tavi
TRANSCRIPT
Procedure
Transfemoral transcatheter aortic valve implantation using the balloon expandable SAPIEN transcatheter heart valve device
Summary
Transcatheter alternatives to standard aortic valve replacement have been developed to reduce the anticipated mortality and morbidity of therapy in patients in whom the risk of conventional surgery for critical aortic stenosis is considered to be too high. Patient selection, multidisciplinary approach and trained physicians are fundamental for the success of the procedure.
Introduction
Aortic stenosis is the most frequent acquired heart valve disease requiring hospitalization in Europe. Although surgery provides excellent and durable results in most patients, advanced age and comorbidities may lead to an increased risk for surgery. Moreover, conservative treatment of aortic stenosis carries a grave prognosis. Therefore, alternative, minimally invasive techniques need to be further developed to treat these very high-risk patients. We describe here an overview of the technique of implantation of a percutaneous balloon expandable aortic valve: the SAPIEN transcatheter heart valve (THV) (Edwards Lifesciences Inc., CA – MMCTSLink 173).
Patient selectionPotential candidates to transcatheter aortic valve implantation (TAVI) are mainly high-risk and elderly symptomatic patients with severe aortic stenosis. At present, the use of TAVI in young patients, at low surgical risk, patients with long life expectancy, and in asymptomatic patients is strongly discouraged
because of the uncertainty regarding long-term durability and clinical results compared to surgery. Patients with life expectancy shorter than one year should also not be considered for TAVI. Surgical risk should be assessed by a combination of scores and by clinical judgment. To be considered for TAVI using the
SAPIEN THV transfemoral approach, annular diameter of the native valve should be between 18 mm and 24 mm, and the iliac vessel anatomy should be favorable for introduction of the given delivery system.
Surgical technique
The SAPIEN THV valves and delivery systemsThe SAPIEN THV valve (Edwards Lifesciences Inc., CA, USA) consists of three bovine pericardial leaflets mounted within a tubular stainless-steel, balloon-expandable stent. It is available in 23 and 26 mm sizes (Photo 1).
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Photo 1 The SAPIEN THV valve (courtesy of Edwards Lifesciences Inc., CA, USA) alone and mounted on a balloon (MMCTSLink 173).
The valve is associated to a retrograde transfemoral delivery system (steerable guide catheter, called Retroflex, Photo 2) available in two sizes, according to the valve size, requiring either a 22F or a 24F introducer sheath. The valve is preserved in glutaraldehyde, and is crimped on the balloon at the time of the implant to preserve the function of the pericardial leaflets.
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Photo 2 The Retroflex catheter (courtesy of Edwards Lifesciences Inc., CA, USA).
Screening processSelection of patients is the most critical step of the procedure. It includes: confirmation of severity of aortic stenosis (by means of Doppler echocardiography, or rarely by catheterization, Photo 3), analysis of aortic valve and root anatomy (by a combination of angiography, echocardiography and MDCT scanning, Photo 4) and analysis of iliofemoral access (by angiography and MDCT, Photo 5). Annular diameter has to be precisely determined, to avoid valve embolization and perivalvular leakage. Annular diameter is measured by transesophageal, transthoracic echocardiography and by MDCT (Photo 6). Iliofemoral anatomy is analyzed by angiography
and/or MDCT scanning to determine size (Photo 7), presence of calcifications (Photo 8) and tortuosity (Photo 9).
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Photo 3 Cath lab and echocardiographic calculation of aortic gradient.
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Photo 4 Echocardiographic imaging of aortic stenosis.
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Photo 5 MDCT imaging 3D reconstruction of iliac artery.
Photo 6 MDCT imaging for calculation of the dimension of the aortic annulus.
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Photo 7 MDCT imaging for calculation of the diameter of iliac/femoral arteries.
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Photo 8 MDCT imaging for arterial calcification.
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Photo 9 Angiographic imaging for calculation of the diameter of iliac/femoral arteries.
