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Electrocardiogram Fundamentals

Electrocardiogram Fundamentals

Introduction
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...

Electrocardiogram

Electrocardiogram

An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

Arrhythmia is a condition characterized by an irregular heart rhythm, with ECG changes that differ based on its origin and nature. The types of arrhythmias discussed below include atrial, junctional, and ventricular arrhythmias.Atrial ArrhythmiasPremature Atrial Complexes (PACs): PACs are early atrial beats caused by stress, caffeine, alcohol, electrolyte imbalances, hypoxia, hyperthyroidism, or certain medications (e.g., bronchodilators and decongestants). The ECG shows early P waves with an...

Cardiac Action Potential

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
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

Correlation between ECG and Cardiac Cycle

Correlation between ECG and Cardiac Cycle

The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the 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...

Electrophysiology of Normal Cardiac Rhythm

Electrophysiology of Normal Cardiac Rhythm

The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase...

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Distinct intracardiac electrogram waveforms with perforation during left bundle branch area pacing implantation.

Heli Tolppanen^1,2, Valerian Valiton¹, Samuel Stempfel¹

¹Cardiac Pacing Unit, Department of Cardiology, University Hospital of Geneva, rue Gabrielle Perret Gentil 4, Geneva 1211, Switzerland.

Europace : European Pacing, Arrhythmias, and Cardiac Electrophysiology : Journal of the Working Groups on Cardiac Pacing, Arrhythmias, and Cardiac Cellular Electrophysiology of the European Society of Cardiology

|February 17, 2026

Summary

Left bundle branch area pacing (LBBAP) perforation causes a drop in current of injury (COI) amplitude. Analyzing unipolar electrogram (iEGM) waveforms can help identify perforation during LBBAP lead deployment, improving patient safety.

Keywords:

Complications Conduction system pacing Current of injury Electrogram Left bundle branch area pacing Perforation

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Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts

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Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts

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Published on: November 7, 2019

Area of Science:

Cardiology
Electrophysiology
Medical Devices

Background:

Left bundle branch area pacing (LBBAP) is an advanced pacing technique.
Perforation during LBBAP lead implantation can lead to complications.
Unipolar electrograms (iEGMs) provide signals during lead placement.

Purpose of the Study:

To systematically analyze unipolar iEGM waveforms during LBBAP perforation.
To compare these waveforms to those recorded at the final lead position.
To identify specific waveform characteristics indicative of perforation.

Main Methods:

Analysis of unipolar iEGMs from 92 patients with LBBAP perforation.
Comparison of current of injury (COI) amplitude and waveform morphology during perforation versus final lead position.
Subgroup analysis based on QRS morphology (narrow/non-LBBB vs. LBBB/paced rhythm) and perforation type (macro vs. micro).

Main Results:

Sensed COI amplitude was significantly lower during perforation (3.0 mV) compared to the final lead position (14.0 mV).
Patients with narrow QRS/non-LBBB showed QS waveforms (67%), while LBBB/paced rhythm patients exhibited positive R/RS morphologies (93%).
A sensed Q or S amplitude greater than COI amplitude had 86% sensitivity and 93% specificity for diagnosing perforation in the narrow QRS subgroup.

Conclusions:

Unipolar iEGM waveform analysis provides additional diagnostic information beyond COI amplitude for LBBAP perforation.
Specific waveform morphologies (e.g., QS in narrow QRS) can reliably indicate perforation.
Careful monitoring of iEGM waveforms during lead deployment enhances the safety of LBBAP.