CoreValve Transfemoral Approach

Introduction

Transcatheter aortic valve implantation (TAVI) was first performed by Alain Cribier in 2002¹ using the balloon-expandable Cribier-Edwards valve. Soon after, the self-expandable CoreValve ReValving system (Medtronic, Inc., Minneapolis, Minnesota) was introduced based on a completely different design concept.² Initial reports on safety and technical feasibility of these two new technologies raised expectations among interventional cardiologists,^3–5 and both prostheses have undergone rapid development and implementation thanks to the information generated from these initial experiences. Following market approval in Europe, the number of patients treated with both technologies has exponentially increased, with more than 8,000 implants to date. Technical aspects and clinical outcomes related to the Edwards-SAPIEN aortic valve (Edwards Lifesciences, Irvine, Calif.) have been summarized in a similar review in this journal. Therefore, this review will discuss the CoreValve transfemoral experience.

Valve Design

The CoreValve ReValving system includes a biological bioprosthesis made of self-expandable nitinol and porcine pericardium and a dedicated delivery system (Figures 1 and 2). The current-generation nitinol frame is 50 mm in length and is hour-glass shaped. The lower (inner) portion of the frame is designed to seat on the left ventricular outflow tract (LVOT), but care must be taken not to impinge the anterior mitral leaflet. This is the part that affixes the valve to its position and thus has the greatest radial strength. The mid-portion of the prosthesis corresponds to the area of the sinuses of Valsalva and the coronary ostia, and it is not attached to the aortic wall so as not to jeopardize coronary flow. Finally, the upper section (outflow) has the lowest radial force and is designed to fix and stabilize the prosthesis in the ascending aorta (Figures 3 and 4). The valve itself consists of three leaflets of porcine pericardium sutured to the frame. Once deployed, the point of coaptation of these leaflets is supra-annular. Hence, the functional diameter of the valve is fixed at 22 mm for the smallest device and 24 mm for the largest one.⁶ The ascending aorta and LVOT dimensions (measured in a parasternal long-axis view just below the point of insertion of the valves, incorrectly described as the “aortic annulus”) are therefore important to select the most appropriate valve size. Two sizes are currently available commercially. The smallest one has a 26 mm inflow diameter and is dedicated for patients with aortic annuli measuring in the range of 20–23 mm; the largest one has a 29 mm inflow diameter and is suitable for patients with 24–27 mm aortic annuli. The CoreValve ReValving system rapidly evolved from the initial 25 Fr delivery system to the current 18 Fr device, which allows for a completely percutaneous arterial access (with the help of closure devices positioned preprocedure). This empowered the transition to a truly percutaneous procedure, avoiding general anesthesia and orotracheal intubation.⁵

Patient Selection

The gold standard for the treatment of severe aortic stenosis is surgical valve replacement⁷ and therefore, initial transcatheter aortic valve implantation (TAVI) studies restricted patient inclusion to those for whom surgery was not an option (patients either already rejected for surgery or at very high surgical risk). Market approval opened the way to more flexible indications, thereby broadening the spectrum of patients treated, although most of them are still high risk. Ascending aorta and LVOT dimensions have already been mentioned as important factors for patient selection, but there are several other issues to be taken into consideration in order to select the most appropriate candidates and anticipate potential difficulties and complications. Vascular complications, although less frequent with the CoreValve than with the Edwards-SAPIEN valve due to the former’s lower profile, do warrant attention and careful planning based on accurate imaging assessment of the vasculature. Therefore, ileo-femoral diameter, tortuosity and calcification must be carefully evaluated before the procedure. Attention should also be paid to the anatomy of the aortic root, as the position of the coronary ostia too low in the sinuses of Valsalva, a short sinus height in relation to the length of the native leaflet, or a narrow diameter at the sinuses level may cause coronary obstruction. A very horizontally positioned aortic root may also cause difficulty in valve crossing and device placement. Piazza et al postulated 15 anatomic criteria that, in their experience, seem to be related to procedural and clinical outcomes.⁸ According to these criteria, patients who are not good candidates for TAVI procedures have one or more of the following:

• left ventricular (LV) thrombus;

• subaortic stenosis;

• aortic annulus 27 mm;

• aortic regurgitation grade > II/IV;

• LV ejection fraction 17 mm;

• annulus-to-aorta angle > 45º;

• sinuses of Valsalva height 43 mm;

• significant angulation of the aortic arch;

• ileofemoral diameter 50%;

• normal LV wall thickness;

• annulus to aorta angle 15 mm and aortic root diameter > 30 mm;

• high coronary ostia;

• no coronary artery stenosis;

• ascending aorta diameter 7 mm.

