Permanent pacing of the left atrium for treatment of WPW tachycardia.

A patient with WPW paroxysmal tachycardia was treated with a permanent artificial pacemaker, with the electrodes attached to the left atrium. The pacemaker is turned off at all times except when the patient activates it by holding a magnet over the implanted power unit. Random atrial pacing at a rate of 108/min has always terminated the tachycardia within 1 min, and usually within 10 sec. Left atrial pacing produced WVPW type A QRS complexes, whereas regular sinus rhythm and right atrial pacing resulted in more normal QRS complexes. The distinct difference in the QRS complexes suggests preferential conduction through an abnormal pathway during left atral pacing.