Related Experiment Video

Updated: Apr 25, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
12:45

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

Published on: December 11, 2017

10.2K

Left septal fascicular block-like ECG pattern in acute coronary syndrome: Clinical presentation and prognostic

Yuko Matsui1, Satoshi Higuchi2, Kao Takehisa3

  • 1Department of Cardiology, Tokyo Women's Medical University, Tokyo, Japan; Department of Cardiology, Yokohama Medical Center, Kanagawa, Japan.

Heart Rhythm
|April 24, 2026
PubMed

Insights

A transient left septal fascicular block-like pattern on ECG is rare in acute coronary syndrome but indicates proximal left anterior descending artery blockages. Recognizing this dynamic ECG finding aids in identifying septal ischemia.

Area of Science:

  • Cardiology
  • Electrophysiology
  • Acute Coronary Syndromes

Background:

  • The left bundle branch is increasingly recognized to have a third component, the left septal fascicle.
  • The clinical significance of left septal fascicular block (LSFB)-like electrocardiogram (ECG) patterns in acute coronary syndrome (ACS) is not well-established.

Purpose of the Study:

  • To investigate the clinical presentation of a transient LSFB-like ECG pattern in ACS patients undergoing emergency percutaneous coronary intervention (PCI).

Main Methods:

  • Retrospective analysis of 789 ACS patients treated with emergent PCI.
  • Identification of a transient LSFB-like ECG pattern (marked increase in anterior QRS forces with attenuation post-revascularization).
  • Exclusion of other causes for prominent anterior QRS forces; analysis of clinical, angiographic, and outcome data.

Main Results:

  • A transient LSFB-like ECG pattern was observed in 1.0% of patients (8/789) and resolved after reperfusion.
  • All culprit lesions were in the proximal left anterior descending artery (LAD) at or proximal to the first septal branch.
  • Ventricular fibrillation occurred in 37.5% of patients before PCI; no recurrence of the pattern was seen on follow-up.

Conclusions:

  • The transient LSFB-like ECG pattern is uncommon in ACS but linked to proximal LAD lesions.
  • This dynamic ECG pattern may assist in identifying septal ischemia and proximal LAD occlusions.
  • Further research is needed to refine LSFB definitions and understand its clinical implications.
Abstract

Keywords:
Acute coronary syndromeLeft septal fascicleLeft septal fascicular blockVentricular fibrillationVentricular tachycardia

More Related Videos

A Research Method For Detecting Transient Myocardial Ischemia In Patients With Suspected Acute Coronary Syndrome Using Continuous ST-segment Analysis18:11

A Research Method For Detecting Transient Myocardial Ischemia In Patients With Suspected Acute Coronary Syndrome Using Continuous ST-segment Analysis

Published on: December 28, 2012

23.8K
Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System10:17

Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System

Published on: April 11, 2025

2.3K

Related Concept Videos

Acute Coronary Syndrome II: Pathophysiology and Clinical Manifestations01:19

Acute Coronary Syndrome II: Pathophysiology and Clinical Manifestations

The pathophysiology of Acute Coronary Syndrome [ACD] involves several key processes:The main underlying cause of ACD is atherosclerosis, a chronic inflammatory disease characterized by the buildup of lipid-laden plaques within the coronary arteries.As the atherosclerotic plaque grows in the coronary artery, it may become unstable due to the formation of a lipid-rich core and a thin fibrous cap. Inflammatory cells within the plaque, such as macrophages, secrete enzymes that degrade the...
878
Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

Bradyarrhythmias are cardiac rhythm disorders characterized by a slower-than-normal heart rate, typically defined as fewer than 60 beats per minute. Some of which are discussed here:Sinus BradycardiaSinus bradycardia presents a heart rate lower than 60 beats per minute, with a regular rhythm originating from the SA node. The ECG typically shows normal P waves preceding each QRS complex, a normal PR interval (0.12 to 0.20 seconds), and a normal QRS duration (0.06 to 0.10 seconds).First-Degree AV...
778
Acute Coronary Syndrome I: Introduction01:30

Acute Coronary Syndrome I: Introduction

Acute Coronary Syndrome (ACS) encompasses a spectrum of heart conditions caused by sudden obstruction of coronary arteries, typically resulting from the rupture of an atherosclerotic plaque and subsequent thrombus (blood clot) formation. This obstruction can lead to partial or complete blockage of blood flow, causing varying degrees of myocardial ischemia or infarction.ACS includes the following clinical entities:Unstable Angina (UA)Non-ST-Elevation Myocardial Infarction (NSTEMI)ST-Elevation...
2.0K
Acute Coronary Syndrome III: Diagnostic Studies01:30

Acute Coronary Syndrome III: Diagnostic Studies

Diagnosing acute coronary syndrome or ACS begins with a thorough patient history. Notable symptoms include central, crushing chest pain radiating to the left arm, neck, jaw, or back, along with shortness of breath, sweating (diaphoresis), nausea, vomiting, dizziness, and palpitations.It is crucial to note any history of cardiac illnesses and assess risk factors, including age, gender, smoking, hypertension, diabetes, hyperlipidemia, and a sedentary lifestyle.During physical examination, vital...
493
Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

Arrhythmia or dysrhythmia refers to an abnormal heart rhythm caused by a defect in the heart's conduction system. It can cause the heart to beat irregularly, too quickly, or too slowly, leading to symptoms like chest pain, shortness of breath, and fainting. Factors such as stress, caffeine, alcohol, nicotine, cocaine, certain drugs, congenital defects, diseases, and electrolyte abnormalities can trigger arrhythmias.
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
5.2K
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

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...
1.1K