Arrhythmias- Bradycardias

Question 1

normal sinus rhythm is characterised by?

Answer 1

p wave preceding every QRS complex

Question 2

what are arrhythmias?

Answer 2

abnormal heart rhythms

Question 3

what are the only 3 normal heart rhythms?

Answer 3

• sinus rhythm
• sinus tachycardia
• sinus bradycardia

Question 4

definition of bradycardias?

Answer 4

<60bpm

Question 5

classification of bradycardias?

Answer 5

• sinus bradycardia
• heart block
  
  • 1st degree
  • 2nd degree
  • complete

Question 6

causes? mnemonic

Answer 6

DIVISIONS

Drugs

• anti-arrhythmics (type 1a, amiodarone)
• beta blockers
• ca channel blockers
• digoxin

Ischaemia / Infarction

Vagal hypertonia

• athletes
• vasovagal syncope
• carotid sinus syndrome

Infection

• viral myocarditis
• IE
• rheumatic fever

Sick sinus syndrome

Infiltration

• restrictive/dilated cardiomyopathy

O

• hypothyroidism
• hypokalaemia
• hypothermia

Neuro: raised ICP

Septal defect: osteum primum ASD / Surgery

Question 7

what is sick sinus syndrome?

Answer 7

structural damage / fibrosis to SAN, AVN or conducting tissue

Question 8

how does sick sinus syndrome present?

Answer 8

SVT alternating with either sinus bradycardia +/- arrest or SA/AV node block

Question 9

outline the classification of heart block

Answer 9

• 1st degree
• 2nd degree
  
  • mobitz type I
  • mobitz type II
• 3rd degree

Question 10

pathology of heart block?

Answer 10

damage to SA/AV node or His/Purkinje fibres

Question 11

symptoms of heart block?

Answer 11

syncope, SOB, HF

Question 12

pathology of 1st degree?

Answer 12

• delayed AV conduction through AV node
• every atrial impulse leads to ventricular contraction (every P wave = QRS complex)
• PR interval >0.2seconds

Question 13

what happens in 2nd degree?

Answer 13

some of the atrial impulses do not make it through to the ventricles

Question 14

pathology of Mobitz type I?

Answer 14

• PR interval gradually increases in length until there is a missed beat
• after failing to stimulate ventricular contraction, atrial impulse returns to being strong & cycle repeats

Question 15

pathology of Mobitz type II?

Answer 15

• interruption of AV conduction- results in missing QRS complexes
• PR interval remains normal
• risk of asystole
• usually set ratio of p waves to QRS (if it’s 3 it’s called 3:1 block)

Question 16

pathology of 3rd degree?

Answer 16

• complete heart block - no observable relationship between p waves & QRS
• significant risk of asystole

Question 17

Rx?

Answer 17

• Stable–> observe
• Unstable/risk of asystole
  
  1. Atropine 500mcg IV

Question 18

if there is no improvement w atropine?

Answer 18

• atropine 500mcg IV again (can give up to 6 doses- max 3mg)
• other inotropes ie noradrenaline
• transcutaenous cardiac pacing ie defib
  
  • any pts w symptomatic 2nd/3rd degree heart block should have this

Question 19

Rx in pts with high risk of asystole?

Answer 19

• temporary transvenous cardiac pacing
• permanent implantable pacemaker when available

Question 20

what kind of drug is atropine?

Answer 20

antimuscarinic- inhibits PNS