Cath Lab Digest

pg. E1 - E9

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Abstract

The development of transcatheter aortic valve implantation may become the primary therapy for high-risk patients with severe symptomatic aortic stenosis. The Edwards Sapien valve (Edwards Lifesciences, Irvine, California) consists of a balloon-expandable stent with an integrated bovine pericardial valve. The technique and the device itself have rapidly evolved; more than 5,000 patients worldwide have undergone implantation with this valve. This review will focus on the Edwards Sapien balloon-expandable heart valve using the transfemoral approach. Risk assessment is important since the current indication is restricted to high surgical risk or non-operable patients, while appropriate patient selection and screening is crucial for success and for avoiding complications. Careful evaluation of the iliofemoral vessels by angiography and high-quality computed tomography (CT) is indispensable since vascular injury is the most common cause of morbidity andmortality for these procedures. Precise measurement of the aortic annulus diameter for valve sizing is very important when choosing the appropriate valve size. The relation among the annulus, plaque in the left coronary leaflet, and the distance to the left coronary ostium is also important. Existing follow-up data show no evidence of restenosis or prosthetic valve dysfunction, and randomized trials currently underway will confirm procedural safety and guide the applicability of this technology.

Key words: aortic stenosis; transcatheter aortic valve implantation

With a prevalence of 4.6% in adults over 75 years of age, aortic stenosis (AS) is the most common valvular heart disease in an aging population.1 Surgical aortic valve replacement is the recommended treatment for symptomatic patients. However, a large proportion of patients are not referred or are deferred due to high risk for surgery.2 Data from the Euro Heart Survey on valvular heart disease revealed that up to 30% of patients with severe AS do not undergo surgery. Trans-catheter aortic valve implantation (TAVI) has been designed to address a new treatment option for this high-risk population. The first human implantation of a percutaneous aortic valve was performed by Alain Cribier in April 2002 with a balloon-expandable valve on a stent. Since then, this procedure has rapidly expanded, and as of today, more than 5,000 patients have had the aortic valve implanted. The Edwards Sapien valve (Edwards Lifesciences, Irvine, California), available in 23 mm and 26 mm, consists of a balloon-expandable stainless steel frame with an integrated trileaflet bovine pericardial valve. The latest version of this valve has a chromium cobalt frame. Valve implantation can be performed safely and effectively utilizing both the transfemoral approach and transapical placement. This article will review the present state of TAVI using the Edwards Sapien valve via the transfemoral approach.

Patient Selection and Risk Assessment

TAVI is intended for use in symptomatic patients with severe calcific AS requiring aortic valve replacement who are at high risk for open chest surgery due to comorbid conditions, and for patients who are inoperable. Defining high-risk surgical patients is not simple. A Society of Thoracic Surgeons (STS) risk score > 10 and/or a logistic EuroSCORE > 20 are most often used to define high risk. The EuroSCORE has been shown to predict long-term mortality after valve surgery.3 This algorithm, however, has been shown to persistently overestimate the mortality rate,4 and this overestimation is greatest in high-risk patients.5 The STS score has been shown to underestimate the true morality rate after cardiac surgery, but it more closely reflects the operative- and 30-day mortality for the highest-risk patients undergoing aortic valve replacement.6 Patients can be at very high operative mortality risk, yet have low scores. There are numerous comorbidities not captured in the EuroSCORE and STS scoring systems such as porcelain aorta, chest-wall radiation, chest-wall deformity, highly compromised respiratory function, frailty, cirrhosis, and others. There have been attempts to quantify the frailty index7 and correlate the frailty index with outcomes,8 however, frailty analysis is particularly difficult and is often not quantifiable. The clinical judgment of experienced cardiac surgeons plays a key role in assessing operative mortality in these cases.

Currently available validated risk score systems have not captured the “non-operable” patient. The definition of “inoperability” is difficult, and often requires the consensus of several surgeons. It is important to emphasize that those scoring systems are not intended to be used as substitutes for clinical decision making. This new treatment for the high-risk populations is aimed at those patients whose comorbidities will not interfere with normal recovery after aortic valve implantation. For example, patients who are bedridden or have a life expectancy of < 12 months should not have this procedure. Patients must be in stable condition prior to the procedure. Those in decompensated heart failure with severely depressed left ventricular function should undergo medical optimization and balloon valvuloplasty to allow for improvement of their ventricular function, along with stress echocardiography to assess the myocardial contractility reserve.

Screening