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Percutaneous Aortic Valve Replacement
Abstract & Commentary
By Andrew Boyle, MBBS, PhD Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco, CA. Dr. Boyle reports no financial relationships relevant to this field of study.
Source: Webb, JG et al. Percutaneous Transarterial Aortic Valve Replacement in Selected High-Risk Patients with Aortic Stenosis. Circulation. 2007;116:755-763.
Surgical aortic valve replacement (AVR) remains the gold standard treatment for patients with severe aortic stenosis (AS). However, a number of patients are at increased risk of mortality during AVR due to advanced age or co-morbidities. These patients have traditionally been denied surgery based on unacceptably high surgical mortality rates, but untreated severe aortic stenosis also has an unacceptably high mortality rate. Webb and colleagues report their experience in the first 50 patients treated with percutaneous AVR via the femoral artery approach. All patients had severe, symptomatic aortic stenosis and had been screened by a panel of cardiac surgeons and deemed too high risk for surgical AVR. The average patient age was 82 ± 7 years. There was one procedural death and the 30-day mortality was 12%. The expected surgical mortality in this cohort calculated by the EuroSCORE surgical risk prediction model was 28%. The procedural success improved from 76% in the first 25 patients to 96% in the second 25 patients, demonstrating a significant learning curve. Valve area increased from 0.6 ± 0.2 cm2 to 1.7 ± 0.4 cm2, and mean echocardiographic gradient fell from 46 ± 17 to 11 ± 5 mmHg. Peri-procedural stroke occurred in 4%. Left ventricular ejection fraction (LVEF) improved from a mean of 53 ± 15% to 57 ± 13% (p < 0.0001) and this was sustained for the 1 year follow-up interval. More importantly, 21% of patients had significant LV dysfunction (with a LVEF of < 40%) at baseline and this fell to 12% of patients at discharge and 6% of patients at 1 year follow-up. Also, percutaneous AVR was associated with improvement in mitral regurgitation (MR). MR fell from a median grade of 2 (moderate) at baseline to 1 (mild) at discharge. Moderate to severe MR was present in 53% at baseline but only 24% at 1 year. The authors concluded that percutaneous aortic valve replacement is an alternative to surgical replacement in high surgical risk patients with severe symptomatic aortic stenosis.
This is a very exciting first-in-man description of a novel technology that may offer a new therapeutic option to the no-option patient that is deemed too high risk for surgical AVR. Importantly, the patients included in this study are representative of "real-world" patients who are refused surgical AVR. They include patients with advanced age, porcelain aorta, severe lung disease, previous thoracotomy, obesity and renal failure. 90% of patients were in NYHA class III or IV heart failure. The low procedural and 30-day mortality rates in this high-risk group are encouraging but require randomized controlled studies comparing percutaneous AVR to surgical AVR, in order to confirm these findings. It should be pointed out that most of the patients had intubation and general anesthesia for the percutaneous procedure, so this risk has to be considered in these high risk patients.
The stroke rate of 4% is also encouraging, as this is a major risk during surgical AVR in this population. Furthermore, the risk of stroke is enough to make some patients who are otherwise fit for surgery refuse the operation. Also, the median length of stay was 5 days in this study, and as short as 2 days, which has the potential to reduce health-care costs.
Despite the promising early results in this trial, a few shortcomings need to be addressed. The data are not compared against surgical or medical therapy for aortic stenosis, only to the EuroSCORE predicted mortality. Comparisons to expected mortality from risk-prediction models need to be confirmed in randomized controlled trials. In addition, the arterial access sheaths were very large (22 and 24 French) in this study and thus major vascular complications occurred in 4 patients (iliac artery injury, retroperioneal bleeding and aortic perforation) requiring surgical or endovascular repair and resulting in 2 deaths. Furthermore, 2 patients developed infections at the vascular access site. These complications became less frequent as the equipment and techniques evolved.
The ongoing randomized controlled trials of this new therapy are eagerly awaited by both physicians and patients. If the findings of this early report are confirmed in larger trials, this could herald the dawn of a new and less invasive management strategy for high-risk patients with AS.