Lecture 7.1 - Arrythmias and ECH changes

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Questions and Answers

What is the name of the type of atrial tachycardia characterized by 3 or more morphologically different p-waves in the same lead?

Atrial flutter

Multi-focal atrial tachycardia (correct)

Ventricular tachycardia

Atrial fibrillation

What is the main difference between a left bundle branch block (LBBB) and a right bundle branch block (RBBB) on an ECG?

The amplitude of the T waves

The direction of the P waves

The duration of the PR interval

The morphology of the QRS complex (correct)

What is the name of the type of ventricular tachycardia characterized by a normal QT interval?

Polymorphic VT (correct)

Monomorphic VT

Ventricular fibrillation

Ventricular flutter

What is the purpose of administering ABCD drugs in the management of atrial fibrillation?

To slow down the heart rate Signup and view all the answers

What is the name of the procedure used as a last resort to shock the heart back into its rhythm?

Cardioversion Signup and view all the answers

What is the characteristic ECG pattern seen in atrial flutter?

Saw-toothed waves in II/III/avF/V1 Signup and view all the answers

Which of the following is a characteristic of sinus bradycardia?

Slower HR but normal PR interval Signup and view all the answers

Which of the following is a cause of bradyarrhythmia?

Increased vagal tone Signup and view all the answers

What is the characteristic ECG feature of Mobitz I (Wenckeback) heart block?

Progressive prolongation of PR interval Signup and view all the answers

Which of the following is a type of tachyarrhythmia?

Atrial flutter Signup and view all the answers

What is the characteristic ECG feature of atrial fibrillation?

No p-waves Signup and view all the answers

Which of the following is a cause of tachyarrhythmia?

Increased sympathetic tone Signup and view all the answers

What is the characteristic ECG feature of ventricular fibrillation?

Irregular QRS complex Signup and view all the answers

Which of the following is a type of bradyarrhythmia?

AV nodal conduction delays Signup and view all the answers

What is the characteristic ECG feature of focal atrial tachycardia?

Inverted p-waves in lead II Signup and view all the answers

Which of the following is a cause of bradyarrhythmia?

Hypothyroidism Signup and view all the answers

Study Notes

Arrhythmias

Abnormal electrical activity in the heart
Abnormality in rate/rhythm/sequence of conduction/origin of conduction
Normal heart rate: 60-100bpm

Bradyarrhythmias

Heart rate < 60bpm
Causes:
- Decreased automaticity
- Increased vagal tone (endurance athletes)
- Inferior wall MI (clot in right coronary artery)
- Drugs that slow down conduction velocity (adenosine, beta blockers, calcium channel blockers, digoxin)
- Slow metabolic activity (hypothyroidism, hypothermia)
- Electrolyte imbalance (hyperkalaemia slows down conduction velocity, K+, Mg2+, and Ca2+ can decrease automaticity)
- High intracranial pressure (Cushing's triad)
- Lyme carditis (bacterial infection that induces bradycardia)

Classification and ECG Changes

Sinus bradycardia:
- Every p-wave has a QRS
- Slower heart rate but normal PR interval
AV nodal conduction delays:
- First degree heart block:
  - Prolonged PR interval (> 5 small boxes)
- Second degree heart block:
  - Mobitz I (Wenckeback):
    - Progressive prolongation of PR interval
    - Dropped QRS complex
  - Mobitz II:
    - PR interval is fixed
    - Sudden drop of QRS complex
- Third degree heart block:
  - Inconsistent PR interval
  - Dropping QRS complex and wide QRS
  - Complete dissociation between atria and ventricles

Tachyarrhythmias

Heart rate > 100bpm
Types:
- Supraventricular tachycardia (SVT)/atrial tachycardia:
  - Sinus tachycardia
  - Focal atrial tachycardia (FAT)
  - Atrial fibrillation (AF)
  - Atrial flutter
  - AVNRT (AV nodal re-entrant tachycardia)
  - AVRT
- Ventricular tachycardia (VT):
  - Monomorphic VT
  - Polymorphic VT
  - Polymorphic VT with prolonged QT interval (Torsades Depointes)
  - Ventricular fibrillation (VF)

Reasons for Tachyarrhythmias

Increased automaticity:
- Increased sympathetic tone
- Sympathomimetic drugs
- Increased metabolic activity
Triggered activity:
- Early after depolarisations (EADs) due to electrolyte imbalance (hypokalaemia)
- Delayed after depolarisation (DADs) due to ischaemia
Re-entrant circuit:
- AVNRT, AVRT
- Atrial flutter, atrial fibrillation
- Wolff-Parkinson-White syndrome (congenital)

Tachyarrhythmias - ECG Variations

Narrow QRS (regular rhythm):
- Sinus tachycardia
- FAT
- AVRT, AVNRT
- Atrial flutter
Narrow QRS (irregular rhythm):
- Atrial fibrillation
- Atrial flutter with variable block
- MAT
Wide QRS (regular rhythm):
- VT (monomorphic)
- Bundle branch blocks
Wide QRS (irregular rhythm):
- VT (polymorphic)
- VF