Table 1. Specific challenges with TMVR.

Domain	TAVR	TMVR
Epidemiology	Single: degenerative sclerotic AS	Complex: non-rheumatic DMR & ischemic FMR
Existing gold-standard of treatment	SAVR; TAVR accomplishes the same thing	Mostly mitral valve repair; TMVR equivalent of surgical replacement only
Unmet need & high-risk patients	Common	Uncommon in overall MR population
Durability of bioprosthetic valve	Good in aortic position	Poor in mitral position
Impact of suboptimal results (PVL, PPM, risk of obstruction)	Low (in older patients; higher in younger patients)	High (generally younger patients; LVOT obstruction; systolic pressure gradient)
Heterogeneity of substrate for implant	Low	High
Other pathologies that need to be addressed	Uncommon	Common (Afib, TR)
Trial enrollment & progress	Fast (prohibitive risk: previously untreated population)	Slow (strict inclusion criteria; uncommon demographic; competing devices)

TMVR, transcatheter mitral valve replacement; TAVR, transcatheter aortic valve replacement; DMR, degenerative mitral valve regurgitation; FMR, functional mitral regurgitation; SAVR, surgical aortic valve replacement; PVL, paravalvular leak; PPM, permanent pacemaker; LVOT, left ventricular outflow track; TR, tricuspid regurgitation.