Cardiothoracic ratio in postmortem computed tomography: reliability and threshold for the diagnosis of cardiomegaly

Abstract

The aim of this study was to evaluate the reliability of the cardiothoracic ratio (CTR) in postmortem computed tomography (PMCT) and to assess a CTR threshold for the diagnosis of cardiomegaly based on the weight of the heart at autopsy. PMCT data of 170 deceased human adults were retrospectively evaluated by two blinded radiologists. The CTR was measured on axial computed tomography images and the actual cardiac weight was weighed at autopsy. Inter-rater reliability, sensitivity, and specificity were calculated. Receiver operating characteristic curves were calculated to assess enlarged heart weight by CTR. The autopsy definition of cardiomegaly was based on normal values of the Zeek method (within a range of both, one or two SD) and the Smith method (within the given range). Intra-class correlation coefficients demonstrated excellent agreements (0.983) regarding CTR measurements. In 105/170 (62 %) cases the CTR in PMCT was >0.5, indicating enlarged heart weight, according to clinical references. The mean heart weight measured in autopsy was 405 ± 105 g. As a result, 114/170 (67 %) cases were interpreted as having enlarged heart weights according to the normal values of Zeek within one SD, while 97/170 (57 %) were within two SD. 100/170 (59 %) were assessed as enlarged according to Smith's normal values. The sensitivity/specificity of the 0.5 cut-off of the CTR for the diagnosis of enlarged heart weight was 78/71 % (Zeek one SD), 74/55 % (Zeek two SD), and 76/59 % (Smith), respectively. The discriminative power between normal heart weight and cardiomegaly was 79, 73, and 74 % for the Zeek (1SD/2SD) and Smith methods respectively. Changing the CTR threshold to 0.57 resulted in a minimum specificity of 95 % for all three definitions of cardiomegaly. With a CTR threshold of 0.57, cardiomegaly can be identified with a very high specificity. This may be useful if PMCT is used by forensic pathologists as a screening tool for medico-legal autopsies.

Distended diameter of the inferior vena cava is suggestive of pulmonary thromboembolism on unenhanced post-mortem CT

“…The authors agree that testing intra-rater or inter-rater reliability of IVC diameter measurements would have improved the methodological foundation of the study. However, a number of studies revealed excellent high intra-rater and inter-rater agreement regarding metric measurements on radiologic images [7,23,24]. Second, the level at which the diameter of the IVC was measured was selected subjectively.…”

Postmortem imaging as a complementary tool for the investigation of cardiac death

“…It was also shown that among the different variables tested, body mass index (BMI) and heart dilatation influence the postmortem CTR [20]. The role of dilatation was not evaluated by Winklhofer et al [40] while cardiac dilatation and terminal central congestion was reported by Michiue et al [41] in cases of drowning, alcohol/sedative-hypnotic intoxication, and some SCDs. Jotterand [42] presented at the International Society of Forensic Radiology and Imaging meeting in 2017 a "new formula for CTR for the diagnostic of cardiomegaly on postmortem CT".…”

“…In postmortem practice, the CTR value was first evaluated on PMCT by Winklhofer et al [40], who suggested a threshold of 0.57 as a cut-off of CTR to detect cardiomegaly with a specificity of 95%. Jotterand et al [20] evaluated the CTR on PMCT for normal hearts considering the normal reference values for the heart weight and observed an overestimation of the CTR measurements made on scout compared to axial view.…”

The role of angiography in the congruence of cardiovascular measurements between autopsy and postmortem imaging

“…However, to our knowledge, there are not any studies on the CV measurements on MPMCTA which includes comparisons with autopsy finding, although CV measurements on native postmortem CT scan already exist in some studies [17][18][19][20][21][22][23][24].…”