Three-dimensional imaging of mitral and tricuspid annuli for total artificial heart implantation.

The establishment of a method to clarify the three-dimensional interrelations among the mitral annulus, tricuspid annulus, ascending aorta, and main pulmonary artery, which constitute the interface between the human and total artificial heart (TAH), is essential to the design of the TAH. In a previous study based on transverse magnetic resonance (MR) images of a live human heart, reconstructed images of mitral and tricuspid annuli were found to be deformed. The present study of cadaver and beating hearts revealed that the optimal conditions for atrioventricular annular reconstruction of a beating heart with electrocardiogram-gated MR imaging include use of four-chamber imaging, 5 mm slice thickness, and a slice interval ranging from 5 to 7 mm. Under these conditions, the mitral and tricuspid annuli of 3 beating hearts were reconstructed successfully. It was recognized that during the systolic phase the mitral and tricuspid annuli move anteriorly, leftward and downward, and that in late systole the right lateral margin of the tricuspid annulus is close to the sternum.

Reconstructed image of the human heart based on magnetic resonance images for total artificial heart implantation.

Parameters used to develop a three-dimensional reconstructed image of the remaining heart after total artificial heart implantation (i.e., for the mitral and tricuspid annuli, ascending aorta (AO), and pulmonary artery [PA]) were calculated based on reconstructed images from data obtained from four magnetic resonance (MR) image views: 1) transverse, 2) coronal, 3) left ventricular long axis (LAX), and 4) four chamber view (FCV). The values obtained were compared with those obtained from silicone models of the same hearts. It was found that, of the four MR image views, LAX and FCV provided the greatest numbers of points reflecting annular contour that were useful in reconstruction of the atrioventricular (AV) annuli, and the highest percentages of segmented outline-connecting points less than 1 cm apart for the total outline. The AV annuli were sliced in the least slice time using FCV imaging. The authors applied FCV MR imaging to a beating heart to reconstruct the AV annuli and obtained accurate results. To quantify more accurately the data for the axis directions of AO and PA, research to establish a new orientation on the thorax is in progress.