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Introduction
Repair rather than replacement of the mitral valve is now demanded as best practice for degenerative mitral valve disease. Despite uptake rates of 30 - 40% in the USA and Europe, minimally invasive mitral surgery is less utilized in Australia. We hypothesise this due largely to the rather long and steep learning curve involved.
Methods
We present analysis of a prospectively collected database. A total of 184 patients undwerwent MIMV repair at our institution since between 2007 and 2010. Mean age was 63.1 years and 121 (62.5%) were male. A right-sided anterolateral mini-thoracotomy with femoral-femoral CPB was used in all cases. The most frequent indication for surgery was symptomatic, severe mitral regurgitation (mean grade 3.94 +/- 0.22). Ten patients (5.4%) presented for reoperative surgery. Mean preoperative ejection fraction was 62% (+/- 11) and LVDD 58.3mm +/-10.8. The majority were single leaflet disease (64.1%) of myxomatous pathology ( 87.0%).
Results
The dataset was analysed in terciles, quartiles and quintiles to define not only the presence of a learning curve but the point at which it was overcome. Mean cardiopulmonary bypass and clamp times showed a significant reduction from first to third terciles (140.5 & 91.1 mins to 107.8 & 69.2 mins, p0.0001). Total LOS, intensive care LOS and complication rates did not significantly differ across terciles or quartiles. Residual MR was significantly less at early follow up (mean 4.2 months) in the third quartile than either the first or second (1.8 vs 1.3 p0.01 & 1.6 vs 1.3 p002). This continued at late follow-up with the third quartile again having significantly less residual MR than the first at mean follow-up of 24.2 months (2.0 vs 1.6 p0.03). Despite the improvement in residual MR, LV end-diastolic diameters did not significantly differ, largely thought due to a trend to elevated pre-operative diameters.
Conclusion
There exists a significant learning curve for minimally invasive mitral valve repair when assessed by echocardiographic outcomes. From our results this curve is overcome after approximately 90 - 100 cases. This presents a significant challenge to many surgeons given the caseload required to achieve this.