Author + information
- Received January 31, 2010
- Revision received August 4, 2010
- Accepted August 6, 2010
- Published online November 1, 2010.
- Namal Wijesinghe, MBBS, MD⁎,
- Jian Ye, MD⁎,
- Josep Rodés-Cabau, MD†,
- Anson Cheung, MD⁎,
- James L. Velianou, MD‡,
- Madhu K. Natarajan, MSc, MD‡,
- Eric Dumont, MD†,
- Fabian Nietlispach, MD⁎,
- Ronen Gurvitch, MBBS⁎,
- David A. Wood, MD⁎,
- Edgar Tay, MBBS⁎ and
- John G. Webb, MD⁎,⁎ ()
- ↵⁎Reprint requests and correspondence:
Dr. John G. Webb, St. Paul's Hospital, 1081 Burrard Street, Vancouver, British Columbia V6Z 1Y6, Canada
Objectives We evaluated transcatheter aortic valve implantation (TAVI) in high-risk patients with bicuspid aortic valve (BAV) stenosis.
Background TAVI shows promise in the treatment of severe stenosis of triscupid aortic valves, especially in high-risk patients. However, BAV stenosis has been considered a contraindication to TAVI.
Methods Eleven patients (age 52 to 90 years) with symptomatic severe BAV stenosis underwent TAVI at 3 Canadian tertiary hospitals between May 2006 and April 2010. All patients were considered high risk for surgical aortic valve replacement. Edwards-SAPIEN transcatheter heart valves (Edwards Lifesciences, Inc., Irvine, California) were used. Transfemoral or transapical access was selected, depending on the adequacy of femoral access.
Results Access was transfemoral in 7 patients and transapical in 4 patients. There were no intraprocedural complications. Significant symptomatic and hemodynamic improvement was observed in 10 of 11 patients. Baseline aortic valve area of 0.65 ± 0.17 cm2 and mean transaortic pressure gradient of 41 ± 22.4 mm Hg were improved to 1.45 ± 0.3 cm2 and 13.4 ± 5.7 mm Hg, respectively. Two patients had moderate perivalvular leaks. At the 30-day follow-up there were 2 deaths due to multisystem failure in 2 transapical patients. In 1 patient an undersized, suboptimally positioned, unstable valve required late conversion to open surgery.
Conclusions TAVI in selected high-risk patients with severe BAV stenosis can be successfully performed with acceptable clinical outcomes but will require further evaluation.
Bicuspid aortic valves (BAV) occur in approximately 1% of the population (1), making this the most common congenital cardiac anomaly. Although silent until adulthood, stenosis and/or incompetence often develop in mid-life, requiring aortic valve replacement. Transcatheter aortic valve implantation (TAVI) is an emerging alternative technique that has shown promise in the treatment of severe aortic stenosis in patient populations at high risk with conventional surgery (2). The presence of a BAV has been considered an exclusion for TAVI. We describe our experience with TAVI in high-risk patients of severe aortic stenosis due to BAV.
Patients referred with severe symptomatic aortic stenosis due to BAV were assessed for TAVI in 3 Canadian tertiary hospitals. All patients were considered to be ineligible or high risk for conventional aortic valve replacement surgery by a multidisciplinary group of cardiologists and cardiac surgeons. Informed, written consents were obtained. Patients with adequate femoral access underwent transfemoral TAVI; otherwise, transapical access was used.
The details of the TAVI procedure have been described elsewhere (3,4). General anesthesia, transesophageal echocardiography (TEE), pre-implantation balloon aortic valvuloplasty, and rapid ventricular pacing to reduce cardiac output were routinely used (5). In transarterial procedures, the Retroflex delivery system was used, followed by percutaneous or surgical closure of the femoral artery. In transapical procedures, the Ascendra delivery system was used with surgical closure of the left ventricular apex and thoracotomy.
Edwards-SAPIEN transcatheter heart valves (Edwards Lifesciences, Inc., Irvine, California) were used. Two sizes were available, with an external diameter of 23 or 26 mm. An echocardiographic annulus diameter between 18 and 21 mm was considered suitable for the smaller valve and between 21 and 26 mm for the larger valve. Transthoracic echocardiography was used for screening purposes, and intraprocedural TEE was used for final measurement of the diameter of the aortic annulus.
TAVI was performed in 11 patients with stenotic BAV between May 2006 and March 2009 at St. Paul's Hospital (n = 8), Quebec Heart and Lung Institute (n = 2), and Hamilton Health Sciences Centre (n = 1). Mean age was 73.2 ± 12.5 years (range 52 to 90 years); there were 6 men and 5 women. The Society of Thoracic Surgeons (STS) estimated surgical mortality was 4.4 ± 2.6%. Although STS scores do not reflect a high-risk population, many patients had comorbidities that are not fully accounted for by the STS score, including end-stage liver failure (n = 2) and frailty (n = 4).
Baseline transthoracic echocardiography before the TAVI reported a mean aortic valve area of 0.65 ± 0.17 cm2 and mean gradient of 41.0 ± 22.4 mm Hg. No patient had more than mild aortic incompetence. One patient had severe mitral regurgitation. Ten of these patients had congenital bicuspid valves, whereas the other had a functional bicuspid valve. Seven of them had severely calcified valves, whereas the other 4 had moderate calcification. Left ventricular ejection fraction was 46.7 ± 16.1%. The diameters of the aortic root were approximately the upper limits of normal; left ventricular outflow tract was 22.1 ± 1.9 mm (transthoracic echocardiography), aortic annulus was 24.0 ± 2.3 mm (TEE), aortic root at the level of sinuses of Valsalva was 39.4 ± 5.8 mm (aortography), and ascending aorta was 38.3 ± 4.6 mm (aortography).
