Fig. 14.1
Components of the LARIAT™ system . The components of the percutaneous LAA ligation procedure include: (panel a) A 0.025-in. endocardial magnet-tipped and 0.035-in. epicardial magnet-tipped guidewire, each with a magnet of opposite polarity enabling an end-to-end alignment, (panel b) A 15 mm compliant occlusion balloon catheter to identify the LAA OS with TEE, (panel c) The LARIAT™ suture delivery device. The higher power inset demonstrates the pre-tied size 0 Teflon-coated, braided polyester suture (blue) mounted within a radiopaque adjustable snare. Panel (d) demonstrates the use of the components as a system to ligate the LAA. Panel (e) is the soft-tipped, 4.3 mm guide cannula for placement and direction of the LARIAT Suture Delivery Device. Panel (f) is the TenSURE™ that eliminates operator variability in suture tightening and assures consistency in closure outcomes. Panel (g) is the SureCUT™ remote suture cutter with easy-load threader designed to terminate remnant suture without risk to the knot (Adapted from Bartus et al. [15] with permission)
(b)
FindrWIRZ Guidewire system : The guidewires consist of endocardial and epicardial guidewires that have magnet tips at their distal ends. The endocardial guidewire is 0.025″ thick and the length is 220 cm with a magnet tip that is 2.57 mm thick. The epicardial guidewire is 0.035″ thick and is 150 cm long and the magnet diameter is 3.5 mm thick. The epicardial and endocardial guidewires require introducers of 8F and 11F, respectively. When deployed, both the endocardial and epicardial guidewires form a railing on which the LARIAT suture can be guided over the epicardial surface of the LAA.
(c)
SOFTIP Guide Cannula : This cannula helps deliver the LARIAT suture from the epicardial surface of the LAA. This soft-tipped cannula helps prevent traumatic injury to the heart while delivering the catheter. This catheter has a diameter of 12.9F and has a working length of 22.5 cm and overall length of 25 cm.
(d)
SURECUT SUTURE CUTTER : This device helps cut the LARIAT suture just proximal to the LARIAT suture.
(e)
TENSURE SUTURE TIGHTENER : This device helps deliver constant and consistent tension while deploying the LARIAT suture. The device has an indicator that indicates the tension applied at the distal LARIAT suture to minimize variability in the amount of tension applied by different operators. Use of this device facilitates grip on the suture and helps deliver a uniform tension on the suture.
(f)
ENDOCATH occlusion balloon : This balloon requires a 9F introducer and has a length of 90 cm. The balloon dimensions are 12 × 15 mm, and when fully inflated, has a maximal volume of 1.5 cm3. This balloon has a distal port through which contrast can be delivered. This balloon is used as a marker for the neck of the LAA.
Indications and Contraindications for LARIAT Procedure
Indications
1.
Nonvalvular AF patients with high risk of stroke (CHADS2 score ≥ 2 or CHA2DS2VASc score ≥ 3) and contraindications to oral anticoagulation due to history of internal or external bleeding (neurological, intraocular, gastrointestinal, urological, pulmonary).
2.
Intolerance to oral anticoagulants (adverse effects, bleeding).
3.
Oral anticoagulation is ineffective (unable to achieve therapeutic INR or thromboembolic events while on therapeutic oral anticoagulation).
4.
AF patients who are perceived to be at increased risk for bleeding (recurrent syncope and traumatic falls, high risk occupations like firefighters, intracranial aneurysms).
Contraindications
1.
LAA diameter >40 mm, because the maximum diameter of the LARIAT suture is only 40 mm and therefore this device cannot be used in patients with LAA diameter >40 mm.
2.
Prior cardiac surgery : In case of previous cardiac surgery, the LARIAT device cannot be used because of fibrotic changes in the pericardium following the surgery. In the presence of these fibrotic changes, it is difficult to position and deliver the catheters and the LARIAT suture accurately and therefore it is recommended not to perform this procedure in patients with prior cardiac surgery.
3.
Pectus excavatum : In this situation, the posteriorly directed sternum poses a challenge for the epicardial access and may result in direct cardiac perforation while attempting this. In addition, the working angle will be extremely difficult to accurately position the LARIAT suture delivery catheter at the tip of the LAA and therefore the LAA cannot be engaged in this situation.
4.
Posteriorly directed LAA : the posteriorly directed LAA cannot be engaged by means of the LARIAT suture from the anterior epicardial approach.
5.
