Background and indications
The transaortic approach (TAo-TAVI) is a recently developed surgical technique to perform transcatheter aortic valve implantation (TAVI) in either high-risk or inoperable patients1-3. TAo-TAVI is predominantly reserved for patients in whom the vascular anatomy does not allow transfemoral valve implantation, and in whom subclavian or transapical implantation is not feasible or desirable. Potential indications for choosing this procedure are (extreme) tortuosity of the femoral vessels and of the thoracic aorta, aneurysms of the abdominal aorta, femoral vessel diameter of less than 6 mm, heavy calcifications of the femoral vessels, patients who have already undergone major surgery of the femoral vessels and patients with increased risks of limb ischaemia. At our institution we prefer to implant the 31 mm CoreValve (Medtronic Inc., Minneapolis, MN, USA) via the transaortic approach. The short distance, immediate tactile feedback and better manoeuvrability makes implantation of these bigger valves easier. Heavy calcifications of the aortic arch, representing one of the possible sources for distal embolisation and major stroke in transfemoral TAVI, may also be a reason to prefer TAo-TAVI over a transfemoral route.
A poor left ventricular function, a fragile left ventricle apex or a left ventricle aneurysm may be reasons to choose TAo-TAVI instead of the transapical approach. Potential contraindications are the presence of a true porcelain aorta, severe COPD making mechanical ventilation undesirable and if the patient is not willing to undergo general anaesthesia. However, as a surgical department, our group considers TAo-TAVI early on in the decision-making process. Our comprehensive experience with self-expandable devices (CoreValve Revalving System; Medtronic Inc.) has been subjected to several refinements and adaptations that need to be addressed. In this report we describe the technique with a number of tips and tricks that can improve valve control and positioning.
Technique, tips and tricks
Similar to other TAVI approaches, patients are positioned on the operating table exposing the anterior chest and the groins. Both surgeon and interventional cardiologists stand at the right side of the patient, the two scrub nurses behind the surgeon and next to the cardiologist. The surgical assistant stands at the left side of the patient (Figure 1). Once femoral or radial artery access is obtained, the interventional cardiologist advances a pigtail catheter to the non-coronary cusp of the aortic valve, leaving it in position for aortographies throughout the procedure. A temporary pacemaker lead is inserted via the right femoral vein into the right ventricle.
Figure 1. Basic set-up Tao-TAVI at the cathlab. S1 and S2: first surgeon and assistant; C1: interventional cardiologist; An: anaesthesiologist; Ca: cathlab nurse; Sn: surgical scrub nurse; N1 and N2: specialised nurses preparing the valve
The TAo-TAVI can be performed through an upper “J” median hemi-sternotomy or a limited right anterior thoracotomy (Figure 2). Usually a 6 cm incision is enough to reach the third right intercostal space. Particular care is taken to isolate the brachiocephalic vein, especially in re-do cases (Moving image 1). It is separated from adhesions and gently retracted cranially with vessel loops or with a gauze to expose the cannulation site better, as well as to protect it from injury (Figure 3).
Figure 2. Access routes: hemi-sternotomy and right anterior thoracotomy.
Figure 3. Exposure of the brachiocephalic vein.
With gentle palpation of the ascending aorta the surgeon identifies a suitable spot for cannulation. Epiaortic scanning may be used for this purpose, particularly if preoperative MSCT shows atheromatous plaques4. Using a graduated pigtail catheter under fluoroscopy, the surgeon can assess the distance between the cannulation site and the aortic annulus by placing a forceps at the desired position of entry (Figure 4). The minimum distance we use is 7 cm. Two purse-string sutures, the inner one without pledgets, the outer one with 4-5 pledgets, are placed at the desired location on the lateral aspect of the aorta (Figure 5 and Moving image 2). It helps to place a small gauze as deep as possible under the outer and lateral aspect of the aorta so that the cannulation site is lifted to improve visibility. The aortic wall is then punctured and a short wire is advanced. The wire should be advanced under fluoroscopy without any resistance in order to avoid an intimal tear and dissection.
Figure 4. Assessing distance to the aortic annulus, using graduated pigtail and forceps.
Figure 5. Two purse-string sutures on lateral aspect of the ascending aorta.
