Capture and fusion beats during atrial fibrillation and ventricular tachycardia.

Two patients were presented, and two previously unreported observations were made. Patient 1, a 50 year old man with episodic palpitations and dizziness for 10 years, exhibited initiation of idiopathic ventricular tachycardia (VT) by atrial fibrillation (AF). Patient 2, a 43 year old woman with a structurally normal heart but recurrent palpitations for one year, demonstrated fusion and capture beats during simultaneous VT and AF. An explanation is given as to why the latter phenomenon is rarely observed.