Transcatheter Aortic Valve Replacement - pediagenosis
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Tuesday, July 28, 2020

Transcatheter Aortic Valve Replacement

Keywords: Transcatheter aortic valve replacement

Transcatheter Aortic Valve Replacement
Transcatheter aortic valve replacement (TAVR) is a relatively new technique that has been clinically applied mostly in higher risk older patients in the past 10 years. Major differences in comparison to conventional aortic valve replacement (AVR) are as follows:
· Indirect visualization of the target by means of fluoroscopy, transesophageal echocardiography (TEE), and computed tomography (CT)
·    Implantation of a specific transcatheter prosthesis consisting of biologic valve leaflets and usually a metal stent, which can be crimped and thus inserted through a small delivery sheath
·    Implantation via remote access on the beating heart, usually without any heart-lung machine support. Due to these major differences in the technical approach, additional preoperative considerations are required for TAVR.

Step 1. Surgical Anatomy
·    Compared to surgical aortic valve replacement (SAVR), some additional anatomic structures need to be taken into account for TAVR. Although in SAVR the calcification amount and pattern, presence of a bicuspid valve, and coronary distance are of minor interest, they are important for preoperative TAVR planning.
·    The coronary distance (distance between the aortic annulus and left main coronary artery) is of importance. A distance less than 10 mm, as well as a previous plaque in the coronary artery, heavily calcified aortic leaflet, narrow aortic annulus, and superficial sinus of Valsalva are risk factors for coronary obstruction after TAVR.
·    Calcifications cannot be removed during TAVR. Thus, aortic valve calcification, depending on its quantity and asymmetry, is associated with paravalvular leaks, whereas left ventricular outflow tract (LVOT) calcification increases the risk for annular rupture.
·    Bicuspid aortic valves often have larger annular dimensions. More calcified, irregular, and bulky leaflets further complicate precise positioning and full apposition of the device with the annulus, thus increasing the risk for paravalvular leaks.
·  A horizontal aorta (in the absence of a standardized definition, according to clinical judgment, this can be considered to be an aorta with an angle ≤ 30 degrees from horizontal) complicates valve crossing, positioning, and aligning of the prosthesis in relation to the annulus.
·  Other anatomic structures that need to be considered depend on the TAVR access route retrograde transfemoral (TF), transsubclavian (TSc), transaortic (TAo), or antegrade transapical (TA) approach.

Step 2. Preoperative Considerations
Because the boundaries between cardiac surgery and interventional cardiology blur in TAVR, a heart team is essential for preprocedure decision making, procedure performance, and postprocedure care. Thus, the heart team has emerged as a class of recommendation I (COR I) indication in both the European and US guidelines for TAVR.
1. Indications for Aortic Valve Replacement for Aortic Stenosis
·    TAVR is recommended for patients with severe symptomatic aortic stenosis (AS) who are not suitable to undergo conventional AVR as assessed by a heart team, who are likely to gain improvement in their quality of life, and who have a life expectancy of more than 1 year after consideration of their comorbidities.
· Transcatheter aortic valve implantation (TAVI) should also be considered for high-risk patients with severe symptomatic AS who are suitable for surgery, but for whom TAVI is favored by a heart team as a COR IIa, level of evidence (LOE) B recommendation.
·   Various risk scores have been used to aid in decision making by the heart team. Among these, the logistic EuroScore (ES) is known to overestimate the effective mortality; a logistic ES of 20% or more has been suggested as an indication for TAVI. Its successor, the ES II, has been shown to correlate better between the anticipated and observed survival. Currently the most reliable score is the Society of Thoracic Surgeons (STS) predicted risk of mortality (STS-PROM) score, with a value of more than 8% to 10% indicating high risk. However, none of these risk scores were designed for TAVR. The STS/American College of Cardiology (ACC) TAVR In-Hospital Mortality Risk score was recently published and combines easy calculation and good correlation with the real in-hospital mortality.
·    Regardless of risk scores, other factors include status post–coronary artery bypass grafting with a patent graft, porcelain aorta, severe chronic obstructive pulmonary disease (COPD), status postradiation therapy, renal failure, low ejection fraction, and significant frailty, among others. These may be clear indicators leading to a heart team decision in favor of performing TAVR.
·  Thus, TAVR is already widely performed in intermediate-risk patients. The transcatheter valve therapy registry (TVT registry) has reported a median STS risk score of approximately 7% in patients treated with TAVI from November 2011 to March 2013. During the same period, the median STS score in the German aortic valve registry (GARY) was 5.0, indicating an intermediate-risk profile. The trend to expand the indications for TAVR to intermediate-risk and eventually low-risk patients has been gaining momentum after recent studies demonstrated the noninferiority of TAVR compared to SAVR in intermediate-risk patients.
·    Despite this trend, it has to be considered that comprehensive long-term follow-up for TAVR prostheses is not available yet. However, long-term durability will be a prerequisite for further expansion of the procedure, especially to younger patients.

