Related Experiment Video
Updated: Jun 22, 2026

Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System
Published on: April 11, 2025
Vectorcardiographic determinants of cardiac memory during normal ventricular activation and continuous ventricular
Alexei Shvilkin1, Bosko Bojovic, Branislav Vajdic
1Department of Medicine/Division of Cardiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA. ashvilki@bidmc.harvard.edu
Background:
Cardiac memory (CM) refers to persistent T-wave changes on resumption of normal conduction after a period of abnormal ventricular activation. Traditionally, to observe CM, normal ventricular activation had to be restored, limiting the exploration of this phenomenon in clinical practice.
Objective:
This study sought to prove that CM can be detected during continuous aberrant activation and to establish factors affecting its magnitude using a vectorcardiographic technique.
Methods:
Sixteen nonpacemaker-dependent patients (11 male, age 72 +/- 8 years, mean +/- SD) undergoing pacemaker/internal cardioverter-defibrillator implantation were paced in DDD mode with a short atrioventricular (AV) delay for 7 days to induce CM. Electrocardiograms were acquired during AAI and DDD pacing at a constant rate before and after CM induction. Dower transform-derived vectorcardiograms were reconstructed and analyzed.
Results:
T vector during AAI pacing changed in both magnitude (baseline, 0.26 +/- 0.10 mV; Day 7, 0.39 +/- 0.13 mV, P < .01) and direction aligning with the paced QRS vector (baseline DDD QRS - AAI T angle 125 degrees +/- 36 degrees; Day 7, 39 degrees +/- 21 degrees, P < .01). During DDD pacing, there was no change in T-vector direction, but T amplitude decreased (baseline, 1.06 +/- 0.32 mV; Day 7, 0.71 +/- 0.26 mV, P < .01). CM measured as T-vector peak displacement (TPD) was identical in AAI and DDD mode (TPD 0.46 +/- .0.17 mV and 0.46 +/- 0.17 mV, respectively). Individual CM magnitude correlated with QRS/T-vector amplitude ratio during DDD pacing at baseline (r = 0.90).
Conclusion:
CM can be reliably shown during continuous ventricular pacing, expanding its application to situations in which abnormal ventricular activation persists. Its magnitude is determined by the QRS/T-amplitude ratio of the ventricular paced beat.
More Related Videos
06:57Ablation of Ischemic Ventricular Tachycardia Using a Multipolar Catheter and 3-dimensional Mapping System for High-density Electro-anatomical Reconstruction
Published on: January 31, 2019
09:52Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts
Published on: November 7, 2019
Related Concept Videos
Electrophysiology of Normal Cardiac Rhythm
Cardiac Action Potential
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
Electrocardiogram
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and the T...
Correlation between ECG and Cardiac Cycle
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
Electrocardiogram Fundamentals
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin to...
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias