Temporary epicardial wires are routinely implanted in patients during cardiac surgery. Historically, four wires are placed with the distal ends of these wires being held in place on the epicardium by a suture or staple. The proximal ends are brought outside the chest wall through subcutaneous tissue. Two atrial wires are placed on the right atrium with the proximal ends of those wires being brought out through the chest wall to the right of the subcostal area. Two ventricular wires are implanted on the anterior surface of the right ventricle with the proximal ends exiting the chest wall to the left of the subcostal area. The location of the atrial wires on the right side of the chest and ventricle wires on the left side is universal. Additionally, skin (or ground wires) may be placed. These wires are the longest of the wires and usually exit on the side of the atrial wires (i.e., the right side). If a skin wire has not been placed, then one of the other wires acts as a ground wire (positive pole).