Transcatheter Aortic Valve Implantation

Clinical Experience with the Self-expanding Medtronic CoreValve Prosthesis Implantation through a Trans-subclavian Approach

VASCULAR DISEASE MANAGEMENT 2010;7(1):E10-E14

Abstract

Calcified degenerative aortic valve stenosis (AS) is currently the most frequent native valve disease in Europe. Furthermore, it is most often seen in elderly patients with comorbidities. Surgical valve replacement is the definitive therapy for patients with severe AS. However, there are patients with high expected operative mortality, thus these patients are declined the option of conventional open heart surgery. Balloon aortic valvuloplasty is now rarely used, mainly due to its limited long-term efficacy. Alternative techniques for treatment of high-risk patients have been therefore developed, namely techniques for transcatheter aortic valve implantation (TAVI). The Medtronic CoreValve prosthesis (CoreValve, Medtronic, Inc., Minneapolis, Minnesota) was first described in 2005 by our group, and has CE certification since 2007. Today, more than 4,000 patients have received a CoreValve implant worldwide.

Introduction

Calcified degenerative aortic valve stenosis (AS) is currently the most frequent native valve disease in Europe. Furthermore, it is most often seen in elderly patients with comorbidities.1 Surgical valve replacement is the definitive therapy for patients with severe AS.² However, there are patients with high expected operative mortality, thus these patients are declined the option of conventional open heart surgery.^3,4 Balloon aortic valvuloplasty (BAV) is now rarely used, mainly due to its limited long-term efficacy.^5,6 Alternative techniques for treatment of high-risk patients have therefore been developed, namely techniques for transcatheter aortic valve implantation (TAVI). The Medtronic CoreValve prosthesis (CoreValve, Medtronic, Inc., Minneapolis, Minnesota) was first described in 2005 by our group,⁷ and has CE certification since 2007. Today, more than 4,000 patients have been undergone CoreValve implantation worldwide.^8,9 Before the TAVI procedure, a screening process takes place, including peripheral vessel imaging. For the TAVI procedure to be feasible, it must be ensured that certain anatomic criteria are fulfilled (Table 1). The peripheral arteries (iliac/femoral) should be of sufficient diameter (>6 mm) and relatively free of calcification or extensive tortuosity. Most of the time, a simple angiogram at the level of the abdominal aorta with peripheral vessel runoff suffices to delineate the anatomy. Multislice computed tomography (MSCT) with three-dimensional (3-D) reconstruction should ideally be used instead, as it provides more information in greater detail (Figure 1).

Why and When To Use the Trans-subclavian Approach

There are patients, however, with symptomatic severe AS who cannot undergo the usual transfemoral 18 Fr sheath CoreValve implantation procedure due to a variety of reasons:

• Peripheral (iliac and femoral) arteries: peripheral artery disease (PAD), namely severe calcification, tortuosity, small diameter 6–7 mm throughout the vessel; 2) its ostium at the aortic arch should not be calcified; 3) it should have a (relatively) high takeoff in the aortic arch; and 4) the presence of a patent left internal mammary artery (LIMA) graft is a relative contraindication. Again, the ideal imaging method to delineate the anatomy is contrast-enhanced computed tomography (CT) (Figure 2).

Procedure

The procedure takes place under general anesthesia, as this is required for surgical cutdown of the left axillary/subclavian artery. We no longer use extracorporeal percutaneous femoro-femoral bypass or any other form of assist device, as the protocol required for the initial implantation cases. The following steps are carried out:

1. A pacemaker lead is placed in the right ventricular apex through either the femoral vein or the internal jugular vein. This will serve two purposes: a) As a temporary pacemaker until permanent pacemaker implantation, in the case of new-onset rhythm disturbances (left bundle branch block [LBBB] or atrio-ventricular block II or III) after aortic valve balloon valvuloplasty or after implantation of the prosthesis, and b) for rapid (~180 bpm) ventricular pacing as a means of effective heart standstill during aortic valve balloon valvuloplasty.

2. The left axillary (subclavian) artery is surgically exposed and an end-to-side 8 mm Dacron graft is placed. Through this graft, an initial 9 Fr, and after exchange for a stiff wire, an 18 Fr sheath, are inserted (Figure 3). Alternatively, some operators prefer direct sheath insertion without the added Dacron graft (surgical cutdown). It is advisable that the 18 Fr sheath only be inserted over a stiff wire.

3. Through the diseased and stenotic calcified aortic valve, the left ventricle is wired, usually with the help of an AL1 or AL2 diagnostic catheter using a hydrophilic guidewire.

4. Next, a 0.035-inch super-stiff guidewire (usually an Amplatz Super Stiff ST1, i.e., 1 cm short-tip) is placed in the left ventricular apex over a pigtail catheter.

5. The valve is subsequently dilated with a standard balloon catheter (aortic valvuloplasty).

6. Immediately afterwards, the prosthesis is advanced and positioned at its intended anatomic position (Figure 4). Advancement of the prosthesis through the 18 Fr sheath, the aortic arch, and finally through the valve, is accomplished using the push-and-pull technique over the super-stiff guidewire. Accurate placement of the prosthesis is achieved by fluoroscopy and injection of small amounts of contrast through a pigtail catheter positioned in the aortic root. This pigtail can be inserted through the right brachial artery.

7. The 18 Fr sheath is removed and the axillary (subclavian) artery is surgically sutured at the end of the procedure.

8. The Dacron graft is stumped and the subclavian wound is sutured.

9. An angiogram of the subclavian artery is performed to check for dissection or any other complications.

10. The patient is extubated and transferred to the intensive care unit for continuous monitoring.

11. The temporary pacemaker cable remains for 24–48 hours, after which it is either removed or substituted by a permanent pacemaker, if required by the patient’s condition.

Results

After an initial, single-case experience with the trans-subclavian approach, the first cumulative results were recently presented.¹¹ Until April 2009, in 41 centers around the world (13 countries), 79 cases of trans-subclavian CoreValve implantation were performed as part of the ongoing 18 French Expanded Evaluation Registry. These 79 patients (38% female; 81.3 ± 5.5 years of age; 75.6% in New York Heart Association [NYHA] Class III/IV; mean ejection fraction, 49.6%) were assessed as being high risk for conventional surgery (logistic EuroSCORE [%] = 28.2) for their symptomatic AS (mean/peak gradient 48.7/79.4 mm Hg; aortic valve area 0.62 cm2). The immediate procedural success and the 24-hour survival rates reached 100%, with no major complications. These include cardiac or other death, aortic dissection, or cardiac perforation, all of which had a rate of 0%. No patient was converted to conventional open-heart surgery, while permanent pacemaker implantation was required in 10.1% of the cases.

Conclusion

Transcatheter implantation of a prosthesis in the aortic valve to treat stenosis considered inoperable by conventional surgery is now an established treatment option. In cases where femoral vessel access is not suitable due to small vessel diameter or other factors, subclavian-axillary access using the Medtronic CoreValve System is feasible, safe, and effective. It is therefore a reliable alternative to the transapical approach for such patients, especially if a “large” 26 mm CoreValve prosthesis (annulus >26 mm) is needed.

From the Department of Cardiology, HELIOS Heart Center, Siegburg, Germany.

Disclosure: Drs. Grube and Gerckens are proctors for CoreValve (Medtronic, Inc.).

Address for correspondence: Ulrich Gerckens, MD, HELIOS Heart Center, Department of Cardiology and Angiology. Ringstr 49, Siegburg, Germany 53721. E-mail: UGerckens@aol.com