transaortic” approach of transcatheter aortic valve implantation (TAVI) using the Medtronic CoreValve prosthesis (Medtronic, Minneapolis, MN, USA) as an alternative minimally invasive surgical access route.20 Two patients were carefully selected from a cohort of 580 patients: two women, aged 93 and 84 years, both with severe peripheral arterial occlusive disease. After a mini-sternotomy the ascending aorta was directly punctured. At the end, the access site was surgically sutured with the pre-positioned sutures. The patients were at all times off-pump and without intra-aortic balloon pump. The authors reported that TAVI was successful in both cases, leading to a fall in the transvalvular gradient with no cases of mortality, stroke, or myocardial infarction. The patients were extubated directly after the procedure, mobilized after 4 days, and were discharged home after 7 and 9 days thereafter. Hospitalization length was 34 days (patient #1) and 24 days (patient #2). These cases may support the notion that on rare occasions, where due to anatomical reasons transfemoral TAVI is not feasible, a minimally invasive “transaortic” approach, as described, provides an alternative option. This line of results follows the report by Bauernschmitt et al. who—based on a single case—also concluded that the “transaortic” approach might help to expand the implantation possibilities for those patients for whom the typical access sites are not available.21 However, the transapical TAVI is still the major alternative for the transfemoral approach due to pertinent potential advantages,22 including: 1) Lower rates of vascular complications, strokes, and use of contrast; 2) Larger sheath diameters which may lessen the need for crimping of the valves and thus improve longevity; and 3) Implementation of solutions for improving paravalvular leakage into clinical practice.
TAVI in Octogenarians
In a recent study, Grimaldi et al. evaluated 145 octogenarians (aged 84.7 ± 3.4 years) who underwent TAVI for AS (97.2%) or isolated aortic regurgitation (2.8%).23
New York Heart Association (NYHA) class was 2.8 ± 0.6; Logistic EuroSCORE: 26.1 ± 16.7; Society of Thoracic Surgeons score: 9.2 ± 7.7. Echocardiographic assessments included aortic valve area (0.77 ± 0.21 cm2
), mean/peak gradients (54.5 ± 12.2/88 ± 19.5 mmHg), left ventricular ejection fraction (LVEF) (21% of patients had an EF of less than 40%), systolic pressure in pulmonary artery (sPAP) (43.1 ± 11.6 mmHg). The main outcome measures of rates of mortality at 30 days, 6 months, and 1 year were 2.8%, 11.2%, and 17.5%, respectively. At 16-month follow-up, 85.5% survived showing improved NYHA class (2.8 ± 0.6 versus 1.5 ± 0.7, P
< 0.001), decreased sPAP (43.1 ± 11.6 mmHg versus 37.1 ± 7.7 mmHg, P
< 0.001), and increased LVEF in those with EF ≤ 40% (34.9 ± 6% versus 43.5 ± 14.4%, P
= 0.006). Concerning QOL: 49% walked unassisted, 79% (39.5% among patients ≥ 85 years) reported self-awareness improvement; QOL was reported as “good” in 58% (31.4% among patients ≥ 85 years), “acceptable according to age” in 34% (16% among patients ≥ 85 years), and “bad” in 8%. These findings suggest TAVI procedures improve clinical outcome and subjective health-related QOL in elderly patients with symptomatic AS.