Intro to EKG Interpretation - Bundle Branch Blocks

Summary

This lecture covers intraventricular conduction delays, focusing on bundle branch blocks. It teaches how to identify right and left bundle branch blocks and differentiate complete from incomplete blocks. The lecture explains the pathways of electrical depolarization through the heart, the roles of the sinoatrial node, atrioventricular node, and bundle branches. It also discusses the causes of these blocks and their appearances on EKG, including criteria for diagnosis and the implications for conditions like LVH and RVH.

Takeaways

• 🌟 Intraventricular conduction delays include bundle branch blocks and are crucial for understanding heart conduction disorders.
• 📍 Right and left bundle branch blocks can be identified by their distinct patterns on an EKG.
• 🔍 Complete and incomplete blocks have different implications for diagnosis and treatment.
• 🏥 The common causes of right bundle branch blocks include coronary artery disease, pulmonary hypertension, and congenital heart disease.
• 🏭 Left bundle branch blocks are often due to conditions like acute anterior MI, chronic coronary artery disease, and heart failure.
• 👨‍⚕️ Vesicular blocks, or hemiblocks, affect the anterior and posterior fascicles of the left ventricle, leading to specific EKG changes.
• 📊 The EKG criteria for diagnosing right and left bundle branch blocks include specific QRS complex durations and morphologies.
• 🚫 The presence of bundle branch blocks can complicate the diagnosis of other conditions like right or left ventricular hypertrophy.
• 🔎 Incomplete blocks are characterized by slowed conduction without complete blockage, often progressing to complete blocks over time.
• 📝 Nonspecific intraventricular conduction delay is diagnosed when the QRS duration is prolonged but does not meet criteria for specific blocks.
• 🔗 Bifascicular block occurs when a right bundle branch block coexists with either a left anterior or left posterior fascicular block, often seen in coronary artery disease.

Q & A

What is an intraventricular conduction delay?

An intraventricular conduction delay refers to a delay in the electrical conduction within the ventricles of the heart, which can include bundle branch blocks and other conduction abnormalities.

What are the two main types of bundle branch blocks?

The two main types of bundle branch blocks are right bundle branch block (RBBB) and left bundle branch block (LBBB).

How is the electrical activity initiated in the heart?

The electrical activity in the heart is initiated by pacemaker cells located in the sinus node, also known as the sinoatrial (SA) node.

What is the function of the atrioventricular node (AV node) in the heart's electrical conduction?

The atrioventricular node (AV node) serves as a delay mechanism for electrical impulses, responsible for the majority of the PR interval, before allowing the impulses to continue to the ventricles.

What happens when there is a right bundle branch block?

In a right bundle branch block, the right ventricle must receive the signal for depolarization from the left ventricle, resulting in a slow depolarization and a wide QRS complex on an EKG.

What is the significance of a wide QRS complex in the context of bundle branch blocks?

A wide QRS complex indicates a delay in ventricular depolarization, which can be a sign of a bundle branch block, where the electrical impulse is slowed down as it travels through the ventricles.

What are the criteria for diagnosing a right bundle branch block on an EKG?

The criteria for diagnosing a right bundle branch block include a QRS duration of 120 milliseconds or greater, an M-shaped QRS complex in V1, and a prominent S wave in leads I and AVL.

What are vesicular blocks and how do they differ from bundle branch blocks?

Vesicular blocks, also known as hemiblocks, refer to blocks affecting the anterior or posterior fascicles of the left bundle. They differ from bundle branch blocks by affecting different parts of the conduction system and presenting with different EKG findings.

What is the difference between a complete and incomplete bundle branch block?

A complete bundle branch block is characterized by a complete disruption of conduction down either the right or left bundle, while an incomplete block is a partial conduction delay with a QRS duration less than 120 milliseconds.

What are some of the causes of left bundle branch blocks?

Causes of left bundle branch blocks can include acute anterior myocardial infarction, chronic coronary artery disease, left ventricular hypertrophy, heart failure, hyperkalemia, digoxin toxicity, or unappreciated artificial right ventricular pacing.

How can nonspecific intraventricular conduction delay be identified on an EKG?

Nonspecific intraventricular conduction delay is identified when the QRS duration is prolonged to 120 milliseconds or greater, but the criteria for neither right nor left bundle branch block are met.