Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe

Transcription

1 Chapter 5 Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe 1 INTRODUCTION A good initial dissection with wide mobilization of the left atrium (LA) by dividing its attachments to the pericardium makes clamp placements easy, precise, and safe. It is crucial for the learning surgeon to understand that once you perfect the initial dissection, the ablations become easy and straightforward to make. We remember the days of struggling to get a clamp around veins for a pulmonary vein isolation (PVI), or difficulty in making a roof or floor line segment as the clamps kept getting caught up in tissue. A good dissection frees up the atrium so that these clamp passages become very easy. The hard part is that most surgeons were never taught how to gain access to the oblique sinus from the dome of the atrium, nor how the pericardial reflections attach to the dome they had no reason to learn this if they weren t being taught how to perform a Maze. If you have the chance to observe a master Maze surgeon, they will likely open these spaces up so quickly that you may miss it but you will suddenly wonder why they are making the clamp passages look so easy. The reason is the proper initial dissection. Once the dissection is mastered, your confidence will grow tremendously. As a general rule, we perform the majority of the dissection on cardiopulmonary bypass (CPB) with the heart decompressed. It makes the dissection much easier, safer, and in the end probably faster. Don t get trapped into trying to make your CPB times as short as possible. Go on pump early, decompress the heart, and make the dissections and passages into the sinuses under no pressure. Getting around the pulmonary veins is the part that most learning surgeons find hardest. The key here is to begin the dissection bluntly and not to hesitate to simply go around the structures using your index finger and thumb to do the dissection digitally. In truth, both the left and right veins are beautifully dissected digitally, and this is by far the safest way to go. Second, you will notice that we don t attempt to retract the heart to go around the left pulmonary veins while it is still beating. We favor doing this with an arrested flaccid and completely decompressed heart. If you have accomplished a good dissection above the dome as discussed later, clamp placement around the left pulmonary veins will now be straightforward and fast. 2 STERNOTOMY AND EXPOSURE The initial exposure is exactly as you would proceed for a mitral valve procedure. The sternotomy is routine. Expect large atria (Fig. 5.1). Typically, the longer the patient has been in continuous AF, the larger the atria will be, and frequently the right atrium and right atrial appendage (RAA) will be large enough to get in the way during cannulation. We tack the right side of the pericardium to the sternal table to elevate this side and improve exposure down into the LA once it is open again just like in a mitral valve procedure (Fig. 5.2). 3 MOBILIZE THE SVC Wide mobilization of the SVC is also a standard element that most expert mitral surgeons think is critical for good exposure. With the Maze this exposure is equally important, and the SVC mobilization also aids in making the LA roof line easy. We typically perform it off CPB, but if there is any concern or trepidation, it is better to go on CPB and mobilize the SVC Surgical Treatment of Atrial Fibrillation Copyright 2017 Elsevier Inc. All rights reserved. 97

