Postmortem CT findings of cardiac and great-vessel blood clots in fatal hypothermia: comparison with autopsy measurements.

OBJECTIVE: This study aimed to investigate the relationship between the clot weight-to-blood volume ratio in postmortem cardiovascular blood measured at autopsy and clot findings on postmortem computed tomography (PMCT) in fatal hypothermia. MATERIALS & METHODS: This retrospective study included 57 forensic autopsy cases of fatal hypothermia. At autopsy, pooled right- and left-sided blood samples from multiple cardiac chambers and great vessels were collected separately. Blood volumes were measured, recovered clots were weighed, and the clot weight-to-blood volume ratio was calculated and compared with corresponding PMCT findings. RESULTS: The median clot weight-to-blood volume ratio was significantly higher in left-sided than in right-sided cardiovascular blood (15.0% and 9.23%, respectively, Wilcoxon signed-rank test, P = 0.0008). The clot weight-to-blood volume ratio was significantly lower in cases with a PMI ≤2 d than in those with a PMI ≥2.5 d, and cases with a PMI ≤2 d frequently showed fluid blood without apparent clot formation. In the present study, all cases with a clot weight-to-blood volume ratio ≥ 20% showed corresponding clot findings on PMCT, whereas PMCT findings were variable in cases with lower clot weight-to-blood volume ratios. CONCLUSION: In fatal hypothermia, PMCT frequently demonstrates blood clots in the left atrium and thoracic aorta, suggesting that evaluation of the left heart in addition to the right heart may provide useful information. In cases where the PMI is ≤2 d, caution is warranted because, even in cases of hypothermia, clots may not have formed, and the blood may exhibit high fluidity.