AV junctional versus left atrial rhythm

Negative P waves in lead V6 during right ventricular pacing

A negative P wave in lead V6 has been proposed as the most reliable criterion of left atrial rhythm, useful in differentiating it from nodal arrhythmias. In this report the electrocardiograms of two patients with right ventricular paced rhythms with 1:1 retrograde atrial capture are shown. The retrograde P waves inscribed after the ORS were negative in polarity in lead V6 in both cases. This documents that an impulse entering the atria from the AV junction can be associated with rightwardly oriented P waves and suggests that the proposed criterion for left atrial rhythm is unreliable.

Tachycardia upon swallowing. Evidence for a left atrial automatic focus

Evaluation of a patient with tachycardia upon swallowing offers evidence of its origin from the left atrium. The tachycardia appears to arise from an automatic focus discharged after mechanical stimulation by the esophagus. Despite a left atrial origin for this arrhythmia, it does not fulfull previously described electrocardiographc criteria for "left atrial rhythms."

P waves during ectopic atrial rhythms in man: a study utilizing atrial pacing with fixed electrodes

Threshold bipolar pacing was performed from one of 12 selected atrial sites with temporary implanted electrodes in 69 patients following open-heart surgery in order to study P wave polarity and morphology and the P-R interval during paced ectopic atrial rhythms. A negative P wave was recorded in lead I only with pacing the left atrium and only when pacing near the left pulmonary veins. A positive bifid P wave in V1 was recorded only with left atrial pacing and only when pacing was near the inferior pulmonary veins and coronary sinus. P wave polarity and morphology were otherwise of no use in localization of the origin of the impulse in these studies. The pacing stimulus to P wave interval was found to vary between 10 and 54 msec, making the duration of the P-R interval an unreliable indicator of the site of origin of the paced impulse. Although the relation of these paced rhythms to spontaneously occurring ectopic rhythms is unclear, the previously published criteria for localizing ectopic atrial rhythms are again demonstrated to be unreliable. P wave polarity and morphology and the P-R interval are of limited value in ascertaining the origin of ectopic atrial rhythms in man.