October 2, 2008 (Lisbon, Portugal) — Surgeons testing the transapical delivery method for the Edwards Sapien transcatheter aortic valve say the latest results from pre- and postapproval studies in Europe reflect the fact that operators are gradually improving their technique and their ability to choose patients best suited to the procedure.
Dr Gerhard Wimmer-Greinecker (Klinik für Herz-Thorax-Chirurgie, Bad Bevensen, Germany) presented results from the PARTNER EU study, as well as the SOURCE registry, during the recent European Association for Cardio-Thoracic Surgery (EACTS) 2008 Meeting here. Most striking in the two presentations was the low six-month survival in PARTNER EU--something early rumors and stock-analyst reports had predicted. But according to Wimmer-Greinecker, the improved survival seen at 30 days in SOURCE, the more recent of the two data sets, as well as other data presented at the meeting, indicates that the device is safe and effective, particularly once operators get more practice using it.
PARTNER-EU was a feasibility study, conducted after the study sponsor, Edwards, had filed for CE mark in Europe but had not yet been granted marketing clearance. The study enrolled 132 patients, of whom 67 were treated with the transapical approach. An additional 54 underwent transfemoral percutaneous valve implantation; results for these patients will be presented at the upcoming TCT meeting in Washington, DC.
As Wimmer-Greinecker reported, PARTNER EU was conducted at nine centers in six countries. Mean logistic European System for Cardiac Operative Risk Evaluation (EUROSCORE) was 33.5% for the transapically treated patients at baseline--significantly higher than the EUROSCORE for those enrolled in the transfemoral arm of the study (25.3%, p=0.002). Implant success rate was high, at 96%, and after six months, the stroke rate was low, less than 5%. Overall, the valve itself appeared to perform well at six months, Wimmer-Greinecker reported, with seemingly durable improvements in mean effective orifice area and valve gradient and no structural valve deterioration.
Patient survival, however, was less impressive. At 30 days, overall survival was 82%, dropping to 55% at six months, lower than that seen in other transapical series, as reported by heartwire . For example, Walther et al recently reported six-month results for 50 patients (mean EUROSCORE 27%) with six-month survival rates of 74% [1,2], while Svensson et al reported six-month survival from the US feasibility study at 59% (mean EUROSCORE 36.6%) [3].
But Wimmer-Greinecker insists the SOURCE postmarketing registry, which he presented two days after the PARTNERS EU data, supports the safety and efficacy of the device as operators grow more comfortable with its use. Showing SOURCE data from 309 patients treated in one of 12 European countries, Wimmer-Greinecker emphasized that the data speak to the value of intensive training and proctoring. Patients in SOURCE so far have a mean logistic EUROSCORE of 30%, but higher survival rates--88.4% at 30 days--than their counterparts in the PARTNER EU data set.
In addition, updated results from the University of Leipzig, Germany, where Dr Thomas Walther and his group are the undisputed leaders in the field of transapical valve delivery, are even more impressive. According to Walther, who presented the update during the EACTS meeting, six- and 12-month results in 113 patients treated in Leipzig were 74% and 71%, respectively.
"Learning-Curve Bias"
In an interview with heartwire , Wimmer-Greinecker explained that of the nine centers that participated in PARTNER EU, only two had had previous experience with the procedure. "So for all the others, this was a completely new procedure and the entire learning curve for this procedure is included in those data.Moreover, with the exception of one center that did 11 procedures, all the others did fewer than 10 procedures. So there is a strong learning-curve bias in these data."
Following device approval, he says, the procedure has become much more widespread, but there has also been greater expertise, allowing more widespread proctoring. As a result, there are several sites where the mortality rate for the first 10 cases has been zero. "So there is more expertise out now, technology became better, and what we found out is that there's not only a learning curve regarding technique, but also--and this is very important--a learning curve regarding patient selection," Wimmer-Greinecker explained. "When this procedure came out, everyone said initially: this is for patients who are not operable. And when that message went out, the cardiologists started sending up a lot of patients who were so lousy that of course they were not operable, but they were not good for this procedure either. . . . There are certain patients that are just not ideal for this procedure, and we had to learn that."
According to Wimmer-Greinecker, researchers are in the process of developing a frailty test that could possibly be used in tandem with the EUROSCORE, which on its own has proved imprecise at identifying patients best suited to transapical valve delivery. "The fact is, the risk-stratification and scoring systems we use now give you some guidance, but they are not accurate in every way. In some patients they underestimate risk, and in some they overestimate risk."
The Future Role of Transapical Delivery
The jury is still out on what role transapical valve delivery--which requires minithoracotomy and an incision in the apex of the heart--will have in the future, as technological innovations to the devices make them smaller and smaller. As previously reported by heartwire , surgeons have embraced the transapical procedure, which offers them a starring role in the transcatheter delivery of the valve. They argue that there will always be a need for this method, since some patients will always be deemed ineligible for fully percutaneous valve delivery. Interventionalists and others, however, have pointed out that the transfemoral method, which requires a different delivery configuration, has consistently been associated with better survival rates, albeit in patients with lower surgical risk by EUROSCORE. While some surgeons, Walther among them, have called for a randomized controlled trial comparing the two transcatheter delivery techniques with conventional aortic-valve surgery, others insist that the two methods are needed for different types of patients with different comorbidities.
Wimmer-Greinecker has no doubts about the future role of the transapical procedure. "Of course, I'm a surgeon, but I think [the transapical approach] will play a very strong role. It has a place in the cases where a transfemoral can't be achieved because of peripheral vascular disease, occlusion in the vessels, abdominal aneurisms, kinking of the vessels, and various other issues," he said.
And if both transfemoral and transapical are feasible, he believes physicians and patients should be able to choose a procedure that has less stroke risk. As his EACTS data showed, risk of neurological deficit and neurological complications was low following the transapical procedures in SOURCE and PARTNER EU. "In patients with plaques and calcifications in the aorta, a transfemoral procedure carries a certain stroke risk, because you can [dislodge] some emboli. If you go the direct way, the transapical way, then you don't have this risk."
Some comparative information, although indirect, will come at the TCT meeting, where investigators are scheduled to present the six-month transfemoral data from PARTNER EU and 30-day transfemoral data from SOURCE. Big-picture results await the US PARTNER trial, which is still enrolling toward its target of 1040 patients, with an estimated completion date of 2010.
Wimmer-Greinecker has previously disclosed being a consultant to Edwards.
Walther T, Falk V, Kempfert J, Borger MA, et al. Transapical minimally invasive aortic valve implantation; the initial 50 patients. Eur J Cardiothorac Surg 2008; 33:983-988. Abstract
Walther T, Simon P, Dewey T, et al. Transapical minimally invasive aortic valve implantation: multicenter experience. Circulation 2007; 116 (11 Suppl):I240-245. Abstract
Svensson LG, Dewey T, Kapadia S, et al. United States feasibility study of transcatheter insertion of a stented aortic valve by the left ventricular apex. Ann Thorac Surg 2008; 86:46-54. Abstract
The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.
Heartwire from Medscape © 2008 Medscape
Cite this: Shelley Wood. Transapical Valve Data: Climbing Survival Rates Speak to Improved Skill, Technology, and Patient Selection - Medscape - Oct 03, 2008.
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