1. Arrhythmias

2. Rhythms and Arrhythmia
SA Node
Normal sinus rhythm
Sinus Bradycardia
Sinus Tachycardia
Sick Sinus Syndrome
Atria
Ectopic beats
Fibrillation
Flutter
Supraventricular tachycardia

3. Rhythms and Arrhythmia
AV Node
Reentrant tachycardia
1st 2nd 3rd degree blocks
Bundle branch block
Ventricles
Ectopic beats
Tachycardia
Preexitation
Ischemia

4. Normal Sinus Rhythm
Normal sequence of conduction, originating in the sinus node and proceeding to the ventricles via the AV node and His-Purkinje system.
EKG Characteristics: Regular narrow-complex rhythm

5. Sinus Tachycardia Aetiologies
Fever
Hyperthyroidism
Hypovolaemia
Anxiety
Pheochromocytoma
Sepsis
Anaemia
Exposure to stimulants (nicotine, caffeine) or illicit drugs (amphetamines)
Hypotension and shock
Pulmonary embolism
Acute coronary ischemia and myocardial infarction
Heart failure
Chronic pulmonary disease
Hypoxia

6. Sinus Bradycardia Sinus Bradycardia HR< 60 bpm
QRS is narrow and preceded by p wave
Can be normal in well-conditioned athletes at rest or children during sleep
So when is it not normal?
Is not normal if the sinus rhythm can’t increase with exercise

7. Sinus Bradycardia - aetiologies
Normal aging
15-25% following AMI
Sick sinus syndrome
Hypothyroidism
Hypothermia
Hypokalemia
Situational: micturation, coughing
Drugs: beta-blockers, digoxin, calcium channel blockers, amiodarone, lithium

8. Sick Sinus Syndrome Aetiology Symptoms Fibrosis
Atheroschlerosis of RC artery
SLE, collagen vasc diseases
Chagas disease - yeay
Injury, heart surgery
Infiltrative diseases
sarcoid
amyloid
Symptoms
Weakness
Palpitations
Syncope

9. Disorders of the SA Node
Sinus arrest
Tachycardia-bradycardia syndrome
Alternating brady-tachy causing palpitations
SA exit block
Normal SA impulse but conduction to atria is impaired

10. Atrial Ectopic Beats Ectopic P waves look abnormal
SA node continues regardless in compensatory delay
SA node timing is reset if premature SA firing caused by ectopic – non compensatory

11. Atrial Fibrillation
Constant conduction within the atria, multiple circuits, loss of contractility
Can be paroxysmal, persistent or permanent
1 in 5 strokes caused by AF: patients require anticoagulation therapy to prevent clot formation

12. Atrial Fibrillation Risk Factors Relative Risk History of hypertension
1.6
Heart failure and/or reduced left ventricular function
1.4
Advanced age
Diabetes
1.7
Coronary artery disease
1.5

13. Atrial Flutter Aetiology Pathophysilogy
30% have no underlying cardiovascular disease
30% CAD
30% hypertension
Pathophysilogy
Single reentrant circuit around the tricuspid valve
Distinctive sawtooth ECG

14. Supraventricular Tachycardias
Any tachycardic rhythm originating above the ventricles
It usually involves ectopic pacemaker cells or an accessory (reentrant) pathway

15. Mechanism of Reentry A: slow conduction, short RP
B: normal conduction and RP

16. SA Node Reentrant Tachycardia

17. AV Node Reentrant Tachycardia
Aetiology
Formation of “beta” pathway
Anxiety
Exertion
Caffeine, alcohol, drugs
Pathophysiology
Dual pathways within AV node
Alpha: fast, long RP
Beta: slow, short RP
Signs & Symptoms
Palpitation
Dizziness, syncope
Chest pain, angina (if coexisting CAD)

18. AV Node Reentrant Tachycardia

19. First Degree Block
If the PR interval is more than 1 small square then this is a 1st degree AV block
Not associated with morbidity or mortality but heralds a more severe block if MI occurs
Risk factor = age

20. Second Degree Block
A conduction delay within the AV node causing increasingly lengthened PR intervals until the node cannot transmit the signal to the ventricles (the Wenkebach phenominum)
Aetiology
Structural heart disease
Drugs: digoxin, Na, beta and Ca channel blockers, tricyclic antidepressants & lithium at toxic levels
Metabolic: hyperkalaemia, hypermagnesaemia, hyperthyroidism, Addison’s
Enhanced vagal tone due to pain, athletes at rest
A shit load more at
Mostly intranodal but poor prognosis if infranodal

21. Second Degree Block
Type I Wenckebach: P waves shown by arrows, lengthening PR interval
Type II: P waves shown by arrows, unpredictable non-conduction and loss of QRS

22. Third Degree Heart Block
Complete interruption of conduction from the atria
Ventricles show escape rhythms
Aetiology
Infectious: Endocarditis, rheumatic fever
Neuromuscular: muscular dystrophy
Drugs (see 2nd degree HB)
Rheumatic, infiltrative, metabolic, electrolyte ...

23. Third Degree Heart Block

24. BBB Normal P waves Normal PR interval
Widening of QRS to more than 0.12s because of delayed depolarisation of the ventricle

25. Ventricular Ectopic BEats
Premature beats originating within the myocardium
Distinctive tall, wide beats precede the P wave

26. VT Reentrant arrhythmia as a result of scarring of the myocardium
The rhythm can stabilise, revert spontaneously to sinus rhythm or lead to VF and death

27. Ventricular Preexitation
Associated with WPW syndrome
Accessory pathway Bundle of Kent allows early ventricular depolarisation forming a blunted Q wave called a delta wave and an abnormal T wave (last 2 beats below)

28. Myocardial Ischemia
Myocardial ischemia caused by narrowing of the coronary arteries results in ST depression
Below the depression is shown in the shaded areas

29. ECG Online Test