Performance and logistic set-upThe implant should be performed in a well equipped suite. Ideally the implant should be done in a hybrid OR with state-of-the-art radiologic equipment and sterility standards, with a radiotransparent operating table, which allows either a complete percutaneous or a surgical approach. The screening process, periprocedural management as well as the implant involves a multidisciplinary team including a surgeon, an interventional cardiologist and an anesthesiologist. The implant requires at least three expert operators acting as a team. In addition, another team takes care of the preparation of the prosthesis (crimping and assembling of the delivery system). Scrub nurses, perfusionist and vascular surgeons are on call. Heart lung machine is in stand-by. Percutaneous fem-fem
bypass system is ready available, as well as the surgical armamentarium to proceed to bailout surgery. The procedure is usually performed under general anesthesia. Central venous catheterization is used to monitor central venous pressure and to administer i.v. therapy under the complete responsibility of the anesthesiologist. An echocardiography machine is in the room and TEE or TTE is used to monitor valve and ventricular function throughout the procedure.
Prepping and draping: the patient is in supine position on the radiotransparent table. A warming blanket is used to maintain the physiologic temperature. Electrodes and defibrillator pads are positioned in the chest having taken care not to have them in the midline.
After anesthesia induction the lower abdominal, inguinal and upper legs regions are prepped and draped with surgical standards. A long drape is used as it is standard for interventional procedures.
Diagnostic arterious access: the femoral artery controlateral to the access planned for the introduction of the delivery system is punctured and a 6F sheath is introduced (Video 1).
Video 1 Controlateral arterial puncture and sheath introduction.
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A pigtail is positioned in the abdominal aorta, just above the bifurcation to obtain an iliofemoral angiography of the controlateral side (Video 2).
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Video 2 Pigtail introduction.
A mosquito is positioned in the skin at the intended location of the puncture as reference (Video 3). The pigtail is then connected to the pressure line for continuous arterial pressure monitoring.
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Video 3 Angiographic indication for the arterial puncture.
Femoral vein access: omolateral to the diagnostic access, the femoral vein is punctured and a 7F sheath is introduced. The vein access is used either for right catheterization and for positioning the temporary lead for rapid pacing (Video 4).
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Video 4 Venous puncture.
Therapy arterial access: according to preoperative imaging (CT scan and/or angiograms), the best iliofemoral access is chosen to position the delivery system. Percutaneous puncture is usually preferred. Alternatively, the access could be surgically prepared.
Femoral puncture is performed using the usual landmarks, and the angiographic guidance. A perfect stick is mandatory because of the large profile of the delivery system. A standard diagnostic J 0.035 guidewire is inserted and a 14F long (24 cm) sheath is inserted in the artery. Heparin is administered (Video 5).
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Video 5 Fluoro-assisted puncture.
Valve crossing: a standard diagnostic J wire is introduced in the ascending aorta to carry an Amplatz (AL1) guide-catheter in the ascending aorta. The J wire is exchanged for a straight tip 0.035 guidewire to cross the aortic valve. Once the valve is crossed, the AL1 is advanced in the ventricle and the wire is exchanged with an Amplatz extrastiff 0.035 inches, 260 cm length guidewire (Video 6).
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Video 6 Crossing the aortic valve with Amplatz extrastiff wire.
Pacing test: the temporary pacing lead is positioned in the right ventricle and output and sensing thresholds are tested at low rate (Video 7).
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Video 7 Introducing the ventricular lead for stimulation.
A rapid pacing test is performed. Pacing rate is usually around 200 bpm, to obtain a mean pressure below 50 mmHg and a pulse pressure lower than 10 mmHg. During rapid pacing the defibrillator is charged and ready to shock.
Balloon aortic valvuloplasty: the valve package is opened. On a separate side table, the valve and the delivery system are assembled (Video 8).
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Video 8 Preparing the balloon on the side table.
The valve is rinsed in saline. A 20x30 mm (for the 23 valve implantation) or a 23x30 mm (for the 26 valve implantation) balloon is advanced over the wire across the aortic valve. The balloon is deaired and indeflators are used filled with a 10% contrast media solution.
