Discussion
TMVR is a new hope for young patients with degenerated bioprosthetic
mitral valves, as it postpones or eliminates the need for repeat
surgeries, especially among women of childbearing age. However, TMVR is
not a regular treatment option at this age and should be considered only
in selected high-risk paediatric patients. Recent retrospective
publications have shown excellent hemodynamic results for TMVR, with
modest adverse events and short hospital stays. 4Transoesophageal echocardiography guides accurate prosthesis size, depth
of insertion, and anchoring to avoid LVOT obstruction.
The
risk for LVOT obstruction increases in the presence of small baseline
LVOT dimensions, basal septal bulge, or a large angle between the
trajectory of the existing bioprosthesis and the aortic root.5 During TMVR, the pre-existing bioprosthetic valve
leaflets can cover the outer frame of the new valve, thereby creating a
potentially narrow “neo” LVOT. 6
Accurate assessment of surgical heart valve anatomy is essential to
optimize TMVR outcomes. Accurate sizing for the TMVR procedure requires
the smallest true internal dimension of the surgical bioprosthesis.7 Because the true internal dimension is not routinely
reported by manufacturers, a free ViV Mitral app was created by V.B. and
UBQO Limited (London, United Kingdom). This app provides the true
internal dimensions and recommended TMVR sizes for each bioprosthesis.8 Oversizing by 10% may be necessary for the mitral
prosthesis, however, given reports of late migration.9
Careful serial follow-up of TMVR is essential to detect and reverse
early valve thrombosis. 10 The Valve-in-Valve
International Data (VIVID) registry includes 660 patients (mean age
73±12 years) who have undergone TMVR procedures. The expected durability
of the bioprosthetic valve averages 8.5 years since last cardiac
surgery. 11 However, it is known to degenerate earlier
in younger patients. In this case, the bioprosthetic mitral valve
degenerated after 3 years in a 13-year-old female patient. Many valves
can be implanted percutaneously in young patients until they reach
adulthood, at which time durable surgical mechanical valves can be
implanted. Additional prospective, multi-centre, longitudinal research
is essential to better understand the long-term risks and benefits of
TMVR, especially in young patients.