Signals and Signal Processing for the Electrophysiologist
Part I: Electrogram Acquisition
Successful mapping and ablation in the electrophysiology (EP) laboratory is critically dependent on acquiring multiple, low-amplitude, intracardiac signals in the presence of numerous sources of electric noise and interference and displaying these signals in an uncomplicated and clinically relevant fashion, with minimal artifact. This represents a significant engineering challenge and, in a real-life EP laboratory, is not always successful. Understanding the challenges and reasons for failure and knowing how to optimize the electronic data acquisition system in the EP laboratory can go a long way toward ensuring smooth procedures and good outcomes.
In this 2-part review, we will present information on the layout of a typical EP laboratory, with emphasis on common approaches to amplification and filtering of ECG and intracardiac signals, sources of noise and interference with techniques to minimize them, and also discuss in detail the subtleties of unipolar/bipolar signals and their clinical relevance.
In all of the electrogram illustrations, the following abbreviations are used:
P1 ART indicates arterial pressure tracing; II and V1, surface ECG leads; RVA and RVAd, proximal and distal right ventricular apex signals; HRA and HRAd, high right atrial catheter proximal and distal signals; His4 to His1, His bundle signals from an octapolar catheter, with His1 being most distal; Lasso 1,2 to Lasso 10,1, circular catheter signals; ABL and ABLd, proximal and distal ablation catheter signals; and CS 19,20 to CS 1,2, coronary sinus catheter signals, with CS 1,2 being most distal.
The small voltages and currents that constitute biopotentials must be manipulated and presented in an easily understandable manner to the electrophysiologist. This involves amplification and filtering of the signals. Signals of interest may be manipulated in the form of voltage or current. A limited but effective analogy is to consider voltage as being the equivalent of water pressure. If a …