A lead for monitoring or stimulating cardiac activity is provided. The lead is adapted for implantation on or about the heart within the coronary vasculature and for connection to a signal generator. The lead body has one or more electrodes associated therewith. The lead is constructed and arranged so that when it is implanted, the electrodes are housed in the coronary vasculature and urged into intimate contact a vessel wall. A method for implanting the lead into the coronary vasculature is also provided, the method comprising the steps of inserting a stylet into the lead, inserting the lead into the coronary sinus, advancing the lead from the coronary sinus toward the toward the left atrium and into a coronary vein, removing the stylet, and sensing and pacing the heart. Alternatively, the method comprises placing a guide catheter into the coronary sinus, threading a guide wire into the coronary veins, pushing the lead over the guide wire and into the coronary sinus or the coronary vein, and sensing and pacing the heart via the lead in its implanted site in the coronary sinus or the coronary vein.