Mechanism for Differences in Post Operative Left Ventricular Ejection Fraction after Mitral Valve Replacement in Patients with Mitral Stenosis

ABSTRACT

Background: The subvalvular apparatus arrangementcan causeventricular torsion& deformation during cardiac cycle and interruption of papillary annular complex. As a result there was impairment of normal left ventricular strain pattern.[2] In patients with mitral stenosis, the left ventricle is small. Preservation of subvalvular apparatus thus become important in moderation of left ventricular volume in long term in patients with mitral stenosis undergoing mitral valve replacement.Methods: This cross sectional study was performed on the 32 consecutive subjects in department of cardiac surgery and cardiology of BSMMU with rheumatic mitral stenosis undergoing MVR from Jan 2013 to June 2014.Mode of surgery was determined by morphology of subvalvular apparatus which dictated the extent of the preservation. The patients were divided into two groups- Group I- With preservation of subvalvular apparatus &Group II- No preservation- where SVA was completely excised. In 2D and M Mode echocardiographic measurementsMid-wall circumferential end systolic LV stress as calculated for ellipsoid, LV mass, the mid wall circumferential end systolic LV stress is calculated by mirsky’s formula.9,10 Results: Patients with sub valvular apparatus resection (group I) had deterioration with postoperative ejectionfraction in compare to group-II. Left ventricular circumferential wall stress analysis showed increased wall stress in group II after MVR. Conclusion: The increased left ventricular wall stress is responsible for poor outcome in non-preserved group after MVR. The wall stress increases further in midterm follow up which may explain the mechanism of long term poor out come in patients with mitral stenosis.