A 6 Fr sheath is advanced over the wire in the aorta (Figure 6 and Figure 7). The surgeon advances the sheath and ensures that the aortic wall is passed by the sheath. This short sheath allows the multipurpose catheter to manoeuvre while crossing the aortic valve. Using this catheter, the valve is then crossed into the left ventricle with a straight, preferably non-hydrophilic wire. The straight wire is followed by another pigtail into the left ventricle, removed and replaced by an Amplatz Super Stiff™ wire (Boston Scientific Corp., Natick, MA, USA) or an Amplatz Extra-Stiff (Cook Medical, Bloomington, IN, USA) wire whose tip has been previously re-shaped in order to avoid ventricular perforations. All manoeuvres mentioned are done by the surgeon while the interventional cardiologist at the caudal and right side of the patient is in charge of visual and tactile control of the stiff wire’s position, making sure it stays in the chosen position in the left ventricle.
Figure 6. 6 Fr sheath to accommodate a catheter to cross the aortic valve.
Figure 7. 6 Fr catheter in place.
A short ring (1 cm) of plastic tubing is cut off, and mounted on the 18 Fr sheath of the delivery system (GORE® DrySeal; W. L. Gore & Associates Inc., Newark, DE, USA) 2 cm from its tip. This “stop ring” prevents the sheath from moving too deep in the aorta and leaves enough distance for deployment of the valve. The position of this silicone ring may be adjusted depending on the distance to the annulus; if there is a distance of more than 8 cm, the tip may be advanced further into the ascending aorta, facilitating steering of the big sheath.
The 18 Fr sheath is advanced over the stiff wire into the aorta (Figure 8). Movement of the sheath in this phase may cause bleeding; this can be controlled by tightening the previously placed purse strings. Predilatation of the aortic valve is usually performed under rapid pacing, but this can be omitted because a direct approach5 allows for a more meticulous valve placement. Patients with a valve perimeter >100 mm on CT scan may have a contraindication for receiving a 31 mm CoreValve. To prevent a potential paravalvular leakage, a 30 mm soft sizing balloon may be used with simultaneous supravalvular contrast injection. In the absence of leakage, a 31 mm CoreValve can be used. If there is leakage the team should reconsider the entire procedure. The possibility of an aborted procedure should be discussed in advance with the patient.
Figure 8. Advancement of the 18 Fr sheath into the aorta. The stop ring prevents a too deep entrance of the sheath.
Under fluoroscopy and direct tactile and visual feedback, the self-expandable valve is slowly released. It is crucial that there is close collaboration and communication between the interventional cardiologist who releases the valve (Figure 9) and the surgeon who maintains the position of the valve and makes small adjustments when necessary. The angle between the axis of the first part of the ascending aorta and the axis of the left ventricular outflow tract has been previously described as an indicator of future valvular and paravalvular leakage after TAVI6. The delivery system should therefore approach the aortic annulus perpendicularly, which can be difficult to achieve particularly when the aorta is short or curved. In these cases the surgeon can, under fluoroscopy, manipulate the sheath and the ascending aorta obtaining the required implant angulations. If the segment between the entry site and aortic annulus is too short (<6-7 cm), it will be necessary to deploy the valve and withdraw the 18 Fr sheath simultaneously in order to achieve extra length (Moving image 3).
Figure 9. Initial flaring of the valve; start of CoreValve deployment.
After valve implantation, LV and aortic pressures are recorded to assess the gradient (Figure 10) and paravalvular leakage. Paravalvular leakage is assessed either with haemodynamic or echocardiographic criteria7. A final supravalvular injection is made 10 minutes after placement (Figure 11). If the result is satisfactory, the sheath can be withdrawn with tying of the purse strings. In cases of a fragile aorta it can be helpful to do this under rapid pacing to lower the pressure in the aorta and allow more time and precision.
Chest closure is performed in the classic fashion with steel wires, using a protection tool to avoid injury of the underlying structures (Figure 12) and leaving pericardial, pleural and wound drains when required.
Figure 10. Post-implantation recordings of aortic and left ventricular pressures to assess the gradient and paravalvular leakage.
Figure 11. Final supravalvular contrast injection, 10 minutes post implantation.
Figure 12. Chest closure in the classic fashion using steel wires.
Conflict of interest statement
A.P. Kappetein is a principal investigator of the SURTAVI trial, which is sponsored by Medtronic. The other authors have no conflicts of interest to declare.
Online data supplement
Moving image 1. Dissection of the vena anonyma or brachiocephalic vein.
Moving image 2. The purse-string sutures.
Moving image 3. Positioning and valve deployment.