Abstract: A catheter assembly for establishing independent electrical connection between a signal generating means and the surfaces of the atrium and ventricle of a heart is disclosed to include an atrial catheter conductor and a ventricular catheter conductor. The conductors are jointly mounted for concurrent introduction into the vicinity of the heart. The atrial catheter is slidably received within an insulating means the terminal end of which is displaced from the distal tip of the ventricular catheter conductor so that the ventricular catheter conductor first may be positioned in electrical contact with the ventricular surface whereafter the atrial catheter conductor may be slidably extended from the insulating means to a position in electrical contact with the surface of the atrium.