Ventricular fibrillation and implantable defibrillators

Ventricular fibrillation can be described as chaotic, random, asynchronous electrical activity of the ventricles, rendering them unable to pump blood effectively to sustain life. Ventricular fibrillation is just one specific tachyarrhythmia and a major cause of sudden cardiac death. The implantable cardioverter defibrillator, ICD, is intended to detect and treat tachyarrhythmias depending on the basic detection criteria of heart rate and the length of time that rate remains above the programmed rate. Additionally, there are enhancement criteria to make the detection process more specific to the arrhythmias detected and whether to treat, e.g. ventricular tachycardias, or not, e.g. atrial fibrillation. The ICD has also been designed to give bradycardia and post-shock bradycardia support. This is currently only in the VVI mode but some systems have independently programmable parameters for these functions in order to save energy. Developments in the ICDs of today, including complications, are discussed