The heart rate control arm used heart rate as the therapeutic target, rather than dose of medications. Drug dosage was adjusted to achieve target heart rates. During atrial fibrillation, heart rate was assessed both at rest and during activity at each clinic visit. The pharmacologic therapies approved for use in this arm included: beta blockers, verapamil, diltiazem, digoxin, or combinations of these drugs . When Step I pharmacologic therapies failed after two or more drug trials, the treating physician could select an approved Step II innovative therapy. The two innovative therapies approved for use with the heart rate control arm were: (1) atrioventricular node modification by catheter ablation, with or without placement of a pacemaker, with or without continued drugs to slow atrioventricular node conduction, and (2) total atrioventricular junctional ablation and placement of a pacemaker.