Abstract 15122: Systolic Anterior Motion of Mitral Valve in Hypertrophic Cardiomyopathy Revisited - A Tale of Two Airfoils?
Introduction: The widely accepted mechanism of systolic anterior motion (SAM) in HCM is a dragging force acting on mitral valve. We sought to expand this by treating anterior and posterior mitral leaflets (AML and PML respectively) as two airfoils. Aerodynamic principles dictate net force acting on an airfoil is the result of integration of all forces that act on its entire surface. The force is also proportionate to area that is exposed to flow. Hence, forces acting on ventricular surfaces of AML and PML during systole would be directing in opposite directions (Figure A). We presume areas measured at early systole just as mitral leaflets co-apt correlate with area of AML and PML that are exposed to ejecting blood (Figure B).
Hypothesis: We hypothesize that SAM occurs when the mitral leaflets experience a net anteriorly directed force. As such, we sought to demonstrate HCM patients with SAM would have a higher ratio of area-below-coaptation/ total area.
Methods: Consecutive 288 patients who have echo diagnosis of HCM from our laboratory from Nov 2007 to Jan 2011 were included. Off-line cine images were analyzed and geometric parameters were obtained.
Results: There were 75 patients with SAM (24%). In multivariable regression analysis, area-below-coaptation/total area, AML length, LV internal diameter in systole and total area are independent predictors of SAM. An ROC curve shows the ratio has the highest area under the curve (0.80). A value of 0.48 would have a specificity of 90% in predicting SAM.
Conclusion: Ratio of area-below-coaptation/total area is the best variable in predicting SAM in HCM patients. A model of two airfoils appears to be plausible to explain this intriguing phenomenon.
- © 2011 by American Heart Association, Inc.