2. Indications for Transcatheter Aortic Valve Replacement in Aortic Regurgitation
·   Aortic regurgitation (AR) causes about 11% of all native valve disease. However, because calcification is usually absent in isolated AR, anchoring of a TAVR valve is more challenging and thus a relative contraindication for TAVR. Various devices have been used off-label for successful implantation in patients with AR, but only small series have been reported.
·    Up to now, the Jenavalve prosthesis (Jenavalve Technology, Munich), which clips on to the aortic valve leaflets, was the first CE mark approved device for the treatment of isolated AR and has shown a high success rate in a multicenter study. (CE marking is a certification mark indicating conformity with health, safety, and environmental protection standards for products sold within the European Economic Area.)
·    However, despite proven feasibility, neither European nor US guidelines recommend TAVR for pure AR.

3. Preoperative Planning
·  Because TAVR is performed without direct vision of the operating field, preoperative planning and imaging are essential.
·    After assessment of the perioperative risk and the heart team’s decision that TAVR might be a treatment option, some anatomic characteristics have to be determined to evaluate if TAVR is feasible and to estimate the technical risk of the procedure.
·    With the currently available devices, TAVR can only be performed in patients with an aortic annulus between 18 and 29 mm (Table 16.1). This, however, applies to more than 95% of potential patients.
·    The distance between the annulus and coronary ostia should be more than 10 mm, and/or the aortic sinus needs to be sufficiently large to prevent occlusion of the coronary ostia by calcifications or by native valve leaflets.
·  Ideally, annulus measurements are performed by TEE in two-dimensional and three-dimensional views, as well as by CT. In recent years, specific CT software tools have been developed that allow for precise and automated measurement of the aortic root, including the effective aortic annulus, based on its area and/or perimeter (e.g., 3mensio Structural Heart, Pie Medical Imaging, Maastricht, The Netherlands).
· The improved preoperative planning and imaging techniques have been an important contributing factor to decrease the incidence of severe paravalvular regurgitation and annulus rupture after TAVR. Thus, careful screening cannot just stratify the risk more precisely than a risk score, but is required for assessment of the feasibility of TAVR and for selection of the most appropriate access and valve.

