ABSTRACT
During cardiac tachyarrhythmias such as fibrillation and polymorphic tachycardia, the normally well-ordered cardiac activation sequence is replaced by an abnormal activation pattern in which wavefronts follow complex, nonrepeating pathways. To understand the mechanisms of these arrhythmias, many investigators have used cardiac mapping techniques. In mapping experiments, spatial and temporal information on cardiac arrhythmias is obtained by simultaneously recording local electrical activity from many sites. In electrical mapping, extracellular potentials are recorded. These signals may be unipolar (relative to a distant reference electrode), or bipolar (both poles closely adjacent). Large electrical mapping systems currently have on the order of 500 channels. In optical mapping, myocardium is stained with a dye that fluoresces in proportion to the transmembrane potential when excited by a strong light source. The optical signals can be recorded using a variety of technologies, including laser scanning systems, photodiode arrays, and fast video cameras. Optical mapping systems can record from hundreds to thousands of sites. Temporal sampling rates for cardiac mapping typically range from a few hundred to a few thousand samples per second.
