12 lead ECG

• P wave (normal sinus activation) triggering right ventricular pacing
• apical right ventricular pacing with wide QRS complexes

EGM recorded simultaneously: the first line corresponds to lead II on which the event markers are added, the second line corresponds to the ventricular bipolar EGM, the third line corresponds to the atrial bipolar EGM lead with intervals (inter-atrial, inter-ventricular and atrio-ventricular) and the fourth line corresponds to a far-field EGM

• atrial sensing
• ventricular pacing
• sensed AV delay 150 ms

Comments

• all modern pacemakers incorporate the ability to transmit information regarding real-time pacing system behavior to the programmer
• real-time intracardiac electrograms and marker channels facilitate the physician’s ability to diagnose appropriate or inappropriate function
• an electrogram is a graphic display of the potential difference between two points in space over time; both filtered and unfiltered EGMs may be available
• markers are valuable in showing that an output has been released or that sensing has occurred
• a native atrial depolarization is usually identified as AS (abbreviation for an atrial sensed event); an atrial stimulus is usually identified as AP (abbreviation for atrial paced event)
• a native ventricular depolarization is usually identified as VS (abbreviation for a ventricular sensed event); a ventricular stimulus is usually identified as VP (abbreviation for ventricular paced event)
• paced or sensed events may be identified by a vertical line, going up for atrial events and down for ventricular events (Abbott devices)
• some systems also display the duration of the atrial and ventricular refractory periods (Abbott devices)
• interval measurements between the various events are calculated automatically; intervals can also be manually measured (cursors aligned with specific events)
• when superimposed above or below a simultaneously recorded surface ECG, markers allow the clinician to correlate the behavior of the pacemaker directly with the patient’s rhythm, to determine whether the system is functioning properly
• markers are valuable in showing that the pacemaker delivers a stimulus or senses a signal but do not mean that the stimulus effectively resulted in appropriate capture, and do not confirm that a sensed event is a true atrial or ventricular depolarization and that all native events are properly and consistently sensed
• confirmation of capture requires recording of a concomitant ECG; false signals suggesting oversensing are reported by telemetry of event markers and electrograms but are invisible on the ECG