Minimally Invasive Therapy. 2015; Early Online, 1–9
REVIEW ARTICLE
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Transcatheter aortic valve implantation – update and evidence ARNAUD VAN LINDEN1, MIRKO DOSS1, MANI ARSALAN1, WON KEUN KIM1,2 & THOMAS WALTHER1 1
Department of Cardiac Surgery, Kerckhoff-Klinik Bad Nauheim, Bad Nauheim, Germany, and 2Department of Cardiology, Kerckhoff-Klinik Bad Nauheim, Bad Nauheim, Germany
Abstract Transcatheter aortic valve implantation (T-AVI) has become the standard of care for high-risk patients suffering from severe aortic valve stenosis. More than 60,000 implants have been performed to date. While the first-generation T-AVI devices had some specific issues, the advancements in these first-generation devices and the development of second-generation devices significantly reduced the incidence of peri-procedural complications. The two major access routes are the transfemoral (TF) and the transapical (TA) approach. Both approaches have their advantages and should be considered equal alternatives for finding the best treatment option for the individual patient. Currently there are discussions about extending the indication to patients with lower risk profiles. However, there is no real evidence to justify an expansion, as results of surgical aortic valve replacement in low and intermediate risk patients are excellent.
Key words: Cardiac surgery, catheter interventions, minimally invasive surgery
Introduction Since its introduction in 2002 (1), the number of transcatheter aortic valve implantations (T-AVI) performed has grown every year. By the end of 2014 more than 60,000 T-AVIs have been performed worldwide, with most of the patients treated in Europe. Nowadays, T-AVI is considered the standard of care for elderly high-risk patients suffering from severe symptomatic aortic stenosis, while surgical aortic valve replacement (SAVR) still is considered the treatment of choice for younger patients and patients with low and intermediate risk profiles (2). Although several alternative access strategies have been developed, the two main approaches are the transfemoral (TF) and transapical (TA) access. Detailed descriptions of the two techniques have been published earlier (3,4) and only marginal modifications in the implantation techniques were made over the past years. The most important modifications included the availability of the newest generation T-AVI devices, minimized sheath sizes and strategies
to reduce the risk of paravalvular leaks. Since the beginning of T-AVI, there are two ongoing debates. One question is whether the TF approach is superior to the TA approach, the other is whether younger patients and/or patients with lower risk profiles should also be treated with T-AVI? A review of the evolution of T-AVI has been published earlier in this journal (5). The aim of the present review is to give an overview of the latest device developments, the debate on cost-effectiveness, the evidence for extending the indication to younger, lower-risk patients and the TA or TF approach decision. First-generation T-AVI devices with second-generation modifications SAPIEN (Edwards Lifesciences, Irvine, CA, USA) The Edwards SAPIEN prosthesis (Figure 1) went through two major design changes and is now available as the 3rd generation SAPIEN 3 prosthesis (6).
Correspondence: A. Van Linden, Herzzentrum, Abteilung für Herzchirurgie, Kerckhoff-Klinik, Benekestrasse 2-8, D-61231 Bad Nauheim, Germany. Fax: +49 6032 996 2567. E-mail: [email protected] ISSN 1364-5706 print/ISSN 1365-2931 online 2015 Informa Healthcare DOI: 10.3109/13645706.2015.1047852
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
2
A. Van Linden et al.
Figure 1. SAPIEN 3 prosthesis (Edwards Lifesciences). Bovine pericardium leaflets in a cobalt chromium stent sealed by a PET skirt.
The SAPIEN prosthesis is still the only approved balloon-expandable T-AVI prosthesis. The current stent consists of cobalt chromium and is sealed by a PET (polyethylene terephthalate) skirt to minimize paravalvular leaks. The valve is made of bovine pericardial tissue. All SAPIEN prostheses are designed for TA and TF delivery. The SAPIEN 3 prosthesis is available in 23, 26 and 29 mm for treating native annulus sizes between 18 and 28 mm. The size of the transapical delivery Certitude sheath is 18 French (F) inner diameter for the 23 and 26 mm valve and 21 F inner diameter for the 29 mm valve, whereas the size of the transfemoral eSheath system is 14 F (23 and 26 mm valve) and 16 F (29 mm valve) inner diameter, respectively. The SAPIEN 3 prosthesis has an outer skirt to prevent paravalvular leakage. CoreValve (Medtronic, Minneapolis, MN, USA) The CoreValve prosthesis (Figure 2) also underwent several design changes. They are all designed for the retrograde TF approach. The latest version is the CoreValve Evolut R which recently received CEmark approval (7). The CoreValve prosthesis consists of a self-expandable nitinol frame with porcine pericardial leaflets in supraannular position. Valve sizes are 23, 26, 29 and 31 mm to treat annulus diameters between 18 and 29 mm. The regular delivery catheter has an 18 F inner diameter and the new EnVeo system for the CoreValve Evolut R has a
Figure 2. CoreValve Evoulut R prosthesis (Medtronic). Porcine pericardial leaflets in a nitinol stent.
