Giant Patch Technique for Reconstruction of the Aortomitral Curtain: How I Teach It

Infective endocarditis is associated with an early mortality up to 30% despite advanced diagnostics and antibiotic therapies, and approximately one-half of patients will require operative management.^1,2 A rare complication presenting a significant technical challenge is destruction of the aortomitral curtain, a condition that often requires combined mitral and aortic valve replacement and reconstruction of the intervalvular fibrosa (Commando or hemi-Commando procedure). This procedure carries an early mortality rate of 14% to 30%, with reintervention rates up to 17% at 1 year.3, 4, 5

However, there are instances in which the aortomitral curtain is destroyed with minimal or no involvement of the mitral valve leaflets. As surgeons operating in a tertiary center (University of Washington Medical Center, Seattle, WA) with a high volume of infective endocarditis cases, we often use a surgical technique involving a “giant patch” reconstruction of the aortomitral curtain with preservation of the native mitral valve. This technique offers a relatively simple option that allows for enhanced resident involvement, comprehension, reproducibility, and excellent patient outcomes.

Preparation

To prepare for this procedure, careful assessment of preoperative imaging is required. Patients undergo cardiac-gated computed tomographic angiography of the chest as well as transthoracic or transesophageal echocardiography. Studies are evaluated carefully by both the attending physician and trainees.

When evaluating computed tomographic angiography, it is important to note the size and location of any abscess cavity or pseudoaneurysm, as well as the relation to other cardiac or other vascular structures. This information is essential for determining mediastinal entry and for ensuring that any problem areas are not dissected before the safe initiation of cardiopulmonary bypass (CPB) and establishment of an aortic cross-clamp site. Note is taken to examine any preexisting aortic disease such as bicuspid or unicuspid valves, calcification of leaflets or the annulus, extension of calcification below the level of the aortic annulus, and aortic aneurysm.

The echocardiogram is a vital part of preoperative assessment. Function of the aortic and mitral valves is carefully assessed. What are the location and severity of any aortic insufficiency (AI)? Does the aortic valve demonstrate additional abnormalities such as calcification or thickening? Is the leak through the valve purely intravalvular, or is there a paravalvular component? Is the abscess or pseudoaneurysm cavity clearly visualized, and is there evidence of flow into this space? Analysis of the mitral valve is performed specifically on the degree and mechanism of mitral regurgitation (MR), the presence of vegetations or leaflet perforation, and the degree of abscess extension to the mitral annulus. Often, even a large abscess of the aortomitral curtain will stop at the level of the mitral annulus without significant mitral valve destruction; however occasionally a portion of the anterior leaflet of the mitral valve or annulus may be involved. The presence of moderate or greater MR is somewhat concerning because there is a risk of additional restriction of the anterior leaflet of the mitral valve and worsened leak after large patch repair of the aortomitral curtain.

How I Teach It

The patient is positioned supine, and the arms are tucked. After sternotomy is performed, CPB is established. Effort is made not to manipulate the ascending aorta before initiation of bypass in the setting of a pseudoaneurysm given the risk of free rupture. A retrograde cardioplegia cannula is placed routinely because of the high frequency of AI in the setting of infective aortic valve endocarditis. To place the retrograde cannula, trainees are instructed to place a pursestring suture approximately 3 cm above the inferior vena cava–right atrial junction and 1 to 1.5 cm lateral to the atrioventricular fat pad surrounding the right coronary artery. The assistant gently retracts that venous cannula toward the patient’s left shoulder while the trainee inserts the catheter, aiming for the tip to contact the heart just medial to the inferior vena cava. The tip is then directed toward the patient’s left shoulder while gently advancing the catheter. The trainee’s nondominant hand can be placed on the inferior aspect of the heart to feel the cannula tip as it enters the sinus and passes into the proximal portion.

After CPB is established, an aortic cross-clamp is placed, and the heart is arrested with retrograde cardioplegia. After diastolic arrest, the aorta is opened transversely approximately 1.5 cm above the sinutubular junction, and the right and left coronary orifices are identified. Ostial cardioplegia is administered. The root is mobilized by dividing the veil of tissue surrounding the pulmonary artery. The trainee is instructed to “stay on the pulmonary artery but not in the pulmonary artery” to avoid injury to the left main coronary artery. Pledgeted 4-0 polypropylene (Prolene, Ethicon) stay sutures are placed in the fat pad superior to the right coronary artery and the fat/adventitia proximal main pulmonary artery and are retracted inferiorly and laterally, respectively. The patient is placed in a ”beach chair” position to improve visualization of the aortic root.

