Intro to EKG Interpretation - AV Block

Summary

This video covers the fundamentals of AV block, a condition where normal electrical conduction from the atria to the ventricles is impaired. It explains the three main degrees of AV block—first degree, second degree (with subtypes), and third degree—with their corresponding ECG patterns, symptoms, and treatments. The video also highlights various causes of AV block, such as idiopathic degeneration, medications, and high vagal tone, while discussing the clinical significance and management strategies for each type. It emphasizes the importance of recognizing these blocks for accurate diagnosis and timely intervention.

Takeaways

• 😀 AV block refers to a lack of normal electrical conduction from the atria to the ventricles through the AV node and His-Purkinje system.
• 😀 The classification of AV block is based on degrees: First degree, Second degree, and Third degree.
• 😀 In First degree AV block, all atrial impulses are conducted to the ventricles, but with a prolonged PR interval (greater than 200 milliseconds).
• 😀 Second degree AV block is where only some atrial impulses are conducted, with two main types—Type 1 and Type 2—each showing different PR interval patterns.
• 😀 Type 1 second degree AV block (Wenckebach block) involves progressively lengthening PR intervals until a P-wave is blocked, leading to grouped beating.
• 😀 Type 2 second degree AV block features a constant PR interval, but P-waves are intermittently blocked, often unpredictably, and can result in a wide QRS complex.
• 😀 2:1 second degree block is a variation of Type 2, where every other P-wave is blocked, and the block location is usually at or near the AV node.
• 😀 Third degree AV block (complete heart block) occurs when no atrial impulses are conducted to the ventricles, resulting in AV dissociation and ventricular escape rhythms.
• 😀 The causes of AV block can be categorized into four groups: pathological causes (e.g., idiopathic degeneration, myocardial infarction), medication-induced causes, physiologic causes (e.g., high vagal tone, tachycardia), and normal variants (e.g., benign first-degree AV block).
• 😀 Treatment for AV block depends on its type and severity, with pacemakers being used for higher degree blocks, especially third-degree block, and type 2 second-degree block when symptoms are present or reversible causes are not found.

Q & A

What is the basic concept of AV block?

AV block refers to a condition where there is a lack of normal electrical conduction from the atria to the ventricles through the AV node and His-Purkinje system.

What are the learning objectives of understanding AV block?

The learning objectives include recognizing the common types of AV block and understanding their etiologies.

What is the classification system of AV block?

AV block is classified into three degrees, with the first degree having all atrial impulses conducted with a prolonged PR interval, second degree having some atrial impulses blocked, and third degree having no atrial impulses conducted to the ventricles.

How is first-degree AV block characterized on an EKG?

In first-degree AV block, every P wave is followed by a QRS complex, but the PR interval is prolonged beyond the normal 200 milliseconds, as seen in the example where the PR interval is about 320 milliseconds.

What is the difference between type 1 and type 2 second-degree AV block?

In type 1 second-degree block, the PR interval progressively lengthens until a P wave is blocked, while in type 2, the PR interval remains constant and P waves are intermittently blocked.

What is a characteristic feature of type 1 second-degree AV block?

A characteristic feature of type 1 second-degree block is 'grouped beats,' where the PR interval progressively lengthens until a P wave is blocked, leading to a regularly irregular rhythm.

What is the key difference between type 1 and type 2 second-degree AV block in terms of PR interval?

In type 1, the PR interval progressively lengthens, while in type 2, the PR interval remains constant and the P waves are intermittently blocked.

What are the common causes of AV block?

Common causes of AV block include idiopathic degeneration of the conduction system, ischemia, infarction, myocarditis, endocarditis, medications, high vagal tone, and certain congenital heart diseases.

What is the significance of third-degree AV block?

Third-degree AV block is the most severe form of AV block, where no atrial impulses are conducted to the ventricles, resulting in AV dissociation. The ventricular rhythm is the only thing keeping the patient alive, and a pacemaker is often necessary.

How does a pacemaker help in the treatment of AV block?

A pacemaker is used in the treatment of AV block, particularly in type 2 second-degree and third-degree AV block, when the block is not reversible. It ensures proper pacing of the heart when natural conduction fails.