14 F inner diameter (18 F outer diameter). The CoreValve Evolut R is fully retrievable before final deployment.
Second-generation T-AVI devices ACURATE (Symetis SA, Ecublens, Switzerland) The ACURATE system (Figure 3) is a secondgeneration device, with CE-mark approval for the TA approach since September 2011. Second generation improvements and design changes have already been incorporated from its launch to the market. The current version is the ACURATE neo valve with supraannular porcine pericardial tissue leaflets in a nitinol self-expanding stent with PET/pericardial skirt for sealing. The first-generation ACURATE was a TA system, whereas the second-generation is available for both TA and TF (8,9). The ACURATE concept is self-seating, self-sealing and stepwise deployment. Unique stent features enable this concept. Three stabilization arches are located at the distal part of the stent
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Update on T-AVI
3
Figure 4. JenaValve prosthesis (JenaValve). Natural porcine root in a nitinol stent with three feelers at the proximal part.
Figure 3. ACURATE neo prosthesis (Symetis). Porcine pericardial leaflets in a nitinol stent. Three stabilization arches at the distal part and the upper crown in the mid-portion of the stent.
for coaxial self-alignment in the aorta. An upper crown in the mid-portion of the stent allows for tactile feedback during supraannular anchoring of the valve. The implantation is performed stepwise. Step one allows for correct positioning and anatomical orientation of the commissures and is fully retrievable. After releasing a safety button of the delivery system, full deployment is achieved (10). Available sizes are S, M and L (23, 25 and 27 mm, respectively) for annulus diameters between 21 and 27 mm. The transfemoral delivery system has an 18 F outer diameter. The transapical delivery system has an outer diameter of 33 F, but the new low profile TA delivery with 21 F outer diameter will be approved soon.
JenaValve (JenaValve Technology GmbH, Jena, Germany) The JenaValve prosthesis (Figure 4) is the only T-AVI device with CE-mark approval for aortic stenosis and aortic regurgitation (11,12). The key features
of the JenaValve are the three feelers at the bottom of the self-expandable nitinol stent. These feelers grasp the native leaflets as an anchoring mechanism. The deployment is partially retrievable. The prosthesis consists of a porcine aortic root with an outer porcine pericardial skirt. Sizes are 23, 25 and 27 mm for treatment of annulus sizes between 21 and 27 mm. The delivery system is a 32 F sheathless catheter. At present, only a TA system is commercially available however, clinical trials for a TF system have started (13).
Engager (Medtronic, Minneapolis, MN, USA) The Engager (Figure 5) self-expandable nitinol stent has three control arms to be placed at the nadirs of the three native valve cusps (14). The valve consists of bovine pericardial tissue with a PET skirt sealing. The available sizes are 23 and 26 mm for annulus sizes between 21 and 27 mm using a TA 29 F system. The implantation is a three-step procedure with initial retrievability.
Portico (St. Jude Medical Inc., St. Paul, MN, USA) The self-expandable nitinol stent has a large open cell design and the valve consists of bovine pericardial leaflets (Figure 6) (15,16). Currently available is an 18 F TF system with valve sizes of 23 and 25 mm for
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4
A. Van Linden et al.
Figure 7. Lotus Valve System (Boston Scientific). Bovine pericardium leaflets in a braided nitinol wire.
Figure 5. Engager prosthesis (Medtronic). Bovine pericardial leaflets in a nitinol stent with three control arms at the proximal part.
annulus diameters between 19 and 23mm. Additional sizes of 27 and 29 mm are anticipated. The system is re-sheathable up to a deployment of 85%. A 24 F TA sheathless system has been presented (17).
