Edwards-SAPIEN Aortic Valve Transapical Approach

Abstract

The Edwards-SAPIEN aortic valve (Edwards Lifesciences, Irvine, California) transapical approach was introduced into clinical practice in 2005. After feasibility studies, CE mark was obtained by the end of 2007. It is applied in operations on high-risk patients with calcific aortic valve stenosis, and allows for a less invasive replacement of the diseased native valve. Initially, patients were placed on cardiopulmonary bypass as a safety net, but improvements in periprocedural management soon allowed for truly off-pump implantation of these prostheses. The follow-up results of the large multicenter trials showed 30-day mortality rates ranging between 10.4% and 19% in high-risk patients with logistic EuroSCORES ranging from 26–35%. The 12-month mortality rates range from 39–43.5%. The purpose of this article is to provide a description of transapical aortic valve implantations with the Edwards-SAPIEN prosthesis.

VASCULAR DISEASE MANAGEMENT 2010;7:E61–E65

Key words: transapical aortic valve implantation

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Introduction

Transapical aortic valve implantations have found their way into clinical practice in Europe. Currently, the only device on the market is the Edwards-SAPIEN prosthesis (Edwards Lifesciences, Irvine, California). The implantation procedure has been standardized by extensive teaching and proctoring programs. Antegrade access to the aortic valve is conducted through the left ventricular apex. A small anterolateral thoracotomy allows for safe placement of delivery sheaths and the catheter-based Edwards-SAPIEN prosthesis. Deployment of the valve is performed under rapid ventricular pacing. Both fluoroscopy and transesophageal echocardiography (TEE) are employed to place the valve. For optimal results, a multidisciplinary team of cardiac surgeons, interventional cardiologists and anesthetists are necessary. The procedures are ideally performed in a hybrid operating room. This technology warrants careful preoperative patient screening with regard to native aortic valve anatomy, dimensions and degree of calcifications. Furthermore, patient-related risk factors need to be evaluated. Initial experimental studies and early clinical cases of transapical aortic valve implantation (TAP-AVI) were typically performed with the use of cardiopulmonary bypass (CPB) to avoid ejection of the heart in systole, thus reducing the likelihood of embolization of the valve across the annulus.^1–5 From the percutaneous experience of Cribier and colleagues and others, we learned that unloading of the heart can be effectively achieved by rapid ventricular pacing.^6–11 However, there are distinct differences between the transfemoral versus transapical aortic valve implantation in terms of patient selection and technical aspects regarding the individual procedure. In general, patients referred to cardiac surgeons for TAP-AVI consideration were previously screened by cardiologists and were not deemed suitable candidates for the transfemoral approach. There may be several reasons for this, including a higher-risk profile with the presence of peripheral vascular disease. The presence of peripheral vascular disease of course not only prevents the introduction of the delivery sheath for AVI, but also increases the risk of complications following cannulation of the groin, including leg ischemia. In contrast to the transfemoral approach, TAP-AVI requires the transventricular placement of a rather large sheath (typically 26 Fr, initially 32 Fr), thereby partly immobilizing the left ventricular anterior wall. This immobilization may further predispose the ventricle to hemodynamic deterioration following rapid pacing. These differences explain why all of the first centers in which TAP-AVI was successfully introduced into clinical practice initially decided to perform the procedure using the additional safety net of CBP. With increasing experience, the use of CPB during TAP-AVI was safely and consistently avoided without compromising postoperative outcomes. The purpose of this article is to provide a description of transapical aortic valve implantations with the Edwards-SAPIEN prosthesis.

