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Volume 14, Number 2 • April 2001		  
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BUMC Proceedings 2001;14:187-188

Bigeminal rhythm
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D. LUKE GLANCY, MD, AND DARRIN M. BREAUX, MD

From the Section of Cardiology, Department of Medicine, Louisiana State University Health Sciences Center and University Hospital, New Orleans, Louisiana.

Corresponding author: D. Luke Glancy, MD, Section of Cardiology, Department of Medicine, Louisiana State University Health Sciences Center, 1542 Tulane Avenue, Room 441, New Orleans, Louisiana 70112.

  

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47-year-old woman with scleroderma, pulmonary hypertension, and a history of mitral valvular replacement for mitral regurgitation had an asymptomatic bout of tachycardia while in the hospital because of infection of a Hickman catheter. She was not taking digitalis. Her electrocardiogram (Figure) shows a rapid ventricular rate and bigeminal rhythm. The V1 rhythm strip reveals an atrial rate of 177 beats per minute. A P wave, seen in the middle of each of the longer R-R intervals, is conducted with a P-R interval of 0.20 seconds. The next P wave occurs just after the QRS and is conducted with a P-R interval of 0.33 seconds. A third P wave can be seen at the beginning of each QRS ending the shorter R-R intervals and is not conducted. The series of events then repeats itself. Thus, the rhythm is atrial tachycardia with 3:2 atrioventricular block of the Wenckebach type. The RS in leads I and V6 and the rsR' in V1 indicate incomplete right bundle branch block.

Bigeminal rhythms have many causes (Table) (1). High among them is 3:2 atrioventricular block that usually is of the Wenckebach type. Any form of group beating suggests the possibility of atrioventricular Wenckebach, and finding P waves and progressive lengthening of the P-R interval before the nonconducted P confirms that diagnosis. Atrial tachycardia with block may result from digitalis excess, in which case the P-wave axis usually is more vertical than in the electrocardiogram shown here (2), but it also may occur whenever there is atrial disease and physiologic and/or pathologic failure of atrioventricular conduction.

Table. Some causes of bigeminal rhythm
 
  • Alternate beats are premature: atrial, ventricular, junctional
  • Nonconducted atrial premature beats after every second QRS
  • Sinus rhythm with 3:2 atrioventricular block: Wenckebach, Mobitz II
  • Other supraventricular rhythms with 3:2 atrioventricular block
  • Atrial flutter with alternating 2:1 and 4:1 block
  • 3:2 exit block: sinoatrial; escape rhythms--atrial, junctional, ventricular; accelerated rhythms--atrial, junctional, ventricular
  • Escape-capture bigeminy with escape focus: atrial, junctional, ventricular, electronic pacemaker
  • Atrial tachyarrhythmias with 3:2 atrioventricular response of an electronic pacemaker
  1. Bayes de Luna A. Clinical Electrocardiography: A Textbook. Mount Kisco, NY: Futura Publishing Co, 1993:341-342.
  2. Wellens HJJ, Conover MB. The ECG in Emergency Decision Making. Philadelphia: WB Saunders Co, 1992:143-144.