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J Thorac Cardiovasc Surg 2007;134:1150-1156
© 2007 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
a Department of Cardiovascular Surgery, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
b Department of Cardiology, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
e Department of Anesthesiology, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
c Department of Interventional Cardiology, Clinique Pasteur, Toulouse, France
d Department of Anesthesiology, Montreal Heart Institute, Montreal, Quebec, Canada.
Received for publication February 9, 2007; revisions received July 3, 2007; accepted for publication July 10, 2007. * Address for reprints: Raymond Cartier, MD, Department of Cardiovascular Surgery, Montreal Heart Institute, 5000 Belanger Street, Montreal, Quebec H1T 1C8, Canada. (Email: rc2910{at}aol.com).
| Abstract |
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Methods: The CoreValve pericardial bioprosthesis (CoreValve, Inc, Paris, France) is sutured on a nitinol frame and delivered in a 21F catheter. All procedures were performed under femoro–femoral cardiopulmonary bypass support consisting of an aortic balloon valvuloplasty followed by prosthesis deployment within the aortic annulus under fluoroscopy. Ten high-risk surgical patients underwent percutaneous valve replacement.
Results: Immediate improvement in aortic valve function was observed in all patients. The aortic valve area increased from 0.57 ± 0.19 to 1.2 ± 0.35 cm2 (P = .00001), the mean transaortic valve gradient decreased from 51 ± 19 to 11 ± 3 mm Hg (P < .001). The 30-day mortality was 20%: one patient died 5 days after the procedure of a massive ischemic stroke and 1 patient died at 20 days of a hemorrhagic stroke. The median New York Heart Association functional class improved from III to II (P = .01).
Conclusions: Aortic valve replacement with the CoreValve bioprosthesis can be performed with favorable early technical results in high-risk patients. However, the morbidity and short-term mortality of such procedures remain significant.
| Introduction |
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Aortic stenosis (AS) is one of the most common forms of acquired valvular heart disease in adults.1,2
Open chest aortic valve replacement (AVR) is the "gold standard," improving survival and alleviating symptoms.2-4
Nevertheless, the surgical approach is associated with substantial operative mortality rates in high-risk patients. Consequently, almost one third of patients with severe AS are not offered surgery owing to a combination of reasons such as advanced age, impaired left ventricular function, redo procedure, or multiple comorbidities.5
The prevalence of AS increases with age,2
and as longevity within the general population is increasing, the proportion of AS patients with contraindications for surgery is also expected to increase. Consequently, a less invasive and safer alternative to surgical aortic valve replacement for these patients is being increasingly recognized.
Balloon aortic valvuloplasty, originally described in the 1980s,6
was the first alternative to surgical therapy. However, despite high rates of procedural success, restenosis led to disappointing results in the longer term in adult patients and has been abandoned.7
Recent success with percutaneous pulmonary valve implantation8
supports the possibility of percutaneous aortic valve replacement (PAVR). So far, early experience with this technique in humans is limited to a few devices.9-11
The optimal approach for PAVR continues to be investigated and several questions require clarification: method of approach (transaortic vs transapical), delivery catheter size, and circulatory support (cardiopulmonary bypass, temporary left ventricular assistance, or rapid ventricular pacing).
We report our early experience with a new endovascular technology allowing retrograde implantation with brief peripheral cardiopulmonary bypass support.
| Patients and Methods |
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We reviewed our initial 9-month experience from December 2005 to August 2006. Patients underwent transthoracic echocardiography, iliofemoral contrast angiography, and coronary angiography. Clinical evaluation and echocardiograms (VIVID7; GE Healthcare, Milwaukee, Wis) were obtained before the procedure, within 24 hours of the procedure, at day 10, and at 1 month after the procedure.
Prosthetic Valve System
The CoreValve aortic valve prosthesis (CoreValve, Inc, Paris, France) consists of a single-size bioprosthetic valve made of porcine pericardial tissue, which is mounted and sutured in a self-expanding hourglass-shaped 55-mm length nitinol frame (Figure 1, A). The lower part of the frame has a high radial force to overcome valvular calcification and prevent recoil, and it serves to anchor the prosthesis in the annulus. The mid part of the frame is constrained to avoid coronary ostia and carries the valve leaflets, whereas the upper part expands in the proximal ascending aorta to ensure stability and central alignment of the prosthesis. The actual valve inner diameter is 22 mm. At the time of the procedure, the nitinol valve is chilled in cold saline and retracted into the 21F delivery catheter by a compression and loading system.
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Preoperative and Postoperative Care
All patients received either vancomycin or cefazolin intravenously (1 g) immediately before the procedure. Antibiotic prophylaxis was systematicaly continued for 48 hours. Combination therapy with aspirin (325 mg) and clopidogrel (300 mg loading dose followed by 75 mg daily maintenance dose) was started preoperatively and given after the procedure for 3 months. Aspirin (80 mg daily) monotherapy was then continued indefinitely. Low-dose subcutaneous heparin (5000 IU twice daily) was administered for thromboprophylaxis until patients were ambulatory.