4. Valve Choice
·   Current devices for performing TAVR are mostly second- or third-generation valves that have shown improved patient outcomes and enhanced safety compared to the first-generation devices. These include specific features to minimize paravalvular leakage, reduction in delivery system and sheath diameter to allow TF access, despite smaller access vessels, options to retrieve the device partly or completely after implantation (if possible, after it is already fully functional), and the possibility of commissural orientation with exact anatomic positioning.
·  TAVR devices consist of a specifically designed valve and application system, which is usually inserted over a guidewire by means of a sheath or in a sheathless manner. The valve consists of a thin stent, which is balloon-expandable (stainless steel or cobalt-chromium) or self- expanding (usually nitinol). Valve leaflets consist of bovine pericardium, porcine pericardium, or porcine leaflets. Some of these valves have an additional anticalcification treatment similar to that of conventional surgical xenografts to protect against tissue degeneration and thus achieve optimal valve durability.
·    An overview of the most common prostheses is shown in Fig. 16.1.
· The balloon-expandable Edwards SAPIEN valve (Edwards Lifesciences, Irvine, CA) is available for retrograde (TF, TAo, TS) and antegrade (TA) access and is currently available in its third generation, the SAPIEN 3. It is a rather short device designed for subcoronary implantation, with the leaflets located in an intraannular position.
· The self-expanding Medtronic CoreValve (Medtronic, Minneapolis) is available for retrograde implantation only. The device stent is longer and thus requires an implantation that surpasses the coronary ostia while obtaining additional aortic stabilization. The leaflets are attached in a supraannular position.
·  In addition to these two most frequently implanted prostheses, several other devices have been developed:
Ø   The Acurate neo system (Symetis, Dusseldorf, Germany) has gained the largest clinical following after the previously mentioned valves and is available for TF-TAVR and TA-TAVR. The Acurate valve has a self-expanding nitinol stent that can be placed in an anatomically correct position, matching the commissures to the native ones quite easily (with the TA approach), and that allows for partial repositioning.
Ø   The Portico device (St. Jude Medical, St. Paul, MN) consists of a nitinol stent that extends from the aortic annulus to the ascending aorta. It allows for retrieval after up to 80% of deployment, for which valve functionality can be assessed.
Ø   The Lotus valve (Boston Scientific, Marlborough, MA) consists of a nitinol mesh, which is quite long in the crimped position and foreshortens during deployment. Complete retrieval of the device is possible, allowing for complete assessment of valve function before final detachment of the delivery system.
Ø   The Direct Flow valve (Direct Flow Medical, Santa Rosa, CA) is unique in design. It consists of two nonmetallic, inflatable, double-ring structures that are interconnected by a tubular bridging system. Initially, the valve is filled with a radiopaque exchange solution that is replaced with a polymer once the correct position in the native aortic annulus has been achieved.
Ø   The Jenavalve TA system (Jenavalve Technology, Munich) is a unique self-expandable stent with additional feelers to guide positioning at the annular level together with commissural alignment and safe anchoring. It is the only device approved for the treatment of AR (CE mark approved device).
Ø   The Venus A-Valve (Venus MedTech, Hangzhou, China) is the only TAVR device meeting China Food and Drug Administration clinical requirements. It is a self-expanding nitinol stent frame that carries porcine pericardial leaflets and can be delivered via TF, TA, TSc, and TAo approaches.
Ø   The Braile Inovare prosthesis (Braile Biomédica, São José do Rio Preto, Brazil) is a balloon expandable device with a cobalt-chromium frame and a single sheet of bovine pericardium comprising the leaflets. It is already commercially available in Brazil, but currently only suitable for TA access.
Ø   Other devices are in clinical trials or are currently still under development.
Figure 16.1 Overview of the most common TAVR prostheses. (A) Balloon expandable bovine pericardial tissue transcatheter bioprosthesis. (B) Self-expanding porcine pericardial tissue transcatheter bioprosthesis. (C) Self-expanding bovine pericardial tissue transcatheter bioprosthesis. (D) Self-expanding native porcine leaflets transcatheter bioprosthesis. (E) Alternative expansion design bovine pericardial tissue transcatheter bioprosthesis.