Lotus Valve System (Boston Scientific, Natick, MA, USA) The Lotus valve (Figure 7) has a completely different concept than most of the other T-AVI prostheses: The native design is an approximately 70 mm long nitinol wire frame, which is braided during delivery to a height of 19 mm. It is designed with the ability to retrieve, to reposition and to redeploy (18,19). The valve consists of bovine pericardium and is surrounded by AdaptiveSeal to prevent leakage. Available prosthesis sizes for the TF approach are 23, 25 and 27 mm for the treatment of annulus diameters between 20 and 27 mm. Sheath size is 18 F for the 23 mm valve and 20 F for the 25 and 27 mm valves.
Direct Flow Medical (Direct Flow Medical Inc., Santa Rosa, CA, USA)
Figure 6. Portico prosthesis (St. Jude Medical). Bovine pericardial leaflets in a nitinol stent with large open cell design.
The Direct Flow Medical T-AVI system (Figure 8) also has a unique design, not comparable to the “typical” devices. A bovine pericardial leaflet valve is fixed in a flexible non-metal and inflatable frame (20). One aortic and one ventricular ring are connected to the frame. The complete valve is deployed in the left ventricle and the ventricular ring is inflated. While pulling the system back, the ventricular ring is anchored below the native aortic valve annulus. After positioning of the prosthesis, the aortic ring is inflated. At this stage the valve can still be repositioned. Valve functionality can be assessed and the radiopaque solution is exchanged for a quickly hardening polymer to
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
Update on T-AVI
Figure 8. Direct Flow Medical prosthesis (Direct Flow). Bovine pericardial leaflets fixed in a flexible non-metal and inflatable frame with aortal and ventricular ring.
achieve the permanent seal. This TF system is available in the sizes 23, 25, 27 and 29 mm for annulus sizes of 19 to 28 mm with an 18 F delivery system.
Evidence for TA or TF and typical complications T-AVI is a heart team procedure, aiming at minimally invasive treatment of mostly elderly and high-risk patients with aortic stenosis. Due to the fact that a retrograde TF approach is not feasible in all patients, especially in the presence of peripheral vascular disease, the heart team should have both therapeutic options - retrograde (TF) and antegrade (TA) TAVI - readily available. Access related complications may be minimized by a balanced approach of using both alternatives, thus specific risks of the different pathologies can be avoided.
Is TF superior to TA? Although the debate about superiority of one over the other approach is ongoing, since the beginning of T-AVI, no randomized, controlled trial of TA vs. TF approach has been performed. All available data and all published opinions are based on retrospective comparisons of single center experiences, registries and subgroup analyses of large trials. There is,
5
however, a general opinion that the TF approach seems to be less invasive and may be associated with better outcomes. This opinion is mainly based on the results of the large Edwards SAPIEN FDA approval trial, called Placement of Aortic Transcatheter valves (PARTNER) (21), but also on several registries and meta-analyses (22–24). They demonstrated either a significant difference or at least a trend towards higher mortality for the TA approach. But a closer look into the patient population often reveals a significant selection bias. Many centers and studies, including PARTNER, have a transfemoral-first strategy. Only the nonsuitable TF patients are assigned to the TA approach, which leads to a non-comparable patient population. This is often expressed in higher risk scoring profiles of the TA patients (25–28). Some risk factors are not represented in the typical risk scoring systems and therefore matching of the STS (society of thoracic surgeons) score and EuroSCORE does not automatically lead to comparable patient groups. Data from high volume centers without TF-first strategy and experienced TA program show excellent (29) and comparable (30) results between TA and TF. The debate about the access route and the comparison of the results revealed one very important fact, the interdisciplinary heart-team. The most experienced centers with an established heart-team seem to find the best treatment strategy for each individual patient leading to the best peri- and postprocedural results. The team approach is not only important for selecting the access route, but also for handling intraprocedural complications (31).
Aortic regurgitation The rate of paravalvular leaks ‡ 1 shows a wide range between 2 and 50%, with a decrease from firstgeneration to second-generation devices (10,28,32,33). Aortic regurgitation ‡ 2 is strongly associated with increased mortality (32,33). Predictors for postprocedural leakage are heavy and asymmetric calcifications of the native aortic valve, suboptimal implantation height and an undersized prosthesis. Post-dilatation of the implanted valve can be a useful tool to reduce initial regurgitation. Too aggressive post-dilatation can again lead to annular rupture. Therefore precise prosthesis selection and implantation are absolutely mandatory.