TAP-AVI Experience at Our Center

Patient selection.Inclusion criteria. High-risk patients with severe symptomatic aortic stenosis and an aortic valve orifice area of 2 are considered for this procedure. High-risk is defined by a logistic EuroSCORE predicted risk for mortality > 20%.^3,4,12,13 Additional inclusion criteria are an age of ≥ 75 years, echocardiographically measured aortic annulus diameter of > 24 mm, as well as symmetrically distributed calcification of the stenotic native aortic valve cusps. Exclusion criteria The presence of one or more of the following comorbidities is considered a contraindication for TAP-AVI: echocardiographically measured aortic annulus diameter of > 25 mm, non-calcified aortic stenosis, subvalvular aortic stenosis, bicuspid aortic valve; intracardiac thrombus or vegetation; endocarditis; untreated symptomatic coronary artery disease; myocardial infarction within Procedure. All operations are performed during general anesthesia in a specially equipped angiography suite that meets the required standards of a hybrid operating room.3 A monoplane fluoroscopic angiography system (Axiom Sensis, Siemens, Munich, Germany) is used. Patients are placed in a supine position. A limited anterolateral incision (5–7 cm) in the fifth intercostal space is used to access the apex of the heart (Figure 1). A bipolar epicardial pacing wire is then placed and tested. Two U-stitches with Teflon felt pledgets using 3-0 Prolene are placed in the apex of the left ventricle. These serve as a purse string for linear closure of the left ventricle at the end of the procedure. The left ventricular apex is punctured and a soft guidewire passed in an antegrade fashion across the stenotic aortic valve under fluoroscopic and echocardiographic guidance. A 14 Fr soft sheath is introduced and positioned across the aortic valve. A 03500 260 cm super-stiff guidewire (Amplatz Superstiff, Boston Scientific Corp., Natick, Massachusetts) is then positioned across the aortic arch and placed into the descending aorta. The sheath is partially withdrawn and a 20 mm balloon valvuloplasty catheter positioned under fluoroscopic and echocardiographic guidance. Balloon valvuloplasty is performed once during a brief episode of rapid ventricular pacing (150/minute) or CPB. The balloon catheter and apical sheath are withdrawn and a 26 Fr transapical delivery sheath inserted bluntly. The valve is then inserted using the specific application system. Fluoroscopic and echocardiographic imaging is used to position the valve and single-shot aortic root angiography is employed to confirm the intra-annular position below the coronary ostia. During a second brief episode of rapid ventricular pacing, the valve is implanted using rapid balloon inflation.

Indication for CPB. In our early experience with TAP-AVI, CPB was deemed necessary for the safe deployment of the Edwards-SAPIEN prosthesis. Therefore, our initial patients all had prophylactic CPB with 50% flow to support implantation of the transcatheter deliverable valve. After significant experience was acquired, our subsequent patients underwent cannulation of the femoral vessels as a safety net without actually going on-pump unless necessary. Of these, only a few were placed on CPB. CPB was required in cases of severe hypotension after rapid ventricular pacing early in our patient series, for conversion to conventional aortic valve replacement (annular rupture, migration), and for partial obstruction of the left main stem causing ventricular fibrillation. The remaining patients only had a 6 Fr sheath in the femoral artery and a guidewire in the femoral vein to be prepared for fast percutaneous cannulation if necessary.

On-pump cases. The femoral vessels are exposed for subsequent cannulation for CPB. A purse-string suture (6-0 Prolene) is placed in the femoral vein while the femoral artery is dissected out and snared with two vessel loops. High-dose heparin (300 IU/kg) is given for all on-pump cases, yielding an activated clotting time of ≥ 500 seconds. A 22 Fr Quick Draw venous cannula (Edwards Lifesciences Cardiovations, Irvine, California) is advanced during TEE guidance so that its tip is positioned in the right atrium. A 6- to 8 mm transverse incision is made in the snared femoral artery and an EOPA 18 Fr flexible arterial cannula (Medtronic, Inc., Minneapolis, Minnesota) is advanced. The mean blood pressure during CPB is targeted at 50–60 mmHg. The pump flow is set at 50%, still allowing for slight ventricular ejection. Inotropic support is administered as needed to maintain the desired blood pressure. The Edwards-SAPIEN prosthesis is then crimped onto an inflatable balloon delivery catheter (Figure 2). During valve deployment, additional rapid ventricular pacing to fully unload the heart is performed. After successful valve deployment, patients are directly weaned from CPB and heparin is reversed.

Off-pump cases with cannulation. The technical aspects of the peripheral cannulation as well as anticoagulation regimens are identical to the planned on-pump cases. In contrast to the on-pump approach, the cannulae are connected to the CBP circuit, but remain clamped.

