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August 14, 1967

Ventricular Fusion Beats

JAMA. 1967;201(7):566. doi:10.1001/jama.1967.03130070086038

To the Editor:—  In the presence of complete atrioventricular (AV) block, the ventricles may be stimulated by two idioventricular pacemakers. When these pacemakers compete with each other, the ventricles may be under the simultaneous control of both pacemakers. Such ventricular beat is called a ventricular fusion beat.1 The QRS complex of the fusion beat shows a contour intermediate between the two principal QRS contours of the idioventricular origin. The appearance of the ventricular fusion beats will depend on the amount of ventricular muscle controlled by each pacemaker.The example described in this report was observed in a 51-year-old man who was admitted to the hospital because of complete AV block resistant to drug therapy. On admission the electrocardiogram revealed complete AV block with idioventricular rhythm. The atrial rate was 92 beats per minute; the ventricular rate was 30 per minute. The contour of the QRS complexes was uniformly that