Conduction system disturbances All T-AVI prostheses more or less reach inside the left ventricular outflow tract and put pressure on the
6
A. Van Linden et al.
conduction system. This leads to an incidence of new AV-blocks requiring permanent pacemaker implantation of 6 to 50% (34,35). The incidence is strongly device-dependent, since the design of the different prostheses varies strongly. The highest rates of new pacemaker implantations are being reported after CoreValve implantation (34).
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
Neurological events There are several steps of T-AVI that are associated with the risk of neurological complications, such as manipulation in the aortic arch, valvuloplasty of the native valve and prosthesis deployment. The stroke rate after T-AVI varies between 1.5 to 9% with a slightly higher incidence after TF-AVI (36,37).
Vascular complications Due to a large spectrum of possible vascular complications with different severity, the total number of vascular complications is difficult to assess. According to VARC-2 (Valve Academic Research Consortium) criteria (38) minor and major vascular complications are defined. The incidence of major vascular complications varies between 5 and 16% (37,39,40). Based on the femoral access for TF-AVI, the incidence of vascular complications is significantly lower after TA-AVI. Common vascular complications are the failure of the femoral closure system, dissection of the femoral arteries and femoral artery occlusion. The ongoing reduction of delivery system diameter leads to a decrease in major vascular complication rates.
Acute kidney injury The degree of acute kidney injury after T-AVI is also defined by VARC-2 criteria (41) and divided into three stages. Due to the use of contrast agent, contrast-induced nephropathy plays an important role (42), as does the post-procedural need for transfusion and pre-procedural kidney function. The incidence of severe kidney injury is 1 to 15% (37,42,43). Every stage of kidney injury is associated with worse outcome for the patients.
Less frequent T-AVI complications Due to the increasing T-AVI experience and the device improvements some of the initial T-AVI complications have become rare (
REVIEW ARTICLE
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
Transcatheter aortic valve implantation – update and evidence ARNAUD VAN LINDEN1, MIRKO DOSS1, MANI ARSALAN1, WON KEUN KIM1,2 & THOMAS WALTHER1 1
Department of Cardiac Surgery, Kerckhoff-Klinik Bad Nauheim, Bad Nauheim, Germany, and 2Department of Cardiology, Kerckhoff-Klinik Bad Nauheim, Bad Nauheim, Germany
Abstract Transcatheter aortic valve implantation (T-AVI) has become the standard of care for high-risk patients suffering from severe aortic valve stenosis. More than 60,000 implants have been performed to date. While the first-generation T-AVI devices had some specific issues, the advancements in these first-generation devices and the development of second-generation devices significantly reduced the incidence of peri-procedural complications. The two major access routes are the transfemoral (TF) and the transapical (TA) approach. Both approaches have their advantages and should be considered equal alternatives for finding the best treatment option for the individual patient. Currently there are discussions about extending the indication to patients with lower risk profiles. However, there is no real evidence to justify an expansion, as results of surgical aortic valve replacement in low and intermediate risk patients are excellent.
Key words: Cardiac surgery, catheter interventions, minimally invasive surgery
Introduction Since its introduction in 2002 (1), the number of transcatheter aortic valve implantations (T-AVI) performed has grown every year. By the end of 2014 more than 60,000 T-AVIs have been performed worldwide, with most of the patients treated in Europe. Nowadays, T-AVI is considered the standard of care for elderly high-risk patients suffering from severe symptomatic aortic stenosis, while surgical aortic valve replacement (SAVR) still is considered the treatment of choice for younger patients and patients with low and intermediate risk profiles (2). Although several alternative access strategies have been developed, the two main approaches are the transfemoral (TF) and transapical (TA) access. Detailed descriptions of the two techniques have been published earlier (3,4) and only marginal modifications in the implantation techniques were made over the past years. The most important modifications included the availability of the newest generation T-AVI devices, minimized sheath sizes and strategies
to reduce the risk of paravalvular leaks. Since the beginning of T-AVI, there are two ongoing debates. One question is whether the TF approach is superior to the TA approach, the other is whether younger patients and/or patients with lower risk profiles should also be treated with T-AVI? A review of the evolution of T-AVI has been published earlier in this journal (5). The aim of the present review is to give an overview of the latest device developments, the debate on cost-effectiveness, the evidence for extending the indication to younger, lower-risk patients and the TA or TF approach decision. First-generation T-AVI devices with second-generation modifications SAPIEN (Edwards Lifesciences, Irvine, CA, USA) The Edwards SAPIEN prosthesis (Figure 1) went through two major design changes and is now available as the 3rd generation SAPIEN 3 prosthesis (6).
