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Arrhythmias

Arrhythmias. Rhythms and Arrhythmia. SA Node Normal sinus rhythm Sinus Bradycardia Sinus Tachycardia Sick Sinus Syndrome Atria Ectopic beats Fibrillation Flutter Supraventricular tachycardia. Rhythms and Arrhythmia. AV Node Reentrant tachycardia 1 st 2 nd 3 rd degree blocks

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Arrhythmias

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  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 http://www.youtube.com/watch?v=zbDtMtJyVtI

  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 http://www.youtube.com/watch?v=Yff9VvNGL5w&feature=related

  8. Sick Sinus Syndrome • Aetiology • 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

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

  14. SupraventricularTachycardias • Any tachycardic rhythm originating above the ventricles • It usually involves ectopic pacemaker cells or an accessory (reentrant) pathway • http://www.youtube.com/watch?v=Y7QdOBYeAS4

  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 withinor alongside the node and exacerbated by • Anxiety • Exertion • Caffeine, alcohol, drugs • 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 large square (0.2s) then this is a 1st degree AV block • Not associated with morbidity or mortality but foreshadows 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 Wenkebachphenominum) • 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 http://emedicine.medscape.com/article/161919-overview • 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 • http://www.andrews.edu/~schriste/HealthTeaching/Practice/Sinus_and_Atrial/si01.html

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