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.