An interesting electrocardiogram caused by lead reversal.

Background: During normal sinus rhythm, atrial depolarization is conducted from right atrium to left atrium through Bachmann's bundle, and a normal P wave axis which is measured on the frontal plane is between 0º and + 75º. The change of P wave polarity is helpful for the analysis of origin point. Case presentation: We report a patient with negative P wave in lead I. The characteristics of QRS complex in leads V₁ to V₆ are helpful to preliminarily differential diagnosis. The 12-lead electrocardiogram (ECG) with correct limb leads (right arm-left arm) placement shows sinus rhythm with complete right bundle branch block (RBBB). Conclusions: The change of P wave polarity as well as characteristics of QRS complex can help identify limb-lead reversals. [ABSTRACT FROM AUTHOR]