Common source of miscalculation and misclassification of P-wave negativity and P-wave terminal force in lead V1.

Background: P-wave terminal force (PTF) > 4000 ms·μV and deep terminal negativity (DTN) are ECG markers of left atrial abnormality associated with both atrial fibrillation and stroke. When the precordial lead V1 is placed higher than the correct position in the fourth intercostal space, it may cause increased PTF and DTN. Several studies have documented that electrode misplacement, especially high placement, is common. The influence of electrode misplacement on these novel ECG markers has not previously been quantified.

Objective: The objective was to assess the influence of electrode misplacement on PTF and DTN.

Method: 12-Lead ECGs were recorded in 29 healthy volunteers from the Department of Cardiology at the Copenhagen University Hospital of Bispebjerg. The precordial electrode V1 was placed in the fourth, third and second intercostal space, giving a total of 3 ECGs per subject. Continuous variables were compared using Dunnett's post-hoc test and categorical variables were compared using Fischer's exact test.

Results: High placement of V1 electrodes resulted in a more than three-fold increase of PTF (IC4 = 2267 ms·μV, IC2 = 7996 ms·μV, p-value < 0.001). There was a similar increase of DTN (IC4 = 0%, IC2 = 28%, p-value < 0.001). P-wave area and amplitude of the negative deflection increased, and P-wave area and amplitude of the positive deflection decreased. The P-wave shape changed from being predominantly positive or biphasic in IC4 to 90% negative in IC2. The PR-duration and P-wave duration were not altered by electrode placement.

Conclusion: High electrode placement results in significant alteration of PTF and DTN in lead V1.