5. Space Requirements: Hybrid Operating Suite
· TAVR procedures will usually be performed in a hybrid operating suite. Because intraoperative imaging plays a major role in TAVR, a high-quality angiography system is favored over a mobile, C arm based system.
·   Furthermore, in case general anesthesia is needed, TEE should be used for periprocedural guidance and assessment. Because a fast connection to a heart-lung machine might be needed in case of hemodynamic instability, an already primed heart-lung machine should therefore be available.
·  Furthermore, conversion to conventional surgery via sternotomy should be possible in a timely manner. All these features, including adequate hygienic standards, can best be realized in a hybrid operating suite. A well-equipped cardiac catheterization laboratory may be the next best alternative. Positioning of the patient, together with hardware setup and operator and assistant positioning, are shown in Fig. 16.2.

Step 3. Operative Steps
The TF approach has become the routine access approach for TAVR. This is especially true in patients with wide and straight access vessels. In patients unsuitable for TF-TAVR, TA access is the most frequently used alternative. We therefore describe the operative steps for these two procedures.

1. Patient Preparation
·    TF-TAVR can be performed under conscious sedation, whereas TA-TAVR requires general anesthesia. Invasive blood pressure monitoring is required independently of the access used.
·  External defibrillator electrode pads should be attached before supine patient positioning. Sterile preparation and covering should be performed in a manner similar to that for a conventional cardiac surgery operation. The sternum should be uncovered in case of a necessary conversion to a median sternotomy.
·    A temporal pacemaker can be inserted transvenously through the jugular or femoral vein. In case of TA access, an epimyocardial pacemaker can be placed directly within the purse-string sutures after a thoracotomy.

2. Safety Net
·  After puncture of a femoral artery (in case of TF-TAVR, on the contralateral side), a 5 F pigtail catheter is placed through a 6 F sheath into the noncoronary sinus as a marker for valve positioning and to allow for angiographic visualization during implantation.
·    An additional 5 F sheath is placed in the femoral vein as a safety net (Fig. 16.3).
Figure 16.2 Example of a hybrid operative theater setup.

Figure 16.3 Safety net: femoral arterial and venous sheath in place.

3. Access
Transfemoral-Transcatheter Aortic Valve Replacement Access
·    It is important that the common femoral artery be punctured above the bifurcation because puncture of the superficial or profunda femoris artery is associated with a higher risk of vascular complications, obstruction, and failure of closure (Fig. 16.4).
·    Several techniques exist to guide correct puncture. It can be done from the contralateral side using a crossover technique or with a small sheath inserted distally on the ipsilateral side in the femoral artery. A contrast agent can be administered to identify the puncture target (see Fig. 16.4B).
·    A 6 F sheath and soft-tipped J-wire are inserted. Next, the artery is prepared with a closure device (e.g., two ProGlide sutures, Abbott Laboratories, Abbott Park, IL).
·  Heparin can now be administered (100 IE/kg body weight). The aim is to achieve an activated clotting time of about 300 seconds.
·   The aortic valve is crossed retrograde using an Amplatz left catheter (AL1; Boston Scientific) and a hydrophilic straight wire with a soft tip.
·  The AL1 catheter is exchanged with a pigtail catheter and a very stiff Amplatz wire or preshaped Safari wire (Boston Scientific) is positioned in the left ventricle.

