Figure 2. Quantitative analysis of electrogram morphology .

A, poles of a catheter (bipolar – close, unipolar – distant) record from distinct mapping fields. B, electrograms reflect single wavefront of an organized rhythm (e.g. atrial flutter). C, fibrillation, characterized by an uncertain number of wavefronts of uncertain rate, relative timing (phase) and spatial size in undefined recording fields. Summation of these waves may produce variable electrograms from the same spatiotemporal mechanism, or similar electrograms from variable mechanisms. Accordingly, ‘qS’, ‘rR’, or other electrogram rules in fibrillation are not specific for any particular mechanism. The same argument may apply to unipolar electrograms, which summate across wider regions of tissue.