Clinical Outcomes

Initial experience. Only 66 patients were treated with the 25 Fr or the 21 Fr system, but more than 3,500 implantations have been performed to date with the 18 Fr device. Valve performance after the deployment has been consistently good,^2,5,6,9 as has clinical improvement, with more than 75% of the patients in New York Heart Association (NYHA) class III–IV before the procedure, but more than 80% in Class I–II at the last follow-up.¹⁰ Procedural success rates have progressively increased, probably explained by more extensive operator experience and a better understanding of the patient selection process, as well as device implementation. In fact, a single-center study comparing the three device generations showed procedural success rates of 70%, 70.8% and 91.2% (p = 0.003) with the first, second and third generations, respectively, and procedural major adverse cardiac or cerebrovascular event (MACCE) rates of 20.0%, 16.7% and 3.9% (p = 0.008), respectively. Mid-term outcomes have also improved,⁹ with 1-year survival rate of 60% with the first-generation device, 79.2% with the second-generation and 84% with the third-generation device.⁹ For this article, Medtronic-CoreValve has provided us with detailed information on the initial Safety and Performance 18 Fr study (S&P-18 Fr), which enrolled 126 patients in Europe and Canada between 2006 and 2008. The mean age of the patients was 81.9 ± 6.4 years and 74.6% of them were in NYHA class III–IV preprocedure. The estimated mean logistic EuroSCORE was 23.4 ± 13.8. At discharge, the all-cause mortality rate was 15.1% (10.3% cardiac deaths), the stroke rate was 6.3% and a permanent pacemaker had been implanted in 26.2% of the patients. The rates of major hemorrhage, cardiac perforation and surgical conversion were 10.3%, 2.4% and 2.4%, respectively. Overall, the MACE rate was 26.2%, with a rate of adverse events of 49.2%. The patients remained very stable after hospital discharge, as shown by the very similar 30-days event rates. Echocardiographic data showed improvement in average aortic gradients (peak gradient decreased from 76.3 mmHg to 17 mmHg at 30 days, and the mean gradient from 49.6 mmHg to 8.4 mmHg) and average aortic valve area (from 0.71 cm² to 1.79 cm² at 30 days). Only 42% of the patients were free of aortic regurgitation immediately after the procedure, but this percentage progressively increased during follow-up with 65% of the patients free of regurgitation at 12-month follow-up. Long-term survival of this cohort was 71.8% at 1 year and 62.7% at 2 years (Kaplan-Meier method).

Post-market evaluation. The reported procedural success rates are even more impressive, as the analysis of the CoreValve Multicenter Expanded Evaluation Registry shows. The first report on 646 patients described a 97% procedural success rate, procedural mortality of 1.5% and all-cause mortality at 30 days of 8% (for an estimated logistic EuroSCORE risk of 23.1 ± 13.8%).⁸ In this registry, 21% of the patients underwent balloon postdilatation of the prosthesis because of residual aortic regurgitation. According to the presentation by Prof. Serruys at EuroPCR 2009 with 1,500 patients analyzed, procedural success was 97.3% and 30-day survival was 89.6%. The Australia-New Zealand (AZN) registry is an ongoing, multicenter, prospective registry with well-defined cardiac and vascular inclusion and exclusion criteria and independant adjudication of clinical events. Procedural success for the initial 62 patients was 96.8% and 30-day mortality was 3.2%, which compares very favorably with previous reports. Cardiac perforation and tamponade occurred in 2% of the patients, access-site bleeding in 21% and the major hemorrhage rate at 30 days was 3%. Permanent pacemakers were implanted in only 10% of the patients immediately post procedure and in 39% at 30 days. That this is an emerging field of investigation is corroborated by the fact that there are in excess of 45 ongoing studies on this area.

