6.1 / IAGS 2019
Session 6: Structural Session 3
Techniques to Avoid LVOT Obstruction in Valve Interventions
Problem Presenter: Tarek Helmy, MD
Statement of problem or Issue
Left ventricular outflow tract (LVOT) obstruction in patients undergoing transcatheter mitral valve replacement (TMVR) typically occurs in a specific group of patients and can result in catastrophic complications. This is related to the aorto-mitral angle, LVOT dimensions, presence of septal hypertrophy, and length of the anterior mitral leaflet (AML). Deliberate laceration of the anterior mitral leaflet using electrified wires (LAMPOON) to prevent LVOT obstruction has previously been described. We present a novel technique to prevent LVOT obstruction during trans-apical retrograde mitral valve replacement, which is performed by penetrating and ballooning the AML, resulting in its laceration or posterior translocation.
Computed tomography (CT) of the chest is obtained to assess the anatomic relationship between the left ventricular (LV) apex, existing coronary grafts, and the chest wall. Dimensions of the LVOT, mitral annulus, thickness of the septum, aorto-mitral-annular angle, and the distance between the papillary muscle and the mitral annular plane can also be evaluated. Transesophageal echo (TEE) can also assess AML length, aorto-mitral-annular (AMA) angle, septal hypertrophy, and dimensions of the mitral annulus or the existing prosthesis.
Patient was intubated, and placed on cardio-pulmonary bypass (as a precaution, to minimize hemodynamic changes). Using fluoroscopy and TEE, the optimal intercostal space for access to the LV apex is determined. The left lung is deflated and the pericardial space is accessed through a mini-left thoracotomy incision. Using TEE guidance, the optimal apical position that allows coaxial alignment with the anterior mitral leaflet is identified. Two purse-string sutures are placed with felt pledgets, and the apex is punctured using a long 18G pericardiocentesis needle.
Cardiopulmonary bypass cannulae are then placed. The pericardiocentesis needle is then advanced through the anterior leaflet into the left atrium using TEE guidance. An accurate puncture site of the AML is a point midway between the base and the tip of the A2 portion. Puncture too close to the base of AML can result in injury to the mitral annulus later during balloon inflation. If the puncture is too close to the tip of the AML, the laceration may not be enough to prevent LVOT obstruction. A 0.035-inch stiff wire is inserted and advanced into the right superior pulmonary vein. The apical access site is enlarged with serial dilators and a delivery sheath is placed. During this time, the prosthetic valve is prepared. The co-planar view of the mitral valve annulus is then established with fluoroscopic guidance using the mitral annular calcification (MAC) or the mitral annular ring as a marker. A 20-mm valvuloplasty balloon is then inserted over a wire, positioned within the anterior leaflet and inflated. Cardio pulmonary bypass allows for minimal flow across the mitral valve during inflation. This can result in one of two scenarios. The first is splitting of the AML. The other possibility is that the balloon causes posterior translocation of the anterior mitral leaflet, by creating a large “hole” in the AML, allowing the transcatheter valve prosthesis to be implanted within the mitral leaflet with further splitting during the deployment of the large valve. Caution should be exercised in cases of a heavily calcified AML tip as inflation of the balloon can be directed towards the annulus with subsequent injury or annular rupture. After balloon inflation, severe MR is anticipated, and the hemodynamic effects are mitigated by using the cardio-pulmonary bypass.
The delivery system is then advanced over the guidewire and the balloon-expandable valve is deployed. Balloon dilation with “flaring” of the ventricular portion is performed. The positioning of the transcatheter valve is an optimal ratio of 30%-40% atrial and 60%-70% ventricular. Placing the valve within the anterior mitral leaflet “defect” may also allow for a “sealing” effect to prevent paravalvular leaks.
The technique we present here of trans-apical ballooning of the AML, with either splitting or posterior translocation of the AML, allows for a chordal-preserving transcatheter mitral replacement option that offers less complexity, and can obtain excellent results. One of the major limitations to the current case is the trans-apical approach needed for the initial puncture of the AML, but with the growing number of devices designed for trans-apical delivery, this technique will have a role in patients with high risk of LVOT obstruction. Other iterations of the technique can be used for trans-septal approach for TMVR.