Transapical-Transcatheter Aortic Valve Replacement Access
·  After a lateral minithoracotomy through an approximately 5-cm-long skin incision in the sixth intercostal cavity, the apex should be identified (Fig. 16.5). If the apex cannot be easily accessed through the intercostal cavity, the same skin incision should be used to switch to a higher or lower intercostal cavity. The preoperative CT scan may indicate the relationship of the apex to the chest wall. Furthermore, preoperative transthoracic echocardiography can be used to localize the apex and mark the exact position for the incision.
·  A soft tissue retractor is then inserted. By usage of a small rib spreader, exposition of the apex can be further improved but is associated with increased postoperative pain and the risk of rib fractures (Fig. 16.6).
·   After longitudinal opening of the pericardium, pericardial retraction sutures are placed, and the left anterior descending (LAD) artery is identified (Fig. 16.7). In case of prior heart surgery and pericardial adhesions, a small incision in the pericardium without retraction sutures may be sufficient.
·    Either U-shaped or O-shaped purse-string sutures are placed lateral to the LAD. This can be performed with 2-0 Prolene sutures with a large needle and Teflon felt pledgets. The stitches should be deep (about 4–6 mm) but not transmural, and secured with a snare. Attention should be given to avoid any tearing of the myocardium (Fig. 16.8). In reoperations, these sutures can be easily placed through the pericardium.
·  Now heparin can be administered (100 IE/kg body weight), with a goal-activated clotting time of about 300 seconds.
·  After puncturing the apex within the purse-string sutures, a soft-tipped wire is advanced antegrade through the aortic valve (Fig. 16.9).
·    TEE should be used to prevent the wire from being caught in the chordae of the mitral valve. Over the soft-tipped wire, a right Judkins catheter is advanced, and the soft-tipped is wire switched to a super-stiff wire, which is placed in the descending aorta (Fig. 16.10).
Figure 16.4 Puncture site for transfemoral TAVR. Yellow dot shows optimal needle entry into the common femoral artery.

Figure 16.5 Access site for transapical TAVR.
Figure 16.6 Transapical access without and with metal rib spreader.
Figure 16.7 Transapical access showing the apex after placing pericardial retraction sutures.
Figure 16.8 Apical access after placement of two O-shaped purse-string sutures.

Direct Aortic-Transcatheter Aortic Valve Replacement Access
·   After an upper partial sternotomy or right anterior minithoracotomy, the ascending aorta is accessed. The preoperative CT scan may provide information regarding the position of the aorta with regard to the midline. A midline aorta is best for an upper partial sternotomy, whereas a right-sided aorta is better for a right minithoracotomy. Care should be taken to ensure that the ascending aorta has minimal calcific disease.
·   After longitudinal opening of the pericardium, retraction sutures are placed. Two pledgeted Ethibond sutures are placed in the distal ascending aorta. A minimum of 6 to 7 cm of the length of the ascending aorta are recommended to use this approach.
·    Heparin is administered, with a goal-activated clotting time of about 300 seconds.
·   After puncturing the aorta with an 18-G needle within the purse-string sutures, a soft-tipped wire is advanced antegrade through the aortic valve. A counterincision may be made through the skin to aid in delivery of the sheath
·  The needle is exchanged for a 7 F sheath, and a multipurpose catheter with a straight soft wire is used to cross the valve. An Amplatz extra-stiff guidewire (Cook Medical, Bloomington, IN) with a bend on its end is placed. A large sheath is advanced 2 to 4 cm and secured in preparation for deployment of the valve. Balloon aortic valvuloplasty is performed under conditions of pacing at 180 to 200 beats/min. The balloon catheter is replaced with the deployment device, and the TAVR valve is deployed under rapid pacing conditions. After completion of deployment, the sheath is removed, the purse strings are tied, and the chest is closed after placement of a single mediastinal tube.

4. Valvuloplasty
·    If valvuloplasty is required, it can be performed using a 14 F sheath and under rapid pacing (about 180–200/min). This will lead to temporary cessation of cardiac output (Fig. 16.11).

Figure 16.9 Soft tip wire antegradely crosses the aortic valve.
Figure 16.10 Super stiff wire in place.
Figure 16.11 Balloon valvuloplasty.

5. Implantation
·   Although there are similarities between devices, there are differences in detail regarding positioning and valve release. Therefore, we briefly describe here the implantation of the two most commonly implanted TAVR devices.

