Correlation of P-wave polarity with underlying electrophysiologic mechanisms of long RP' tachycardia.

Analysis of surface electrocardiograms from patients with long RP' tachycardia due to either atypical atrioventricular node reentrant tachycardia, permanent junctional reciprocating tachycardia, or low atrial tachycardia was performed. Although a negative P wave in the inferior leads is common to all 3 mechanisms, the results suggest that a positive or isoelectric P wave in electrocardiographic lead I strongly supports a diagnosis of atypical atrioventricular node reentrant tachycardia, whereas a negative or biphasic P wave in lead I argues against this mechanism.