Preservation of left ventricular function after degenerative mitral valve repair: Refocusing on timing, techniques, and teaching

Abstract

Changes in left ventricular (LV) size and function are expected after correction of severe chronic degenerative mitral regurgitation. Although it was previously thought that a postoperative decrease in ejection fraction (EF) was relatedtoinadequatemyocardialprotection,itisnowrecognized that elimination of regurgitant volume after mitral valve repair is often associated with an increase in LV end-systolic volume, producing a decline in EF while maintaining normal or increased LV stroke volume. 1-4 The report by Imasaka and colleagues 5 investigated differences in myocardial performance after repair in relation to whether chordal replacement versus leaflet resection was used to correct posterior mitral leaflet prolapse in 72 consecutive patients. In addition to EF, end-systolic elastance, effective arterial elastance, and ‘‘ventricular efficiency’’ were assessed by echocardiography before and approximately 1 month after mitral valve repair. The authors suggest that chordal replacement resulted in significantly less reduction in LV EF and greater increases in end-systolic elastance than leaflet resection. They further posit that postoperativeventricular efficiency in the chordal replacement group was ‘‘superior’’ to that after leaflet resection, with multivariate analysis suggesting that LV EF and ratio of stroke work to pressure-volume area were better in patients undergoing neochordal repair. Thisinterestingworkraises important questions.First,do the reported differences make sense physiologically? Second, are the echocardiographic parameters assessed robust enough to support the intended conclusion? Third, where does this work take us? The notion that the resection of leaflet tissue itself alters ventricular performance to a greater degree than neochordal insertion is difficult to understand unless it relates to the authors’ preference for large quadrangular resection plus sliding leaflet plasty. In fact, it is unclear why a limited removal of a triangular segment of unsupported posterior leaflet tissue could have any impact on myocardial performance at all. The need for large resections in the report does lead us to suspect that baseline lesions within this small population (n ¼ 72) may not have been similar, with more extensive removal of tissue required for thosewith diffuse myxomatous disease and neochordal implantation preferred for those with fibroelastic deficiency. The distinction is important, because these 2 pathologic extremes of the degenerative mitral disease spectrum also may be associated with differing ventricular-valvar complex physiology 6 and may affect