NEW YORK (Reuters Health), Oct 23 - Dyssynchronized motion of the left ventricle is an independent risk factor for functional mitral valve regurgitation, Italian researchers report.
Dr. E. Agricola and colleagues at San Raffaele Hospital in Milan observed that mitral regurgitation was significantly mitigated immediately after cardiac resynchronization therapy in patients with life-threatening arrhythmias.
The researchers therefore evaluated left ventricular wall motion in 74 patients with left ventricular dysfunction and ejection fractions below 40%.
They measured the effective regurgitant orifice and evaluated indices of mitral deformation, including systolic valvular tenting and mitral annular contraction. Global left ventricular function and remodeling was assessed using ejection fraction, end systolic volume, and sphericity index. Local remodeling was assessed by papillary-fibrosa distance and regional wall motion score index.
Finally, tissue-derived Doppler-derived dyssynchrony index was measured according to time to peak systolic contraction of eight left ventricular segments supporting the papillary muscle.
Dr. Agricola's group reports in the October issue of Heart that all of the variables correlated significantly with the effective regurgitant orifice. Systolic valvular tenting was the strongest independent predictor of regurgitation. The main determinants of systolic valvular tenting were local left ventricular remodeling, papillary-fibrosa distance and global remodeling indices.
The technique "improved coordinated timing of mechanical activation of papillary muscle insertion sites and the remote decrease of functional mitral regurgitation secondary to left ventricular reverse remodeling," the authors write.
The findings suggest that cardiac resynchronization can reduce the degree of functional mitral regurgitation by coordinating "the tethering forces on the papillary muscles and...counteracting the increased tethering forces that impair mitral valve competence."
Reverse left ventricular remodeling has an additive role in correcting mitral valve closure, they conclude.
Editorialists in Holland, Drs. J. J. Bax and D. Poldermans, describe previous studies using intermittent cardiac resynchronization therapy to correct mitral valve regurgitation with good results, including a reduction in regurgitant volume by 30% to 40%.
The precise criteria for when cardiac resynchronization therapy would be appropriate in this setting has not yet been determined, the physicians note.
"If the theory is right, patients with mitral regurgitation secondary to left ventricular dyssynchrony, resulting in incomplete closure of the mitral valve, will benefit immediately from cardiac resynchronization therapy, with an acute reduction in mitral regurgitation," Dr. Bax of the Leiden University Medical Center told Reuters Health.
"We need a trial on applying cardiac resynchronization therapy in patients with severe mitral regurgitation and to do immediate and long-term follow-up."
"Data so far show the effects of remodeling will occur after few months and have thus far been demonstrated to last up to two years," Dr. Bax added.
Dr. Poldermans is based at the Thorax Center Rotterdam.
By Martha Kerr
Last Updated: 2006-10-20 11:30:21 -0400 (Reuters Health)
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