Comparison of p-wave patterns derived from correct and incorrect placement of V1-V2 electrodes

Precordial electrode misplacement is an important source of error in electrocardiogram (ECG) interpretation. Previous studies have shown important changes affecting P wave morphology when V1 and V2 electrodes are placed in higher intercostal spaces. We aimed to identify ECG signs that could alert professionals performing or interpreting the ECG about the incorrect placement of V1 and V2 electrodes.

This cross-sectional study included 101 apparently healthy individuals. Five P wave patterns were compared, placing electrodes V1 and V2 on the fourth (correct position), third, and second intercostal spaces (incorrect position).

Incorrect V1-V2 electrode placement produced statistically significant differences in 3 of 5 ECG patterns. The presence of a negative component of the P wave in V2 (P < .001), negative P wave in V1 (P < .001), and rSr' preceded by negative P wave (P < .001) was strongly indicative of high placement. Patterns where the amplitude ratio between the positive and negative components of the P wave in V1 was less than or equal to 1 were observed in 27 of 101 cases with correct placement. However, on comparing correct and incorrect electrode placement, significant differences were found (P < .001)

Patterns that indicate high placement of V1 and V2 were (1) negative component of the P wave in V2 lead recorded in either second and third intercostal spaces, (2) negative P wave in V1 lead recorded in either second and third intercostal spaces, and (3) rSr' preceded by negative P wave recorded only when V1 is placed on the second but not on the third intercostal space.