Anterior Leaflet Laceration to Prevent Ventricular Outflow Tract Obstruction During Transcatheter Mitral Valve Replacement

Abstract

Background: Left ventricular outflow tract (LVOT) obstruction is a leading cause of mortality and exclusion from transcatheter mitral valve replacement (TMVR). Intentional laceration of the anterior mitral valve leaflet to prevent LVOT obstruction (LAMPOON) is a transcatheter mimic of surgical chord-sparing leaflet resection.

Objectives: The purpose of this prospective multicenter trial was to study LAMPOON with transseptal (Edwards Lifesciences, Irvine, California) TMVR in annuloplasty rings or native mitral annular calcification (MAC).

Methods: Subjects at high or extreme surgical risk and prohibitive risk of LVOT obstruction from TMVR were included. Eligibility was modified midtrial to exclude subjects with threatened LVOT obstruction from a Sapien 3 valve fabric skirt. The primary endpoint was procedure survival with successful LAMPOON, with successful TMVR, without reintervention, and with LVOT gradient <30 mm Hg ("optimal") or <50 mm Hg ("acceptable"). Secondary endpoints included 30-day mortality and major adverse cardiovascular events. There was universal source-data verification and independent monitoring. All endpoints were independently adjudicated. Central laboratories analyzed echocardiogram and CT images.

Results: Between June 2017 and June 2018, 30 subjects were enrolled equally between the MAC and ring arms. LAMPOON traversal and midline laceration was successful in 100%. Procedure survival was 100%, and 30-day survival was 93%. Primary success was achieved in 73%, driven by additional procedures for paravalvular leak (10%) and high-skirt neo-LVOT gradients observed before a protocol amendment. There were no strokes.

Conclusions: LAMPOON was feasible in native and annuloplasty ring anatomies in patients who were otherwise ineligible for treatment, with acceptable safety. LAMPOON was effective in preventing LVOT obstruction from TMVR. Despite LAMPOON, TMVR using Sapien 3 in annuloplasty rings and MAC still exhibits important limitations. (NHLBI DIR LAMPOON Study: Intentional Laceration of the Anterior Mitral Leaflet to Prevent Left Ventricular Outflow Tract Obstruction During Transcatheter Mitral Valve Implantation; NCT03015194).

Keywords: mitral annular calcification; structural heart disease; transcatheter electrosurgery; transcatheter mitral valve replacement; transseptal interventions; valve-in-ring.

FIGURE 1. Study Flow Chart

A total of 87 subjects were screened and 30 were enrolled. Reasons for exclusion are listed. AVR = aortic valve repair; LAMPOON = intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow obstruction; LVOT = left ventricular outflow tract; SMVR = surgical mitral valve replacement; TMVR = transcatheter mitral valve replacement; ViV = valve-in-valve.

FIGURE 2. LAMPOON Procedure

(A) Transesophageal echocardiography visualization of retro-grade LVOT catheter contacting the middle of the anterior mitral leaflet (arrow) and pointed toward a snare positioned by a second retrograde catheter in the left atrium. (B) The focally denuded lacerating guidewire straddles the anterior mitral leaflet (arrowhead) during electrification to achieve laceration (Online Video 1). Ao = Aorta; LA = left atrium; LV = left ventricle.

FIGURE 3. LAMPOON Outcomes

(A) Successful laceration of the anterior mitral leaflet before TMVR depicted on 3-dimensional transesophageal echocardiography (Online Video 2). (B) Color-flow across open cells of the Sapien 3 valve frame that without leaflet laceration would have completely obstructed the LVOT. The arrowhead shows the vena contracta, indicating the “leaflet lampooned” diameter; the arrow points to the edge of the valve abutting septum, indicating “leaflet intact” diameter. (C) A 3-dimensional computed tomography volume rendering after TMVR showing the split anterior mitral leaflet (black-outlined brown) splayed by the Sapien 3 valve frame (white) in the context of annular calcification (blue). (D) A 3-chamber perspective shows the valve frame contacted the interventricular septum across the LVOT (Online Video 3). Abbreviations as in Figure 1.

FIGURE 4. Neo-LVOT and Skirt Neo-LVOT Areas

Illustration of computed tomography-based prediction of neo-LVOT (A and B) and skirt neo-LVOT (C and D) area using 3-chamber projections (top) and LVOT short-axis projections (bottom) and a simulated valve (purple outline). A Sapien 3 valve is superimposed, illustrating covered and uncovered sections of the valve frame. LVOT = left ventricular outflow tract.

FIGURE 5. Predicted Neo-LVOT, Skirt Neo-LVOT, and Observed Gradients

LVOT catheter gradient after TMVR is compared with predicted neo-LVOT area (diamonds) and predicted skirt neo-LVOT area (circles). Red, orange, and yellow symbols indicate subjects who underwent bailout alcohol septal ablation. Red indicates subjects with inadequate skirt neo-LVOT. Orange indicates a subject with calcific anterior mitral leaflet patch and inadequate skirt neo-LVOT. Yellow indicates a subject with insufficiently basal LAMPOON. Abbreviations as in Figure 1.

FIGURE 6. Quality of Life and Function

Changes before and 30 days after LAMPOON TMVR in New York Heart Association (NYHA) functional class (p = 0.004), 6-min walk test (nonsignificant p = 0.15 based on n = 20 nonmissing pairs), and Kansas City Cardiomyopathy Questionnaire (Kansas City Cardiomyopathy Questionnaire)-15 Overall (p = 0.007) and Clinical Summary (p = 0.050) scores. Abbreviations as in Figure 1.

CENTRAL ILLUSTRATION. Anterior Leaflet Laceration to Prevent Ventricular Outflow Tract Obstruction During Transcatheter Mitral Valve Replacement

(Top) View from left ventricular outflow tract with and without intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow obstruction. (Bottom) Summary trial results. LAMPOON = intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow obstruction; LVOT = left ventricular outflow tract; PVL = paravalvular leak; TMVR = transcatheter mitral valve replacement.