2 98 Surgical Treatment of Atrial Fibrillation FIGURE 5.1 Typical appearance of enlarged atrium in patients presenting with a long duration of AF. This view of the heart is taken from head of the table and shows massive enlargement of the right atrium and appendage. FIGURE 5.2 Wide mobilization of the SVC is critical to good exposure. Here the SVC is elevated and connecting tissue between it and the pulmonary artery is dissected from both sides of the SVC until it has a wide passage underneath which will typically be large enough to admit two fingers. with the heart empty and the vein under no pressure. We tend to do it early, just prior to cannulation (see later). Find a way that suits you, either on pump or off, but make it safe and routine. The passage under the SVC should be enough to insert your index and middle fingers through for optimal exposure. To completely mobilize the SVC, we begin by taking a pair of forceps in the left hand and placing them across the SVC as it passes over the PA, and then gently grasping the back walls of the SVC. Now elevate the SVC anteriorly placing the posterior attachments on traction. Use a Bovie at a low setting of 30 to lyse the initial attachments on both sides of the SVC. Work back and forth on both sides of the SVC keeping the tips of your forceps as posterior on the vessel as possible. (Note: this is demonstrated in the online video.) When the SVC begins to elevate, release the tissue in the forceps and grab more posterior on the tissue just freed. The Bovie tip works well cold as a blunt dissector, and keeping the tissue on stretch and never burrowing down with the Bovie makes it safe. After a bit of work, the SVC is freed up and you have an initial opening. Now work carefully to make the opening larger superiorly, continuing to lyse the attachments between the PA and SVC on both sides until the SVC is widely elevated. The opening to the transverse sinus is now also very wide. 4 CANNULATION AND BYPASS The next step is cannulation. When choosing the sites for the SVC/IVC cannulae, take a moment and consider where the intercaval circuit interruption line will run. Remember, this line is designed to interrupt MRCs orbiting around the SVC/ IVC atrial areas and it should be well under the SA node and land on the SVC and IVC. On the IVC side, it is typically also on the right lateral wall. It is helpful to have the IVC cannulation site as far away from the intercaval line as possible, because the inferior caval tissue is thin and fragile. Accordingly, when choosing the IVC cannulation site, stay anterior on the IVC and well away from the intended intercaval line path. Begin with the SVC cannulation. We do this even before the aortic cannulation, because retraction to expose the SVC involves pulling the aorta to the left, and it is easier and safer to minimize retraction on the aorta with the cannula in place. For the SVC cannula, place a purse string suture well above the atrial/caval junction and well away from the SA node. Typically, a 24F metal right-angle cannula for the SVC works well. Using the metal Codman Myocardial Dilator 5 3/4 also works well to dilate the venotomy while minimizing bleeding and plugging the opening until you are ready, and to make the insertion of the cannulae controlled and perfect (Fig. 5.3). When inserting the cannula tip, be very cognizant that the tip is traveling just under the anterior surface of the SVC and that it may in some cases head into the azygous vein, so that you will have poor drainage. If there is any question, use your fingers to confirm that it is where you want it. Perform the aortic cannulation next this is routine. For the IVC, a 28F metal-tipped right-angle cannulae placed on the anterior aspect of the IVC works well, but any IVC cannulae will suffice. As noted earlier, keep the cannulation site well away from where the IC line will run. Here again the Codman Myocardial Dilator works well to control the site as you place the cannula.

3 Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe Chapter 5 99 FIGURE 5.3 Codman Myocardial Dilator. Don t waste time and energy placing caval tapes at this point they will just be in the way and there will be a better opportunity later. Keep the field as clear and as uncluttered as you can at this point. Go on pump and decompress the heart. 5 OPEN THE OBLIQUE SINUS INFERIORLY This gives you access to the floor of the LA and allows good visualization of the back atrioventricular (AV) groove and the coronary sinus (CS), which is important later. It is also needed to easily insert the clamp for the floor line. Do this bluntly and use a pair of pickups and a Yankar sucker to tease the tissue away from the attachments on the pericardium. First study the anatomy to make sure you are in the right area (Fig. 5.4). Identify the inferior vena cava (IVC), the right inferior pulmonary vein (RIPV) and the pericardium just lateral to these two. Place the forceps tips in the middle of the atrial wall between the RIPV and the IVC and then use the Yankar sucker to push the pericardium away in gentle sweeping motions. Replace the forceps a bit deeper into the dissection plane as the tissue sweeps away, and with several repetitions the oblique sinus is opened from below (Fig. 5.5). Now place the Yankar tip deep into the sinus and onto the posterior pericardium; pushing up on the forceps and down on the Yankar sucker, widen the passage with further blunt dissection (Fig. 5.6). Once the oblique sinus has been opened from below, study the superior border of the sinus opening as it joins on the fat pad in the intraatrial groove. Remember that this is where your clamp will be going eventually for the right pulmonary vein isolation (PVI), and make some mental notes on making sure you will be inferior enough when it comes time to develop the intraatrial groove (see later). FIGURE 5.4 Review of the anatomy right posterior pericardium.

4 100 Surgical Treatment of Atrial Fibrillation FIGURE 5.5 Opening the oblique sinus under the IVC. Pick-ups are used to bluntly elevate the inferior atrium superiorly. FIGURE 5.6 Progress of opening of oblique sinus: a sucker pushes posteriorly as the forceps push anteriorly. The oblique sinus is now opened inferiorly. 6 OPEN THE OBLIQUE SINUS SUPERIORLY OVER THE LA DOME AND TAKE DOWN THE SUPERIOR PERICARDIAL REFLECTIONS This is the one that scares learning surgeons but don t let it. If it gets hard, defer to your own fingers and perform the maneuver digitally. With practice, it becomes very easy and straight forward, and is again done primarily bluntly and using Bovie at a low setting (we favor 30). Being good at this maneuver means learning to retract the superior pericardium (and PA just above it) superiorly, and the dome of the atrium inferiorly (Fig. 5.7). This puts the thin areolar tissue on stretch and allows you to see where to go as you head posteriorly over the dome and down eventually into the oblique sinus. Just like with the inferior oblique sinus opening discussed earlier, proceed bluntly and use the two instruments in a walking or pawing motion. Use forceps and gentle dissection to open the plane under the PA and dome (Fig. 5.8) and then place a Yankar sucker inferior to the PA retracting it superiorly as you use blunt dissection to pull the tissue between the PA and dome inferiorly. This back and forth is a walking motion. Gently pull superiorly and hold with one instrument while the other one goes a bit deeper into the recess just created and then pulls inferiorly several times gaining further room (Fig. 5.9). Two Kitners on tonsil clamps work well, for example. Again, if you are not sure, defer to your fingers: place your right hand under the heart in the middle of the pericardium (left of the IVC) and your thumb over the dome of the atrium and

