The cardiothoracic ratio in postmortem chest radiography: Reliability and threshold to predict cardiomegaly

Abstract

The cardiothoracic ratio (CTR) is a useful technique to investigate the prevalence of cardiomegaly, an important clinical manifestation of several cardiovascular diseases. The aim of this study was to determine the relationship between various macroscopic measurements of heart size on postmortem chest X-rays and CTR as well as develop a new CTR threshold or scoring system to improve reliability of CTR in forensic settings. We selected 131 forensic autopsy cases aged more than 18. The heart length and width, wall thicknesses, chamber diameters, and heart weights were measured during autopsy. The postmortem CTR was measured in an anteroposterior chest radiography. In autopsy cases among the Thai population, two groups were defined: normal and overweight heart, with cut-off values based on average heart weight + 1SD. The results showed that the wall thickness and chamber diameter were not related to CTR, but the heart length and width were. A multivariable analysis was performed and showed good discriminating power, with an area under the ROC curve of 0.88. A new formula was developed, which included age, BMI, and CTR. The recommend cut-off score was 122 for the diagnosis of cardiomegaly, in which the sensitivity and specificity were 78.3% and 72.9%. The findings of increased CTR cannot be equated to cardiac wall hypertrophy and chamber enlargement. This study suggests that a combination of CTR, BMI, and age of the deceased improves the level of discrimination between the condition of normal heart and cardiomegaly before autopsy.