Trifascicular Block

Background

• Conduction disease of all three fascicles: fight bundle branch, and left posterior and left anterior fascicles
• Trifascicular blocks can deteriorate into high grade blocks

Clinical Features

• ECG will show a bifascicular block and a prolonged PR interval

Differential Diagnosis

Differential includes ischemic events, electrolyte abnormalities, and medication overdoses in addition to rheumatologic conditions

• Anterior MI
• Rheumatic fever
• Myocarditis
• Lyme disease
• Lenegre's disease
• Lev's disease
• SLE
• Systemic sclerosis
• Amyloidosis
• Hemochromatosis
• Sarcoidosis
• Hyperkalemia
• Toxicology
  • Beta blocker toxicity
  • Calcium channel blocker toxicity
  • Digoxin toxicity
  • Amiodarone

Types of second degree AV block

AV blocks

• First degree AV block
• Second degree
  • Second degree AV block type I (Wenkebach)
  • Second degree AV block type II
• Third degree AV block
• AV dissociation without complete heart block

Bundle and Fascicular Blocks

• Right Bundle Branch Block
• Left Bundle Branch Block
• Left Anterior Fascicular Block
• Left Posterior Fascicular Block
• Trifascicular Block

Premature Beats

• Premature atrial contraction
• Premature junctional complex
• Premature ventricular contraction

Evaluation

• If symptomatic, standard ACLS guidelines for symptomatic bradycardia to include
  • Atropine 0.5mg IV q3-5min PRN total dose of 3mg
  • Transcutaneous pacing, followed by transvenous pacing
  • Dopamine IV consider for low BP 3mcg/kg/minute titrate up to 20 mcg/kg/minute
  • Dobutamine IV consider for heart failure at 5mcg/kg/minute titrate up to 20mcg/kg/minute if needed for HR and BP augmentation
• Treat underlying etiology
• Avoid AV nodal blocking agents (e.g. β-blockers)