Correspondence: A. Van Linden, Herzzentrum, Abteilung für Herzchirurgie, Kerckhoff-Klinik, Benekestrasse 2-8, D-61231 Bad Nauheim, Germany. Fax: +49 6032 996 2567. E-mail: [email protected] ISSN 1364-5706 print/ISSN 1365-2931 online 2015 Informa Healthcare DOI: 10.3109/13645706.2015.1047852
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
2
A. Van Linden et al.
Figure 1. SAPIEN 3 prosthesis (Edwards Lifesciences). Bovine pericardium leaflets in a cobalt chromium stent sealed by a PET skirt.
The SAPIEN prosthesis is still the only approved balloon-expandable T-AVI prosthesis. The current stent consists of cobalt chromium and is sealed by a PET (polyethylene terephthalate) skirt to minimize paravalvular leaks. The valve is made of bovine pericardial tissue. All SAPIEN prostheses are designed for TA and TF delivery. The SAPIEN 3 prosthesis is available in 23, 26 and 29 mm for treating native annulus sizes between 18 and 28 mm. The size of the transapical delivery Certitude sheath is 18 French (F) inner diameter for the 23 and 26 mm valve and 21 F inner diameter for the 29 mm valve, whereas the size of the transfemoral eSheath system is 14 F (23 and 26 mm valve) and 16 F (29 mm valve) inner diameter, respectively. The SAPIEN 3 prosthesis has an outer skirt to prevent paravalvular leakage. CoreValve (Medtronic, Minneapolis, MN, USA) The CoreValve prosthesis (Figure 2) also underwent several design changes. They are all designed for the retrograde TF approach. The latest version is the CoreValve Evolut R which recently received CEmark approval (7). The CoreValve prosthesis consists of a self-expandable nitinol frame with porcine pericardial leaflets in supraannular position. Valve sizes are 23, 26, 29 and 31 mm to treat annulus diameters between 18 and 29 mm. The regular delivery catheter has an 18 F inner diameter and the new EnVeo system for the CoreValve Evolut R has a
Figure 2. CoreValve Evoulut R prosthesis (Medtronic). Porcine pericardial leaflets in a nitinol stent.
14 F inner diameter (18 F outer diameter). The CoreValve Evolut R is fully retrievable before final deployment.
Second-generation T-AVI devices ACURATE (Symetis SA, Ecublens, Switzerland) The ACURATE system (Figure 3) is a secondgeneration device, with CE-mark approval for the TA approach since September 2011. Second generation improvements and design changes have already been incorporated from its launch to the market. The current version is the ACURATE neo valve with supraannular porcine pericardial tissue leaflets in a nitinol self-expanding stent with PET/pericardial skirt for sealing. The first-generation ACURATE was a TA system, whereas the second-generation is available for both TA and TF (8,9). The ACURATE concept is self-seating, self-sealing and stepwise deployment. Unique stent features enable this concept. Three stabilization arches are located at the distal part of the stent
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
Update on T-AVI
3
Figure 4. JenaValve prosthesis (JenaValve). Natural porcine root in a nitinol stent with three feelers at the proximal part.
Figure 3. ACURATE neo prosthesis (Symetis). Porcine pericardial leaflets in a nitinol stent. Three stabilization arches at the distal part and the upper crown in the mid-portion of the stent.
for coaxial self-alignment in the aorta. An upper crown in the mid-portion of the stent allows for tactile feedback during supraannular anchoring of the valve. The implantation is performed stepwise. Step one allows for correct positioning and anatomical orientation of the commissures and is fully retrievable. After releasing a safety button of the delivery system, full deployment is achieved (10). Available sizes are S, M and L (23, 25 and 27 mm, respectively) for annulus diameters between 21 and 27 mm. The transfemoral delivery system has an 18 F outer diameter. The transapical delivery system has an outer diameter of 33 F, but the new low profile TA delivery with 21 F outer diameter will be approved soon.
