Establishing the Cardiothoracic Ratio Using Chest Radiographs in an Indigenous Ghanaian Population: A Simple Tool For Cardiomegaly Screening

Abstract

Background: Cardiothoracic ratio is a simple and cheap tool in the estimation of heart size. It is a useful index of cardiac size evaluation, and a value of 50% is generally considered to indicate the upper limit of normal. Study Objective: This study is to ascertain the normal mean value in cardiothoracic ratio of Ghanaians using chest radiography to serve as baseline for screening for cardiomegaly. Methodology: Standard postero-anterior radiographs of the -clients/patients were used in the study. The cardiothoracic ratio (CTR) was obtained by dividing the transverse cardiac diameter [sum of the horizontal distances from the right and left lateral-most margins of the heart to the midline (spinous processes of the vertebral bodies)] by the maximum internal thoracic diameter. Systematic sampling with appropriate inclusion and exclusion criteria were used to obtain a sample size of 1989. Results: The mean transverse cardiac diameter and cardiothoracic ratio increased with age. The transverse thoracic diameter increased with age until the sixth decade when it reduced with age. The mean CTR increased gradually with age with females having greater values than males. The mean CTR of the study population were 0.459, 0.467 and 0.452 for the general population, females and males respectively. Conclusion: This study has been able to establish 0.459 as the mean CTR values for Ghanaians. It has also shown the relationship between age and clients /patient’s cardiothoracic ratio which compares favourably with findings of a similar study in Nigeria, a neighbouring country in the West African sub region with similar ethnic and social structure.