Severe mitral annular calcification (MAC) remains one of the most challenging settings in mitral valve surgery. Extensive annular decalcification may be associated with major complications, including atrioventricular disruption, massive bleeding, or prosthetic instability.

In recent years, a hybrid alternative combining open surgery and transcatheter technology has emerged: transatrial implantation of balloon-expandable prostheses. In Heart Surgery Today, we have recently reviewed 2 relevant studies assessing this strategy and its clinical outcomes in patients with severe MAC, including an analysis of trends and outcomes of transatrial balloon-expandable prosthesis implantation in the United States and a multicenter registry of transatrial implantation in massive mitral annular calcification. Both studies show how transatrial transcatheter mitral valve replacement is becoming established as an increasingly used option in high-risk patients.

Against this background, the review of several surgical videos allows attention to be directed toward a different but equally important aspect: the technical details of the procedure. These videos clearly illustrate the key implantation steps and help identify maneuvers that may facilitate safer and more reproducible execution.

• Mitral exposure
  After institution of cardiopulmonary bypass and aortic crossclamping, a standard left atriotomy is performed to expose the mitral valve. In the CTSNet video on robotic transatrial implantation, mitral exposure is achieved through a robot-assisted minimally invasive approach, showing that the technique can be adapted to different surgical accesses. In the videoOpen Transatrial TMVR in Severe MAC, the more classic median sternotomy approach is shown. In both cases, the first step is to assess the extent and distribution of mitral annular calcium.
• Anterior leaflet resection
  One of the most important technical steps shown in the videos is complete resection of the anterior mitral leaflet. This maneuver is performed systematically before prosthesis implantation, with the main objective of preventing left ventricular outflow tract obstruction (LVOT obstruction), one of the most feared complications in TMVR. In the CTSNet video, it is clearly shown how anterior leaflet resection enlarges the outflow tract area and subsequently facilitates prosthesis expansion.
• Preparation of the calcified annulus
  Unlike conventional mitral surgery, this technique does not aim to remove annular calcification. The videos show how the surgeon leaves most of the calcium intact, removing only unstable fragments that may interfere with implantation. The calcified annulus subsequently serves as the anchoring structure for the balloon-expandable prosthesis, thereby avoiding the need for extensive decalcification.
• Valve positioning
  Once the annulus has been prepared, the balloon-expandable valve mounted on its delivery system is introduced. In theOpen Transatrial TMVR video, the prosthesis is inserted directly through the left atrium and carefully positioned within the calcified annulus under direct vision. This direct visualization is one of the main advantages of the surgical approach over fully percutaneous techniques, because it allows adjustment of prosthesis position before expansion.
• Prosthesis expansion
  After correct positioning has been confirmed, balloon expansion of the prosthesis is performed. During this phase, the videos show how the surgeon maintains manual control of the prosthesis to prevent displacement during inflation. The rigidity of the calcified annulus favors valve anchoring and contributes to prosthetic stability.
• Final assessment
  Once the prosthesis has been expanded, implant stability and the presence of possible paravalvular leaks are visually assessed. After aortic unclamping, transesophageal echocardiography confirms adequate prosthetic opening, absence of LVOT obstruction, and absence of significant leaks.

COMMENTARY:

At CHUAC, we have accumulated some experience over the past 5 years with the transatrial implantation technique for balloon-expandable prostheses in patients with severe MAC. Over the course of our most recent cases, we have progressively incorporated small technical adjustments during planning and surgery that have proved especially useful.

Many of these details are not usually described in either articles or technical videos, yet in practice they can make a major difference during the procedure. The aim of this commentary is to share some of these tricks and maneuvers that, in our experience, may help surgeons beginning to adopt this technique.

1. Ideal patient according to CT study

Planning with ECG-gated cardiac CT is essential to identify appropriate candidates for this procedure.

In our experience, the ideal patient has severe, circumferential MAC, with sufficient calcium burden to allow anchoring of the balloon-expandable prosthesis. As a rough guide, the total calcium burden should be ≥750–1000 mm³, which generally provides adequate prosthetic support.

CT also allows assessment of MAC morphology, with particularly favorable cases being those showing thickness ≥10 mm, extension ≥270°, and involvement of the trigones or leaflets. This circumferential calcium distribution provides a rigid annulus that facilitates prosthetic stability.

Another relevant aspect is estimation of the neo-LVOT. In conventional transcatheter techniques, values <170–180 mm² are associated with a high risk of outflow tract obstruction. However, with the transatrial approach this limitation becomes less important, because systematic resection of the anterior leaflet significantly reduces this risk.

Finally, it is advisable to confirm that mitral annular dimensions fall within the usual ranges for balloon-expandable prostheses, generally corresponding to annular areas between 500 and 800 mm².

2. Cardiopulmonary bypass and exposure

The procedure is performed on cardiopulmonary bypass according to the principles of conventional mitral surgery through a median sternotomy.

A relatively common feature in these patients is a history of thoracic radiotherapy, which may result in significant mediastinal adhesions. For this reason, careful mobilization of the lateral aspect of the heart is recommended, as this subsequently facilitates mitral exposure. In some cases, this maneuver even allows placement of a surgical pad to improve valve visualization.

During the procedure, endoscopic assistance may be very useful, as it improves visualization at key moments such as prosthesis positioning and deployment. In selected cases, a Heart Port approach may provide excellent mitral exposure and facilitate some implantation steps.

3. Surgical technique

• Valve resection and preparation

The first step is complete resection of the anterior mitral leaflet, a fundamental maneuver to prevent ventricular outflow tract obstruction. The mitral annulus is then measured with conventional sizers, which provides an approximate reference for balloon-expandable prosthesis size. Once size has been confirmed, preparation of the balloon-expandable prosthesis is undertaken, and during this time several sutures are placed in the annular and posterior leaflet areas with the least calcium burden; these are later passed through the prosthetic skirt to reinforce fixation.

• Prosthesis implantation.

Implantation can be performed with the prosthesis fully crimped, although in practice it is usually more convenient to use it partially crimped (25%-50%), allowing it to be progressively accommodated within the calcified annulus.

Initial expansion may be performed with the balloon supplied with the Myval prosthesis itself, as in our case, although this is often insufficient. The excessive length of the delivery system frequently makes it impossible to fully advance the delivery catheter/balloon into the left ventricle, thereby limiting adequate prosthesis expansion. For this reason, it is especially useful to employ an alternative semicompliant balloon, such as the Cristal balloon, which offers several advantages: a more flexible tip, improved ventricular navigability, and greater capacity for prosthetic centering.

During dilation, it is very helpful to hold the prosthesis with surgical forceps, allowing stabilization or repositioning if it tends to shift during balloon inflation.

• Definitive fixation

Once full expansion has been confirmed, the previously placed sutures are passed through the prosthetic skirt, reinforcing valve anchoring. These sutures help reduce the risk of paravalvular leaks. In some cases, it may be useful to place additional stitches or interpose small Teflon pledgets in areas where a residual leak is suspected. The use of automated fastening systems such as Cor-Knot facilitates this phase, shortening operative time and avoiding unexpected traction.

Small technical details such as those described may simplify procedural execution and help make transatrial implantation of a mitral prosthesis in patients with severe MAC an increasingly reproducible technique for other surgeons

REFERENCIAS:

• Robotic-Assisted Transatrial Balloon-Expandable Valve Placement in Severe Mitral Annular Calcification
• Open Transatrial TMVR in Severe Mitral Annular Calcification