Superior vena cava syndrome: a complication of transvenous pacemaker implantation.

Superior vena cava syndrome developed in 4 of 1,000 patients in whom a transvenous pacemaker had been implanted. In all cases, endocardial leads were inserted through the cephalic vein and positioned at the apex of the right ventricle. The classical signs and symptoms of superior vena cava hypertension were observed from two weeks to one year after implantation, and the diagnosis was confirmed by cavography. Symptoms resolved following heparin therapy and long-term anticoagulation.