Three-dimensional ultrasonic cardiac reconstruction: general aspects and application to finite element analysis of the left ventricle

Abstract

Two-dimensional (2-D) echocardiography is well suited to evaluate regional left ventricular dynamics because of its ability to depict wall motion and thickening in real time throughout the cardiac cycle. Recently, several investigative groups have combined the fine spatial and temporal resolution of 2-D echocardiography with a method of three-dimensional (3-D) spatial registration of individual images to produce 3-D geometric reconstructions of the intact heart. We have devised a method of finite element analysis of left ventricular myocardial elastic properties based upon 3-D echocardiographic reconstructions and simultaneous high-fidelity pressure measurements. The technique consists of predicting left ventricular cavity expansion and wall thinning during diastole, using; (1) an assumed myocardial elastic modulus, and (2) the measured change in cavitary pressure during diastole as the endocardial loading condition. The predicted cavity expansion is compared to that actually derived from echocardiographic data. An iterative algorithm is used to derive an ‘optimal’ elastic modulus for the myocardium- that elastic modulus which allows the closest prediction of chamber expansion during diastole. We have used this technique in preliminary studies in open-chest dogs to derive normal and abnormal regional and global left ventricular elastic modulus.