Multi-lobed LAA : In the case of multi-lobed LAA, the LARIAT suture cannot be positioned accurately at the neck of the appendage and some of the lobes of the LAA may be missed leading to incomplete sealing of the LAA.
6.
Comorbidities such as severe heart failure, metastatic malignancy, and/or life expectancy less than 1 year.
Preoperative Assessment
Highly skilled operator and suitable cardiac anatomy are the key requisites for performing the LARIAT procedure. The patients therefore need to be worked up appropriately to determine their suitability for this procedure. Multimodality cardiac imaging (CT scan, TEE, and LAA contrast angiography) helps in the preoperative assessment and successful completion of the procedure (Fig. 14.2). All patients undergo a cardiac CT scan with contrast to assess the anatomy of the thorax, heart, and the LAA. All CT scan are then converted to a 3D reconstruction model to visualize the anatomy of the LAA and its surrounding structures. The LAA size and morphology are assessed to determine their eligibility for this procedure. A preoperative TEE is also recommended to confirm the size of the LAA and also to rule out left atrial and LAA thrombus. Comorbidities are assessed to see if the patient can tolerate this procedure with general anesthesia. General anesthesia allows stability of the patient for epicardial puncture and continuous TEE for visualization and closure of the LAA. It is recommended to perform this procedure at a high volume center where considerable expertise is available. The use of cardiac anesthesiologist is recommended for the procedure. Once the eligibility for the procedure is determined, all patients who can tolerate anticoagulation for a limited time are continued on oral anticoagulation. If the patient has absolute contraindication to oral anticoagulation, anticoagulation is not recommended for these patients. Oral anticoagulants are stopped 24–48 h prior to the procedure and patients are bridged with unfractionated heparin.
Fig. 14.2
Imaging. The lateral view of the CT (panel a), RAO caudal fluoroscopic view (panel b) and the 120–135° TEE view (panel c) are complimentary views that can provide information regarding LAA size and morphology. The most anterior aspect of the LAA can be seen in the lateral view of the CT that is analogous to a true left lateral view. The anterior lateral view of the CT (panel d) is analogous to a shallow, 30° LAO fluoroscopic view (panel e). Panel (f) demonstrates a 60° TEE view with the magnet tip in the anterior lobe. The white asterisk represents the anterior aspect of the LAA. LAT lateral, AL anterior-lateral, LUPV left upper pulmonary vein (Reproduced from Koneru et al. [14] with permission)
LARIAT Procedure
Directionally and anatomically accurate pericardial access and appropriate placement of the endocardial magnet wire within the LAA are the two most critical steps to assure a successful procedure.
Epicardial Access
Accessing the anterior pericardial space is one of the key steps for positioning the LARIAT suture over the LAA (Fig. 14.3). Standard pericardiocentesis needle or micro-puncture needle can be used for accessing the anterior pericardial space. The goal is to enter the pericardial space anteriorly and the needle should be directed laterally [14]. This orientation will help access the LAA from the anterior surface of the right ventricle and will ensnare the LAA tip lateral to the pulmonary vasculature anteriorly [14]. As the LARIAT suture device is advanced further, the suture will move across from the tip of the LAA to the neck and base of the LAA in an anterio-posterior direction. Posterior pericardial access will preclude accessing the LAA from its most anterior aspect [14]. Similarly, positioning of the needle more medially will present the challenge of manipulating the LARIAT suture laterally towards the tip of the LAA [14]. Preoperative assessment of cardiac anatomy using 3D-reconstructed CT scan will therefore help plan this procedure more efficiently. The lateral view of the CT demonstrates the space between the sternum and the anterior surface of the heart and allows for estimation of the steepness of the pericardial needle. The CT also delineates the most inferior aspect of the sternum in relationship to the inferior aspect of the myocardium. This allows for a pre-procedure assessment of how far the pericardial needle needs to be advanced in order to obtain pericardial access. In our center, we always keep the reconstructed cardiac CT scan readily available during the procedure to review and reposition the pericardial access.
