Endocardial electrograms from pacemaker catheters.

Proper placement of pacemaker catheters can be facilitated by recording endocardial electrograms from the catheters. These electrograms are also helpful in the investigation of pacemaker failure. Endocardial contact is indicated by S-T segment elevation. When bipolar catheters are used, these "contact currents" may be visible in electrograms from the tip or ring electrodes, or both. Right ventricular cavity electrograms are characterized by their high voltage and are influenced by intraventricular conduction defects and acute myocardial infarction. Serial changes have been described indicating myocardial injury, infarction, and healing in the area underlying the catheter tip.