Society of Cardiovascular Anesthesiologists

April 2002 Newsletter

Chordal Cutting: A New Therapeutic Approach for Ischemic Mitral Regurgitation.

Messas E, Guerrero JL, Handschumacher MD, Conrad C, Chow C-M, Sullivan S, Yoganathan AP, Levine RA. Circulation 2001;104:1958-1963.

Reviewer: Andrew D. Maslow, MD
Assistant Professor
Brown University
Rhode Island Hospital

Background: Mitral regurgitation (MR) is a common complication of ischemic heart disease. In the absence of primary valve pathology, ischemic MR is caused by changes in ventricular geometry, size, and the position of the papillary muscles. Ischemic heart disease and ventricular dilation cause apical or posterior-lateral displacement of the papillary muscles. This altered geometry decreases the angle between the papillary muscle and the mitral annulus and increases the distance from the papillary muscle to the mitral annular plane. These changes cause tethering of the mitral leaflets, thereby decreasing mobility and coaptation. The combination of reduced ventricular function, decrease in the coapting force, and mitral annular dilation produce MR. The authors of the current study proposed that cutting the anterior leaflet basilar chordae (tertiary chordae tendinae attached at the base of the leaflet) would correct MR by reducing leaflet tethering.

Methods: The chordal cutting technique for correction of ischemic MR was tested in an in vitro system and an animal model. In sheep, 30 minute occlusion of the first obtuse marginal coronary artery caused distention of the basal inferior left ventricular wall and MR. The two centrally acting basilar chordae of the anterior leaflet were then cut. The severity of MR was assessed using three-dimensional echocardiographic analysis of regurgitant volume, leaflet tethering, and coapting force.

Results: Coronary occlusion caused a bulging out of the involved segment of myocardium, apical tenting of the anterior mitral leaflet, and MR. The altered geometry decreased coapting force, increased mitral annular area, and caused MR. The anterior mitral leaflet became angulated at the attachment of the basilar chordae. Cutting of the basal chordae eliminated the

angulation producing a more mobile or `relaxed' leaflet without causing prolapse. As a consequence, there was improved leaflet coaptation. Mitral regurgitation was eliminated despite the persistent wall motion abnormality and increased mitral annular area.

Comments: The present study by Drs. Levine and Yoganathan adds to their previous work building upon an improved understanding of the mechanisms of functional MR caused by ischemic ventricular dysfunction. Use of a flow lab and cardiac ultrasound demonstrated that apical and posterior-lateral displacement of the papillary muscles after infarction of the basal inferior wall restricted the mobility of the mitral leaflets. Tenting or tethering of the anterior mitral valve leaflet together with an increased annular diameter caused significant MR. Bulging outward of the basal inferior left ventricular wall specifically restricted motion of the body of the anterior mitral valve leaflet causing it to angulate at the site of attachment of the basilar chordae tendinae impairing leaflet coaptation. The findings of this study were consistent with a recent report by Calafiore et al (Ann Thoracic Surg 2001;71:1146-52) who observed that the severity of mitral regurgitation after valve repair was greater when the point of leaflet coaptation was greater than 10 mm below the mitral annular plane. The increased mitral valve coaptation depth may indicate restriction or angulation of the anterior mitral valve leaflet from ventricular enlargement and may be an important predictor of successful repair. Transection of the basilar chords to the anterior mitral valve leaflet was a novel approach to correct this defect and was effective for the correction of ischemic MR in a large animal model. Chordal cutting eliminated MR by restoring the shape of the anterior mitral valve leaflet in systole and improving coaptation forces. Although this technique has yet to be tried in a clinical setting, employing this technique when echocardiography demonstrates angulation or tethering of the anterior mitral valve leaflet may improve the success of mitral valve repair for ischemic mitral regurgitation.

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