The aortic root is then inspected. Resano forceps are helpful to grasp the valve leaflets, and the aortic valve is removed using a combination of long Metzenbaum scissors and a #11 blade. Trainees are taught that a blade is often more precise than scissors when removing the valve leaflets. Careful attention is paid to ensure that dissection is not carried too deeply into the annulus or that the underlying anterior leaflet of the mitral valve is not damaged. With the valve removed, the aortic annulus is inspected. Residual calcium is debrided. The annulus is assessed for extent and location of abscess, pseudoaneurysm, or devitalized tissue. It is critical that all areas of abscess are opened widely and allowed to drain into the mediastinum. This often means carrying the root dissection deeply to the level of the dome of the left atrium on the noncoronary sinus. The trainee is advised to debride widely to remove all devitalized tissue. This is often an intimidating process because it involves destruction or removal of a significant portion of the noncoronary sinus and aortic root in this region. Inspection and debridement of the aortic root can be seen in Figures 1 and 2. In the giant patch technique, the extent of infection is limited to the region superior to the anterior mitral annulus and is often bounded by the left/noncoronary commissure and the right/noncoronary commissure of the aortic valve. Should the infection extend farther into the mitral annulus, a Commando procedure is required. Extension of the infection beyond the commissures of the noncoronary sinus superiorly is not a significant issue provided the coronary arteries are not affected.

Figure 1.

Careful inspection of the aortic root to determine the extent of devitalized tissue fully.

Figure 2.

Wide debridement of all devitalized tissue.

After all devitalized tissue is debrided, the aortic root is irrigated thoroughly, and the process of reconstructing the annulus is begun. Appropriate resection of affected tissue typically necessitates removal of the entirety of the aortomitral curtain. The trainee is encouraged to palpate the medial and lateral fibrous trigones of the mitral annulus between the thumb and forefinger. Careful attention is paid to locate the trigones because this is the area that will effectively anchor the patch and provide strength to the patched region. An understanding of the location of the fibrous trigones is essential to ensure that the dissection has been carried far enough to allow for anchoring the patch in this region. We emphasize to the trainee that simple placement of sutures through the mitral annulus will allow for aortic valve or root replacement; however, this is likely to distort the anterior leaflet of the mitral valve, cause significant MR, and result in an off-axis valve with an abnormal position. Therefore, a patch must be used to reconstruct the aortomitral curtain and recreate the natural anatomy of the left ventricular outflow tract (LVOT) and aortic root.

A large piece of bovine pericardium is sized by measuring the distance from trigone to trigone of the mitral annulus and oversizing the patch by approximately 3 to 4 mm on either side to account for placement of sutures. The patch is anchored to the drape on the surgeon’s side, and the trainee begins sewing the patch using a 5-0 Prolene suture at the patch midpoint. Sutures are anchored in the anterior mitral annulus, and after approximately 3 to 4 stitches, the patch is parachuted into position. It is important to ensure that the patch is placed with its edges internal to the LVOT to ensure hemostasis. The trainee is instructed to use a combination of forehand and backhand sutures given the difficult angles at the inferior aspect of the patch. Attention is paid to ensure that sutures are symmetrical and regular because bleeding from the subannular portion of the patch becomes challenging, if not impossible, to manage after aortic cross-clamp removal. The patch is then sewn to the wall of the aorta and is continued to the level of the sinutubular junction. The second arm of the suture is used to duplicate the process on the other side of the patch. Typically, a second 5-0 suture is used to create a double-layer anastomosis because this significantly reduces the risk of bleeding from the anastomosis. Patch implantation is demonstrated in Figures 3 and 4.

Figure 3.

Securing the giant patch into position.

Figure 4.

Demonstration of proper patch positioning with the edges internal to the left ventricular outflow tract to ensure hemostasis.

