September 23rd, 2010
CardioExchange welcomes Mike Mack and E. Murat Tuzcu, investigators for the PARTNER trial, an ongoing, randomized study of transcatheter aortic valve implantation (TAVI) in patients with severe aortic stenosis at high surgical risk. The first reported findings, published in the New England Journal of Medicine, showed an impressive 20% absolute reduction in 12-month mortality with TAVI compared with standard treatment in 358 patients who were ineligible for surgical aortic valve replacement (AVR). Here, the investigators answer a series of questions posed by David Hillis and Rick Lange, moderators of the Interventional Cardiology blog.
Q: Almost 85% of patients in the standard-therapy group underwent balloon aortic valvuloplasty (BAV), which is known to be largely ineffective and potentially harmful. How many of the complications in the standard-therapy group were due to valvuloplasty?
A: Overall survival was slightly better in standard-treatment patients who received a BAV compared with those who did not. There were 2 strokes within 7 days of a BAV.
Q: Of the patients who underwent TAVI, 30% died within a year, and 25% of the survivors continued to have NYHA class III/IV symptoms. Did these individuals differ from those who survived and had an improvement in symptoms? If so, how?
A: 95 TAVI patients (53%) survived with NYHA class I/II symptoms, whereas only 38 (21%) patients in the standard-therapy group survived with NYHA class I/II symptoms. We have not yet analyzed the data to determine the differences between patients whose symptoms improved and those whose symptoms did not.
Q: Despite the fact that all patients in the study were deemed unsuitable for surgery, 12 (7%) of those assigned to standard therapy underwent AVR, with a 1-year death rate of 33%, which is similar to the rate of death with TAVI (31%). Why should TAVI — rather than AVR — be the new standard of care for these patients?
A: 12 patients is too small a group from which to draw any conclusions. We will gain further data regarding this question when the results of Cohort A, which compared TAVI and surgical AVR, are available.
Q: Only 358 (12%) of the 3105 patients screened for the study were randomized. Of patients determined not to be suitable candidates for AVR, were only a minority suitable for TAVI?
A: An additional 700 screened patients were entered into Cohort A of the PARTNER trial. Therefore, approximately 1/3 of screened patients were enrolled, which is in line with other published studies.
Q: What was the operator experience with TAVI before participation in the study?
A: Only 3 of the 21 centers had any previous experience from feasibility trials. For the other 18 centers, this represented their initial TAVI experience after intensive training and proctoring.
Q: Based on the results of a study with 12 months of follow-up, you propose that TAVI should be the new standard of care for patients with aortic stenosis who are not suitable candidates for surgery. Why not wait for longer follow-up before making this claim?
A: Of course, longer-term follow-up is important and ongoing. The median follow-up to date is 1.6 years, and the longest patient follow-up is 2.8 years. Based on an absolute 20% improvement in survival at 12 months and survival curves that continue to diverge, we are confident in this recommendation.