JenaValve (JenaValve Technology GmbH, Jena, Germany) The JenaValve prosthesis (Figure 4) is the only T-AVI device with CE-mark approval for aortic stenosis and aortic regurgitation (11,12). The key features
of the JenaValve are the three feelers at the bottom of the self-expandable nitinol stent. These feelers grasp the native leaflets as an anchoring mechanism. The deployment is partially retrievable. The prosthesis consists of a porcine aortic root with an outer porcine pericardial skirt. Sizes are 23, 25 and 27 mm for treatment of annulus sizes between 21 and 27 mm. The delivery system is a 32 F sheathless catheter. At present, only a TA system is commercially available however, clinical trials for a TF system have started (13).
Engager (Medtronic, Minneapolis, MN, USA) The Engager (Figure 5) self-expandable nitinol stent has three control arms to be placed at the nadirs of the three native valve cusps (14). The valve consists of bovine pericardial tissue with a PET skirt sealing. The available sizes are 23 and 26 mm for annulus sizes between 21 and 27 mm using a TA 29 F system. The implantation is a three-step procedure with initial retrievability.
Portico (St. Jude Medical Inc., St. Paul, MN, USA) The self-expandable nitinol stent has a large open cell design and the valve consists of bovine pericardial leaflets (Figure 6) (15,16). Currently available is an 18 F TF system with valve sizes of 23 and 25 mm for
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
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A. Van Linden et al.
Figure 7. Lotus Valve System (Boston Scientific). Bovine pericardium leaflets in a braided nitinol wire.
Figure 5. Engager prosthesis (Medtronic). Bovine pericardial leaflets in a nitinol stent with three control arms at the proximal part.
annulus diameters between 19 and 23mm. Additional sizes of 27 and 29 mm are anticipated. The system is re-sheathable up to a deployment of 85%. A 24 F TA sheathless system has been presented (17).
Lotus Valve System (Boston Scientific, Natick, MA, USA) The Lotus valve (Figure 7) has a completely different concept than most of the other T-AVI prostheses: The native design is an approximately 70 mm long nitinol wire frame, which is braided during delivery to a height of 19 mm. It is designed with the ability to retrieve, to reposition and to redeploy (18,19). The valve consists of bovine pericardium and is surrounded by AdaptiveSeal to prevent leakage. Available prosthesis sizes for the TF approach are 23, 25 and 27 mm for the treatment of annulus diameters between 20 and 27 mm. Sheath size is 18 F for the 23 mm valve and 20 F for the 25 and 27 mm valves.
Direct Flow Medical (Direct Flow Medical Inc., Santa Rosa, CA, USA)
Figure 6. Portico prosthesis (St. Jude Medical). Bovine pericardial leaflets in a nitinol stent with large open cell design.
The Direct Flow Medical T-AVI system (Figure 8) also has a unique design, not comparable to the “typical” devices. A bovine pericardial leaflet valve is fixed in a flexible non-metal and inflatable frame (20). One aortic and one ventricular ring are connected to the frame. The complete valve is deployed in the left ventricle and the ventricular ring is inflated. While pulling the system back, the ventricular ring is anchored below the native aortic valve annulus. After positioning of the prosthesis, the aortic ring is inflated. At this stage the valve can still be repositioned. Valve functionality can be assessed and the radiopaque solution is exchanged for a quickly hardening polymer to
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
Update on T-AVI
Figure 8. Direct Flow Medical prosthesis (Direct Flow). Bovine pericardial leaflets fixed in a flexible non-metal and inflatable frame with aortal and ventricular ring.
achieve the permanent seal. This TF system is available in the sizes 23, 25, 27 and 29 mm for annulus sizes of 19 to 28 mm with an 18 F delivery system.
Evidence for TA or TF and typical complications T-AVI is a heart team procedure, aiming at minimally invasive treatment of mostly elderly and high-risk patients with aortic stenosis. Due to the fact that a retrograde TF approach is not feasible in all patients, especially in the presence of peripheral vascular disease, the heart team should have both therapeutic options - retrograde (TF) and antegrade (TA) TAVI - readily available. Access related complications may be minimized by a balanced approach of using both alternatives, thus specific risks of the different pathologies can be avoided.
