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Endoscopic Mitral Repair in Severe MAC: Permissive Decalcification to Achieve an Effective Repair

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posted on 2023-09-28, 14:25 authored by Mario Castillo-Sang

Severe mitral annular calcification remains a challenge for the mitral valve surgeon. The past decade has introduced promising new technologies in the mitral valve replacement space, and ongoing clinical trials are evaluating the use of percutaneous technologies for this purpose.

Mitral valve repair can be achieved safely in the setting of mitral annular calcification (MAC) (1). Certain features need to be present to achieve a good repair: the presence of enough pliable anterior and posterior leaflets to open and create coaptation; a wide enough mitral orifice to allow for an inflow with low mean transmitral gradient after repair; and MAC permissive enough to apply an annuloplasty treatment. There are tools and techniques that aid in avoiding resecting the entire calcium bar when performing these MAC cases including ultrasonic cavitation devices, transcatheter balloon expandable valves, and mechanical strategic debulking using conventional instruments (2).

Most cases of repairable regurgitant mitral valves with MAC have a component of degenerative disease with ruptured or elongated chords and deep indentations or clefts that contribute to the regurgitation accentuated by the MAC. Most repairable mitral valves with severe MAC have noncircumferential calcium deposition, predominantly posterior.

These complex operations can be safely performed endoscopically or through other minimally invasive platforms. As always, in-depth preoperative planning aided by TEE and CT scan imaging allow the surgeon to predict with accuracy the probability of repair.

The Patient

This video illustrates the concept of permissive strategic decalcification in a case of severe mitral regurgitation complicated by severe MAC that extended from A1 to P3 posteriorly. The patient is a seventy-four-year-old woman with significant symptoms of dyspnea on exertion and fatigue, referred for severe mitral regurgitation. Her transesophageal echocardiogram showed a functional bileaflet prolapse with a dominant posterior (P2) true anatomical prolapse. The regurgitation was occurring at end-systole with several central jets, most prominently in the P1-P2 deep indentation region. Computerized tomography showed a C-shaped MAC extending posteriorly, and angiography showed normal coronaries.

The Surgery

The patient underwent an endoscopic mitral valve operation with left femoral-femoral cannulation using a 17 Fr arterial and 25 Fr venous cannula. Cardioplegic arrest was performed with antegrade del Nido cardioplegia. The endoscope was a 10 mm thirty-degrees scope placed in the third intercostal space, and a 1.5 inch minithoracotomy in the fourth intercostal space was used as the working port. An anterior chest atrial lift retractor was inserted in the fourth intercostal space. Liposomal bupivacaine was used for field block and intercostal block.

Once the left atrium was opened, it was clear that there was annular dilatation when static testing using a laparoscopic suction irrigator with del Nido cardioplegia showed poor to no coaptation of the anterior and posterior leaflets with a dominant prolapse of P2. Inspection of the valve revealed the medial P1, all P2, and lateral P3 segments were frozen in a prolapsed position by underlying calcium shelf, but the P2 segment and P3 segment were not infiltrated by calcium. There was a dominant infiltration of lateral P3 and lateral A1 segments with calcium. With this analysis, it became apparent that if function of the medial P1, P2, and lateral P3 was gained to allow diastolic excursion, a repair would be possible. It is customary to place the annuloplasty sutures first to conform the mitral annulus and in this case, this would play a role in showing if an annuloplasty ring would in fact correct the annular dilation and promote leaflet coaptation.

The first challenge was to achieve mitral annular sutures placement. This process requires adequate instrumentation to allow force transmission to the needle to pierce through MAC. The authors of this video have found 2-0 polyester sutures used with tapered microtips to be excellent for this purpose. Once the sutures were placed and pulled for tension, the annulus did conform, and static testing revealed there would be enough coaptation. At this point, strategic decalcification was next. The authors call this permissive, as the sole purpose is to allow movement of the leaflets and they were not looking to decalcify the entire posterior annulus.

Decalcification was performed using a valve hook to pull on the P2 segment, exposing the calcium shelf underlying it, which was then debrided completely using a combination of endo rongeurs and wall suction tip filling. The P2 segment was then made mobile. The medial P1 segment required more aggressive fracturing and debridement of calcium that made the closure of P1-P2 indentation necessary. Medial P3 was decalcified without problems using rongeurs, and then the corresponding deep indentation was closed. Once finished, medial P1, all P2, and all P3 were mobile.

Prior to correcting the P2 prolapse, an annuloplasty ring with the smallest AP diameter was applied with the intent of correcting the annular dilation. A Physio ring was selected for this purpose, and it was downsized by one to the full annular measurement. Once the ring was applied, the height of the needed neochords was selected with posteromedial papillary muscle using the Mohr sizer. Premeasured ePTFE chords 16 mm in length were chosen. Static testing showed a competent valve and an ink test revealed at least 8 mm depth of coaptation. The postoperative transmitral gradient was 4-4.3 mmHg with a heart rate of 85 bpm.

The patient was extubated in the operating room and was discharged home the afternoon of postoperative day three. The one-month follow-up showed that mean transmitral gradients remained low at 4 mmHg with no residual mitral regurgitation and resolution of symptoms.

Reference(s)

1) Tomšič, Anton, Yasmine L. Hiemstra, Thomas J. van Brakel, Michel IM Versteegh, Nina Ajmone Marsan, Robert JM Klautz, and Meindert Palmen. "Outcomes of valve repair for degenerative disease in patients with mitral annular calcification." The Annals of Thoracic Surgery 107, no. 4 (2019): 1195-1201.

2) Shi, William Y., Navyatha Mohan, Thoralf M. Sundt, Sophie Butte, Jordan P. Bloom, Nathaniel B. Langer, and Serguei I. Melnitchouk. "Complete Excision of Mitral Annular Calcification Can Be Achieved With a Low Mortality Risk." Annals of Thoracic Surgery Short Reports (2022).

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