Cardiac Arrhythmias

Question 1

What are the two causes of bradycardias?

Answer 1

• Failure of impulse formation (sinus bradycardia).

* failure of impulse conduction from the atria to the ventricles (atrioventricular block)

Question 2

What are common extrinsic causes of sinus bradycardia?

Answer 2

• Hypothermia / hypothyroidism / cholestatic jaundice / raised intracranial pressure
• Drug therapy: beta blockers / digitalis / other antiarrythmic drugs
• Neurally mediated syndromes

Question 3

What are common intrinsic causes of sinus bradycardia?

Answer 3

• Acute ischaemia and infarction of the SAN (as a complication of MI)
• Chronic degenerative changes: fibrosis of the atrium and sinus node (sick sinus syndrome)

Question 4

What is the main cause of sick sinus syndrome (sinoatrial disease)

Answer 4

• Idiopathic fibrosis of the SAN

* Other causes of fibrosis: ischaemic heart disease / cardiomyopathy / myocarditis

Question 5

How is chronic sick sinus syndrome treated?

Answer 5

• Requires permanent pacing (DDD)
• Antiarrythmic drugs to manage any tachycardic element
• Anti-coagulated (thromboembolism is common in tachy-brady syndrome)

Question 6

How should vasovagal attacks been managed?

Answer 6

• Avoidance of situations known to cause syncope
• Sitting/lying down and applying counter-pressure manoeuvres (palm-palm and crossing legs)
• • salt intake

Question 7

What is AV block and what are the three forms?

Answer 7

• Conduction between the atria and the ventricles are impaired. The block occurs in the AVN or the His bundle.
• First-degree / second-degree / third-degree AV block

Question 8

What is first degree AV block?

Answer 8

•Prolongation of PR interval to >0.22s. A QRS always follows a P wave.

Question 9

What is second-degree AV block and what three types?

Answer 9

• Some P waves conduct and others do not.
• Mobitz I block
• Mobitz II block
• 2:1 or 3:1 block

Question 10

What is Mobitz I block?

Answer 10

• Progressive PR interval prolongation until a P wave fails to conduct.

Question 11

What is Mobitz II block?

Answer 11

• A dropped QRS complex is not proceeded by progressive PR interval prolongation.

Question 12

What is 2:1 or 3:1 block?

Answer 12

• Occurs when every second or third P wave there is a QRS complex.

Question 13

What is third-degree block?

Answer 13

• All atrial activity fails to conduct to the ventricles

Question 14

What does incomplete bundle branch block look like on the ECG?

Answer 14

• Widening of the QRS complex up to 0.11s

Question 15

What does complete bundle branch block look like on the ECG?

Answer 15

•Widening of QRS complex ≥0.12s

Question 16

What does right bundle branch block look like?

Answer 16

•Seen as deep S waves in leads I and V6 and as a tall late R wave in leave V1

Question 17

What does left bundle branch block look like?

Answer 17

• A deeps S wave in lead V1 and a tall late R wave in leads 1 and V6
• Also produces abnormal Q waves