The Mitral Patch Technique for Mitral Annular Calcification (MAC)

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This video demonstrates a novel pericardial patch for mitral valve replacement in the setting of mitral annular calcification (MAC). MAC confers certain perioperative risks, such as increased risk of paravalvular leak and atrioventricular (AV) dehiscence, and higher mortality overall. The patch was used at the posterior aspect of the mitral valve near the posterior annulus. The patch can be anchored to the left atrial portion near the valve that is not calcified, allowing it to be sutured safely without a paravalvular leak.  

Current options for managing severe MAC include extensive debridement with and without high frequency ultrasound and forced suture placement through calcifications. However, these techniques may lead to higher rates of AV dehiscence and paravalvular leak. The video includes a schematic demonstrating how the patch will overlay onto the mitral valve orifice.  

This approach offers several advantages: It reduces need for decalcification, allows for a larger valve to be implanted by atrializing the valve, and there is a low risk of dehiscence by avoiding intraannular decalcification and suturing to healthier tissue.  

This patient is a 71-year-old male with severe mitral regurgitation, who presented with orthopnea and dyspnea, worsening on exertion. Preoperative investigations demonstrated mitral and aortic calcifications. The mitral valve mean pressure gradient was 20. A preoperative CT scan showed severe aortic and mitral valve calcification, which were also present on the 3D echocardiography.  

In the operating room, a median sternotomy was performed, followed by standard aortic and bicaval cannulation. The heart was arrested using antegrade and retrograde cardioplegia. The aortic valve was addressed first and debrided for later repair, then the mitral valve was exposed. Calcium was resected as much as possible without getting into the annulus. The concern with putting the valve through the calcifications was that it may contribute to the risks that the authors noted earlier. The video demonstrates how it looks once the anterior leaflet has been removed. This technique allows for safer debridement with a lower risk of AV dehiscence given that intraannular calcification can be maintained. The posterior leaflet was then debrided. SONOPET was utilized to enlarge the mitral valve orifice, ensuring an effective orifice area as the sizer was passed through the mitral valve orifice. However, sizing can typically be liberalized one to two sizes larger because the newly implanted valve will be atrialized, making it possible to insert a much larger valve than the size of the actual annulus. Sutures were placed circumferentially from the native annulus to the left atrial tissue. You can see the sutures passed through the annulus with pledgets on the atrial side. Whether the pledgets are placed on the atrial or ventricular side probably does not matter. 

The sutures were continued circumferentially and were placed in areas that were soft, demarcating the transition of when sutures were placed to the back wall of the left atrial tissue. Calcifications were carefully avoided as the surgeons transitioned to the back wall fold.  

Pledgeted sutures were continued, creating a fold on the back wall of the left atrium. This allowed for full thickness bites to be created, which served to securely anchor the valve and prevent paravalvular leak. Ensuring that these bites were through the posterior wall of the left atrium and away from the AV groove. The authors transitioned from atrial tissue to the annulus at the posteromedial commissures. The ring of sutures was then completed.  

To achieve a valve ready for implantation, the patch was created and sewn to the valve skirt, which could be done simultaneously at the back table by an assisting surgeon. Bovine pericardium was used to create a crescent moon or C shape. Once the crescent shape had been created, a larger crescent was created 2-3 centimeters away from the valve. After the patch was cut out, it was attached to the valve ring using 4-0 Prolene on an RV1 needle, run from commissure to commissure. Here was the final product. The valve ring and the pericardial patch could be sutured to the left atrium in a continuous or interrupted fashion. While the valve can be sutured in either way, in this case, the authors are demonstrating anchoring with horizontal mattress pledgeted sutures. The posterior left atrium was used as a landing zone for the patch, avoiding the densely calcified posterior mitral annulus, which eliminates the need to debride and decalcify the posterior mitral valve annulus entirely.  

The valve was lowered and seated normally, as with any other valve. Sutures were tied using either standard knot tying techniques or a COR-KNOT device. The ideal length of the patch is approximately 4-5 mm from the posterior left atrium to facilitate the placement of the anchoring sutures.  

Here is the final appearance upon visual inspection. This technique provides an added benefit of decreased risk of left ventricular outflow tract (LVOT) obstruction due to some aspects of atrialization of the valve. Postoperative echocardiograms demonstrated a well-functioning valve with a gradient of 2, no mitral insufficiency, no paravalvular leak, and no LVOT obstruction. Benefits of this technique included its technical ease, lower risk of AV dehiscence, and the ability to place a larger valve, resulting in lower mitral valve gradients and a larger valve indexed to body surface area. This mitral patch technique proved to be a promising option for surgeons treating patients with severe mitral annular calcification. 

References

1. El-Eshmawi A, et al. Contemporary surgical techniques for mitral valve replacement in extensive mitral annular calcification. JTCVS Techniques. 2023;22:1–12
2. Millar, JK; Ailawadi, G. Current techniques for severe mitral annular calcification. JTCVS Techniques. 2023;22;53–58

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