Complications

Vascular. The 18 Fr device is introduced through a femoral artery and must be navigated through the iliac, abdominal and thoracic aorta. Access-site complications are similar to those of coronary catheterization, including hemorrhage and, rarely, infection. Nevertheless, hemorrhage may be more difficult to cease due to the higher profile of the devices and may require surgical repair. Vascular complications may occur at any vascular level, primarily dissection and rupture. In cases of severe peripheral disease in which arterial complications may be expected, the subclavian approach is emerging as an excellent alternative.¹¹

Cardiac. Cardiac complications are multiple, and are usually related to the device itself or to the wires and catheters used. The most frequent complications include:

• Cardiac perforation and tamponade. Extra care should be taken during attempts to cross the valve and when manipulating straight and stiff guidewires. Oversizing the annulus with the pre-deployment valvuloplasty balloon should be avoided (risk of annular rupture).

• Myocardial infarction. As in any catheterization procedure, careful manipulation should help avoid air embolism. Potential coronary compromise caused by valvular calcium mobilization with the CoreValve prosthesis has been rare, but should always be assessed before the procedure – preferably by cardiac computed tomographic angiography – and checked during and after deployment.

• Conduction abnormalities. Atrioventricular block requiring a permanent pacemaker is one of the most frequent complications after CoreValve implantation, especially when the patient has preexisting bundle branch block. It has ranged from 19–35%, with a weighted average of 23%, according to Dr. Laborde in his presentation at EuroPCR 2009. The indications and timing for permanent pacemaker implantation are yet unclear, although it is generally recommended to wait for 2 days for conduction to recover. The risk of conduction disturbances has been related to deeper implantation in the LVOT,¹² thus valve deployment is currently attempted in a slightly higher position than was previously done.

• Aortic regurgitation is not uncommon after the initial deployment; mild-to-moderate regurgitation has been described in more than 50% of the patients. It may be central (and usually not relevant) or periprosthetic. In the latter cases, balloon postdilatation to achieve better fixation to the aorta can be carefully performed. The consequences of new-onset aortic regurgitation in these non-compliant ventricles is yet not completely known; however, at 2-year follow-up it has been documented that 70% of all patient had no aortic regurgitation, 30% had trace to 1+ and no patients had ≥ 2+. The percentage of patients with aortic regurgitation decreases over time, but whether this is due to a real decrease in the regurgitant volume or to a natural selection of the patients without regurgitation is unknown.

Prosthesis malpositioning and migration. The valve should seat in the LVOT, above the mitral level, without interfering with valve movement. Valve malpositioning is infrequent, but can lead to significant periprosthetic regurgitation or to impingement on the mitral valve. In cases in which the lowest segment of the prosthesis is too low in the LVOT, soft traction of the device before complete deployment may help to reposition it. Nevertheless, in some cases, this traction is enough to detach the valve from the aortic annulus into the ascending aorta. If this is the case and the device cannot be recaptured, a good alternative is to implant this valve in the descending aorta and a second one in the aortic annulus.

Other complications. The stroke rate with transfemoral CoreValve implantation needs to be carefully evaluated. It may be due to atherosclerotic disease, plaque detachment when navigating through the ascending aorta leading to embolization, hemorrhage as a consequence of procedural heparinization, and so forth. Finally, long-term durability and performance should be tested and compared to surgical standards.

