Usefulness of Holter Recordings in the Evaluation of Pacemaker Function: Standard Techniques and Intracardiac Recordings

A dedicated pacemaker Holter system facilitates recognition of the pacemaker stimulus by amplifying and displaying it in an ECG channel without any other data. Such a Holter pacemaker channel may occasionally generate electrostatic charges that produce deflections resembling pacemaker stimuli (pseudopacemaker spikes) arising from a loose ECG electrode, crushed tape, or a dirty recording head. False‐positive spikes or spurious marker deflections in Holter pacemaker channels and occasional failure to detect tiny bipolar stimuli can present challenging problems in the interpretation of pacemaker function. In multiple‐channel recorders, skewing of the recording heads may lead to timing errors and puzzling recordings when one of the ECG or pacemaker channels lags behind others producing asynchrony or malalignment in simultaneously recorded tracings. The interpretation of Holter recordings from contemporary complex pacemakers requires knowledge of pacemaker timing cycles and their interrelationships, a large variety of programmable parameters or functions, behavior of the nonatrial sensor or sensors in rate‐adaptive systems, device‐specific responses to protect the system from a variety of undesirable situations, and an appreciation of pacemaker eccentricities. There are a few prospective studies on the value of routine Holter recordings in pacemaker patients. The real value of Holter recordings lies with symptomatic patients when symptoms occur during the recording period. Correlation between symptoms and occasional abnormality of pacemaker function during Holter monitoring remains poorly characterized. The cause of the symptoms is frequently unrelated to the pacemaker system and may not be related to coexisting arrhythmias. In asymptomatic patients, Holter recordings are particularly useful to uncover a lead problem after an unrevealing thorough investigation in the pacemaker clinic. Special instrumentation was recently developed to register telemetry data from implanted pacemakers simultaneously with ambulatory electrocardiography. In this way, diagnostic marker signals and/or intracardiac electrograms transmitted from the pacemaker can be recorded continuously for 24 hours by a Holter recorder. Advanced technology involving the memory capability of pacemakers will transform the pacemaker itself into a 24‐hour Holter recorder, probably in 4 to 5 years. At present, the memory for storage of intracardiac electrograms is limited from a few seconds to less than a minute according to the manufacturer, but even such mini‐Holter recordings can be diagnostically important.