🌾 Lyme Carditis & AV Block Simulator

Spirochetes Invade the AV Node

Borrelia burgdorferi spreads hematogenously and colonizes cardiac tissue.

• ~3 wks: Onset after tick bite (placeholder figure)
• ~1-10%: Cardiac involvement (placeholder figure)
• AV node: Site of predilection (placeholder figure)
• young adult: Typical age (placeholder figure)

Mechanism of invasion

Spirochetes trigger local inflammation in nodal tissue.

PR Interval Prolongation Begins

Conduction delay through the inflamed AV node lengthens the PR interval.

• 120-200ms: Normal PR (placeholder figure)
• >200ms: First-degree PR (placeholder figure)
• often none: Symptoms (placeholder figure)
• variable: Progression risk (placeholder figure)

ECG correlate

PR prolongs but every P wave still conducts.

Intermittent Conduction Failure

Some atrial impulses fail to reach the ventricles.

• I or II: Mobitz type (placeholder figure)
• intermittent: Dropped beats (placeholder figure)
• telemetry: Monitoring (placeholder figure)
• often: Reversibility (placeholder figure)

Wenckebach vs Mobitz II

Progressive vs fixed-ratio dropped beats.

Third-Degree Complete Heart Block

Atrial and ventricular activity become fully dissociated.

• complete: AV dissociation (placeholder figure)
• junctional/ventricular: Escape rhythm (placeholder figure)
• syncope risk: Symptoms (placeholder figure)
• high: Urgency (placeholder figure)

Hemodynamic consequence

Independent chamber rates reduce cardiac output.

Temporary Pacemaker Placement

High-grade block prompts temporary pacing pending antibiotic response.

• high-grade block: Indication (placeholder figure)
• transvenous temp: Device type (placeholder figure)
• days: Duration (placeholder figure)
• rare: Permanent pacer need (placeholder figure)

Bridge to recovery

Pacing supports rhythm while antibiotics clear infection.

Block usually resolves fully with antibiotic treatment.