APPLICATION OF GEOMETRICAL PRINCIPLE FOR STATISTICAL ESTIMATION OF AREA REDUCTION FACTOR IN IMPLANTED MITRAL VALVE PROSTHESIS

AIMS AND OBJECTIVES: 1. To compare the mitral annulus area measured through indirect 2-dimensional Echocardiography and direct intraoperative measurement with implanted prosthesis area. 2. To determine the existence of area reduction factor (if any) after mitral valve implantation. CONTEXT (BACKGROUND): A frequent mismatch was observed between the anticipated mitral prosthesis dimensions through 2-D Echocardiography and actual best fit size of mitral valve prosthesis. The mitral valve prosthesis was observed of shorter length especially in anterior- posterior dimension on comparing the projected short axis dimensions of annulus by 2-D trans-thoracic Echocardiography. This fact encouraged researchers to investigate the existence of 'area-reduction' on geometrical and statistical parameters. METHODOLOGY: This hospital based longitudinal study was conducted in a tertiary set up for the duration of one year. Sixty-seven Rheumatic Heart Disease (RHD) patients with severe mitral valve disease were included with exclusion of simultaneous significant aortic valve disease. The 2-dimensional trans-thoracic echocardiography was performed on all these patients preoperatively and direct measurement was made intra-operatively to determine mitral valve annular dimensions. Geometrical principles in regards with area of ellipse and circle were used in order to detect the constant related with area reduction. Mean with standard deviation and t-distribution values were calculated for each variable. RESULTS: Prosthetic valve area was not found to be identical with annulus valve area. Calculated value of both coefficients (KE and KD) respectively were 1.961 and 1.644. Further the mean difference in area of annulus fibrosis ((Area echo- Area direct) by ECHO and intraoperatively was calculated as 192.8400(135.017-250.663) which was statistically significant {t=6.5961(df=134); p<0.0001}. CONCLUSION: This study proved the existence of reduction of area during mitral valve prosthesis implant mathematically; which may further affect the fluid dynamics and hemodynamic changes in