Valves were successfully implanted in all 11 patients. Access was transfemoral in 7 patients and transapical in 4 patients. The 26-mm Edwards-SAPIEN valve (Edwards Lifesciences, Inc.) was used in 10 patients, whereas a 23-mm valve was used in 1 patient. Pre-implantation balloon valvuloplasty was done with a balloon 2 to 3 mm smaller in diameter compared with the aortic annular size. Full balloon expansion could be achieved in all the cases. None of the patients developed significant aortic incompetence after balloon valvuloplasty.
The position of the implanted valve was optimal in 10 patients. In these 10 patients, there was significant hemodynamic improvement with a reduction in mean pressure gradient to 13.4 ± 5.7 mm Hg and an increase in mean valve area to 1.45 ± 0.3 cm2. All valves appeared to open relatively symmetrically with a circular appearance on TEE (Fig. 1). No patient had significant valvular aortic incompetence after valve implantation. Three patients had moderate perivalvular leaks. In the single patient with severe mitral regurgitation, this was reduced to moderate and remained stable. Left ventricular ejection fraction rose from 46.7 ± 16.1% to 56.0 ± 16.3%.
In 1 transapical case the annulus was thought to be suitable for a 26-mm valve on the basis of transthoracic echocardiography. However, intraprocedural echocardiography documented a 28-mm annulus. The valve was deployed too ventricular with a native leaflet incompletely covered by and extending over the valve frame. There was an initial modest improvement in valve area and gradient.
The 30-day survival was 82%. At a median follow-up of 208 days (interquartile range: 21.5 to 534.5 days, longest follow-up: 1,172 days), 7 patients (all transfemoral access patients) remained alive. They also remained with minimal symptoms (New York Heart Association functional class II dyspnea in all 7 patients, and Canadian Cardiovascular Society functional class II angina in 1 patient). Of the 4 transapical access patients, 2 died of multisystem failure on days 2 and 5. The transapical patient with a malpositioned prosthesis was documented to have progressive displacement of the prosthesis into the left ventricular outflow tract with recurrent stenosis and worsening regurgitation. Late conversion to open surgery was followed by death at 63 days. The last transapical patient died of a noncardiac cause at 208 days.
Follow-up transthoracic echocardiography (median follow-up of 387 days [interquartile range: 88 to 602 days, longest follow-up: 1,074 days]) showed well-functioning valve prostheses in all living patients with a mean aortic valve area of 1.4 ± 0.35 cm2 and mean gradient of 13.9 ± 5.7 mm Hg. No patient had significant valvular aortic incompetence, whereas 1 remained with a moderate perivalvular leak. The patient who had severe mitral regurgitation before aortic valve implantation remained to have moderate mitral regurgitation. Left ventricular ejection fraction improved from 49.4 ± 15.6% (before aortic valve implantation) to 62.6 ± 9.5%.
BAV is the most common congenital cardiac anomaly. It has been suggested this condition might be responsible for more morbidity and mortality than all other congenital cardiac malformations (6). It is heritable (7,8) and more common in men (9,10), and the pathogenesis is unknown. In a large clinicopathologic study of 542 patients with BAV, 75% had pure aortic stenosis, 13% had pure aortic insufficiency, and 10% had combined aortic stenosis and insufficiency (9).
BAV stenosis reportedly comprises 30% to 50% of all adult patients undergoing aortic valve replacement surgery for severe aortic stenosis (11,12). However, BAV have generally been considered to contraindicate TAVI, because of the presumed risk of poor seating or paravalvular regurgitation due to severe distortion of the native valve leaflets. Because BAV disease has generally been an exclusion criterion in major trials of TAVI, there is little clinical experience available.
Little is known about the biomechanical requirements for TAVI in the setting of BAV disease. In 1 intraoperative study, an experimental transcatheter valve was temporarily implanted in patients with both bicuspid and tricuspid aortic stenosis before conventional aortic valve replacement (13). Noncircular stent expansion consistently occurred in the bicuspid valves compared with one-third of tricuspid valves. However, balloon dilation of the native valve was not performed, and the mechanical characteristics of this particular self-expanding stent used might not be comparable to clinically available transcatheter valves. In addition, self-expanding stents typically rely on the unique properties of nitinol, which include an increase in maximal radial force with the passage of time, initial overexpansion, and core body temperature (14,15).
It is notable that valve expansion appeared relatively circular on TEE in all 11 cases. This suggests that a bicuspid valve does not necessarily preclude symmetric expansion of a balloon-expandable valve with sufficient radial strength. Paravalvular regurgitation was trivial or mild in most patients, suggesting that bicuspid valves do not necessarily preclude effective sealing. However, moderate paravalvular leaks in 2 patients and the occurrence of late migration in 1 patient suggest that secure seating of the prosthesis within the native annulus might be more difficult and accurate sizing might be more critical than with tricuspid valves.
The success of TAVI in bicuspid aortic stenosis might depend on the selection of appropriate patients. Successful results could likely be achieved in patients with calcified bicuspid valves and predominant aortic stenosis. Patients with bulky leaflets, enlarged aortic root, dilated ascending aorta, and significant aortic incompetence might be at a higher risk of failure to achieve successful results.
Selected high-risk patients with bicuspid aortic stenosis can be successfully treated with TAVI with acceptable clinical outcomes.
Drs. Ye, Cheung, Rodés-Cabau, Dumont, and Webb are consultants for Edwards Lifesciences, Inc. All other authors have reported that they have no relationships to disclose.
- Abbreviations and Acronyms
- bicuspid aortic valve(s)
- Society of Thoracic Surgeons
- transcatheter aortic valve implantation
- transesophageal echocardiography
- Received January 31, 2010.
- Revision received August 4, 2010.
- Accepted August 6, 2010.
- American College of Cardiology Foundation
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