5 Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe Chapter FIGURE 5.7 Surgeon s view as the aorta is retracted to the left by the assistant to show the SVC and the relationship of the RPA (below and just left of the sucker tip) and the dome of the LA. This is the working exposure needed to dissect the dome of the LA from its attachments to the RPA and the superior pericardium. FIGURE 5.8 Anatomical view of the right superior LA dome and PA interface. Slight retraction of the RPA superiorly defining the beginning of the plane between the RPA and the dome of the LA. then bring the index or middle finger toward the tip of the thumb with both moving in circular motions to thin the tissue out; in moments they connect and the passage is open. With practice though you will learn how to enter the oblique sinus from above safely using instruments. As you proceed further posterior, begin to look for the opening to the oblique sinus (Fig. 5.10). Once seen now place the tip of the Yankar sucker or the instrument in your left hand down and into the hole and into the oblique sinus and retract the pericardium superiorly placing the adjoining attachments on stretch and opening the hole (Fig. 5.11). Once you have an opening into the sinus, keep working over the dome to release the pericardial reflections between the LA and the superior pericardium. Have your assistant place their forceps or sucker down and into the superior/posterior

6 102 Surgical Treatment of Atrial Fibrillation FIGURE 5.9 RPA retracted superiorly as the plane deepens down over the LA toward the oblique sinus below. FIGURE 5.10 Close-up of the dome dissection view showing initial entry into the oblique sinus below. The RPA is to the left and the dome of the LA to the right, and the small opening shown in the middle is the opening to the oblique sinus. pericardium and pull superiorly. You use your instruments to pull the dome of the LA inferiorly, which puts the attaching ligaments between the dome of the LA and the middle of the pericardium on stretch so that you can see them. Working from the right side of the dome over to the left, use Bovie to begin to divide these attachments; understand that you are beginning to get close to the left side of the atrium and the ligament of Marshall (LOM) (Fig. 5.12). There are typically two sets of pericardial attachments (or reflections) and you need to go through both of them. With each one, as

7 Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe Chapter FIGURE 5.11 Gentle dissection with electrocautery to further extend the opening large enough to admit the tip of the sucker into the passage into the superior oblique sinus. FIGURE 5.12 View of dome dissection from the right side of the heart working under the aorta showing the superior LA dome attachments to the superior pericardium. Here the suction tip pulls superiorly while forceps or other blunt instruments gently retract inferiorly to bluntly dissect the opening further. you go through the reflection, you will see pericardial fluid on the other side. It is common at this point for the learning surgeon to suffer a moment of dread that you have inadvertently entered the atrium this feeling is common and is to be expected. Take a breath, confirm your landmarks, and work a bit more. The more you free up here, the easier the left PVI dissection will be. Once you go through the second reflection you will be into the LOM (Fig. 5.13). Keep an eye on the LAA which will be in full view here and also helps as a landmark. Now at this point you have a wide passage superiorly over the dome of the atrium and into the oblique sinus below and you have also performed the majority of the left side of the dissection. When it comes time to create the left atrial lines, you will be amazed at how easy the left PVI is now as the dissection is basically done. At that moment after the heart is arrested and retracted up and to the right you will see the remaining LOM to be divided. With a good dissection it is basically ready to accept a clamp nearly immediately; however, if there is any concern the space is not completely free then be ready to go around with your fingers.