Balloon valvuloplasty is used to enlarge the valve and allow easier passage of the delivery system, but also to rehearse the procedural steps of the valve delivery. An appropriate angiographic projection is chosen in line with the plane of the annulus. In most occasions this is around LAO20°/CRAN20°. Angiography tests are used to fine adjustments. This step is critical for reliable delivery of the prosthesis. The midpoint of the balloon is then positioned at the annular level. The
first operator is the only one allowed to talk. He delivers the commands in this sequence: ‘PACE’ the operator responsible for pacing starts pacing; once pressure is low and ejection is abolished (Video 9), the first operator commands ‘INFLATE’, the second operator rapidly inflates the balloon. Calcium shifting is observed during the inflation. In case of doubts, before balloon deflation the operator may command ‘CHECK’ and the technician/nurse will inject contrast from the pigtail. Once the balloon is fully expanded
the operator commands ‘DEFLATE’. Only when the balloon is fully deflated the operator commands ‘STOP PACING’. If the balloon inflation has been suboptimal (balloon escape, residual neck on the balloon), the procedure is repeated after a period of recovery. The balloon is removed, leaving the guidewire in place (Videos 10 and 11).
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Video 9 Lowering of blood pressure during rapid cardiac pacing.
video
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Video 10 Introduction of a 14 Fr sheath and the balloon for valvuloplasty.
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Video 11 Angiographic image of valvuloplasty.
Access preparation: the 14F sheath is removed, leaving the wire in place. The femoral artery is progressively dilated under fluoroscopic guidance with a set of dilators (16F, 18F, 20F, 22F...) (Video 12).
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Video 12 Introduction of crescent diameter sheaths.
In the meanwhile the valve is crimped on the balloon, and the orientation of the valve is checked by the first operator (Videos 13 and 14).
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Video 13 Preparation of the balloon on the side table.
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Video 14 Valve crimping.
The introducer sheath (22F for the 23 mm valve and
24F for the 26 mm valve) is then positioned and secured at the skin with a stay suture to avoid any displacement. The dilator is left in place until the valve is ready to be implanted to avoid kinking of the introducer sheath. ACT is checked (Video 15).
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Video 15 Introduction of the sheath for the valve delivery.
Retroflex delivery system introduction: The retroflex catheter and the valve crimped over the balloon system are advanced in the introducer using a presenter to avoid displacement of the prosthesis while crossing the sheath sealing valve (Videos 16 and 17).
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Video 16 Introduction of the delivery system into the sheath.
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Video 17 Progression of the retroflex catheter.
The catheter is advanced under fluoroscopic guidance. At this time it is still possible to check again the orientation of the valve, since the distal (upper) portion of the stent is more radiopaque. The retroflex catheter is steerable, and this property could be used to purchase difficult aortic anatomy and reach the aortic arch.
Retroflex positioning and crossing of the native valve: at the isthmus, using an LAO projection, the retroflex is partially steered to safely cross the arch avoiding scratching the outer curvature (Video 18).
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Video 18 Angiographic progression of the retroflex catheter.
Once in proximity to the valve, the catheter is fully steered to get the maximum curvature and gain a central and coaxial orientation to the native valve. The native valve is crossed and the retroflex catheter is retracted to fully expose the balloon.
Delivery of the valve: the angiographic view in line with the annulus is again obtained. Prosthesis position relative to the native leaflet is checked with angiographic checks. A final check is done during rapid pacing to observe the position in a stable condition prior to the definitive deployment. The midportion of the prosthesis is positioned at the level of the bottom line of the angiographic root. Two-thirds of the valve should stay in the ventricle at this time.
The pigtail is pulled back to avoid jailing in the prosthesis. First operator commands ‘PACE’, the pacing operator starts pacing and pressure drops, first operator commands ‘CHECK’ and a root shot is given, the first operator commands ‘INFLATE’, the second operator inflates forcefully using the indeflator
system; after full deployment of the valve the operator commands ‘DEFLATE’ and once the balloon is completely deflated he commands ‘STOP PACING’ (Videos 19 and 20).
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Video 19 Valve expansion.
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Video 20 Correct positioning.
