14 Identify Some Basic Disturbances of Rhythm

Question 1

State normal values/pattern of ECG for: P wave, PR interval, Q wave, QRS complex, QT interval and T wave

Answer 1

P wave: < 0.11s and < 2.5 mm on V2
PR wave: 0.12 - 0.20s
Q wave: < 0.04s and < 25% of duration of QRS complex
QRS complex: < 0.12s and < 25 mm on V6; axis between -30 to 90 degrees
QT interval: 0.38 - 0.42s
T wave: may be inverted on Lead III, aVR, V1 and V2

Question 2

Describe significant ECG findings on patients with atrial fibrillation

Answer 2

• No P wave
• Irregularly irregular pattern
• Atrial: 350 - 650 bpm; Ventricular: slow to rapid

Question 3

Describe significant ECG findings on patients with atrial flutter

Answer 3

• Sawtoothed appearance
• More regular pattern with regular ventricular rhythm
  Some
• Some P waves may not reach AV node (4:1 ratio is typical)

Question 4

Describe significant ECG findings on patients with AVNRT (AV nodal reentrant tachycardia)

Answer 4

• P wave may be buried within QRS or just after
• Narrow QRS complex - otherwise normal
• Adenosine responsive
• Synchronous contraction of atria and ventricles

Question 5

Describe significant ECG findings on patients with pre-excitation syndrome

Answer 5

• Small P wave and short PR interval
• Ventricular pre-excitation
• Pre-excitation due to the existence of accessory pathway and predispose patient to AVRT (accessory pathway tachycardia)
• Curative from accessory pathway ablation

Question 6

Describe significant ECG findings on patients with primary AV block

Answer 6

• Prolonged PR interval due to ageing and sclerosis of AV node
• PR < 200 ms

Question 7

Describe significant ECG findings on patients with secondary Mobitz Type I

Answer 7

• Gradual prolonging of PR interval

- Some QRS complex is absent following P wave

Question 8

Describe significant ECG findings on patients with secondary Mobitz Type II

Answer 8

• No pattern of prolonging PR interval accompanied with unexpected loss of QRS complex
• Requires a pacemaker

Question 9

Describe significant ECG findings on patients with tertiary AV block

Answer 9

• No coordination between P wave and QRS complex

- Regular but no atrioventricular association

Question 10

What is the characteristic ECG finding for bundle branch block and why does this occur

Answer 10

Broadening of QRS complex
QRS morphology changes

Takes longer time for impulses to pass to the ventricles due to blockage of conduction pathway

Question 11

Describe significant ECG findings on patients with left bundle branch block and right bundle branch block. What lead is best to visualise these changes

Answer 11

LBBB: broadening deep S wave
RBBB: rabbit ear appearance
Both best visualised on V1 or V2 leads

Question 12

Describe significant ECG findings on patients with ventricular tachycardia

Answer 12

• No P wave
• Fast waves
• Broadening of QRS complex
• More uniform sizes between each peaks than ventricular fibrillation
• If left long enough, patient can develop ventricular fibrillation