Electrocardiogram Lead Placement Accuracy and Its Implications on Universal Screening in Athletes

Abnormalities on the electrocardiogram (ECG) of athletes are common and are thought to reflect remodeling of the heart as an adaptation to physical training. Significant inter-individual variability exists in ECGs due to geometric factors-heart position, orientation, body habitus, height, and weight. Standard bony landmarks used for lead placement reflect chest wall anatomy, but not necessarily the true cardiac silhouette.  Methods: Forty male National Collegiate Athletic Association (NCAA) Division I athletes of varying body morphologies were enrolled in a prospective study. Eight different measurements were taken to define individual chest dimensions. An ECG was performed using standard lead placement based on bony landmarks. Cardiac ultrasound identified the left parasternal long view and the apical four-chamber view to represent a cardiac-based V2 and V4, respectively. The rest of the precordial leads were placed relative to these cardiac landmarks, and a second ECG was performed.  Results: The average distance between bony and cardiac-based leads was 29.8 mm (V2) and 58 mm (V4). For most subjects, cardiac V2 moved superiorly. With the exception of five subjects, cardiac V4 moved medially and superiorly. Wilcoxon's signed-rank test was performed for the P, QRS, and T wave axes as well as the amplitude of the R, S, and T waves, ST segment, and R:S ratio for the precordial leads. Cohen's d was used to determine the effect size. There was a consistent and significant difference between bony and cardiac ECGs in the R, S, T, and ST segment amplitudes in leads V2, V3, and V4. Despite the significant movement of precordial leads and amplitude changes, the ECGs based on the cardiac silhouette did not reveal any new abnormalities or changes in the abnormalities already present on the conventional ECGs.

There is a statistically significant difference in ECG lead measurements from the cardiac silhouette when compared with the standard bony landmarks. However, the overall interpretation of ECGs did not suggest any clinically significant alterations when leads are shifted to correlate with cardiac anatomy. Therefore, the study does not support the clinical use of cardiac silhouette over standard bony landmarks for ECG lead placement for athletic screenings or otherwise.