The US Food and Drug Administration has approved the SAPIEN heart-valve system (Edwards Lifesciences) for use in patients at prohibitively high risk for surgical aortic valve replacement. Aortic stenosis is a common condition in which the aortic valve (through which blood flows from the heart to the rest of the body) narrows due to thickening and calcification. The process is not simply one of wear-and-tear: aortic stenosis appears related to atherosclerosis, which causes narrowing of the coronary arteries.
When severe enough, aortic stenosis can cause chest pain, heart failure and episodes of passing out (known as “syncope”). Once symptomatic, the course is rapidly progressive, with mortality rates as high as 50% at 2 years from onset. The only treatment is replacement of the valve via open heart surgery. However, approximately 30% of patients are too high risk due to age, frailty and having multiple, complicating medical problems.
Transcatheter Aortic Valve Replacement (TAVR) finally provides a viable alternative to medical therapy (which is ineffective) and open heart surgery (too risky). The new valve is inserted into the heart via a flexible tube (catheter) threaded up from a blood vessel in the thigh; a second approach—which requires a limited surgical procedure—uses the tip, or apex of the heart fro access. The valve is “crimped” on the catheterover a small balloon. Once positioned across the narrowed native valve, the balloon is inflated, expanding the artificial valve and excluding the diseased one. The catheter is withdrawn, leaving a functioning new valve in place. Long term anticoagulation is not needed as the valve is not mechanical (it is made from cow heart tissue), but treatment with aspirin and clopidogrel for at least 6 months is.
Approval of the SAPIEN system was based on the PARTNER trial. The trial consisted of 2 groups of patients: those who were inoperable due to frailty and illness (“cohort B”) and those who, while high risk, were still potential operative candidates (“cohort A”). Patients in cohort B were randomized to either TAVR or standard therapy (medication with or without valvuloplasty—a procedure where a balloon is inflated across the valve without a new valve in an attempt to “stretch” the valve open). Cohort A subjects were assigned to TAVR or surgical aortic valve replacement (sAVR). The outcome of interest in PARTNER B was death from all causes at 1 year in TAVR patient versus standard therapy patients. PARTNER A was designed a bit differently: the investigators wanted to prove TAVR was just as good as (i.e. noninferior to) sAVR at preventing death.
PARTNER B showed an impressive 20% reduction in one year mortality versus standard therapy. Patients treated with TAVR were also symptomatically better, and the valve maintained functional durability. In PARTNER A, TAVR proved noninferior to sAVRin preventing death at one year. TAVR patients felt better more quickly, but at one year symptoms were similar.
Of course, TAVR wasn’t perfect. There tended to be more strokes with TAVR than with standard therapy or sAVR. Because rather large catheters need to be inserted into blood vessels to deliver the valve to the heart, there were more associated bleeding and vascular complications with TAVR. Transcatheter valves also tend to be “leakier,” and in several cases, repeat procedures were required to correct this. Also, not everyone is a candidate for TAVR: a number of exclusion criteria exist, including the need for bypass, severely compromised heart function and severe kidney disease, among others.
However, in this sickly, high risk population of patients, TAVR preformed remarkably well and provided a real chance at a longer and healthier life. A second transcatheter valve (Medtronic CoreValve) is currently undergoing clinical trials and likely will become another option for those who, a short time ago, had none.
FDA approves first artificial aortic heart valve placed without open-heart surgery (Available at URL: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm278348.htm)
Leon MB, Smith CR, Mack M, et al for the PARTNER Trial Investigators. Transcatheter aortic valve implantation for aortic stenosis in patients who cannot undergo surgery. N Engl J Med 2010; 363:1597-1607.
Smith CR, Leon MB, Mack MJ, et al for the PARTNER Trial Investigators. Transcatheter versus surgical aortic valve replacement in high risk patients. N Engl J Med 2011; 364:2187-2198.