Medtronic CoreValve
· The CoreValve Evolut R System (Medtronic, Minneapolis, MN) is currently the most commonly used self-expanding TF-TAVR device.
·    After valvuloplasty, which is optional with the CoreValve Evolut R, the system is advanced over the stiff wire through the annulus. The distal part of the valve should be placed just below the annulus and the distal horizontal marker at the level of the pigtail (annulus). The position can be controlled by contrast agent administration through the pigtail catheter (Fig. 16.12).
·    The valve is slowly deployed by counterclockwise rotation of the catheter handle. During the first phase of deployment, the valve tends to dive into the ventricle. This has to be manually corrected.
·  A drop in blood pressure occurs once the valve touches the aortic annulus. At this point, deployment of the valve should be performed faster. The valve can be recaptured and repositioned until it is released to almost 80%. This allows for control of valve function and AR.
·    Further rotation of the device handle fully releases the valve.
·  The delivery system is slowly pulled back into the descending aorta, reassembled, and removed. A 14 F sheath is inserted, and a pigtail catheter is used to remove the stiff wire.
Figure 16.12 Valve position CoreValve.
Edwards SAPIEN
·    The Edwards SAPIEN valve (Edwards Lifesciences, Irvine, CA) is the only US Food and Drug Administration (FDA)–approved device for TF, direct aortic, and for TA-TAVR, and is the most commonly used device for TA-TAVR.
·   After valvuloplasty, which is optional with the SAPIEN valve, the system’s own introducer sheath is advanced over the wire, beneath the annulus and into the left ventricle. In the vast majority of patients, in the past 2 years as of this writing, valvuloplasty has been avoided with this approach.
·   Then the already crimped valve is connected to the sheath, and the system is de-aired. The valve is advanced to the annular position, and the pusher is retrieved (not required for SAPIEN 3). The valve is positioned under fluoroscopic control. About 30% to 50% of the valve should be positioned supraannularly (Fig. 16.13).
·  The valve should be oriented in a perpendicular position toward the annulus. This can be achieved by changing the tension of the super-stiff wire by pulling or giving slack to the wire.
· In the optimal position, the valve can be released by inflation of the balloon under angiographic control with administration of contrast agent over the pigtail in the noncoronary sinus, rapid pacing, and apnea. In a first step, the balloon should be inflated up to 50%, enabling minor positional corrections followed by complete inflation for approximately 3 seconds (Fig. 16.14).
·    After valve implantation, termination of rapid pacing, and apnea, the mean pressure should recover immediately.

6. Access Closure
·  Prior to access closure, angiography and/or echocardiography is performed for final evaluation of valve function. After confirmation of proper valve function, all wires and sheaths can be removed. The already positioned vascular closure devices can be used to close the femoral artery access. In case of TA-TAVR, the purse-string sutures can be tied. Before closure of the pericardium, a hemostat based on collagen (e.g., Surgicel Absorbable Hemostat—Tabotamp, Johnson & Johnson, New Brunswick, NJ) can be applied to the apex. A thoracic drain should be advanced into the pleural space, followed by standard wound closure. For both access routes, the femoral sheaths can be retrieved and the femoral artery access closed by compression or a vascular closure device.
Figure 16.13 Valve positioning SAPIEN.
Figure 16.14 SAPIEN implantation.
Step 4. Postoperative Care
·   In SAVR, oral anticoagulation is recommended for 3 months after bioprosthesis implantation. However, there is no recommendation for a TAVR-specific anticoagulation regimen. New findings using four-dimensional CT imaging and TEE have shown that leaflet immobility and, occasionally, valve thrombosis occur in up to 40% of TAVR patients.  We recommend dual-antiplatelet therapy with aspirin and clopidogrel for 3 months, followed by lifelong aspirin. If oral anticoagulation with warfarin is indicated, we recommend warfarin and clopidogrel administration for 3 months, followed by warfarin (as long as indicated) and aspirin (lifelong).
·  Pain management is of importance for TA-TAVR patients to allow for the early start of specific respiratory therapy and avoid any pulmonary complications. Intraoperatively, long-lasting local anesthesia can be administered intercostally to reduce the necessity of postoperative oral pain medication.

