The Art of SAPIEN 3 Transcatheter Mitral Valve Replacement in Valve-in-Ring and Valve-in-Mitral-Annular-Calcification Procedures

Mitral annulus calcification (MAC) is a chronic, degenerative process in the fibrous base of the mitral valve. Although MAC was initially thought to be an age-related degenerative process, there is accumulating evidence that other mechanisms, such as atherosclerosis and abnormal calcium-phosphorus metabolism, also contribute to the development of MAC. Despite its frequency, the clinical relevance of MAC is grossly underappreciated. Indeed, MAC is associated with an increased incidence of cardiovascular disease, mitral valve disease, arrhythmias, and mortality. MAC also influences the outcomes of cardiac surgery and interventions, and its clinical relevance may well increase substantially in the forthcoming era of transcatheter mitral valve replacement. In this paper, we review the available published data to provide a consistent, clinically relevant description of MAC on the basis of contemporary imaging. We describe the pathophysiological mechanisms contributing to the formation of MAC and the clinical implications of this disease entity.

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)

This study sought to use a new catheter technique to split the anterior mitral valve leaflet (AML) and prevent iatrogenic left ventricular outflow tract (LVOT) obstruction immediately before transcatheter mitral valve replacement (TMVR).