8 104 Surgical Treatment of Atrial Fibrillation FIGURE 5.13 This view shows the extent of the dissection performed from the right side and how far it can go. The yellow LOM is on stretch and in full view from under the aorta through this working space that started over the RPA. In Fig we have now changed sides and have retracted the heart hard over to the right putting the left pulmonary veins on tension and we are retracting the LPA superiorly. This is the first view from our working angle from the left side of the heart now. Fig zooms in from this view point to focus on the intact LOM. Notice in this image how much progress we had made from working from the right side and under the aorta. Indeed, the dissection is basically done at this point with the exception of the LOM which will now be divided with ease (Fig. 5.16). FIGURE 5.14 Nonmagnified working view point from the left side of the heart. The heart has now been retracted to the right and the LPA is being retracted superiorly showing the yellow LOM (seen from under the aorta in Fig. 5.13), now seen from the left side of the heart from above.

9 FIGURE 5.15 Close-up LOM with heart retracted to the right showing intact LOM and illustrating the extent of dissection reached while working from the right side of the heart under the aorta. Notice the far lateral extent tracks up to the superior side of the LSPV. FIGURE 5.16 Division of the LOM. (A) Initial pass with Bovie cautery. (B) Deepening the incision. (C) Final remaining bridge of LOM tissue.

10 106 Surgical Treatment of Atrial Fibrillation FIGURE 5.17 (A) Bipolar clamp passing with ease around the left antrum. (B) Clamp closed and ready to fire. After division of the LOM the passage behind the left pulmonary antrum is typically complete and unobstructed. In both Figs and 5.16, you can actually see into the posterior oblique sinus going under the left superior pulmonary vein (LSPV) under the LOM. Left clamp placement is now made easy because of this dissection. This is illustrated in Fig. 5.17, which in panel (A) shows the clamp effortlessly going around the veins, and in panel (B) the clamp closing in position for the left A-PVI (B). In summary, freeing up the dome of the LA with a wide passage into the oblique sinus now makes placement of the bipolar clamps for both PVIs very easy as there is so much room. It s common for learning surgeons to be visibly stressed when they try to place the bipolar clamps around the veins and antrum as they are worried about the posterior jaw of the clamp perforating as it passes. However, once you have this wide dissection accomplished, you can take a Yankar sucker from above, insert it over the dome moving posteriorly and under the back LA wall, and with a little superior traction you can see the tip inferiorly down into the oblique sinus from above. Once we developed this skill we were able to just slide the clamps right in using the Yankar sucker to lift the tissue superiorly, reducing clamp placement time to several seconds. This is the benefit of a good dissection. 7 WIDE DEVELOPMENT OF SONDERGAARD S GROOVE This is critically important for a medial antral high quality right PVI. Remember, RF clamps don t work as well going through adipose tissue and there is a significant amount of adipose tissue if Sondergaard s groove is not developed. By mobilizing the groove wide, you make it possible to apply the electrodes of the top jaw of the clamp directly on muscle and thereby play to the clamp s strength. Have your assistant pull the atrium anteriorly and put the groove on stretch; then, use a Bovie at a low setting (we find 30 is safe). Begin to lyse the attachments in the groove following the superior wall of the LA (Fig. 5.18). There are a couple of crossing veins that will need to be secured with the Bovie. For learning surgeons, study these veins and their positions. It is common for the learning surgeon to get into the small vein and then assume they have entered the atrium. It is almost certainly just the vein. Pause and confirm the situation and then keep working with a bit more attention the Bovie will seal it. One important point though is to minimize Bovie-related char on the antrum where the RF ablation will go remember char will sabotage the ablation and create breaks in the lines. Keep the char from the Bovie to a minimum and use the Bovie as a blunt dissector frequently. Work along the line from one end to another. Stay directly on the left atrial muscular plane as the accurate landmark to guide the dissection. In (B) we are beginning the groove dissection and deepening it through the adipose tissue, but not down on the cuff yet. There is typically a tremendous amount of adipose tissue here and it helps to work through that so that the clamp will be right on atrial muscle when it fires. Keep working the groove further and further medially from superior to inferior until the atrial junction begins to materialize (C). There is typically a small white patch or white spot and this tells you that you have gone far enough (D). At this point you should have a very wide muscular antrum for the bipolar clamp to ablate. After the groove has been widely developed, take a moment and study it looking for how free of adipose tissue it is you will be impressed. Now when the PVI line is placed, the clamp will be working on muscular tissue only and these are optimal circumstances for it to perform.