Conclusions

Transfemoral CoreValve implantation with the 18 Fr system is technically feasible and can be performed safely and with a high probability of success in patients with favorable anatomy. The anatomic characteristics that define the most suitable candidate for the procedure are yet to be clearly defined and correlated to outcomes. Without doubt, the anatomy of the aorto-iliac system and the aortic root are among the most important variables, and 15 different characteristics have been proposed as being associated with procedural success without complications (aortic root diameter, height, angle, arch turn, LVOT size, iliac diameter, etc.). In cases of aorto-iliac disease, alternate access sites should be investigated. Procedural success rates currently range from 90–95%. The most frequent complications include, among others, new-onset need for permanent pacemaker implantation, aortic regurgitation and vascular injury. Hemodynamic improvement is generally immediate after implantation, and valve function and hemodynamics remain stable over the follow-up periods studied. Although information on long-term follow-up is lacking, this technology is very promising and will most likely become a standard of care for high-risk patients in the near future. High expectations are focused on the long-term durability of CoreValve impantation in an attempt to broaden the indications to lower-risk and younger patients.

References

1. Cribier A, Eltchaninoff H, Bash A, et al. Percutaneous transcatheter implantation of an aortic valve prosthesis for calcific aortic stenosis: First human case description. Circulation 2002;106:3006–3008.

2. Grube E, Laborde JC, Gerckens U, et al. Percutaneous implantation of the CoreValve self-expanding valve prosthesis in high-risk patients with aortic valve disease: The Siegburg first-in-man study. Circulation 2006;114:1616–1624.

3. Cribier A, Eltchaninoff H, Tron C, et al. Early experience with percutaneous transcatheter implantation of heart valve prosthesis for the treatment of end-stage inoperable patients with calcific aortic stenosis. J Am Coll Cardiol 2004;43:698–703.

4. Cribier A, Eltchaninoff H, Tron C, et al. Treatment of calcific aortic stenosis with the percutaneous heart valve. Mid-term follow-up from the initial feasibility studies: The French experience. J Am Coll Cardiol 2006;47:1214–1223.

5. Grube E, Schuler G, Buellesfeld L, et al. Percutaneous aortic valve replacement for severe aortic stenosis in high-risk patients using the second- and current third-generation self-expanding CoreValve prosthesis: Device success and 30-day clinical outcome. J Am Coll Cardiol 2007;50:69–76.

6. Grube E, Gerckens U, Wenaweser P, Buellesfeld L. Percutaneous aortic valve replacement with the CoreValve prosthesis, letter to the editor, reply. J Am Coll Cardiol 2008;51;170–171.

7. Vahanian A, Baumgartyner H, Bax J, et al. on behalf of the task force on the management of heart valve disease of the European Society of Cardiology. Guidelines on the management of valvular heart disease. Eur Heart J 2007;28:230–268.

8. Piazza N, Grube E, Gerckens E, et al, on behalf of the clinical centres that participated in the study. Procedural and 30-days outcomes following transcatheter aortic valve implantation using the third generation (18F) CoreValve revalving system. Results from the multicenter, expanded evaluation registry 1-year following CE mark approval. EuroInterv 2008;4:242–249.

9. Grube E, Buellesfeld L, Mueller R, et al. Progress and current status of percutaneous aortic valve replacement: Results of three device generations of the CoreValve ReValving System. Circ Cardiovasc Intervent 2008;1:167–175.

10. Serruys PW. Keynote address — EuroPCR 2008, Barcelona, May 14th, 2008. Transcatheter aortic valve implantation: State of the art. EuroInterv 2009;4:558–565.

11. Bauernschmitt R, Schreiber C, Bleiziffer S, et al. Transcatheter aortic valve implantation through the ascending aorta: An alternative option for no-access patients. Heart Surg Forum 2009;12:E63–E64.

12. Piazza N, Onuma Y, Jesserun E, et al. Early and persistent intraventricular conduction abnormalities and requirements for pacemaking after percutaneous replacement of the aortic valve. JACC Interventions 2008;1:310–316.

From the Structural and Congenital Heart Disease Department, Lenox Hill Heart and Vascular Institute, New York.

Disclosure: Dr. Ruiz discloses that he is a stockholder in CoreValve/ Medtronic.

Address for correspondence: Carlos E. Ruiz, MD, PhD, Lenox Hill Heart and Vascular Institute, 130 East 77th Street. 9th Floor Black Hall, New York, NY 10021-10075. E-mail : cruiz@lenoxhill.net

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VASCULAR DISEASE MANAGEMENT 2010;7(3):E66–E70