[Cardiac memory in patients with permanent artificial pacemakers]

Area of Science:

• Cardiology
• Electrophysiology

Background:

• Cardiac memory describes the phenomenon where the heart's electrical activity retains a 'memory' of preceding activation patterns.
• Understanding cardiac memory is crucial for interpreting electrocardiograms (ECGs) in patients with cardiac implantable electronic devices.

Purpose of the Study:

• To investigate the correlation between the direction of QRS complexes during pacing and the subsequent T wave polarity in patients with artificial pacemakers.
• To identify factors influencing the presence and manifestation of cardiac memory in pacemaker recipients.

Main Methods:

• Analyzed 35 patients with pacemakers, correlating QRS complex direction of paced beats with post-pacing T wave polarity across all 12 ECG leads.
• Defined cardiac memory as identical polarity between paced QRS complexes and post-pacing T waves.
• Assessed correlations with spontaneous rhythm, QRS duration, stimulation type/modality, and implant chronicity.

Main Results:

• Cardiac memory was observed in 77% of patients in the frontal plane and 50% in the horizontal plane.
• The phenomenon was more prevalent in patients with supraventricular pacing (82%) compared to idioventricular pacing (50%).
• Normal intraventricular conduction was associated with a higher incidence of cardiac memory; no correlation found with stimulation type, modality, or chronicity.

Conclusions:

• Cardiac memory is a frequent occurrence in patients with artificial pacemakers.
• A normal ventricular activation pattern appears to be the most significant factor for the development of cardiac memory.