In this article, we study the problem of rhythm classification and event detection based on intracardiac electrogram (EGM) signals. At present, only a very limited scope of signal processing is possible in implantable cardioverter defibrillators (ICDs), due to the scarcity of available resources. As a result, relatively simple beat-by-beat time-domain analysis of the EGM signal(s) is employed for rhythm detection. Recently, researchers have attempted to exploit more sophisticated signal processing methods, such as wavelet transforms and template matching (Astrom, Olmos, & Sornmo, 2006; Brown, Christensen, & Gillberg, 2002; Koyrakh, Gillberg, & Wood, 1999). However, the new methods have rarely been employed in practical systems because of their computational and power demands.
Key Terms in this Chapter
Supraventricular Tachycardia (SVT): AFIB and other rapid heartbeats that arise in the atria, or in the juncture between the atria and the lower chambers (ventricles).
Atrial Flutter (AFLUT): A heart rhythm disorder in which the upper chambers of the heart (the atria) contract faster than the lower chambers (the ventricles) in an organized, predictable pattern.
Atrial Fibrillation (AFIB): A common heart rhythm disorder caused by a problem in the conduction of electrical impulses in the upper chambers, or atria, of the heart, causing it to beat chaotically.
Electrogram (EGM): Sensed electrical activity of the heart by an electrode implanted in the heart.
Tachycardia: A rapid heart rate, usually defined as greater than 100 beats per minute.
Ventricular Fibrillation (VFIB): In VFIB, the heartbeat is rapid and chaotic, which causes the lower heart chambers, or ventricles, to go into a spasm.
Defibrillation: The use of a carefully controlled electric shock, administered either through a device on the exterior of the chest wall or directly to the exposed heart muscle.
Cardioversion: The conversion of one cardiac rhythm or electrical pattern to another, almost always from an abnormal to a normal one. This conversion can be pharmacologic or electrical.
Atrial Tachycardia (AT) and Ventricular Tachycardia (VT): Refer to tachycardia originating from the ventricular and atrial chambers, respectively.
Implantable Cardiac Defibrillator (ICD): A device that is put within the body, and is designed to recognize certain types of abnormal heart rhythms (arrhythmias), and correct them through cardioversion and defibrillation.