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(Circulation. 1968;38:880.)
© 1968 American Heart Association, Inc.

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The Mechanism of Synchronization in Isorhythmic A-V Dissociation

Some Observations on the Morphology and Polarity of the P Wave During Retrograde Capture of the Atria

ALBERT L. WALDO M.D.¹; KARI J. VITIKAINEN M.D.¹; PAUL D. HARRIS M.D.¹; JAMES R. MALM M.D.¹; BRIAN F. HOFFMAN M.D.¹; Bruce J. Innes M.D.¹; Gerard A. Kaiser M.D.¹

¹ From the Departments of Pharmacology and Surgery, College of Physicians and Surgeons, Columbia University, and the Surgical Service, The Presbyterian Hospital, New York, New York.

We studied 11 patients with spontaneous isorhythmic atrioventricular (A-V) dissociation occurring during cardiac surgery. The period of synchronization or accrochage was shown to result from retrograde capture of the atria by an A-V junctional rhythm. The P wave in leads II, III, and aV_F was biphasic (–, +) during the period of synchronization, with the initial negative portion of the P wave or the entire P wave often buried within the QRS complex. It was concluded that isorhythmic A-V dissociation occurs only during the period when the rhythm alternates between an atrial rhythm and an A-V junctional rhythm and results when either the dominant pacemaker slows or the latent pacemaker accelerates.

Key Words: Accrochage • Retrograde P waves • A-V junctional rhythm • Arrhythmia