Purpose: To examine the accuracy of the cardiothoracic ratio (CTR) at routine computed tomography (CT) of the chest to diagnose cardiomegaly by using echocardiography (ECHO) as a criterion standard, and secondarily, to search for CT cardiac measurements correlating with left ventricular hypertrophy (LVH) at ECHO.
Materials and methods: We searched 2 databases: cancer patients who had chest CT who also underwent routine ECHO by one experienced cardiologist, from January to March 2008. Consecutive patients were enrolled who had chest radiography (CXR) within 1 month and ECHO within 6 months of CT. Cardiothoracic ratio was defined as the transverse greatest cardiac diameter from outer to outer myocardium on axial images divided by the transverse greatest thoracic diameter from inner to inner chest wall on axial images, as measured by 2 board-certified radiologists. Left ventricular short diameter on CT was measured from inner to inner myocardium. Left ventricular hypertrophy at ECHO was defined using the standard American Society of Echocardiography criteria. Other data captured included cardiac and chemotherapy history, and secondary signs of heart failure. The Pearson correlation coefficient (r) and Wilcoxon rank sum tests and receiver operating characteristic (ROC) curves were used for statistical analysis.
Results: 101 patients, 52 men and 49 women, with a mean age of 58 years met the entry criteria. Cardiothoracic ratio at CXR and CT were highly correlated (r = 0.802) (P < 0.001). There was moderate ability of CT CTR to identify LVH (area under the receiver operating characteristic curve AUC = 0.70; 95% CI, 0.51-0.90). The CT left ventricular short diameter showed moderate correlation with the ECHO left ventricular internal diameter (r = 0.49) and left ventricular mass (r = 0.37).
Conclusion: In patients with cancer undergoing routine ECHO, the cardiothoracic ratio at routine CT scans was highly correlated with that at CXR. Preliminary estimates in this small study indicate a low likelihood of LVH when the CTR is less than 0.49.