A method for regulating the heart rate of a patient comprises inserting into a blood vessel of the patient a catheter having an electrode assembly at its distal end. The electrode assembly comprises a generally circular main region that is generally transverse to the axis of the catheter and on which is mounted at least one electrode. The catheter is directed to an intravascular location wherein the at least one electrode on the electrode assembly is adjacent a selected cardiac sympathetic or parasympathetic nerve. The at least one electrode is stabilized at the intravascular location. A stimulus is delivered through the at least one electrode, the stimulus being selected to stimulate the adjacent sympathetic or parasympathetic nerve to thereby cause a regulation of the patient's heart rate.