Micro Computed Tomography Imaging and Subsequent Quantifications of the Associated Changes in Cardiac Anatomies Relative to Various Methods of Specimen Fixation

Various research studies utilize formalin to preserve cardiac tissues, which are then used to investigate and quantify cardiac anatomies and/or device-tissue interactions. However, it is known that various fixation processes will alter cardiac anatomies. One needs to quantify such and determine which fixation method may minimize these changes. To do so, human hearts were scanned fresh and then again after formalin fixation in an end-diastolic state using one of three different methods, including submerging, submerging while perfusing the coronaries, and submerging while pressurizing all four chambers. High resolution computational 3D models from micro computed tomography (micro-CT) scans were generated, and measurements of the aorta, right and left ventricle (RV and LV) lateral walls and septum thicknesses were performed and compared. The ventricular wall and septum thickness tended to increase after fixation; however, the degree of change was relatively inconsistent. Yet, pressurizing all four chambers internally seems to minimize the ventricular wall thickening and reduction in blood volume. Though, additional studies are needed to determine if this method will consistently reduce anatomical changes and if the changes are constant or predictable over a large sample size. Regardless of the fixation method, an average 1.4 mm of LV and 4 mm of RV wall thickening were observed, which may contribute to potential error in anatomical measurements within fixed hearts. Therefore, one needs to consider fixation methods of study specimens and how it changes the given cardiac anatomies when performing pre-clinical studies on formalin fixed human hearts.