ECG Question-2
What is the diagnosis of ECG?
A. LBBB + LAFB
B. LBBB + LPFB
C. RBBB + LAFB
D. RBBB + LPFB
RBBB + LAFB is called Bifascicular Block ?
What are the types of bifascicular block [ECG patterns]?
- Right bundle branch block (RBBB) with left anterior fascicular block (LAFB) – left axis deviation (LAD)
- RBBB and left posterior fascicular block (LPFB) – right axis deviation (RAD) in the absence of other causes
| Bifascicular Block | ||
| 1 | RBBB + LAFB | More common |
| 2 | RBBB + LPFB | Less common |
Why RBBB + LAFB is more common than RBBB + LPFB in ?
| Why commonest type is RBBB + LAFB ? [ECG patterns] | Vulnerability to Damage |
| The LAF is supplied by a single branch of the left anterior descending artery (LAD). The LPF, on the other hand, receives a dual blood supply from both the right and left circumflex arteries. | Because the LAF has a single blood supply, it’s more susceptible to damage and block due to ischemia or other factors affecting the LAD. The LPF’s dual blood supply makes it more resistant to damage and block compared to the LAF. |
Anatomy and Blood Supply:
The LAF is supplied by a single branch of the left anterior descending artery (LAD).
The LPF, on the other hand, receives a dual blood supply from both the right and left circumflex arteries.
Vulnerability to Damage:
Because the LAF has a single blood supply, it’s more susceptible to damage and block due to ischemia or other factors affecting the LAD.
The LPF’s dual blood supply makes it more resistant to damage and block compared to the LAF.
Location and Relation to LV Outflow Tract:
The LAF’s location and relationship to the left ventricular (LV) outflow tract can also contribute to its vulnerability to damage, as it can be subjected to mechanical trauma.
Clinical Significance:
RBBB + LAFB is a common finding in patients with coronary artery disease (CAD), and its presence can indicate underlying structural and electrical abnormalities.
RBBB + LPFB is less common and may be associated with more extensive underlying cardiac pathology.
| Blood supply | |||
| Left anterior fascicle (LAF) | More common for block | Single blood supply | LAD |
| Left posterior fascicle (LPF) | Less common for block | Dual blood supply | RCA + LCX |
| Question | Answer |
|---|---|
| What is a bifascicular block? | Block involving two of the three main fascicles—commonly right bundle branch block plus left anterior or posterior fascicular block. |
| Which ECG finding defines bifascicular block? | Right bundle branch block combined with either left anterior or left posterior fascicular block. |
| What is the clinical risk of bifascicular block? | Risk of progression to complete heart block. |
| When is pacemaker indicated in bifascicular block? | Symptomatic patients with syncope or advanced conduction disease. |
| What QRS duration suggests bifascicular block? | QRS duration >120 milliseconds. |
| Which fascicle is most commonly involved with RBBB in bifascicular block? | Left anterior fascicle. |
| What is the typical axis deviation in left anterior fascicular block? | Left axis deviation. |
| What diagnostic test assesses risk for progression to complete heart block? | Electrophysiological study (EPS). |
| Is immediate pacemaker required for asymptomatic bifascicular block? | No, usually observation is enough. |
| Name one common cause of bifascicular block. | Degenerative conduction system disease or ischemic heart disease. |
