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Related Concept Videos

Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

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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...
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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.
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ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

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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...
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Class IV antiarrhythmic drugs, such as verapamil and diltiazem, block calcium channels. They primarily affect the heart, slowing the conduction in calcium-dependent tissues like the SA and AV nodes. These drugs manage reentrant supraventricular tachycardia (SVT) and reduce ventricular rate in atrial flutter/fibrillation.
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The heart beats rhythmically in a sequence called the cardiac cycle—a rapid coordination of contraction (systole) and relaxation (diastole).
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Conduction System of the Heart

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The cardiac conduction system produces and transmits electrical impulses that prompt myocardial contraction, ensuring efficient heart function. This intricate system ensures that the heart beats in a coordinated and efficient manner, beginning with the atria and then the ventricles. The conduction system optimizes cardiac output by maintaining this precise sequence, which is crucial for adequate blood circulation.
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Related Experiment Video

Updated: Mar 31, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
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Intra-His bundle block in 2:1 atrioventricular block.

Seung Pyo Hong1, Yon Woong Park1, Young Soo Lee1

  • 1Seung Pyo Hong, Yon Woong Park, Young Soo Lee, Division of Cardiology, Department of Internal Medicine, Daegu Catholic University Medical Center, Daegu 705-718, South Korea.

World Journal of Cardiology
|October 31, 2015
PubMed
Summary

Intra-hisian atrioventricular (AV) block, though rare, can lead to advanced heart block. Precise catheter positioning during electrophysiological studies is crucial for accurate diagnosis and treatment.

Keywords:
Atrioventricular blockBundle of HisCardiac electrophysiologic techniques

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Area of Science:

  • Cardiology
  • Electrophysiology

Background:

  • Intra-hisian atrioventricular (AV) block is an uncommon condition.
  • It is a significant precursor to advanced or complete AV block.

Observation:

  • A 77-year-old female patient presented with a 2:1 AV block attributed to an intra-hisian block.
  • Initial electrophysiological study (EPS) showed an alternating AH conduction pattern, complicating block site detection.
  • This ambiguity was potentially due to catheter instability during His potential recording.

Findings:

  • Minimal catheter manipulation resolved the ambiguity, revealing His-electrogram splitting indicative of an intra-hisian block.
  • The study highlights the critical role of catheter stability in EPS.

Implications:

  • Accurate His potential recording is essential for precise diagnosis of intra-hisian AV block.
  • Catheter stability is vital for both electrophysiological studies and radiofrequency catheter ablation procedures.