Glossary

Implantable Cardioverter-Defibrillator (ICD) is a small battery powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation.  The device is programmed to detect cardiac arrhythmia and correct it by delivering a jolt of electricity.  In current variants, the ability to revert ventricular fibrillation has been extended to include both atrial and ventricular arrhythmias as well as the ability to perform biventricular pacing in patients with congestive heart failure or bradycardia.

The process of implantation of an ICD is similar to implantation of a pacemaker.  Similar to pacemakers, these devices typically include electrode wires which pass through a vein to the right chambers of the heart, usually being lodged in the apex of the right ventricle.

ICD’s constantly monitor the rate and rhythm of the heart and can deliver therapies, by way of an electrical shock, when the electrical manifestations of the heart activity exceeds the preset number.

Inappropriate Sinus Tachycardia (IST) is an uncommon type of cardiac arrhythmia within the category of supraventicular tachycardia (SVT).  The mechanism of the arrhythmia primarily involves the sinus node and per-nodal tissue and does not require the AV node for maintenance.  Treatments in the form of pharmacological therapy or catheter ablation are available, although it is currently difficult to treat successfully.

An interpolated premature ventricular contraction is one where the overall pace and rhythm of the heart is not altered by the ectopic beat. (Usually a PVC is followed by a compensatory pause, which the heart uses to re-establish a normal rhythm.) There does not appear to be any diagnostic or prognostic difference between PVCs with and without compensatory pauses.