Fig. 14.3
Utility of Cardiac CT angiography (CTA) for estimation of the direction and depth of the pericardial needle. Pericardial access for LAA ligation utilizing the LARIAT™ suture delivery device requires an anterior access approach into the pericardial space. As seen in the anteroposterior view (AP) of the 3D reconstruction of the CT angiogram (panel a), the LAA (delineated by the dashed line) is lateral to the pulmonary artery (PA) and appears to be in front of the hilum. The needle is directed (direction of the arrow) just lateral to the LAA that is generally toward the left shoulder. In the fluoroscopic image, the needle (arrow) would be directed just lateral to the hilum (panel c). The lateral view of the 3D reconstruction of the CT angiogram (panel b) demonstrates the virtual space of the anterior mediastinal space (Ant). The needle (arrow) is directed through the sternocostal triangle that allows for the needle to pass under the xyphoid process and above the diaphragm into the anterior mediastinal space, thus avoiding damage to the diaphragm and avoiding abdominal organs. The 90° left lateral fluoroscopic view allows for the needle to be advanced to the myocardial border (panel d). Ant anterior mediastinal space, Sup Superior mediastinal space, Post posterior mediastinal space, RV right ventricle, PA pulmonary artery, LV left ventricle (Reproduced from Koneru et al. [14] with permission)
After cleaning and prepping the sub-xiphoid area, the xiphoid process is palpated and an area 2–3-finger breadth below the xiphoid process is infiltrated with local anesthetic. After this, the pericardiocentesis needle is directed superior-laterally towards the left shoulder under fluoroscopic guidance in the AP view. In this view, the needle should be directed between 1 and 2:30° clock position [15]. Orientation in this position increases the chance of successful pericardial access [15]. The needle is also directed posteriorly by about 10–15° or between 3:30 and 4:30 clock position for successful pericardial access [15]. This posterior positioning of the pericardiocentesis needle is evaluated in left lateral view on fluoroscopy. The use of AP and the left lateral perpendicular fluoroscopic views help accurate localization of the needle and lead to successful pericardial access with one single attempt in >97 % of the patients undergoing LARIAT procedure.
The entry into the pericardial space is made 1–2 cm above the apex of the heart. This ensures that the guidewire will traverse anteriorly. If the pericardial access is at or near the apex, despite anterior pericardial access, the wire could traverse along the lateral border of the heart and slip posteriorly. Entry into the pericardial space can be confirmed by one of the two methods: “Contrast dye technique” or “Guidewire technique” [14]. In the contrast dye technique , small amounts of contrast are injected through the pericardial access needle. This allows visualization of the tenting of the pericardium, and once the needle enters the pericardial space, the contrast dye will track along the cardiac silhouette confirming the entry into the pericardial space. Subsequently, the guidewire can be introduced and the needle can be withdrawn. In the guidewire technique , the operator perceives the tactile pulsations of the heart and the pericardiocentesis needle is advanced slowly by about an mm at a time [14]. Once the parietal pericardium is approached, the operator can feel the heart pulsations and gentle advancement will result in a popping sensation. Then the guidewire can be slowly introduced through the pericardial access needle and the guidewire should hug the lateral heart border and cross the midline in LAO view to confirm placement in pericardium [14]. The needle is then withdrawn and serial dilators are used to dilate the tract from the skin surface to the pericardium. Dilators should be advanced carefully to avoid compression of the RV or kinking of the guidewire. RV compression can be seen by TEE examination and prevented by mild depression of the abdomen to alleviate the acute angle of the entry of the dilator into the pericardial space. After the dilation of the tract, the epicardial SOFTIP guide cannula is inserted into this tract and held in place.
Transseptal Access
The femoral vein is accessed using the Seldinger technique and a sheath is left in place. At this time the ACT is measured and additional heparin boluses are given to keep the ACT >300 s. The Brockenbrough needle is then introduced towards the interatrial septum. The interatrial septum is then visualized by means of TEE and atrial septal puncture is done with the help of the Brockenbrough needle. The interatrial septal puncture is done in the mid-portion of the septum and the angle is directed postero-superiorly to facilitate a more direct access to the LAA (Fig. 14.4). Once the interatrial septum is punctured, additional 2000 Units of heparin bolus is given.
Fig. 14.4
Transesophageal echocardiography for transseptal catherization . Bicaval and short-axis views of the intra-atrial septum are useful for an inferior–posterior transseptal puncture. The bicaval views (panels a and c) allow for superior (closer to the SVC) to posterior (closer to the IVC) orientation, while the short-axis view allows for anterior (near the Ao) position. The arrows in panels (a) and (b) indicate the transeptal sheath in the SVC. Panels (c) and (d) demonstrate “tenting” of the transeptal needle on the foramen ovale. LA left atrium, RA right atrium, SVC superior vena cava, IVC inferior vena cava, Ao aorta (Reproduced from Koneru et al. [14] with permission)
Next, the ENDOCATH balloon occlusion catheter is introduced across the atrial septal puncture to gain access to the left atrium. A pigtail catheter is then introduced into the left atrium and is positioned in the LAA. Contrast is injected through this pigtail catheter to visualize the LAA in multiple planes and the size and lobes of the LAA are reassessed during this step (Fig. 14.5a). After verifying the size of the LAA and its suitability for LARIAT procedure, the endocardial FindrWIRZ magnet-tipped guidewire is introduced into the LAA and positioned at the distal most tip of the LAA (Fig. 14.5b).
