PANCE - AV Node Block, Sick Sinus Syndrome, & Bundle Branch Block

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Here are key facts for PANCE from the AV Node Block, Sick Sinus Syndrome, & Bundle Branch Block tutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links.

VITAL FOR PANCE

First-Degree AV Block

1. Definition and ECG finding: Long PR interval on ECG (> 200 milliseconds). 2. Clinical presentation: Typically asymptomatic. 3. Management approach: Usually no treatment required. 4. Risk factors: Myocarditis, hypokalemia, hypomagnesium, and certain medications (channel blockers or digoxin).

Second-Degree AV Block

1. Type differentiation:

Mobitz Type 1 (Wenckenbach's Block): PR interval gets progressively longer until AV node completely fails.
Mobitz Type 2: PR interval doesn't change, but ventricular depolarization is skipped.

2. Clinical manifestations:

Type 1: Dizziness, fainting
Type 2: Chest pain, difficulty breathing, tiring easily, hypotension

3. Management approach:

Type 1: No treatment if asymptomatic; consider medications as source.
Type 2: Pacemaker implantation indicated.

Third-Degree AV Block

1. Diagnostic hallmark: AV dissociation with no relationship between P waves and QRS complexes. 2. Clinical presentation: Fatigue/lethargy, dizziness, fainting, slow heart beat. 3. Definitive treatment: Pacemaker implantation required. 4. Pathophysiologic consequence: Low cardiac output deprives organs of oxygen.

Sick Sinus Syndrome

1. Clinical manifestations: Episodes of bradycardia, sinus pauses or arrest, and junctional escape beats. 2. Management: Often requires pacemaker implantation.

HIGH YIELD

First-Degree AV Block

1. Population consideration: Common in highly-trained athletes due to enlarged heart muscle. 2. Complication risk: May increase risk of atrial fibrillation.

Second-Degree AV Block

1. Clinical context:

Type 1 may be physiologic in healthy athletes.
Type 2 is pathologic and requires intervention.

2. Etiology assessment:

Cardiac injury (fibrosis, sclerosis, scarring from heart attack)
Lyme disease (particularly Type 2)
Medications: beta blockers, calcium channel blockers, digoxin, amiodarone
Valvulopathy

3. Progression risk: Type 2 can lead to complete heart block (3rd degree).

Third-Degree AV Block

1. Etiology classification:

Congenital: In infants from mothers with autoimmune conditions or infants with other cardiac conditions.
Acquired: Complications of heart surgery, radiotherapy, infection (diphtheria, rheumatic fever), hypertension, cancer, radiofrequency ablation.
Medication-induced: digoxin, calcium-channel blockers, beta blockers, tricyclic antidepressants, clonidine.

Bundle Branch Blocks

1. Diagnostic criteria: QRS complex greater than 120 ms in complete bundle branch block. 2. Right Bundle Branch Block:

May occur in otherwise healthy individuals.
ECG findings: Wide, upwardly deflected QRS in lead V1; rsR' "bunny ear" pattern in leads V1-V3; slurred S waves in I, aVL, V5 and V6.
Clinical significance: May indicate cardiac damage in the right side of the heart.

3. Left Bundle Branch Block:

ECG findings: Wide downwardly deflected QRS in V1; broad monophasic R wave and absent Q waves in I, V5, V6; ST and T wave displacement opposite to QRS.
Clinical significance: Indicative of left heart disease.

Beyond the Tutorial

Below is information not explicitly contained within the tutorial but important for PANCE.

AV Blocks - Clinical Pearls

1. Acute management: Recognizing indications for temporary transcutaneous pacing in symptomatic high-grade blocks. 2. Pharmacologic interventions: Role of atropine, dopamine, and epinephrine in emergency management of symptomatic bradycardia. 3. Preoperative assessment: Evaluating conduction disorders before non-cardiac surgery.

Sick Sinus Syndrome - Advanced Concepts

1. Diagnostic approach: Utilizing event monitors and implantable loop recorders for intermittent symptoms. 2. Medication management: Balancing rate control medications in patients with tachy-brady syndrome. 3. Syndromic associations: Recognizing sick sinus syndrome in specific patient populations (e.g., muscular dystrophies, infiltrative diseases).

Bundle Branch Blocks - Practice Considerations

1. Incidental findings: Appropriate management of newly discovered bundle branch blocks on routine ECGs. 2. Stress testing implications: Understanding the significance of rate-dependent bundle branch blocks. 3. Consultation guidelines: When to refer to electrophysiology for further evaluation of conduction disorders.