Cath Lab Digest

pg.E34 - E36

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To evaluate the current and future role of percutaneous aortic valve replacement, we need to ask three main questions:

1. What is the natural history of the disease and where did we stand after the widespread availability of surgical aortic valve replacement?

2. Where do we currently stand?

3. Where are we going from here?

Regarding the first question, before the advent of surgical aortic valve replacement in the early 1960s, symptomatic severe valvular aortic stenosis was uniformly associated with a poor prognosis, with an average life-expectancy of less than three years similar to that of some malignancies.1,2 Likewise, the quality of life was frequently miserable. Moreover, to the frustration of all caretakers involved, no medical treatment was or, for that matter is, available to either improve survival or quality of life.3 Unlike few other procedures, surgical valve replacement dramatically improved longevity such that, apart from the generally low perioperative mortality rate, survival and quality of life are now comparable to that of an age-matched population without valvular heart disease.1 Therefore, surgical aortic valve replacement has revolutionized the care of these patients as well as those with aortic insufficiency, and has rightfully become the treatment of choice with an expected surgical mortality of 4% or less in the ideal candidate.4 Nevertheless, despite the availability of this well-established treatment, a substantial number of patients with severe symptomatic valvular aortic stenosis and comorbid conditions do not undergo surgical valve replacement due to high surgical morbidity and mortality rates.5,6 Hence, the concept of the less invasive aortic balloon valvuloplasty was developed by Cribier et al7 in 1986 and was more widely adopted until it became clear that it offers only modest hemodynamic and symptomatic improvement, is almost invariably associated with recurrent symptoms, has no proven survival benefit, and is associated with a significant periprocedural risk.8–12 Yet, until recently, this has remained the only alternative treatment option for patients with severe aortic stenosis deemed too high-risk to undergo surgical valve replacement.

Where do we currently stand?

The concept of a valve, mounted on a stent, delivered via a percutaneous route was first entertained by Andersen et al in 1989.13 Subsequently, in the same year, an aortic pig valve was sutured onto a balloon-expandable stent and delivered and implanted via the surgically exposed abdominal aorta to various sites of the ascending and descending aorta in a pig model.13 Implantation at the subcoronary position, however, was unsuccessful due to impingement of the coronary arteries after valve deployment. This early experience demonstrated the feasibility of the percutaneous valve replacement concept, however, due to the size of vascular access required and questionable long-term performance, enthusiasm was limited. Aided by the rapid developments of percutaneous coronary, structural heart and peripheral vascular technology, interest to further explore this concept had reemerged in 2000, and was followed by the first human implantation of a stent-mounted valve into the pulmonary position by Bonhoeffer et al in 200014 and subsequently into the aortic position by Cribier et al in 2002.15 As with most new technology, early complication rates were high. More importantly, however, the feasibility had been demonstrated and ignited new excitement to rapidly improve the technology of this desperately needed alternative. It was immediately clear that the most dreaded complications would be related to vascular access, device migration, malposition, embolization related to aortic atherosclerotic plaque or the native aortic valve, and valvular regurgitation due to incomplete apposition of the stent. In the meantime, many technical refinements have been implemented which allow lower-profile sheaths for valve delivery, and less bulky and somewhat steerable devices are easier to maneuver through the iliac vessels, aortic arch and aortic valve. In addition, early experience has allowed better patient selection for this procedure.