11 Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe Chapter FIGURE 5.18 Dissection of the intraatrial groove. Panel (A) shows the optimal exposure to begin the dissection. Panel (B) going through adipose tissue to get down and onto the atrial cuff. Panel (C) two thirds of the way into the dissection. Panel (D) completed dissection. 8 RIGHT PVI ACCESS If the dissection described earlier (involving opening the oblique sinus from below and dissecting off the pericardial attachments superiorly to enter the oblique sinus from above along with a wide development of the intraatrial groove) has been performed, then access to the right antrum is straightforward. Again, if there is any question, digital dissection is by far the safest maneuver to get around the antrum without a perforation (Fig. 5.19). FIGURE 5.19 (A) Right-handed digital dissection around the right PV antrum. (B) Close-up: Index finger is seen coming up through the passage between the PA and dome from behind the heart.

12 108 Surgical Treatment of Atrial Fibrillation FIGURE 5.20 Superior view from over the RPA into the transverse sinus and under the right antrum. The tip of the sucker is just to the left of the IVC. The sucker is retracting the right antrum superiorly. The IVC cannula can be seen in the distance. This dissection makes clamp placement easy and safe. Once developed fully through, posterior access is straightforward. A helpful trick is to again place the Yankar sucker between the PA and LA dome and down into the pericardium posteriorly and then slide the tip down the back wall of the pericardium until the tip is at the inferior posterior pericardium. This is shown in Fig and we are looking down from the head of the bed, to view the posterior right antrum down to the inferior pericardium. The sucker itself when lifted compresses the LA and creates a large passage for the inferior jaw of the clamp to easily pass (Fig. 5.21). Now the clamp can be slid into position with the bottom jaw easily passing through the large space behind made with elevation of the atrium by the Yankar Sucker (Fig. 5.22). After completing the passage safely and in seconds, the jaws are closed and the clamp is in an ideal position (Fig. 5.23). Again, PVI clamps will be discussed extensively in Chapter 12, however it is mentioned here to reiterate the importance of a thorough dissection in making clamp placements easy, quick, and safe. FIGURE 5.21 View of the fully dissected right PV antrum from above as continued from Fig. 5.18d. Here the sucker tip can be easily seen under the right antrum and just below the IVC lifting the posterior right antrum superiorly.

13 Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe Chapter FIGURE 5.22 The bipolar clamp advancing into position with the inferior jaw maneuvering through the passage in the posterior pericardium under the right antrum. Anterior retraction on the sucker maintains the wide opening by retracting anteriorly. The tip of the sucker can be seen protruding below the posterior right antrum as the clamp moves forward. FIGURE 5.23 Clamp in position around the right PV antrum and closed. The sucker removed prior to firing to limit any tension on the antrum. 9 LEFT PVI ACCESS The left PVI access is really facilitated (and almost completed) by the dome dissection as described earlier. After the division of the LOM again, it is relatively easy to drop down into the oblique sinus and have access around the left veins. Again, as in the right side, digital dissection is by far the safest way to develop wide access, and retracting the heart to the right side of the table to put the veins on stretch and then with the right hand reaching around the antrum, palm side down, and curling your index and middle fingers up under the back wall and LSPV, while your thumb curls around from the top, allows circular motions of the fingers to thin out the remaining connective tissue to open up the space.

14 110 Surgical Treatment of Atrial Fibrillation 10 CORONARY SINUS CANNULATION A brief word about CS cannulation is appropriate here. Once the vertical atriotomy (VA) has been made (Chapter 7), the CS is controlled with a purse string suture secured with a Rummel tourniquet secured around the retrograde coronary catheter providing spectacular cardiac protection via retrograde cardioplegia. It also allows easy insertion and removal of the retrograde cannulae. Fig shows the view through the VA and into the septal wall of the right atrium and the opening of the CS. Studying the CS carefully shows the small medial ligament and the lateral inferior wall (Fig. 5.25). Lifting up on the inferior edge FIGURE 5.24 Surgeon s View CS through the VA. Purse string suture being placed. FIGURE 5.25 View of the CS os from inside the right atrium. The forceps are grasping the inferior boarder of the sinus and putting it on a slight degree of stretch to make suture placement for the purse string suture straightforward and easy.

15 Mastering the Initial Dissection and Cannulation: Making Ablation Easy and Safe Chapter of CS with forceps brings it into very good control and allows placement of a purse string suture (Fig. 5.26). The purse string is then controlled with the Rummel tourniquet and once the retrograde CS catheter has been placed, the tourniquet tightens the purse string around the CS os, so that all of the cardioplegia will be delivered to the heart during administration (Fig. 5.27). FIGURE 5.26 Placement of the purse-string suture around CS os. FIGURE 5.27 Retrograde catheter in position and purse-string tightened.

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