Prosthesis-patient mismatch due to small ring annuloplasty in patients with degenerative mitral insufficiency.

BACKGROUND: Avoidance of prosthesis-patient mismatch (PPM) is important when selecting a mitral valve prosthesis. This study investigated the effect of PPM after small ring mitral valve annuloplasty on postoperative hemodynamics and the clinical course.

METHODS: This study retrospectively reviewed 227 patients with symptomatic severe mitral insufficiency (MI) who underwent mitral valve repair for degenerative MI using an Edwards ring or band (size: 26-32mm) between 2003 and 2012. Echocardiography was performed postoperatively and at follow-up to evaluate cardiac function, including residual MI, mean transmitral pressure gradient, left atrial diameter (LAD), and tricuspid regurgitant pressure gradient (TRPG).

RESULTS: There were no operative deaths. Actuarial freedom from major adverse cardiac events was 91% at 10 years. The postoperative MI grade was not significantly different between different sizes of prosthesis (26mm, 0.67±0.8; 28mm, 0.73±0.9; 30mm, 0.85±0.9; 32mm, 0.3±0.6). LAD and TRPG were significantly lower for each size of prosthesis at follow-up (all p<0.05). Patients with a smaller body surface area received a significantly smaller prosthesis (p<0.05). The transmitral pressure gradient was significantly higher in patients with a 26-mm prosthesis than in patients with a larger size of prosthesis. Thirty-three patients had a follow-up transmitral pressure gradient ≥5mmHg. The follow-up LAD was larger in patients with a transmitral pressure gradient <5mmHg than in patients with that ≥5mmHg (43.2±9.4mm vs 47.1±9.6mm, p<0.05).

CONCLUSIONS: Mitral valve repair results in excellent clinical outcomes with significant reductions in MI, LAD, and TRPG for all sizes of prosthesis. However, use of a smaller prosthesis may result in a higher mean transmitral pressure gradient, and may inhibit reverse remodeling of the left atrium. Therefore, PPM should be avoided.