16 Questions
What is the name of the type of atrial tachycardia characterized by 3 or more morphologically different p-waves in the same lead?
Multi-focal atrial tachycardia
What is the main difference between a left bundle branch block (LBBB) and a right bundle branch block (RBBB) on an ECG?
The morphology of the QRS complex
What is the name of the type of ventricular tachycardia characterized by a normal QT interval?
Polymorphic VT
What is the purpose of administering ABCD drugs in the management of atrial fibrillation?
To slow down the heart rate
What is the name of the procedure used as a last resort to shock the heart back into its rhythm?
Cardioversion
What is the characteristic ECG pattern seen in atrial flutter?
Saw-toothed waves in II/III/avF/V1
Which of the following is a characteristic of sinus bradycardia?
Slower HR but normal PR interval
Which of the following is a cause of bradyarrhythmia?
Increased vagal tone
What is the characteristic ECG feature of Mobitz I (Wenckeback) heart block?
Progressive prolongation of PR interval
Which of the following is a type of tachyarrhythmia?
Atrial flutter
What is the characteristic ECG feature of atrial fibrillation?
No p-waves
Which of the following is a cause of tachyarrhythmia?
Increased sympathetic tone
What is the characteristic ECG feature of ventricular fibrillation?
Irregular QRS complex
Which of the following is a type of bradyarrhythmia?
AV nodal conduction delays
What is the characteristic ECG feature of focal atrial tachycardia?
Inverted p-waves in lead II
Which of the following is a cause of bradyarrhythmia?
Hypothyroidism
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
- Mobitz I (Wenckeback):
- Third degree heart block:
- Inconsistent PR interval
- Dropping QRS complex and wide QRS
- Complete dissociation between atria and ventricles
- First degree heart block:
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)
- Supraventricular tachycardia (SVT)/atrial tachycardia:
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
ECG Changes in Hyper and Hypokalaemia
- Hyperkalaemia:
- Peaked T waves
- Widened QRS
- Prolonged PR interval
- Hypokalaemia:
- Flat T waves
- Prolonged QT interval
- U waves
Learn about abnormal heart rhythms, including bradyarrhythmias, and their causes, such as decreased automaticity and inferior wall MI.
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