Isolated chordal shortening: a novel mechanism of functional mitral regurgitation

Introduction
Mitral regurgitation (MR) that occurs in the absence of primary leaflet disease is known as functional MR. MR that occurs in the absence of primary leaflet disease is known as functional MR. Functional MR generally results from left ventricular (LV) enlargement, altered geometry of the papillary muscles, and/or dilatation of the mitral valve annulus. At our institution, we noted a group of patients with surgical MR, who did not have either primary leaflet disease or obvious alteration in LV geometry. We present a cohort of patients with MR secondary to isolated chordal shortening.

Material and methods
The study population consisted of subjects with normal mitral leaflet appearance, left ventricular size and function, and mitral annular dimension by echocardiography. Valve morphology and appearance were confirmed by inspection during surgery and by pathological examination when available. Mitral valve tethering parameters were compared to sample subjects with normal valves, and to sample subjects with severe ischaemic functional MR. Both control groups were matched to the study cohort both by age, sex, and body surface area.

Results
Ten subjects met the inclusion criteria. On surgical inspection, chordal shortening or restriction was reported in six and chordal thickening or fibrosis was mentioned in two subjects. Compared to normal controls, the study group had shorter chordae, increased mitral tenting height, and smaller mitral annular diameter. Compared to the control group with severe ischaemic MR, the study group had shorter chordae, smaller leaflet tenting height, smaller tenting area, and smaller mitral annular diameter.

Conclusions
We report 10 subjects who underwent mitral valve surgery for severe MR attributable to pathologically short chordae. To the best of our knowledge, this is the first description of this mechanism of disease. Further work is needed to define the underlying factors that cause isolated mitral chordal disease.