Study of cardiac structures in relation to the pericardial cavity for total artificial heart implantation.

To enhance the design of the completely implantable total artificial heart (TAH), we developed a coordinate system that expresses the geometry of the heart, including that at the interface with the TAH and that of the pericardial cavity. This coordinate system (ventricular coordinate system) was developed using 3D images of the heart which were obtained from magnetic resonance images. The origin is located on the centroid of the mitral annulus at 25 ms delay from the ECG R wave (M0), and the y axis is the axis from M0 to the apex at 25 ms delay (Apex0). The x-y plane includes M0, Apex0, and the centroid of the tricuspid annulus at 25 ms delay. Since the y axis expresses the apical orientation of the heart, data using this coordinate system are not affected by individual variation in heart orientation. Heart geometry data were obtained in 5 normal subjects. Compared with that using the coordinate system based on the thoracic wall, the expression of the data of interface geometry for the heart and the TAH is simplified when the ventricular coordinate system is used. A method of expressing the geometry of the pericardial cavity using the ventricular coordinate system is also proposed. These methods may be applicable in obtaining data in patients suffering from cardiomyopathy.