Intermittent superior caval venous syndrome due to permanent transvenous electrode.

A 75-year-old man began suffering from intermittent episodes of superior caval venous syndrome, seven years after implantation of an endocardial pacemaker via the right cephalic vein. The obstruction of the superior caval vein was confirmed by venography and computed tomography of the chest. Changes of the intrathoracic pressure were considered to be the mechanism responsible for the intermittence of the syndrome.