Evaluation of the implant: the balloon is pulled back in the ascending aorta, maintaining the guidewire across the valve. The need for additional inflation is ruled out, otherwise the guidewire is pulled back and the final result of the valve implant is assessed by a full root angiogram (Video 21), by a transaortic gradient measurement (Graph 1) and by TEE or TTE (Photo 10).
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Video 21 Angiographic control.
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Graph 1 Post procedural mean hemodynamic transaortic gradient.
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Photo 10 Echocardiographic transthoracic mean aortic gradient assessment.
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Delivery system retrieval and access closure: the retroflex catheter is fully released to abolish any curve and it is removed. A crossover wire from the controlateral of the therapeutic access site provides a safety removal of the introducer sheath, especially
when small peripheral or diseased vessels may suspect some vascular troubles. A peripheral balloon should be advanced into the therapeutic site, usually into the origin of the commune iliac artery and then the introducer sheath is pulled back until the tip is at
the level of the distal external iliac artery. A control angiogram is performed through the side arm of the long armed sheath, positioned at the Carrefour. The introducer sheath is completely removed and the access is closed either surgically or percutaneously. A final angiogram of the access is done. The pacing leads are removed and the sheaths left in place for at least 12 h. Patient is either weaned from anesthesia or transferred to the intensive or intermediate care unit.
Results
TopSummaryIntroductionSurgical techniqueResultsDiscussionReferences
Initial published data on procedural mortality and morbidity have demonstrated acceptable preliminary results in a high-risk environment. Webb et al. [3] published their TAVI experience on 50 symptomatic patients with severe aortic stenosis. Valve
implantation was successful in 86% of patients. Intraprocedural mortality was 2%. Discharge home occurred at a median of five days (interquartile range, 4–13). Mortality at 30 days was 12% in patients in whom the logistic European System for Cardiac Operative Risk Evaluation risk score was 28%. With experience, procedural success increased from 76% in the first 25 patients to 96% in the second 25 (P=0.10), and 30-day mortality fell from 16 to 8% (P=0.67). Mild paravalvular regurgitation was common but was well tolerated. After valve insertion, there was a significant improvement in left ventricular ejection fraction
(P<0.0001), mitral regurgitation (P=0.01), and functional class (P<0.0001). Improvement was maintained at one year. Structural valve deterioration was not observed with a median follow-up of 359 days.
Discussion
TopSummaryIntroductionSurgical techniqueResultsDiscussionReferences
TAVI is a new technology. Self-expanding and balloon expanding valves are currently implanted in Europe. At the moment TAVI are performed only in selected centers with a multidisciplinary approach. Their role in the management of aortic stenosis is evolving. Initially TAVI was only performed in end-stage patients. Today TAVI is performed also in high-risk patients. Before TAVI being proposed for current surgical candidates, safety efficacy and durability of the implants have to be determined on a large scale.
Footnotes
1 Consultant for Edwards Lifesciences LLC.
References
TopSummaryIntroductionSurgical techniqueResultsDiscussionReferences
1. Iung B, Baron G, Butchart EG, Delahaye F, Gohlke-Bärwolf C, Levang OW, Tornos P,
Vanoverschelde JL, Vermeer F, Boersma E, Ravaud P, Vahanian A. A prospective survey of patients with valvular heart disease in Europe: the Euro Heart Survey on Valvular Heart Disease. Eur Heart J 2003;24:1231–1243.[Abstract/ Free Full Text]
2. Varadarajan P, Kapoor N, Bansal RC, Pai RG. Clinical profile and natural history of 453 nonsurgically managed patients with severe aortic stenosis. Ann Thorac Surg 2006;82:2111–2115.[Abstract/ Free Full Text]
3. Webb JG, Pasupati S, Humphries K, Thompson C, Altwegg L, Moss R, Sinhal A, Carere RG, Munt B, Ricci D, Ye J, Cheung A, Lichtenstein SV. Percutaneous transarterial aortic valve replacement in selected high-risk patients with aortic stenosis. Circulation 2007;116:755–763.[Abstract/ Free Full Text]
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