The multicenter Placement of Aortic Transcatheter Valves (PARTNER) trial in North America is continuing to enroll patients, with enrollment projected to be complete by the end of 2008. The aim of this prospective randomized clinical trial is to enroll 1,040 patients in two separate treatment arms. The surgical arm of the trial is comparing the Edwards SAPIEN valve with standard surgical aortic valve replacement, with the objective of demonstrating non-inferiority. The medical management arm of the trial is comparing percutaneous valve replacement against medical therapy or balloon valvuloplasty in patients considered too high-risk for conventional surgical valve replacement.
The primary end point in both arms is death at 1 year; secondary end points focus on long-term (1-year) composite cardiovascular events, valve performance, and quality-of-life indicators. Preliminary data on the first 100 patients (74 via the transfemoral [ie, retrograde] and 26 via the transapical approach) who underwent percutaneous Edwards SAPIEN valve implantation for compassionate use showed device durability and symptom relief at up to 2 years. 38 Overall procedural success was 91%, but, as with other trials, there was a steep learning curve, so that excluding the first 25 patients increased the procedural success rate to 96%. 38 Aortic valve size and hemodynamics, left ventricular systolic function, mitral regurgitation, and functional class were all significantly improved. Mild aortic regurgitation was common, but none of the patients had severe aortic regurgitation. Importantly, the 15% 30-day death rate was significantly lower than the expected rate of 33%. The 6-month survival rate was 78%, but the 2-year rate was 60% in this high-risk elderly cohort.
Walther et al 39 recently reported outcomes on their first 50 patients who underwent transapical implantation of the Edwards SAPIEN valve. The operators were able to implant the prosthesis in all 50 patients, but 3 required early conversion to open surgery with sternotomy. The overall survival at 30 days was 92%, but in the last 25 patients the 30-day survival rate was 96%, with a 1-year survival rate of 80%.
PUTTING THE DATA IN PERSPECTIVE
As noted in this review, a number of factors make a strong case for timely aortic valve replacement: the aging population, the increase in incidence and prevalence of aortic stenosis, 1,3,4,27,40 the multiple comorbidities in older patients, and the eventually aggressive natural course of aortic stenosis. 1,3,4,27,40–43 Yet current standards dictate not to proceed with standard surgical aortic valve replacement in patients who are truly asymptomatic and who have normal left ventricular systolic function, 1,40 mainly because the risks of surgical valve replacement outweigh the benefits in this population. 1,40 Aortic valve surgery carries a risk of early death of 15% for patients ages 80 to 84 and of 18% for patients age 85. 3,9,10,12,43–45
These figures seem high when compared with death rates of 12% in recent studies of percutaneous valve replacement in similar patients. 11,23,30,33 The rates become lower as the learning curve improves. 11,21,23,27,30,33 Thus, as the design of aortic valve prostheses and the techniques to implant them are refined and tested for safety, the risk-benefit balance may change in favor of earlier intervention in aortic stenosis with a percutaneous approach. 11,21,27,46 Some experts believe that in 10 years 10% to 30% of patients undergoing conventional valve replacement will be candidates for a percutaneous approach.