Related Experiment Video
Updated: Jun 20, 2025

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice
Published on: June 29, 2022
Pacing on the tail of paced QRS: What is the mechanism?
Sudipta Mondal1, Nayani Makkar1, Narayanan Namboodiri1
1Division of Cardiac Electrophysiology, Department of Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, India.
Abstract:
An electrocardiogram on the day after implantation of a dual-chamber pacemaker revealed 2 closely coupled pacing spikes at 100-ms intervals, with the latter being on the trailing edge of the paced QRS complex. Differential diagnoses of such closely coupled pacing pulses include atrial lead displacement, lead reversal on the pulse generator, ventricular premature complex in the post-atrial ventricular blanking period, and backup pacing pulse following a loss of capture. Critical analysis of the pacemaker timing intervals led to the mechanism and cause of the problem.
Related Concept Videos
Electrophysiology of Normal Cardiac Rhythm
Conduction System of the Heart
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
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...
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
The Cardiac Cycle
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and...
Disturbances in Heart Rhythm
Arrhythmias are categorized by their speed, rhythm, and origin. A slow...

