Left ventricular outflow tract (LVOT) obstruction is a leading cause of mortality and screen failure for transcatheter mitral valve replacement (TMVR). Preventative strategies include percutaneous laceration of the anterior mitral leaflet (LAMPOON), pre-emptive alcohol septal ablation, and transatrial surgical anterior mitral leaflet resection. Of these, the best evidence is for LAMPOON, which has been studied prospectively in a clinical trial with independent endpoint adjudication and core laboratory image analysis.1 LAMPOON was successful in all patients irrespective of anatomy and calcification and 30-day survival in patients with a mean neo-LVOT of 81 mm2 or mean anterior mitral leaflet length of 28 mm was 93%.1 However, LAMPOON was unable to prevent obstruction from the covered valve skirt in cases where the skirt neo-LVOT was reduced.2 Pre-emptive alcohol septal ablation was studied in a retrospective registry with self-reported endpoints.3 Alcohol septal ablation led to two deaths (7%) and a 17% pacemaker implantation rate, and enabled standalone TMVR in only 50% of patients studied. Transatrial surgical leaflet modification and TMVR has been studied in case series, with 27% 30-day mortality,4 and is being investigated prospectively in an ongoing clinical trial (SITRAL NCT02830204).
In this landscape, there is need for further innovation, and Helmy et al present a novel solution of deploying the transcatheter mitral valve within the anterior mitral valve leaflet (BATMAN) in this issue of Catheterization and Cardiovascular Interventions. In the ideal situation, this results in posterior translocation of the anterior leaflet tip and chords, mimicking surgical posterior translocation during mitral valve replacement. In its present formulation, BATMAN requires apical access for skewering the leaflet and for valve delivery, and was performed on cardiopulmonary bypass. However, these are the first three patients reported and it is certainly conceivable that this procedure, with minor modifications, can be performed percutaneously from an entirely transseptal approach and with intra-aortic balloon pump mechanical support.
With any new procedure, the results need to be assessed carefully and potential risks investigated thoroughly. Preclinical benchtop and animal studies can often help with procedure development and risk stratification. In our laboratory, we had variable results when we performed balloon dilatation and Sapien 3 (Edwards Lifesciences, Irvine, CA) valve deployment in the anterior mitral leaflet in freshly explanted pig hearts. Most concerning in our experiments was the unpredictable extension of the tear in the anterior mitral leaflet from balloon expansion, with cases of tears extending up the aortomitral curtain or laterally into the trigone and avulsing it from the annulus. It is possible that in patients with mitral valve disease, the results would be different. However, these are important risks to consider in any future BATMAN procedures.
In terms of the outcomes in these three patients, the authors chose an unconventional approach to stratifying LVOT obstruction risk using transesophageal echocardiograph instead of CT derived neo-LVOT. By echocardiography, only one of the three patients appeared to have a small neo-LVOT (of 150 mm2 after TMVR). This patient had an increase in LVOT gradient of 11 mmHg from baseline, but would have likely had a much greater increase without BATMAN. Like LAMPOON, BATMAN does not address the problem of a reduced skirt neo-LVOT found in many patients with small ventricles.
While BATMAN is an innovative hybrid approach to prevent LVOT obstruction from TMVR, the dangers of uncontrolled ballooning of the anterior mitral leaflet should not be underestimated. We believe the LAMPOON approach is more controlled, is completely percutaneous, and has been further simplified as an antegrade transseptal procedure.5 We therefore recommend that BATMAN undergo considerable further refinement and investigation before it is adopted more widely to treat patients.
Key Points.
BATMAN is a new technique to prevent left ventricular outflow tract (LVOT) obstruction from transcatheter mitral valve replacement (TMVR) by deploying the transcatheter heart valve from the apex through a perforation of the anterior mitral valve leaflet.
The risks of uncontrolled balloon dilatation of the anterior mitral valve leaflet include extension of the tear superiorly into the aorto-mitral curtain or laterally to avulse the trigone from the annulus.
Percutaneous laceration of the anterior mitral leaflet, pre-emptive alcohol septal ablation, and transatrial leaflet resection are alternative strategies that prevent LVOT obstruction from TMVR
Footnotes
CONFLICT OF INTEREST
NHLBI and Edwards Lifesciences have a cooperative research and development agreement towards transcatheter modification of the mitral valve (principal investigator: Dr. Lederman).
REFERENCES
- 1.Khan JM, Babaliaros VC, Greenbaum AB, et al. Anterior leaflet laceration to prevent ventricular outflow tract obstruction during transcatheter mitral valve replacement. J Am Coll Cardiol. 2019;73:2521–2534. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Khan JM, Rogers T, Babaliaros VC, Fusari M, Greenbaum AB, Lederman RJ. Predicting left ventricular outflow tract obstruction despite anterior mitral leaflet resection: the "skirt NeoLVOT". JACC Cardiovasc Imaging. 2018;11:1356–1359. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Wang DD, Guerrero M, Eng MH, et al. Alcohol septal ablation to prevent left ventricular outflow tract obstruction during transcatheter mitral valve replacement: first-in-man study. JACC Cardiovasc Interv. 2019;12:1268–1279. [DOI] [PubMed] [Google Scholar]
- 4.Praz F, Khalique OK, Lee R, et al. Transatrial implantation of a *transcatheter heart valve for severe mitral annular calcification. J Thorac Cardiovasc Surg. 2018;156:132–142. [DOI] [PubMed] [Google Scholar]
- 5.Lisko JC, Greenbaum AB, Khan JM, Kamioka N, Gleason PT, Byku I, Condado JF, Jadue A, Paone G, Grubb KJ, Tiwana J, McCabe JM, Rogers J, Lederman RJ, Babaliaros VC. Antegrade intentional laceration of the anterior mitral leaflet to prevent LVOT obstruction (LAMPOON): a simplified technique from bench to bedside” [Under Review]. [DOI] [PMC free article] [PubMed] [Google Scholar]