Right Ventricular Function After Mitral Valve Surgery: Insights From the United Kingdom Mini Mitral Study

Right ventricular (RV) function is frequently reduced after cardiac surgery, with persistent impairment associated with increased mortality. This study aimed to compare RV function after mitral valve repair through right minithoracotomy vs sternotomy.

In the UK Mini Mitral trial, patients were randomized to mitral valve repair through right minithoracotomy (small lateral pericardial incision) or sternotomy. Prespecified secondary outcomes included assessment of cardiac function by blinded echocardiography preoperatively and at early (12 weeks) and late (52 weeks) time points. RV function was assessed by tricuspid annular plane systolic excursion (TAPSE). RV to pulmonary artery coupling was determined by the TAPSE to systolic pulmonary artery pressure ratio.

Of 330 patients randomized, 224 had suitable echocardiographic data for analysis. Baseline demographic, clinical, and echocardiographic data were comparable between groups. Cross-clamp and bypass times were significantly longer in the minithoracotomy group. At 12 weeks, there was a significant reduction in TAPSE from baseline in both groups (TAPSE minithoracotomy, -7.52 mm [95% CI, -8.52 to -6.53; P < .001], vs sternotomy, -8.75 mm [95% CI, -9.80 to -7.71; P < .001]), which recovered, but not to preoperative levels, by 52 weeks. The degree of RV impairment was significantly less in the minithoracotomy group at both early (between-group difference in TAPSE at 12 weeks, 1.47 mm [95% CI, 0.37-2.56; P = .009]) and late time points (between-group difference in TAPSE at 52 weeks, 1.37 mm [95% CI, 0.29-2.45; P = .013]).

Despite longer cross-clamp and bypass times, mitral valve repair through minithoracotomy was superior to sternotomy at preserving RV function (measured by TAPSE) at 12 weeks and 1 year.