In addition to defibrillation, electrical therapy may be delivered via the following devices:
Implantable cardioverter-defibrillator (ICD) is a sophisticated device that automatically discharges an electric current to provide bradycardia and antitachycardia pacing, synchronized cardioversion, and defibrillation (convert abnormal cardiac rhythms to normal sinus rhythm) when it senses ventricular bradycardia and tachyarrhythmias. Patients with a history of ventricular fibrillation or ventricular tachycardia, with poor ejection fraction (;35%), or with nonischemic dilated cardiomyopathy (New York Heart Association [NYHA] functional class II or III), as well as patients with other conditions may be candidates for this type of device (Morton & Fontaine, 2018).
Synchronized cardioversion is the treatment of choice for arrhythmias that do not respond to vagal maneuvers or to drug therapy, such as atrial tachycardia, atrial flutter, atrial fibrillation, and symptomatic ventricular tachycardia. Cardioversion is performed similarly to defibrillation but is synchronized with the heart rhythm and uses fewer joules. Cardioversion works by delivering an electrical charge to the myocardium at the peak of the R wave. This causes immediate depolarization, interrupting reentry circuits, and allowing the sinoatrial node to resume control. Synchronizing the electrical charge with the R wave ensures that the current will not be delivered on the vulnerable T wave and thus disrupting repolarization. It is usually performed in a critical care area, in the presence of a physician, an anesthesiologist, and emergency equipment. The patient is sedated as the procedure is painful (Burns & Delgado, 2019).
Pacemakers are electronic devices that can be used to initiate the heartbeat when the heart's intrinsic electrical system cannot effectively generate a rate adequate to support cardiac output. Pacemakers are used to treat some arrhythmias and may be used for patients with heart failure to improve cardiac output (NHLBI, 2021). Pacemakers can be temporary: placed on the skin (transcutaneous) (refer to Skill 15-6); via temporary epicardial pacing wires inserted during surgery; or transvenous via a pacing electrode wire passed through a vein (the brachial, internal, or external jugular, subclavian, or femoral) and into the right atrium or right ventricle. Pacemakers can also be permanent surgically implanted devices.
Biventricular pacemakers (cardiac resynchronization therapy pacing device) use electrical current to improve synchronization of left ventricular contraction. Biventricular pacemakers are used in patients with heart failure (NYHA class III or IV), with an intraventricular conduction delay (QRS >120 ms), and in patients with left ventricular ejection fraction ;35%. These devices improve right and left ventricle contraction, resulting in improved cardiac function, with improved ejection fraction (Cleveland Clinic, 2019).