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Where do we stand with transcatheter aortic valve implantation?
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It has been more than five years since the first patient underwent percutaneous aortic valve replacement in Europe.
Initial antegrade techniques have given way to the more familiar retrograde approaches, and for patients with peripheral atherosclerotic disease, minimally invasive transapical ventricular valve placement is now possible. In Europe two first generation devices, CoreValve and the Edwards Lifesciences Sapien valve, have received CE Mark approval, and are being placed in multiple centers. Two “second generation” devices are undergoing safety and efficacy testing — the Direct Flow Medical and Sadra Lotus valves — have had early success, are repositionable, retrievable and have the added advantage of smaller diameter sheath sizes. Plans are underway to expand their use in selected centers outside of the United States. Other valve designs are in early animal testing.
The Edwards Sapien valve is the first transcatheter device that is being evaluated in the United States. A successful phase-1 U.S. trial has been completed and the randomized PARTNER phase-2 trial is well underway.
Available data
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What data are available to support the enthusiasm that accompanies transcatheter aortic valve implantation? What we do know is available from registries and phase-1 trials. REVIVAL II and REVIVE II are feasibility registry studies for North America and Europe, respectively. The numbers are relatively small: 105 patients were enrolled in REVIVE II and 55 in REVIVAL II. Inclusion criteria for patients treated by transfemoral valve placement in these two studies were severe, symptomatic aortic stenosis, age >70 years, high surgical risk (Euroscore >20) or documented surgical refusal. The primary safety endpoints were death, MI, stroke or urgent cardiac surgery. Data were collected at 30 days, three, six, and 12 months.
Patients entered into both registries all had high-risk conditions: prior cardiac surgery (29%), previous cerebrovascular accident or transient ischemic attack (16%), chronic obstructive pulmonary disease (27%), renal dysfunction (22%), diabetes (26%), porcelain aorta (6%), chest wall radiation (7%), and chest deformity (4%). Eighty percent of patients had a predicted operative risk of >20% (Euroscore). In these studies 142 out of 161 (88%) patients had successful deployment of the aortic prosthesis. Unsuccessful deployment was due to failed access (n=9), inability to cross the native aortic valve (n=3), cardiac perforation from a guidewire or transvenous pacemaker (n=3), malplacement of the valve (n=2), and anesthesia complications (n=2). Major adverse cardiac events were not trivial: 19% after more than 30 days and 17% less than 30 days of follow-up. Death occurred in 11% and 16% at <30 and >30 days, respectively; stroke occurred among 4% and 2%; and urgent cardiac surgery occurred for 1%. Procedural complications, renal failure requiring dialysis and need for permanent pacemaker implantation within 30 days occurred in 16%, 1% and 5% of patients, respectively.
Looking on the bright side
But there is also a lot to be said on the positive side. The vascular complication rate, initially as high as 30% in the first group of patients, was reduced to 6% with the institution of formalized vascular screening at a core laboratory. For those patients with successful implantations, hemodynamics improved greatly. Valve gradient dropped from approximately 43 mm Hg to 10 mm Hg and aortic valve area rose from about 0.6cm2 to 1.7 cm2. Perhaps the most striking outcome after transcatheter valve placement in these registries was the change in NYHA Class. At baseline 91% of patients were NYHA III or IV. At one-year follow up, 87% were NYHA I or II and only 13% were in NYHA III or IV. Kaplan-Meier curves showed a 74% survival at 12 months, a far cry from the anticipated 50% survival that was reported in the BAV registries from the late 1980’s.
Conclusions that can be drawn from these data must be stated cautiously, as these are not randomized data. Certainly it is fair to state that transcatheter aortic valve replacement is not without risk, but one-year mortality appears far better than “standard care” historic data. Nearly all patients have impressive improvement in NYHA class after successful valve implantation, and valve performance is stable up to one year.
My prediction is that as operators gain experience with these new devices the initial complication rates will decrease and outcomes will continue to improve. Our job as interventional cardiologists is to minimize risk and improve patient outcomes. For high risk patients with aortic stenosis, the early transcatheter aortic valve data show us that the learning curve is real, but apparently steep, and the outcomes at one year are striking. Stay tuned for the results of PARTNER which will give us data from randomized patients.
Peter C. Block, MD, is Director, Clinical Trials Office, Department of Cardiology, Emory University Hospital. He is Co-Section Editor of Cardiology Today’s Vascular Medicine/Intervention Section.
For more information:
- Otto CM, Mickel MC, Kennedy JW et al. Three-year outcome after balloon aortic valvuloplasty. Insights into prognosis of valvular aortic stenosis. Circulation. 1994;89:642-650.
- O’Keefe JH Jr, Vlietstra RE, Bailey KR, Holmes DR. Natural history of candidates for balloon aortic valvuplasty. Mayo Clin Proc. 1987;62:986-991.
- Lieberman EB, Bashore TM, Hermiller et al. Balloon aortic valvuloplasty in adults: Failure of procedure to improve long-term survival. J Amer Coll Cardiol. 1995;26:1522-1528.