Computed Tomography Guided In Vivo Cardiac Orientation and ECG Correlation in Individuals Without Structural Heart Disease

Abstract

Background: Limited data has suggested that in vivo cardiac orientation has the greatest effect on the cardiac electric field and thus surface electrical activity. We sought to determine the correlation between in vivo cardiac orientation using cardiac computed tomography (CT) and the electrical cardiac axis in the frontal plane determined by surface electrocardiogram (ECG). Methods: Patients aged between 30 and 60 years old with a normal body mass index (BMI) who underwent CT coronary angiography between July 2010 and December 2012 were included. Patients with diabetes, hypertension, arrhythmias, structural heart disease or thoracic deformities were excluded. In vivo cardiac orientation was determined along the long axis and correlated with the electrical cardiac axis on surface ECG. Results: Fifty-nine patients were identified, with 47% male, mean age of 50 and mean BMI of 22.39. Twenty-nine (49%) had no cardiac risk factors. The mean cardiac axis on CT was 49.1 ± 8.1 and the mean electrical cardiac axis on ECG was 50.5 ± 25.9. Bivariate analysis was performed indicating that there is no correlation between the two readings (Pearson r value 0.147, p = 0.267 and Spearman ρ value 0.205, p = 0.119). Conclusion: The ECG determined electrical axis of the heart is on average similar to the true long axis of the heart, at approximately 49° in adults without structural heart disease. However the electrical axis of the heart showed more variability. Therefore variations of the frontal plane electrical axis from 49° do not seem to indicate a change in cardiac orientation but may be due to conduction disturbances.