Surgical and transcatheter therapy for secondary mitral regurgitation.
Michael J. Mack M.D.
Badhwar, V., M. Alkhouli, M. J. Mack, V. H. Thourani and G. Ailawadi (2019). “Surgical and transcatheter therapy for secondary mitral regurgitation.” J Thorac Cardiovasc Surg May 21. [Epub ahead of print].
The importance of myocardial revascularization for viable myocardium is the cornerstone for the management of ischemia whenever appropriate targets exist. For patients with ischemic cardiomyopathy undergoing surgery for secondary MR, incomplete revascularization is a marker of mortality, but evidence that it influences residual MR in all patients remains lacking. For example, patients with chronic severe secondary MR often have papillary muscle fibrosis and the subsequently tethered MV apparatus is unlikely to improve regardless of the revascularization strategy. This is similar to the point that Nappi and colleagues make when discussing their approach to patients with nonviable myocardium. Although their experience with subvalvular papillary muscle repositioning or polytetrafluoroethylene tube reapproximation is compelling, widespread reproducibility of this technique remains limited. The nomenclature and assessment of MR is clear. Prolapse is defined in a patient with primary MR when leaflet motion extends above the annular plane in systole. There is no such entity in secondary MR, as the authors may suggest. In the case of a tethered posterior leaflet following myocardial infarction remodeling, a posteriorly directed jet of MR may be commonly misinterpreted as anterior leaflet prolapse and primary MR when it is in fact best defined as anterior leaflet override and secondary MR. Appropriate identification of pathology directs appropriate management. Nappi and colleagues are to be congratulated for their steadfast outcome reporting of adjunctive subvalvular papillary muscle repair and their institutional results are admirable, yet their recent identification of failures of this technique indicate that it may not actually be for everyone. They report failures of MV annuloplasty and subvalvular repair with MV tenting area ≥3.1 cm2 and left ventricle end-diastolic diameter ≥64 mm. In fact, their findings that patients with significant left ventricle remodeling and MV tenting have a higher incidence of recurrent MR aligns precisely with the recently proposed grading system. The cumulative evidence and surgical outcomes with MV repair and replacement in secondary MR do not amount to forfeiture of this complex disease state to transcatheter therapy. To the contrary, the proposed grading system suggests that MV repair still has a role in at least Grade I secondary MR in patients the heart team believes may benefit from surgical therapy. Perhaps MV annuloplasty and subvalvular repair may have a role in Grade II secondary MR, provided the patient does not have the predictors identified by Nappi and colleagues. (Excerpts from text, article in press, p. e1; refers to Nappi F., Santana O., and Mihos C.G.: Geometric distortion of the mitral valve apparatus in ischemic mitral regurgitation: should we really forfeit the opportunity for a complete repair? J Thorac Cardiovasc Surg 2019.)
