Characteristics of intracardiac electrograms.

Cardiac electrograms were measured on endocardial leads on patients undergoing pacemaker implantation. The data show that small area electrodes reduce R wave amplitude, decrease width of the complex, and increase slopes. The bandwidth of the electrogram increases as the electrode area decreases. The loading of the sensing amplifier changes these characteristics. Distortion is most pronounced for small area electrodes and low lead resistances.