Ch 13 - ECG Interpretation

Question 1

Sinoatrial Block

Answer 1

1. Sudden cessation of P waves

Question 2

Atrioventricular Block

Answer 2

1. Ischemia of the A-V node or A-V bundle fibers
2. Compression of the A-V bundle
3. Inflammation of the A-V node or A-V bundle
4. Extreme stimulation of the heart by the vagus nerves

Question 3

Prolonged P-R - 1st Degree

Answer 3

• Normal P-R interval is 0.16 seconds
• First-degree incomplete heart block
  • ​> 0.20 seconds

Question 4

Prolonged P-R - 2nd Degree

Answer 4

• *P-R interval * = 0.25 to 0.40 seconds
• Atrial P wave but no QRS-T wave
• “Dropped beats” of the ventricles
  
  • strong enough to pass through the bundle but not strong enough to initiate ventricular contraction

Question 5

• *Complete A-V Block
• 3rd Degree block**

Answer 5

• Ventricles develop their own signal - A-V Node
• Atria rhythm ~100 BPM
• Ventrical rhythm ~40 BPM

Question 6

Stokes-Adams Syndrome

Answer 6

• A-V block comes and goes
• Borderline ischemia hearts
• Overdrive suppression
  
  • 5 to 30 second delay –> ventricular escape
  • 15 to 40 BPM
  • Syncope

Question 7

Extrasystole

Answer 7

• result from ectopic foci
  
  • ​local areas of ischemia
  • small calcified plaques
  • toxic irritation of the A-V node

Question 8

Long QT Syndrome

Answer 8

• long repolarization –> torsades de pointes
  
  • arrhythmias
  • tachycardia
  • ventricular fibrillation
• Plasma electroylte disturbances
  
  • Hypomagnesemia
  • Hypokalemia
  • Hypocalcemia
• Drugs (quinidine, ABX: fluoroquinolones, erythromycin)
• Na+/K+ gene mutations (10x, rare)