Off-pump cases without cannulation. As we gained experience, we moved away from prophylactic peripheral cannulation. However, to allow for quick cannulation of the groin if necessary, a 6 Fr arterial sheath and venous guidewire are placed. This allows for rapid implementation of CPB via the groin in an emergency situation. For anticoagulation, 10,000 units of heparin are administered. Under TEE guidance, the ventricle is filled, aiming for a central venous pressure of 10–14 mmHg. A systolic blood pressure of 120–140 mmHg is desired prior to rapid ventricular pacing. Considering the pathophysiology of severe aortic stenosis (left ventricular hypertrophy in response to chronic elevated afterload), systemic blood pressure, in our experience, is best maintained with low-dose norepinephrine infusion. In our experience, it is of great importance to maintain the blood pressure at this level since after rapid pacing pressure, recovery is usually about 40 mmHg lower compared to pre-pacing pressure. In the hypertrophic left ventricle, this is of utmost importance, as perfusion pressures of less than 60 mmHg almost immediately lead to subendocardial ischemia. Therefore, if critically low pressures occur after valve deployment, the patient is placed on CPB quickly for reperfusion.

Trials Involving TAP-AVI

Apart from several single-center experiences published in the literature, there have been four large multicenter clinical trials evaluating transapical aortic valve implantations with the Edwards-SAPIEN prosthesis (TRAVERCE, REVIVAL II, PARTNER EUROPE and SOURCE, presented at EuroPCR in Barcelona, May 2009).

TRAVERCE Trial. A total of 172 patients were included at three European centers. Mean age was 82 ± 5.6 years and the logistic EuroSCORE was 26.7%. At 1 year, freedom from myocardial infarction was 95%, freedom from explantation was 93% and freedom from structural valve deterioration was 100%. Survival was 85% at 30 days, 68% at 6 months and 61% at 12 months. Freedom from stroke was 97% at 30 days, 95% at 6 months and 94% at 12 months. Pacemaker implantations were necessary in 5.8% and conversion to open surgery in 7% of patients.

REVIVAL II Trial. A total of 40 patients were included at four American centers. Mean age was 83.7 ± 15.3 years and the logistic EuroSCORE 35.5 ± 15.3%. At 1 year, freedom from myocardial infarction was 78.2%, freedom from explantation was 100% and freedom from structural valve deterioration was 100%. Survival was 82.4% at 30 days, 64.3% at 6 months and 56.5% at 12 months. Freedom from stroke was 94.5% at 30 days, 91% at 6 months and 91% at 12 months. Pacemaker implantations were necessary in 2.5% and conversion to open surgery in 7.5% of patients.

PARTNER EUROPE Trial. A total of 70 patients were included at nine European centers. The mean age was 82 ± 5.7 years and the logistic EuroSCORE was 33.8 ± 14.7%. At 1 year, freedom from myocardial infarction was 94%, freedom from explantation was 97% and freedom from structural valve deterioration was 100%. Survival was 81% at 30 days and 58% at 6 months. Freedom from stroke was 99% at 30 days and 97% at 6 months. Pacemaker implantations were necessary in 4.3% and conversion to open surgery in 2.9% of patients.

SOURCE Trial. This is an ongoing trial, and patients are currently still recruited. However, 30-day data on 1,038 patients from 32 European centers are available. The mean age was 80.7 years and the logistic EuroSCORE 29.2%. At 30 days, freedom from myocardial infarction was 99.3% and freedom from structural valve deterioration was 100%. Survival was 89.6% at 30 days, and freedom from stroke was 94.5%. Pacemaker implantations were necessary in 7.3% of patients.

