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Related Concept Videos

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which indirectly block calcium...
Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers01:12

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers

Class III antiarrhythmic drugs are a group of medications that can prolong action potentials in the heart. They achieve this by blocking potassium channels or enhancing inward currents from sodium channels. However, these drugs have a unique property of "reverse use-dependence," which is most pronounced at slower heart rates and can lead to torsades de pointes—a specific type of arrhythmia. However, it is essential to note that excessive QT interval prolongation—a measure of the heart's...
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers01:20

Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers

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.
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
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...
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...
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...

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Related Experiment Video

Updated: Jun 23, 2026

Robotic Ablation of Atrial Fibrillation
11:21

Robotic Ablation of Atrial Fibrillation

Published on: May 29, 2015

Second degree atrioventricular block.

R S Bexton, A J Camm

    European Heart Journal
    |March 1, 1984
    PubMed
    Summary
    This summary is machine-generated.

    Second-degree atrioventricular (AV) block carries risks for heart block progression. Type I AV block with narrow QRS may be acceptable for aircrew after evaluation, but Type II or wide QRS blocks disqualify them.

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    Area of Science:

    • Cardiology
    • Electrophysiology
    • Aviation Medicine

    Background:

    • Second-degree atrioventricular (AV) block, specifically Type II or Type I with bundle branch block, poses a significant risk of progressing to higher degrees of AV block.
    • Long-term outcomes for Type I AV block with narrow QRS complexes are debated, with some studies suggesting a benign course and others indicating a high rate of progression to complete heart block requiring pacemakers.

    Purpose of the Study:

    • To evaluate the risks associated with different types of second-degree AV block in the context of aviation medical certification.
    • To clarify the prognosis of Type I AV block with narrow QRS complexes in aircrew.

    Main Methods:

    • Review of existing long-term follow-up studies on patients with Type I AV block and narrow QRS complexes.
    • Analysis of risk stratification for different subtypes of second-degree AV block relevant to aviation safety.

    Main Results:

    • Type II AV block and Type I AV block with wide QRS complexes are associated with a high risk of progression and should preclude medical certification for flying.
    • Aircrew with Type I second-degree AV block and narrow QRS complexes require thorough evaluation but may be deemed fit for multi-crew operations.

    Conclusions:

    • The risk stratification for second-degree AV block subtypes is crucial for determining fitness for aviation duties.
    • While Type II or wide QRS AV blocks are disqualifying, Type I AV block with narrow QRS warrants careful individual assessment for aircrew.