CardioverterDefibrillators

Cardioverter-defibrillators are medical devices designed to monitor heart rhythm and treat life-threatening arrhythmias by delivering electrical therapy. They are used to prevent sudden cardiac death by detecting dangerous ventricular tachyarrhythmias and terminating them, either with pacing or a high-energy shock. The term encompasses implantable devices and external or wearable forms used in different clinical contexts.

The most common type is the implantable cardioverter-defibrillator (ICD). An ICD consists of a pulse generator placed under the skin and one or more leads that connect to the heart. These devices continuously monitor heart rhythms, detect abnormal rates, and deliver therapy as needed. Therapies include anti-tachycardia pacing to interrupt certain fast heart rhythms and high-energy defibrillation shocks for ventricular fibrillation or sustained ventricular tachycardia. Subtypes include transvenous ICDs, with leads threaded through veins to the heart, and subcutaneous ICDs, which have a lead placed under the skin away from the heart. Wearable or temporary external forms, including automatic external defibrillators (AEDs) and wearable cardioverter-defibrillators, provide short-term protection when implantation is not yet possible or during a high-risk period.

Indications for ICD therapy include primary prevention in patients at high risk of sudden cardiac death due to reduced heart function or cardiomyopathy, and secondary prevention in patients who have survived a cardiac arrest or experienced sustained VT. Decisions are guided by clinical guidelines and individual risk assessment. Follow-up involves regular device interrogation, battery life monitoring, and monitoring for lead integrity or inappropriate shocks. Potential risks include infection, lead malfunction, and inappropriate therapy, which are weighed against the potential to save lives.