A pacemaker is a small, battery–powered device made up of two parts, a pulse generator and the leads. This 3D medical animation provides an anatomical overview of the heart and demonstrates the steps involved in placing a pacemaker. The pulse generator of the pacemaker gives off impulses that cause the atria and/or ventricles to contract. It is positioned under the skin, below the collarbone on either side of the chest. The leads carry signals between the pulse generator and the heart in both directions. The surgeon will make a small incision beneath your collarbone. The pacemaker’s leads will be inserted into the subclavian vein and then threaded toward the right side of your heart. Your surgeon will view x–ray images on a video screen to position the leads correctly.