Statistical Analyses
Continuous normally distributed variables are expressed as mean ± SD and analyzed by the paired Student t tests or analysis of variance. Continuous non-normally distributed data are expressed as median (interquartile range) and analyzed with a Wilcoxon or Kruskal–Wallis test Categorical data were analyzed by a Pearson
2 test. All statistical analyses were undertaken with StataCorp version 7 software (StataCorp, College Station, Tex). Adjustments were not made for multiple testing.
| Results |
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Postoperative Course
Mean mechanical ventilation time was 7.8 ± 4.7 hours. All patients had mild transient elevation of creatine kinase MB and troponin T as indicated in Table 3. The operative (30-day) mortality was 20% and hospital mortality was 30% (including operative mortality). Postoperative complications are shown in Table 3. Patient 7 died on the fifth postoperative day after a massive hemispheric ischemic stroke. One patient had a postoperative ophthalmoplegia related to an embolic event. Three other patients had transient confusion without computed tomographic evidence of cerebral embolization. Two patients required pacemaker implantation because of persistent atrioventricular block. Two patients had transient nonsustained atrial fibrillation. Vascular access complications were encountered in 5 patients: 1 had a hematoma, 2 had lymphoceles, and 2 required femoral arterial reconstructions (patch angioplasty). Femoral wound infection was encountered in 1 patient with bilateral lymphoceles. Two patients required reoperation, 1 (patient 7) because of intra-abdominal bleeding related to pericardial (and inadvertent hepatic) puncture (patient 7) and another for an infected inguinal lymphocele. The mean intensive care unit stay was 4.6 ± 2.2 days and the mean hospital stay was 15 ± 12 days.
Perioperative Prosthesis Evaluation
The prosthesis was assessed at the end of each procedure by utilizing TEE and angiography. Immediate improvement in aortic valve function was observed in all patients. The aortic valve area increased from 0.57 ± 0.19 to 1.2 ± 0.35 cm2 (P = .00001) (Figure 2, A) and the mean transaortic valve gradient decreased from 51 ± 19 to 11 ± 3 mm Hg (P < .001) (Figure 2, B). Five patients had mild intraprosthetic insufficiency (<1) and 8 patients had a mild-to-moderate periprosthetic leak (grade 1/4 [n = 7] or 2/4 [n = 1]; Figure 2, C). Perivalvular leak remained stable over the first month.
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Postmortem Prosthesis Assessment
An autopsy was performed in the patient who died on day 5 (patient 7). Postmortem assessment confirmed good prosthetic valve position and function and found no evidence of any device-related complication. The coronary ostia were patent.
| Discussion |
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grade 2 and
grade 1 in most) in all cases. Short-term follow-up in survivors confirmed that these initial results were maintained. None of the patients had problems as a result of unstable coronary artery disease during follow-up. These results confirm the potential for safe and effective PAVR.
Our approach differs from the Cribier–Edwards LifeSciences system in several important ways. By contrast with this latter balloon-expandable stent prosthesis,12,13
the device used in this series is a self-expanding aortic valve prosthesis designed for retrograde implantation via the arterial iliofemoral arteries. Whereas animal studies have shown that the balloon-expandable prosthesis requires exact device positioning to avoid device embolization,14
the longer profile and self-expandable properties of nitinol could enhance the stability once deployed.15
Even though nitinol devices could be susceptible to fracture with time, the same self-expandable technology is commonly used in thoracic aortic stent grafts and has shown good midterm results.16
After device deployment, intraprosthetic balloon expansion can also be performed to minimize periprosthetic regurgitation but is seldom required.
Mild-to-severe paravalvular aortic regurgitation has been observed in most patients who have undergone percutaneous implantation of the balloon-expandable valve prosthesis.17
One possible advantage of a self-expanding prosthesis is the potential for continued expansion over time, which may in turn reduce paravalvular leaks after implantation.15
One theoretical advantage of the antegrade approach is a lower risk of atheroma embolism during delivery catheter advancement through an atheromatous aorta. Nevertheless, the need for transseptal puncture, unavoidable traction on the anterior mitral valve leaflet inducing potentially severe mitral regurgitation, and hemodynamic instability constitute the main drawbacks of this approach.15,18
Emerging advances in percutaneous procedures include reduced delivery catheter size (ie, 18F delivery system) and alternative approaches (retrograde subclavian or transapical approaches), which may reduce the risk of implantation failure in patients with severe peripheral vascular disease. These new approaches may limit the risk of femoral access site complication.
The relatively brief cardiopulmonary bypass times in this series were sufficient to unload the left heart cavities, ensure hemodynamic stability, and secure the release of the prosthesis in the correct position. Circulatory support may represents a safer alternative to brief rapid cardiac pacing (200–220 beats/min) in patients with severe AS and left ventricular hypertrophy inasmuch as low cardiac output may lead to myocardial ischemia and subsequent hemodynamic instability. Therefore, this was chosen as our method of choice for the beginning of our experience with endovascular replacement of the aortic valve.
The mortality rate observed in our series was similar to that which was predicted using the Parsonnet and EuroSCOREs (20% vs 23%–24%). Three patients were not candidates for surgery and the others were deemed to be very poor candidates for conventional surgery. Two had severe lung disease prohibiting any kind of thoracic exploration and 1 had severe kyphoscoliosis making a classic operative approach impossible. Other scoring systems may help to obtain a better stratification and uniform preoperative risk reporting for endovascular aortic replacement in the future.19
The high 1-month mortality was associated with neurologic complications in 2 patients. These complications could possibly be prevented by alternate vascular access in patients with peripheral vascular disease. However, the hemorrhagic stroke at 20 days can be related to the anticoagulation regimen; this was adjusted for the following patients. These comorbidities and the complex postprocedural support needed for these patients before discharge are reflected by a prolonged hospital stay. Long-term follow-up of our patients is ongoing. Immediate improvements of the aortic valve surface area were observed in all patients, device-related complications did not occur, and New York Heart Association functional class improved in all patients, despite their comorbidities.
As reported in aortic endovascular interventions, the main risks for this type of procedure are also embolic stroke and technical problems related to peripheral vascular disease.20
The significant length of hospital stay in our patients indicates their complex postprocedural supportive needs before discharge.
| Conclusions |
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| Footnotes |
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2 Dr Berry was supported by a British Heart Foundation International Fellowship. ![]()
| References |
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