LBBB Flashcards
(28 cards)
What are the two fascicles of the Left Bundle Branch?
Left Posterior Fascicle (LPF) and Left Anterior Fascicle (LAH)
These fascicles are crucial for proper ventricular depolarization.
What is the QRS duration characteristic of Left Bundle Branch Block (LBBB)?
QRS duration > 0.12 seconds
This indicates a delay in ventricular conduction.
What ECG characteristics are associated with LBBB?
- Deep QS waves in V1/V2
- Notched QRS complex in V5/V6
- Discordant T waves
These characteristics help in diagnosing LBBB on an ECG.
List some causes of Left Bundle Branch Block (LBBB).
- Hypertensive heart disease
- Cardiomyopathy
- Ischemic heart disease
- Ventricular wall enlargement
LBBB is rarely seen in healthy individuals.
How can LBBB with Tachycardia be differentiated from Ventricular Tachycardia (VT)?
- LBBB with Tachycardia: Sinus rhythm (P wave present) followed by wide QRS complex
- VT: Wide QRS complex with no associated P wave (AV dissociation)
Extreme Right Axis Deviation (RAD) is also a diagnostic clue for VT.
What is Aberrant Ventricular Conduction?
Occurs when a premature atrial beat conducts to the ventricles while the Right Bundle Branch is refractory
This can lead to abnormal QRS morphology on the ECG.
What are the ECG criteria for Aberrant Ventricular Conduction?
- Premature beat, P wave precedes QRS
- QRS duration of 0.11 seconds or wider
- RsR’ morphology in V1
The initial deflection of the wider QRS follows the same direction as the preceding normal QRS.
What is Ashman’s Phenomenon?
Pattern of R-R interval lengths that initiate an aberrantly conducted beat during Atrial Fibrillation
It involves a long R-R interval followed by a short R-R interval, then an aberrant beat.
Differentiate between SVT with Aberrancy and VT based on QRS duration.
- SVT with Aberrancy: Wide QRS <0.14 seconds
- VT: Wide QRS >0.14 seconds
This is a key diagnostic feature to distinguish between the two.
In SVT with Aberrancy, what is the morphology of QRS complexes in V leads?
Both negative and positive
This differs from VT where QRS in V leads are either all positive or all negative.
What is a key diagnostic clue for differentiating SVT with Aberrancy from VT?
Close observation in V1/V2
This allows for better assessment of QRS morphology and associated characteristics.
True or False: LBBB can be identified by notching of the QRS in V5, V6, and Lead I.
True
This is a classic finding on an ECG for diagnosing LBBB.
How does VT differ from Sinus tachycardia with LBBB?
VT shows AV dissociation
This is a crucial differentiating feature in the diagnosis.
What does SVT with rapid aberrant conduction show in precordial leads?
Both positive and negative polarity
This indicates the presence of aberrant conduction.
What are the key features of Left Bundle Branch Block (LBBB)?
QRS duration > 0.12 sec, Deep QS waves in V1/V2, Notched QRS complex in V5/V6, Discordant T waves
LBBB is characterized by specific changes in the ECG that indicate delayed conduction in the left bundle branch.
What are common causes of Left Bundle Branch Block (LBBB)?
- Hypertensive heart disease
- Cardiomyopathy
- Ischemic heart disease
- Ventricular wall enlargement
- Rarely seen in healthy individuals
These conditions can lead to structural changes in the heart that affect the conduction pathways.
How can you differentiate between LBBB with Tachycardia and Ventricular Tachycardia (VT)?
LBBB with Tachycardia has a sinus rhythm (P wave present) and wide QRS complex, while VT has a wide QRS complex with no P wave (AV dissociation)
Understanding the presence of P waves is critical for distinguishing these two conditions.
What is the structure of the Left Bundle Branch?
Consists of two fascicles: Left Posterior Fascicle (LPF) and Left Anterior Fascicle (LAH)
These fascicles are responsible for conducting impulses to the left ventricle.
Describe the impulse conduction in LBBB.
Impulse travels first down the Right Bundle Branch, then to the Left in a slowed reverse depolarization
This delayed conduction results in the characteristic ECG changes seen in LBBB.
What ECG characteristics are indicative of LBBB?
QRS duration > 0.12 sec, Deep QS waves in V1/V2, Notched QRS complex in V5/V6, Discordant T waves
These features help in the identification of LBBB on an ECG.
What are the characteristics of Aberrant Ventricular Conduction?
Occurs when a premature atrial beat conducts while the Right Bundle Branch is refractory
This condition can mimic other forms of conduction disturbances.
What ECG criteria are used to identify Aberrant Ventricular Conduction?
- Premature beat
- P wave precedes the QRS
- QRS duration 0.11 sec or wider
- RsR’ pattern in V1
- Initial QRS deflection follows the preceding normal QRS direction
These criteria help distinguish aberrant conduction from other arrhythmias.
What is Ashman’s Phenomenon?
Pattern of R-R interval lengths where a long R-R interval is followed by a short R-R interval resulting in an aberrant beat
This phenomenon is often seen in the context of atrial fibrillation.
How can you differentiate between Supraventricular Tachycardia (SVT) with aberrancy and Ventricular Tachycardia (VT)?
SVT with Aberrancy has a wide QRS < 0.14 sec, conducted P waves, and RBBB morphology, while VT has a wide QRS > 0.14 sec, AV dissociation, and uniform polarity in V leads
These differences are crucial for accurate diagnosis and management.
