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The cardiothoracic ratio (CTR) is considered to be a reliable detector of cardiomegaly on computed tomography for livings, with a threshold of 0.5. Our study aimed to establish an adjusted CTR-based score to predict cardiac hypertrophy at PMCT. We selected adult's autopsy cases examined between 2009 and 2016. Two groups were considered, a normal heart weight group and an overweighed heart group. The CTR was measured on axial images. Logistic regression analysis was performed to investigate the discriminating power of the CTR between groups when adjusted to the confounding factors. Sixty-six cases with normal heart weight and 94 cases with overweighed heart were analyzed. The factors associated to the cardiac hypertrophy are CTR (p value 0.003, OR 3.57), BMI (p value 0.055, OR 1.09), age (p value < 0.001, OR 1.67), and gender (p value 0.002, OR 4.85). The area under the ROC curve (receiver operating characteristic curve) was 0.77 when using CTR alone and 0.88 when considering BMI, age, and gender. In conclusion, CTR alone cannot be used to discriminate between normal heart weight and overweighed heart at PMCT. A new formula has been developed, including age, gender, and BMI. Dilatation of the cardiac chambers, which is a subjective evaluation, influences the CTR measure and could be not related to a pre-existing cardiac hypertrophy. This new score formula allows to overpasses this subjective step. We proposed a cut-off value of the score of 32 for the diagnosis of cardiac hypertrophy. The Internet/smartphone application (http://calc.chuv.ch/CTR) facilitates its routine application.

In clinical practice, the cardiothoracic ratio (CTR) was first utilized on plain chest radiography, and subsequently with computed tomography (CT) to diagnose cardiomegaly with a threshold of 0.5. Using CTR in forensic practice could help to detect cardiomegaly on post-mortem CT (PMCT) prior to the autopsy. However, an adaption of the threshold could be necessary because of post-mortem changes. Our retrospective study aimed to measure the CTR on PMCT and test the possible influence of variables. We selected 109 autopsy cases in which the heart weight was within normal limits. A forensic pathologist and a radiologist measured separately the CTR on axial and scout views on PMCT. We tested the statistical concordance between the two readers and between the axial and scout view and identified factors that could be associated with a modification of the CTR. The CTR measurements revealed an overestimation of the measurements made on scout compared to axial view. The inter-reader correlation was very high for both views. Among the different variables statistically tested, heart dilatation and body mass index (BMI) were the only two factors statistically associated with an augmentation of the CTR. The CTR can be useful in the diagnosis of cardiomegaly on PMCT. However, dilatation of the cardiac chambers caused by acute heart failure may be misinterpreted radiographically as cardiomegaly. Inter-observer reliability in our study was very high. CTR may be overestimated when measured on the scout view. Further investigations with larger cohorts, including cases with cardiac hypertrophy, are necessary to better understand the relationship between radiological CTR and the morphology of the heart.