Once the patch is in place, the neoannulus is sized. Generally, we prefer to perform a full root replacement for patients with endocarditis and significant abscess. Although it is occasionally possible to perform aortic valve replacement with giant patch reconstruction, it is significantly more challenging to ensure that all abscess or pseudoaneurysm spaces are fully drained and that we are better able to ensure adequate tissue quality or reconstruction with full root replacement. Sizing of the annulus is critical and is performed as follows:

• 1.The barrel end of a valve sizer is used and is placed such that it contacts the nadir of the right and left coronary sinuses.
• 2.The sizer is positioned such that an approximately 5- to 7-mm gap exists between the bottom of the patch and the sizer. To assist with sizing, a line is drawn on the patch 5 to 7 mm from the base of the patch with a marking pen. This represents the neoaortic annulus.
• 3.The appropriate-size valve is selected such that it reasonably fits in the reconstructed annulus without significant angulation.

Once the annulus is sized, alternating 2-0 braided polyester Tevdek pledgeted valve sutures (Teleflex Medical) are placed (Figure 5). Sutures are placed in standard fashion on the left and right coronary sinuses; however, the junction of the patch with native tissue is potentially more challenging. The trainee is instructed to ensure that sutures come out just above the aortic annulus when approaching the area of the patch because often thse patch is anchored near a commissure. If sutures follow the native annulus and come out above the annulus, this will lead to a large discrepancy between the previously drawn line on the patch and the location of the last suture on the native aortic annulus. To mitigate this, the trainee is instructed to leave space for the last suture in the left or right coronary sinus to be taken from the outside in, with the arms of the stitch spanning the junction of the patch and native aorta to promote hemostasis. Sutures along the patch are then taken with pledgets externally. Care is paid to ensure that sutures have no more than a 1-mm gap between the previous suture to decrease the risk of bleeding or perivalvular leak. This may cause pledgets to overlap on the external surface of the patch; however, this is not a significant issue. Once all sutures are placed, the annulus is inspected, and the conduit is prepared for implantation.

Figure 5.

Placement of valve sutures in relation to the neoannulus.

Sutures are then passed through the sewing ring of the valved conduit, and the conduit is slid into position. Before placing sutures, the trainee is asked to determine the appropriate position of the commissures with respect to the coronary orifices. All sutures are tied, and coronary buttons are reimplanted in standard fashion with 5-0 Prolene sutures. Junior trainees start by reimplanting the right coronary button, which is often more accessible for repair after removal of the aortic cross-clamp, whereas the senior surgeon reimplants the left coronary button. More senior trainees implant both buttons. The patch is then trimmed of excess length, and the valved conduit is inspected with a nerve hook for any areas concerning for possible leak. These are addressed with an additional pledgeted valve suture taken either internally (native right and left annulus) or externally(patch). The final aortic root replacement with a giant patch reconstruction of the aortic root can be seen in Figure 6, and the operation can be viewed in the Video.

Figure 6.

Illustration of the completed aortic root replacement with giant patch reconstruction of the aortomitral curtain.

Once the procedure is completed, the heart is deaired, and the patient is weaned from CPB. It is not uncommon for there to be slightly more MR than preoperatively in the immediate postarrest period; however, this generally improves as the heart reperfuses.

Comment

The giant patch technique of aortic valve replacement for complicated aortic valve endocarditis is reproducible, straightforward, and easily teachable. Trainees have an unobstructed view of the LVOT and aortic annulus, and placement of the patch and sutures in this scenario is straightforward. The attending surgeon can carefully observe all parts of the operation and ensure a successful repair. In particular, the view of the patch from the left side of the operating table is excellent, and any areas of possible coaptation deficit are easily correctable with repair sutures before placement of a valved conduit. The use of a double-layer running suture on the patch ensures excellent hemostasis without putting undue tension on the mitral annulus or anterior mitral leaflet. This technique is similar to the Y aortic root enlargement, and the skill set between these procedures is highly overlapping.

In summary, the giant patch technique for aortomitral curtain reconstruction in the case of complicated endocarditis with aortic root abscess is simple, effective, reproducible, and teachable. It is more straightforward than a full Commando or hemi-Commando procedure and offers trainees the opportunity to appreciate the complex anatomy of the aortic root and aortomitral continuity.