Discussion

The first transcatheter-based valves for aortic valve stenosis were implanted percutaneously.^6–10 This approach served as a last resort when no other treatment option was available. It soon became evident that due to access limitations, an alternative approach might be warranted. Thus, TAP-AVI became a clinical reality in selected centers worldwide, and the number of treated patients is steadily increasing.^3,4,14 With the transapical approach, an additional safety net became available with the use of CPB. Pushed by cardiothoracic surgeons, new strategies were developed to make this type of procedure available to a broader spectrum of patients. As a result, CPB was routinely performed in all of the early cases to allow for safe deployment of the valve without the risk of severe hemodynamic compromise. This way, the surgeons and cardiologists were able to fully concentrate on the technical aspects of delivering, positioning and deploying the valve on target. Another aspect of the learning curve was to correctly interpret the two-dimensional images from TEE and fluoroscopy with regard to finding the exact annular plane, positioning of wires, sheaths and the prosthesis within the ventricle. Interdisciplinary hemodynamic management during rapid ventricular pacing was another important lesson to be learned. For all the possible complications arising from the lack of clinical experience at the beginning of TAP-AVI, the possibility of CPB provided a comforting safety net. Yet, from the percutaneous experience, we soon learned that transcatheter AVI without CPB is feasible and reproducible. Thus, first attempts were made to avoid CPB in TAP-AVI as well.^15,16 There are, however, distinct differences between the two approaches. While in transfemoral procedures the introduction sheath is placed in the iliac vessels, it is positioned in the left ventricular cavity in the transapical approach, thereby immobilizing parts of the left ventricular anterior wall and potentially interfering with the subvalvular apparatus of the mitral valve. It came as no surprise to us that rapid ventricular pacing in the first off-pump TAP-AVI cases seemed to have a greater impact on left ventricular hemodynamics. In order to avoid the anticipated hemodynamic compromise due to the specific technical aspects of TAP-AVI, we prophylactically placed our first patients on-pump. With greater experience at our and other centers, we decided to only cannulate the femoral vessels in subsequent patients without actually going on-pump. Of these 13 patients, only a few required secondary initiation of pump flow for various reasons. From the hemodynamic behavior of the patients, we learned that an adequate systolic blood pressure prior to rapid ventricular pacing is the key to avoiding substantial post-pacing hypotension. Bearing in mind that we can expect an initial systolic blood pressure drop of approximately 30 mmHg after pressure recovery following rapid pacing, we set the minimum permissible level of pre-pacing systolic blood pressure at 120–140 mmHg. This pressure, in our experience, sufficiently prevented critical hypotension causing subendocardial ischemia, even if severe left ventricular hypertrophy was present. In order to achieve and maintain this pressure during the procedure, noradrenalin seemed to work best, as it causes a rise in peripheral vascular resistance without increasing left ventricular contractility. In contrast, we have seen detrimental hemodynamic effects with the use of adrenalin or other inotropic agents that seemed to cause left ventricular outflow tract obstruction in the presence of a hypertrophic septum, thus aggravating hypotension rather than preventing it. There were several severe complications associated with femoral cannulation including right ventricular perforation, Leriche syndrome and severe leg ischemia requiring surgical revascularization. With almost 20% of patients suffering from severe peripheral vascular disease, TAP-AVI candidates in ours as well as other series, represent a high-risk cohort for peripheral vascular complications and are typically considered unsuitable for the transfemoral approach simply because of this access site limitation. In order to optimize the operative outcome of TAP-AVI, while at the same time reducing the risk of associated peripheral vascular morbidity, we decided to go one step further by avoiding prophylactic cannulation of the femoral vessels. Another potential benefit of avoiding primary cannulation is the use of low-dose heparin, with a reduced risk for postoperative bleeding. In our experience, the move from on-pump to off-pump TAP-AVI is the result of CAREFUL pre-valve deployment hemodynamic management with a well-trained interdisciplinary team. Furthermore, conversion to on-pump cases — even in difficult situations — is rarely needed, since cardiothoracic surgeons as well as interventionists learned to successfully treat any procedural complications that arise endovascularly. Typical scenarios include valve migration, paravalvular leaks, partial coronary obstruction and pericardial effusion. In the case of valve migration, the embolized valve may be re-anchored in the descending aorta followed by a second valve deployment at the aortic annulus. Severe paravalvular leaks due to malpositioning of the valve may be treated with a valve-in-a-valve procedure. Partial coronary obstructions can be successfully treated by percutaneous coronary interventions, and related pericardial effusion may be drained by placement of a pigtail catheter.

Summary

In summary, after implementing the lessons learned early in the series in clinical practice, most patients do not require secondary conversion to an on-pump case. Consistent with the latest worldwide experience, current findings suggest that TAP-AVI can be safely and consistently performed off-pump. Nonetheless, we still advocate the presence of a CPB circuit in the angiography suite or hybrid operating room where transcatheter-based aortic valve procedures are performed.

References

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16. Ye J, Cheung A, Lichtenstein SV, et al. Six-month outcome of transapical transcatheter aortic valve implantation in the initial seven patients. Eur J Cardiothorac Surg 2007;31:16–21.

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From the Department of Thoracic and Cardiovascular Surgery, J.W. Goethe University, Frankfurt, Germany.

Disclosure: Dr. Mirko Doss discloses that he is a consultant and proctor for Edwards Lifesciences.

Address for correspondence: Mirko Doss, MD, Department of Thoracic and Cardiovascular Surgery, J.W.Goethe University, Frankfurt, T. Stern Kai 7, 60590 Frankfurt am Main, Germany. E-mail: mirkodoss@aol.com