Patient-Prosthesis Mismatch Associated With Somatic Growth After Mechanical Mitral Valve Replacement in Small Children: Metrics for Reoperation and Outcomes.

Reoperation after pediatric mitral valve replacement (MVR) is inevitable due to patient-prosthesis mismatch (PPM) associated with somatic growth. We analyzed potential metrics for PPM and outcomes of redo MVR for valve upsizing. Between 1999 and 2018, 15 children without obstructive left heart lesions other than mitral stenosis underwent initial MVR with a 16-mm ATS-Advanced Performance valve. We analyzed hemodynamic data from 28 postoperative catheterizations and concomitant echocardiograms. The median age and body weight at initial MVR were 4.9 months (25th, 75th percentile: 3.6, 6.6) and 5.9 kg (5.0, 7.3). Redo MVR was planned when patients had congestive heart failure and postcapillary pulmonary hypertension (PH) due to PPM: systolic pulmonary arterial pressure (SPAP) >35 mm Hg and pulmonary capillary wedge pressure (PCWP) >15 mm Hg on catheterization. Indexed effective orifice area (iEOA) and mean transmitral pressure gradient (TMPG) were strongly correlated with SPAP (r = -0.72, P < 0.001 and r = 0.75, P < 0.001) and PCWP (r = -082, P < 0.001 and r = 0.84, P < 0.001). Cut-off values for detecting postcapillary PH due to PPM were 1.0 cm/m for iEOA and 18 mm Hg for mean TMPG. Nine patients underwent redo MVR for postcapillary PH due to PPM at a median postoperative interval of 10 years (9.2, 11.9). All the patients survived, and PH was improved one year after surgery. iEOA and mean TMPG can be metrics for PPM in children after MVR. Careful follow-up is required to confirm the improvement of preoperatively existing PH after redo MVR for valve upsizing.