Transcatheter Aortic Valve Implantation (TAVI) for AS Patients at High Surgical Risk

Abstract & Commentary

By Andrew J. Boyle, MBBS, PhD

Source: Rodes-Cabau J, et al. Transcatheter aortic valve implantation for the treatment of severe symptomatic aortic stenosis in patients at very high or prohibitive surgical risk. J Am Coll Cardiol. 2010;55:1080-1090.

Surgical aortic valve replacement (SAVR) remains the gold standard treatment for calcific aortic stenosis (AS). However, AS is predominantly a disease of the elderly and, thus, many patients have significant comorbidities that make SAVR very high risk. Risk scores, such as the Society of Thoracic Surgeons (STS) risk score, can predict the likelihood of mortality after SAVR. Transcatheter Aortic Valve Implantation (TAVI) is an emerging therapy that has advanced significantly over recent years and may offer a reasonable alternative therapy for patients that are deemed to be at high surgical risk. An additional consideration in assessing the role for TAVI in clinical practice is the presence of a porcelain aorta or frailty. These conditions are often reasons that patients are considered inoperable or too high risk for SAVR, yet they are not included in risk scores. Thus, their role in evaluation for TAVI remains ill-defined. Therefore, Rodes-Cabau et al examined data from their multi-center registry in Canada to determine the outcomes of all patients who underwent TAVI by both the trans-apical and trans-femoral routes. In addition, they describe the outcomes in patients who were deemed inoperable due to frailty and porcelain aorta.

Since January 2005, TAVI has been approved in Canada for "compassionate use" in patients with severe symptomatic AS who were deemed too high risk for SAVR. Data have been prospectively collected in a multi-center registry at six Canadian centers. All patients were evaluated by a team that included an interventional cardiologist and a cardiac surgeon and were deemed too high risk or inoperable for SAVR, but suitable for TAVI. All patients underwent evaluation with echocardiography, coronary angiography, aorto-ilio-femoral angiography, and computed tomography. From January 2005 to June 2009, 339 patients underwent "compassionate use" TAVI, using exclusively the Edwards Sapien valve (three different generations of valve as the technology evolved), 167 via the trans-femoral route and 172 via the trans-apical route. Six patients had unsuccessful trans-femoral procedure and required a second procedure (five trans-apical, one trans-femoral). The patients were high risk: average age was 81 ± 8 years, 45% were male, mean aortic valve gradient was 46 ± 17 mmHg, valve area was 0.63 ± 0.17cm2, renal impairment in 56%, COPD in 30%, porcelain aorta in 18%, frailty in 25%, and 91% were NYHA class III-IV heart failure.

Results: The procedure was successful in 93.3% of cases. Mean aortic valve gradient decreased from 46 ± 17 mmHg to 10 ± 4 mmHg (p < 0.0001) and mean valve area increased from 0.63 ± 0.17 cm2 to 1.55 ± 0.41 cm2. Aortic regurgitation was present after the procedure in 84% of cases (trivial or mild 78%, moderate 5%, severe 1%).

TAVI procedural mortality was 1.7% (n = 5), compared to the expected surgical AVR mortality of 9.8% ± 6.4% by STS score. Reasons for procedural death were major vascular complications (n = 2, 0.6%), severe left ventricular dysfunction after valve implantation (n = 2, 0.6%), and cardiac perforation (n = 1, 0.3%). In the 30 days following TAVI, there were an additional 30 deaths, for a cumulative 30-day mortality of 10.4%. The post-procedural deaths were due to multiorgan failure (n = 6), major bleeding (n = 5), pneumonia/septicemia (n = 4), stroke (n = 2), ventricular arrhythmia (n = 2), heart failure (n = 2), sudden unexplained death (n = 2), cardiogenic shock, myocardial infarction, late valve embolization, pulmonary embolism, peripheral embolism, aortic rupture, and severe mitral regurgitation due to leaflet perforation (n = 1 each). Importantly, patients with porcelain aorta and frailty had similar mortality acutely and at 30 days to the entire cohort, but frail patients were more likely to develop renal failure requiring dialysis after the procedure. Multivariate analysis identified three predictors of 30-day mortality: pulmonary hypertension (Odds Ratio [OR] 2.1), severe MR (OR 3.0), and the need for peri-procedural hemodynamic support (OR 6.8). Frailty, porcelain aorta, and route of valve implantation were not significantly associated with mortality.

Survival at one year was 76% and at two years was 64%. Predictors of late mortality were post-procedural sepsis (Hazard Ratio [HR] 3.5), need for peri-procedural hemodynamic support (HR 2.6), pulmonary hypertension (HR 1.9), renal impairment (HR 2.3), and COPD (HR 1.8). The authors conclude that TAVI via both transapical and transfemoral routes was associated with comparable mortality, as predicted with STS score for the treatment of patients at very high or prohibitive surgical risk, including porcelain aorta and frail patients. Baseline and procedural factors, but not route of approach, predicted worse outcomes.

Commentary

This is the largest series using the Edwards Sapien valve, and the data are made more robust by the fact that it is a multi-center study, not just performed in a single center with particular expertise. The procedural mortality compares favorably with the predicted surgical mortality by STS score, but there is significant mortality in the month and years following the procedure. Thus, TAVI does not appear to be a panacea for this patient group, which has significant co-existing medical problems. Importantly, the patients with porcelain aorta, who are often refused SAVR, had comparable outcomes with the entire cohort, even with ~ 50% being performed via the transfemoral route.

STS risk score was not predictive of poor outcomes in this series of patients undergoing TAVI. New risk predictors need to be established for this emerging technology in order to guide clinicians in appropriate patient selection. As data continue to accumulate in TAVI, it appears that this is a promising technology with the potential to benefit patients who have traditionally been untreatable or very high risk with SAVR.