METHODS An 80-year-old woman was admitted because of confusion episodes, difficulty of finding words and transitory clouding of consciousness on that day. There were moderately moist rales over both lung bases and mild pretibial oedema. The ECG showed atrial fibrillation with an irregular ventricular rate of 30/min. Attempted emergency implantation of a pacemaker electrode via the right subclavian vein failed because the catheter could not be advanced in the usual manner due to complete obstruction of unknown cause. METHODS Fluoroscopy and venography of the upper great veins demonstrated a persistent left superior vena cava (LSVC), connecting to an aneurysmally enlarged coronary sinus (CS), as well as atresia of the right SVC (RSVC). METHODS A temporary pacemaker was introduced transfemorally, subsequently replaced electively by a permanent one-chamber pacemaker system, the electrode wire having been introduced via the left cephalic vein--left SVC--CS, with its tip positioned in the right ventricle. CONCLUSIONS If emergency placement of a pacemaker electrode proves impossible via the usual route because of a persistent LSVC and RSVC atresia, a transfemoral route should be used for temporary pacing. Permanent placement can usually be accomplished subsequently without much problem via the LSVC and coronary sinus.