University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

48

Pages:

2
Author:

Mariam A. A.

Bifascicular block Bifascicular blocks occur when conduction is impaired in two of these fascicles, resulting in delayed or blocked activation of the affected ventricular regions. The most common combination of fascicular blocks is right bundle branch block (RBBB) with either left anterior fascicular block (LAFB) or left posterior fascicular block (LPFB). Types of Bifascicular Blocks: • • • Right Bundle Branch Block (RBBB): RBBB is characterized by delayed activation of the right ventricle due to conduction block in the right bundle branch. This results in a characteristic QRS complex morphology on ECG, with a widened (>120 ms) QRS duration and a broad, slurred S wave in leads I, V5, and V6, along with an RSR' pattern in lead V1. Left Anterior Fascicular Block (LAFB): LAFB occurs when conduction is impaired in the anterior fascicle of the left bundle branch. This leads to delayed activation of the left ventricular septum, resulting in a left axis deviation (QRS axis between -45° and -90°) on ECG and characteristic findings such as qR pattern in leads I and aVL, and R wave progression in leads V1-V6. Left Posterior Fascicular Block (LPFB): LPFB involves conduction block in the posterior fascicle of the left bundle branch, resulting in delayed activation of the left ventricular free wall. LPFB is less common than LAFB and typically manifests as a right axis deviation (QRS axis greater than +90°) on ECG, with characteristic findings such as rS pattern in leads I and aVL, and q wave in leads II, III, and aVF. Clinical Significance of Bifascicular Blocks: Bifascicular blocks are important markers of conduction system disease and may indicate underlying structural heart disease or an increased risk of developing more severe conduction abnormalities, such as complete heart block or atrioventricular (AV) dissociation. While asymptomatic bifascicular blocks may not require immediate intervention, symptomatic individuals or those with additional risk factors may require further evaluation and management to prevent adverse cardiac events. Diagnosis of Bifascicular Blocks: The diagnosis of bifascicular blocks is based on ECG findings consistent with RBBB and either LAFB or LPFB. Additional diagnostic tests, such as echocardiography, cardiac stress testing, or ambulatory ECG monitoring, may be performed to assess for underlying structural heart disease, ischemia, or arrhythmias. Evaluation for reversible causes, such as electrolyte imbalances, myocardial ischemia, or medication effects, is also important in the assessment of bifascicular blocks. Management of Bifascicular Blocks: The management of bifascicular blocks depends on the presence of symptoms, underlying cardiac pathology, and associated risk factors for adverse outcomes. In asymptomatic individuals with stable bifascicular blocks, close monitoring with periodic evaluation may be sufficient. However, symptomatic patients, those with evidence of progressive conduction disease, or those at high risk for adverse cardiac events may require implantation of a permanent pacemaker to prevent bradycardia-related complications, such as syncope or sudden cardiac death.