Fig. 14.5
Overview of LAA ligation with the LARIAT device . Percutaneous LAA ligation with the LARIAT suture delivery device requires an anterior pericardial access and a transseptal puncture. After transseptal puncture, a LA angiogram is performed in the RAO caudal (panel a) and LAO (panel c) fluoroscopic views to allow placement of the endocardial magnet-tipped guidewire into the most anterior lobe of the LAA (panels b and d). Connection of the epicardial magnet-tipped guidewire to the endocardial magnet is facilitated by rotating the epicardial sheath in the LAO view, so that the tip of the sheath is directed toward the endocardial magnet-tipped guidewire (panel e). Connection of the magnet-tipped guidewires should result in symmetrical alignment of the guidewires in both the LAO (panel f) and RAO caudal (panel g) fluoroscopic views. The LARIAT snare is then advanced over the epicardial magnet-tipped guidewire through the epicardial sheath. Alignment of the LARIAT snare is performed in the LAO fluoroscopic view to assure that the snare is positioned to move freely over the posterior aspect of the LAA (panel h). This should also result in the LARIAT snare being aligned in the RAO fluoroscopic view (panel i). Connection of the magnet-tipped guidewires stabilizes the LAA and allows positioning of the LARIAT suture delivery device over the LAA in an “over-the-wire” approach (panel j). Proper positioning of the snare over the LAA is guided by TEE-guided placement of the inflated balloon catheter at the mouth of the LAA and closure of the snare over the balloon (panel k). Confirmation of complete capture of the LAA is obtained with TEE and contrast LA angiography prior to release of the suture. If the snare closure does not result in complete capture of the entire LAA, the snare can be opened and repositioned to ensure complete LAA capture. Complete closure of the LAA is seen by the lack of color flow Doppler and LA angiography (L) (Reproduced from Koneru et al. [14] with permission)
Following the positioning of the endocardial magnet-tipped guidewire, the epicardial magnet-tipped guidewire is introduced through the epicardial soft-tipped guide cannula and is carefully guided through the pericardial space towards the endocardial magnet. Once the magnet tips are aligned, they attach to each other and form a continuous railing (Fig. 14.5f, g). Next, the LARIAT snare device catheter is introduced through the epicardial guide catheter over the epicardial magnet guidewire. The LARIAT suture is carefully guided on top of this guidewire until the LARIAT suture reaches the ostium of the LAA (Fig. 14.5j). Disengagement of the magnet tips is frequent during this step. When the magnet tips disengage, the LARIAT suture has to be withdrawn and the magnet tips are realigned and then the LARIAT suture is moved over the LAA. To identify the neck of the LAA, the balloon of the ENDOCATH balloon occlusion device is inflated and this acts as a guide to identify the neck of the LAA. Fluoroscopy and TEE guidance are used to accurately position the LARIAT suture at the neck of the LAA. The LAA is again imaged in multiple planes to ensure all the lobes of the LAA are proximal to the LARIAT suture. The LARIAT suture is then deployed and tightened (Fig. 14.5k). Next contrast is injected to verify complete sealing of the LAA (Fig. 14.5l). This is verified further on TEE with color Doppler. If there is flow into the LAA, then the LARIAT suture is released and repositioned until complete sealing of the LAA can be demonstrated. Once it is confirmed on both fluoroscopy and TEE that the LAA is sealed off, then the LARIAT suture is tightened and tension applied by means of TENSURE suture tightener for about 3–5 min. Again the sealing of the LAA is confirmed on fluoroscopy and TEE. Complete sealing of the LAA is defined as absence of flow across the neck of the LAA on TEE color Doppler and no leakage of the dye into the LAA. Further, there should not be any leftover stump of the LAA. However, leaks <5 mm and stump size less than 5 mm have been considered as acceptable results. The goal of the procedure should be to secure complete sealing of the LAA. After tension has been applied to the LARIAT suture, the LARIAT suture is cut by means of SURECUT suture cutter. After the suture is cut, all the magnet guidewires are withdrawn.
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