Is TF superior to TA? Although the debate about superiority of one over the other approach is ongoing, since the beginning of T-AVI, no randomized, controlled trial of TA vs. TF approach has been performed. All available data and all published opinions are based on retrospective comparisons of single center experiences, registries and subgroup analyses of large trials. There is,
5
however, a general opinion that the TF approach seems to be less invasive and may be associated with better outcomes. This opinion is mainly based on the results of the large Edwards SAPIEN FDA approval trial, called Placement of Aortic Transcatheter valves (PARTNER) (21), but also on several registries and meta-analyses (22–24). They demonstrated either a significant difference or at least a trend towards higher mortality for the TA approach. But a closer look into the patient population often reveals a significant selection bias. Many centers and studies, including PARTNER, have a transfemoral-first strategy. Only the nonsuitable TF patients are assigned to the TA approach, which leads to a non-comparable patient population. This is often expressed in higher risk scoring profiles of the TA patients (25–28). Some risk factors are not represented in the typical risk scoring systems and therefore matching of the STS (society of thoracic surgeons) score and EuroSCORE does not automatically lead to comparable patient groups. Data from high volume centers without TF-first strategy and experienced TA program show excellent (29) and comparable (30) results between TA and TF. The debate about the access route and the comparison of the results revealed one very important fact, the interdisciplinary heart-team. The most experienced centers with an established heart-team seem to find the best treatment strategy for each individual patient leading to the best peri- and postprocedural results. The team approach is not only important for selecting the access route, but also for handling intraprocedural complications (31).
Aortic regurgitation The rate of paravalvular leaks ‡ 1 shows a wide range between 2 and 50%, with a decrease from firstgeneration to second-generation devices (10,28,32,33). Aortic regurgitation ‡ 2 is strongly associated with increased mortality (32,33). Predictors for postprocedural leakage are heavy and asymmetric calcifications of the native aortic valve, suboptimal implantation height and an undersized prosthesis. Post-dilatation of the implanted valve can be a useful tool to reduce initial regurgitation. Too aggressive post-dilatation can again lead to annular rupture. Therefore precise prosthesis selection and implantation are absolutely mandatory.
Conduction system disturbances All T-AVI prostheses more or less reach inside the left ventricular outflow tract and put pressure on the
6
A. Van Linden et al.
conduction system. This leads to an incidence of new AV-blocks requiring permanent pacemaker implantation of 6 to 50% (34,35). The incidence is strongly device-dependent, since the design of the different prostheses varies strongly. The highest rates of new pacemaker implantations are being reported after CoreValve implantation (34).
Minim Invasive Ther Allied Technol Downloaded from informahealthcare.com by Nyu Medical Center on 05/13/15 For personal use only.
Neurological events There are several steps of T-AVI that are associated with the risk of neurological complications, such as manipulation in the aortic arch, valvuloplasty of the native valve and prosthesis deployment. The stroke rate after T-AVI varies between 1.5 to 9% with a slightly higher incidence after TF-AVI (36,37).
Vascular complications Due to a large spectrum of possible vascular complications with different severity, the total number of vascular complications is difficult to assess. According to VARC-2 (Valve Academic Research Consortium) criteria (38) minor and major vascular complications are defined. The incidence of major vascular complications varies between 5 and 16% (37,39,40). Based on the femoral access for TF-AVI, the incidence of vascular complications is significantly lower after TA-AVI. Common vascular complications are the failure of the femoral closure system, dissection of the femoral arteries and femoral artery occlusion. The ongoing reduction of delivery system diameter leads to a decrease in major vascular complication rates.
Acute kidney injury The degree of acute kidney injury after T-AVI is also defined by VARC-2 criteria (41) and divided into three stages. Due to the use of contrast agent, contrast-induced nephropathy plays an important role (42), as does the post-procedural need for transfusion and pre-procedural kidney function. The incidence of severe kidney injury is 1 to 15% (37,42,43). Every stage of kidney injury is associated with worse outcome for the patients.
Less frequent T-AVI complications Due to the increasing T-AVI experience and the device improvements some of the initial T-AVI complications have become rare (
