Shape analysis of the left ventricular surface using three-dimensional echocardiography: validation and application to LV remodeling following myocardial infarction

Abstract

Analysis of LV shape can aid in characterizing LV remodeling following myocardial infarction. The authors developed and validated a method of detecting abnormalities in left ventricular (LV) shape using three-dimensional (3D) echocardiography. LV endocardial surfaces were reconstructed by piecewise smooth subdivision method from traced echocardiographic scans in end diastole. Artificially distorted surfaces were created to test the method which aligns two LV surface reconstructions along regions of similar shape. Five different functions with decreasing degree of penalty for large variation in shape were tested. Difference in shape was computed as distance between the LV surface being compared. Function performance in detecting a shape difference was assessed by comparison of distances from alignment by different functions. The mean variability of normal LV shape was defined from the LVs of 14 normal subjects. Variation in size was normalized by the right ventricular apex to aortic valve distance. Reconstructions of 9 patients studied <10 days after myocardial infarction (MI) were compared to normal LV. Four patients were analyzed both 24 hrs and 10 days after MI to assess LV remodeling. The function that most accurately measured synthetic distortions was applied in clinical tests. Normal LV shape variability was 2.9 mm. In all 9 MI patients LV dilatation was in the infarct region. Remodeling between 24 hrs, and 10 days ranged from 5.1 to 7.4 mm (maximal remodeling in the infarct region). In conclusion, normalization of size permits detection of differences in shape independent from differences in size. The method of alignment of the LV meshes in 3D space resulted in detection of both location and magnitude of LV remodeling after myocardial infarction independent of anatomical landmarks.