Step 5. Pearls and Pitfalls
1. Procedure-Related Issues
·    Circulatory problems may occur throughout the entire procedure. Especially rapid pacing for valvuloplasty and/or valve implantation itself can be critical. If, during this, circulation cannot be fully improved after the peripheral administration of inotropes, direct injection of 1 to 2 mL adrenaline 1 : 100 (1 mg/100 mL saline) through a pigtail catheter in the aortic root can be helpful. In case of persisting hemodynamic suppression, the heart-lung machine should be connected using the femoral venous safety net wire to place a venous return cannula and a femoral arterial cannula in TF-TAVR, usually through the valve delivery access site. This safety net should always be placed at the beginning of the operation because circulation problems can already occur in the early stage of the procedure.
·   Strokes occur due to embolization of native aortic valve calcifications or thromboembolic events. Embolic protection devices aim to address this issue. However, studies have focused on surrogate markers of the clinical disease, primarily on silent central nervous system lesions. Because no study has confirmed the reduction of cerebral embolism and stroke after TAVR, the use of these devices has not yet become established in everyday clinical routine.

2. Valve-Related Issues
· Paravalvular leakage usually results from incomplete prosthesis apposition to the native annulus due to morphologic patterns or extent of calcification, undersizing of the device, or malpositioning of the valve. Several studies have identified AR of 2 or more to be an independent predictor of short- and long-term mortality. Due to increasing experience and novel device technology, AR rates could be lowered. However, in case of at least moderate AR, different strategies, depending on the underlying cause, can be used to minimize AR.
·    With good valve position and size, postdilation should be performed. Therefore, a balloon size corresponding to the diameter of the annulus is generally used. Undue postdilation, however, could lead to central regurgitation or rupture of the aortic root and therefore should be avoided.
· If the valve was undersized after unsuccessful postdilation rescue, valve-in-valve implantation should be considered.
·    In case of inappropriate positioning, repositioning using a snare may be attempted; otherwise rescue valve-in-valve implantation or conversion to SAVR is mandatory.
·    Coronary obstruction can occur due to a valve malposition or, eventually, to severe native valve calcifications coming to rest in front of the ostia. This situation can be resolved by coronary intervention but, in the event of failure, conversion to a coronary bypass operation should be performed. Coronary guidewires, however, are not placed routinely before valve implantation.
·    Embolization of the prosthesis occurs mostly in case of incorrect valve size, insufficient rapid pacing during valve deployment, or implantation that is too low. In case of embolization into the ventricle, conversion with harvesting of the prosthesis and AVR is indicated. If the valve is still crimped, harvesting through the apex with a catching loop can be possible in TA-TAVR, but is associated with a high risk of apical injury. In case of distal embolization, the prosthesis can be anchored in the ascending or descending aorta by overdilation, followed by intraannular implantation of a second valve.
·    Annulus rupture and type A dissection can occur intraoperatively or delayed due to incorrect sizing, excessive oversizing, or postdilation in a heavily calcified annulus. Extravasation of contrast medium during intraoperative control angiography is often the first indicator of a rupture. Fortunately, this complication has become rare with optimized perioperative patient assessment, mostly by means of CT aortic root analysis. Heavy bleeding after apex closure without any visible bleeding site is another hint. Immediate conversion to conventional surgery, using patch closure of the defect and conventional AVR, is necessary.

3. Access-Related Issues
·    Apical bleeding can usually be stopped with additional felt-reinforced sutures. The mean arterial pressure should be 100 mm Hg or lower; some temporary fast pacing can lead to more stable conditions for suturing. In case of heavy apical bleeding, temporary connection to the heart-lung machine might be useful to stop the bleeding under controlled conditions.
·    Vascular access complications are more likely in TF-TAVR, but have been declining due to better preoperative patient assessment and imaging and technical improvements, especially smaller sheath sizes and the use of techniques such as an expandable sheath (Table 16.2). Local dissections can be treated by implantation of a stent or surgery. In case of surgery, a peripheral vascular balloon can be used in a contralateral crossover technique or via ipsilateral antegrade access to occlude the external iliac artery.

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