Intracardiac Electrocardiography in the Analysis and Understanding of Cardiac Arrhythmias

Cardiac arrhythmias have recently been studied with techniques not previously available in clinical investigation. Catheterization techniques allow depolarization of discrete areas of the cardiac conduction system to be recorded when their electrical signals are of insufficient magnitude to generate potential differences at the body surface. Intracardiac stimulation sequences permit spontaneous arrhythmias to be replicated, initiated, and terminated, thereby not only suggesting their probable electrophysiological mechanisms but also new modes of therapy. The techniques of intracardiac electrocardiography are reviewed, and their application to the recognition and understanding of common cardiac arrhythmias—sinus dysrhythmias, premature depolarizations, atrial tachycardias, atrial flutter and fibrillation, ventricular tachycardia, A-V conduction, and A-V block—is discussed.