Leads are used to deliver electrical energy into the heart, either in the form of pacing pulses or higher field voltages to elicit defibrillation. An array of catheters, stylets, and/or guide wires can be used to deliver leads to their desired locations within the heart. Once there, they can be passively placed into the heart anatomy (e.g., in trabeculations within the apex of the right ventricle). The tip electrode of other styles of leads can be actively engaged into the myocardium using helixes which look like cork screws. Leads are typically placed within the right heart (atrium and ventricle) to allow for treatment of bradyarrhythmia (slow heart rate).
In some patients, there is a need to simultaneously pace the left ventricle in order to better resynchonize the ventricles (right and left). These leads can be delivered to the epicardial surface of the left ventricle by passing the lead through the coronary sinus and into veins draining the left heart myocardium (transvenous lead placement). These leads are placed near the sites of latest activation to allow resynchronization with activation of the right ventricle.
Some patients may greatly benefit from an implantable defibrillation system to minimize the potential for sudden cardiac death due to elicitation of fibrillation. Often specially designed leads with coils are also placed directly within the heart to allow for these high energies to dissipate through large volumes of the myocardial tissues. These defibrillation leads may additionally have the capability to allow for cardiac pacing.