Postmortem Micro-Computed Tomography (micro-CT) Scanning of a Fetal Heart: A New Protocol for Determining Cause and Manner of Fetal Death

After attending this presentation, attendees will better understand the importance of a micro-CT study of fetal heart specimens, which provides highly accurate 3D renderings of complex congenital fetal heart disease. This presentation will impact the forensic science community by offering an alternative to postmortem dissection that permits a diagnosis in small hearts when a conventional invasive autopsy would have severe limitations. Abnormalities of the heart and great arteries are the most common Congenital Defects (CHDs). They account for approximately 20% of all stillbirths and 30% of neonatal deaths due to congenital defects. Furthermore, cardiac defects are seen at autopsy in approximately 10% of sudden deaths in infants and could be the cause of death in up to 84% of these cases. Fetal and pediatric cardiac autopsies play a crucial role in the counseling of parents in regard to both the cause of death of their fetus or child and the implications of such findings for future pregnancies. They also serve as a tool for assessing quality assurance of antenatal screening programs and antemortem diagnostic procedures. In the past ten years, there has been a shift in the diagnosis of CHDs from the second to the first trimester of pregnancy; however, the feasibility and value of postmortem confirmation that can result in the modification or refinement of the prenatal diagnosis is only apparent in about 30% of cases, and findings are severely limited in small fetuses. When a determination is attempted in such small specimens, erroneous findings are more likely to result, and these can prejudice the diagnosis. Missed cardiac defects and discordance from prenatal diagnosis may also raise the potential for litigation. Several groups have proposed alternatives to postmortem dissection, including Magnetic Resonance Imaging (MRI). The resolution offered by scanners used for conventional MRI in the clinical setting is too low for the successful examination of fetuses in the first half of the pregnancy. More promising results have been obtained with high-field micro-MRI scanners designed for imaging small animals; however, like all MRIbased approaches, their use in a clinical setting is limited by cost, time, and space constraints. For these reasons, the method based on micro-CT was explored. Micro-CT is X-ray imaging in 3D by the same method used in hospital CT scans, but on a smaller scale with massively increased resolution. The prefix micro-CT is used to indicate that the pixel sizes of the cross-sections are in the micrometer range Methods: Iodine contrast micro-CT scannings were used to examine 22 hearts. Images were obtained from routinely fixed whole human fetuses (n = 7, weights 0.1g-90g, gestational ages: 7-17 weeks), isolated fetal hearts (n = 14, weights 0.1g-20 g, gestational ages: 11-27 weeks) and one isolated heart in a neonate. Samples were scanned using an isotropic resolution of 18μm. Findings were interpreted jointly by four fetal pathologists, a fetal cardiologist, and a radiologist. Samples with gestational ages ≥13 weeks also underwent conventional autopsy or dissection. Postmortem assessments were compared to prenatal findings. Results: Micro-CT identified all anatomical structures and abnormalities documented by the echographic prenatal examination. In all seven cases involving first trimester pregnancies, micro-CT excluded the presence of structural anomalies. In 14 of the 22 cases, it provided all the information obtained with invasive autopsy or dissection, and in seven of these 22, it furnished additional diagnostic details. In one neonatal case, which was the object of litigation for a missed diagnosis of a complex cardiac anomaly, the micro-CT 3D rendering proved useful as a basis for discussion among courtroom experts about the features of heart disease and associated clinical implications. Conclusions: Micro-CT study is useful for refining or modifying prenatal diagnosis later in fetal gestation on in neonates. Micro-CT 3D renderings of heart disease have been found to be very useful when a second opinion about controversial specimens is required. Reference(s): 1. Lombardi C.M., Zambelli V., Botta G., Moltrasio F., Cattoretti G., Lucchini V., Fesslova V., Cuttin MS. Postmortem microcomputed tomography (micro-CT) of small fetuses and hearts. Ultrasound Obstet Gynecol. 2014 Nov;44(5):600-9. 2. Hutchinson J.C., Arthurs O.J., Ashworth M.T., Ramsey A.T., Mifsud W., Lombardi C.M., Sebire N.J. Clinical utility of postmortem microcomputed tomography of the fetal heart: diagnostic imaging vs macroscopic dissection. Ultrasound Obstet Gynecol. 2016 Jan;47(1):58-64. 3. Rutty G.N., Brough A., Biggs M.J., Robinson C., Lawes S.D., Hainsworth S.V. The role of micro-computed tomography in forensic investigations. Forensic Sci Int. 2013 Feb 10;225(1-3):60-6.