Bridging the gap between basic and clinical electrophysiology: what can be learned from monophasic action potential recordings?
With rapid advances occurring in both basic and clinical electrophysiology, the gap between the two disciplines appears to be widening rather than narrowing. In most instances, we cannot apply the knowledge derived from cellular studies directly to clinical practice. Monophasic action potential (MAP) recording by contact electrode technique allows us to measure basic electrophysiological phenomena in the human heart and thus provides an important bridge between basic and clinical electrophysiology. MAP recordings produce the time course of cellular repolarization during cycle length changes and antiarrhythmic drug administration, lending insights into use dependency and reverse use dependency of antiarrhythmic drug effects in the clinical electrophysiology laboratory. The ability to deliver electrical stimuli at the MAP recording site further allows one to investigate drug-induced postrepolarization refractoriness. MAP recordings provide precise local activation times, important for mapping of abnormal ventricular activation, and detect areas of abnormal repolarization due to ischemia or scarring. MAP recordings are uniquely suited to detect early and delayed afterdepolarizations in the human heart, thereby helping to unravel the arrhythmia mechanisms in the long QT syndrome. By embedding the MAP electrode in a radiofrequency electrode, arrhythmogenic foci may be both detected and ablated. In many instances, MAP recordings are more accurate than ECG tracings in defining and distinguishing ventricular fibrillation and ventricular tachycardia. This can be of clinical importance during testing of the implantable cardioverter/defibrillator. An area of growing interest is stretch-activated arrhythmias. Here, MAP recordings are of particular value because no other method is available to record mechanically induced electrophysiological changes in the vigorously beating heart. It can be expected that MAP recordings will, in the future, provide this important bridge between "cell and bedside" also in atrial tachyarrhythmias, such as in atrial fibrillation and flutter.
Franz
M R
MR
Division of Cardiology, Georgetown University Medical School, Washington, DC.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001145:Arrhythmias, Cardiac / Q000209:etiology; D017147:Defibrillators, Implantable; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D017202:Myocardial Ischemia / Q000503:physiopathology; D012032:Refractory Period, Electrophysiological / Q000187:drug effects
D000889:Anti-Arrhythmia Agents