Introduction: the cardio-thoracic ratio (CTR) and the transverse cardiac diameter (TCD) on Plain chest radiography are the two parameters commonly used to diagnose cardiomegaly and heart disease. A CTR of greater than 50% on a PA film is abnormal and normally indicates cardiac or pericardial effusion, whiles an increase of 1.5 to 2cm on two consecutive radiographs, taken at short interval, suggests possible cardiac pathology. The aim was to determine the suitability of using the same TCD and CTR to detect cardiomegaly for all age groups and genders respectively.

Methods: a retrospective study involved the review of 1047 radiological images of adults aged 20 to 80 years, who had plain posterior-anterior chest radiographs between January 2012 and November 2013 by 3 radiologists. Data recorded included the transverse cardiac, thoracic diameter and the cardiothoracic ratios. Descriptive analyses were carried out using the Microsoft excel 2010.

Results: the mean age and standard deviation for the study population was 35.1 ± 12.7. The mean and standard deviations for the transverse cardiac diameter, thoracic diameter, and the cardiothoracic ratios for male participants were 13.08cm ± 1.2, 29.7cm ± 2.7 and 46.6% ± 3.9; and 12.9 cm ± 1.3, 27.1 cm ± 2.6, and 47.8% ± 4.8 for females. An increase in TCD of 1cm resulted in a CTR of greater than 50.0% in all but the males aged 21-40 years.

Conclusion: the study found that the same TCD and CTR values are not suitable in detecting cardiomegaly for all age groups and genders.