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Cardiac Arrhythmias-Bradycardia

Cardiac Arrhythmia- Bradycardia

1. Heart Block Definition

A. First Degree - PR interval > 0.2 seconds
B. Second Degree - Intermittent AV conduction
C. Third Degree - Atrial impulses do not conduct

2. Bradycardia

Heart Rate < 60 beats/min:
A. Asymptomatic
1) Athletic conditioning
2) Sinus bradycardia
B. Symptomatic
1) Inadequate cardiac blood flow
2) Loss of atrial augmentation
3) Dizziness, syncope (inadequate cerebral blood flow

3. Heart Block - Complete

A. Causes
1) Congenital- often asymptomatic
2) Valvular calcification- Aortic, Mitral
3) Myocardial infarction- inferior, anterior septal
4) Surgical- VSD repair, subvalvular stenosis resection, valve replacement (IHSS)

4. Sinus Node Dysfunction

Amyloid deposition
A. Surgical damage
1) Fontan repair, atrial switch, Maze II, superior approach for Mitral valve repair
B. Sick sinus syndrome
1) Tachycardia, bradycardia
2) Diagnosis by prolonged ambulatory ECG

5. Carotid Sinus Syndrome

A. Cardio-inhibitory- Carotid sinus stimulation
1) 3 second or greater pauses
2) pacemaker appropriate
B. Vasodepressor- Carotid sinus depression with Atropine
1) BP drops without slowing
2) pacemaker may not help symptoms

6. Indications

A. Symptomatic bradycardia
1) Syncope, dizziness, exercise intolerance, CHF
B. Asymptomatic bradycardia
1) profound bradycardia, usually brief
2) congenital third degree heart block with wide QRS complex
3) BBB?? with intermittent second degree heart block post-MI
4) bifasicular block with intermittent second degree heart block


NBG Code

Chamber PacedChamber SensedResponse to SensingProgrammable Function
V- VentricleV- VentricleT- Trigger pacingP- Simple programmable
A- ArtiumA- AtriumI- Inhibits pacingM- Multi-programmable
D- Dual (A&V)D- Dual (A&V)D- Dual (T&I)C- Telemetry
O- NoneO- None)O- NoneR- Rate responsive
   O- None

7. Lead placing

A. Atrial
1) Threshold
2) Pacing
3) Sensing >/= 2 mVolt
B. Ventricular
1) Threshold
2) Pacing
3) Sensing >/= 5 mVolts
4) Slow rate >/= 0.8 mVolts/sec.