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Arrhythmias

Arrhythmias. Cardiac dysrhythmia. Cardiac dysrhythmia (arrhytmia) Abnormal electrical activity in the heart. Electrical conduction system of the heart. Sinus node. AV node. Bundle of His. Left bundle branch. Internodal pathways. Right bundle branch. Purkinje fibers.

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Arrhythmias

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  1. Arrhythmias

  2. Cardiac dysrhythmia • Cardiac dysrhythmia (arrhytmia) • Abnormal electrical activity in the heart

  3. Electrical conduction system of the heart Sinus node AV node Bundle of His Left bundle branch Internodal pathways Right bundle branch Purkinje fibers

  4. The effect of autonomic nervous system sympathetic parasympathetic heart rate (chronotropic) b1 increases decreases contractility (inotropic) b1 increases decreases conduction in AV node b1 increases decreases (dromotropic) excitability (bathmotropic) increases decreases

  5. Cardiac action potential

  6. Phase 4 Phase 4

  7. Phases of the cardiac action potential • Phase 0 – rapid depolarization phase - Na+ channels • Phase 1 – K+ and Cl- channels • Phase 2 – „plateau“ - Ca2+ channels • Phase 3 – rapid repolarisation - K+ channels • Phase 4 – resting potential (diastole) - K+ channels, 3Na+-2K+-ATPase, Ca2+-ATPase, 3Na+-1Ca2+-exchager

  8. SA node action potential Phase 4 spontaneous diastolic depolarisation Ca2+ channels

  9. ECG P wave – atrial depolarisation PR segment – delay in the AV node QRS complex – ventricular depolarisation T wave – ventricular repolarisation

  10. Ethiology • Ischaemia, acidosis – coronary artery disease • Ion disbalance – hypo-/hyperkalemia... • Heart diseases – myocarditis, cardiomyopathies • Autonomic nervous system dysbalance • Thyroid diseases – hypo-/hyperthyreosis • Toxins and drugs – caffeine, digitalis • Other diseases – anaemia • Genetic mutation • Age

  11. Mechanisms of arrythmias • Increased automaticity • Increased normal automaticity (in SA node) • Abnormal automaticity (ectopic focus) • Triggerd activity • Early afterdepolarization • Delayed afterdepolarization • Reentry

  12. Increased automaticity • Increased automaticity - classification • Increased normal automaticity (in SA node) • Abnormal automaticity (ectopic focus) Automaticity –ability to generate impuls • Increased normal automaticity– hyperirritability of SA node – faster activation of SA node • Abnormal automaticity (ectopic focus) – hyperirritability of other myocardial cells (e.g. ventricular cells)

  13. threshold membrane potential • Mechanisms Faster spontaneous depolarization (catecholamines) More rapid slope of spontaneous depolarization (SA) or resting potential (e.g. ventricular cells) Increased resting membrane potential (ischemia – lower activity of Na/K-ATPase)  resting potential leads to earlier threshold membrane potential Decreased threshold membrane potential = earlier threshold membrane potential

  14. Triggerd activity Characterization: abnormal phase of repolarization in the previous impuls leads to earlier new depolarization 2 types: Early afterdepolarization • New depolarization appears in phase 3 of previous action potential • Cause: slower repolarization – e.g. because of hypokaliemia Delayed afterdepolarization • New depolarization appears in phase 4 of previous action potential but sooner than normal • Cause:  intracellular Ca concentration (digitalis)

  15. Reentry • Circulation of the impulse Possible mechanisms • Shorter refractory period • 2 places in the heart are connected with 2 ways for impulse. In the case of blocade of one way (extra beat, scar) – impulse is conducted by one way, returns by the second one and starts circulate • The way for impulse is longer than refractory period (hyperthrophy) • Atrioventricular reentry impulse returns through accessory pathway (WPW syndrome)

  16. Inherited arrhytmias Long QT syndrome • Mutations (AD) of ion channels (K+, Na+, Ca2+ ) genes • Ventricular extra beats, ventricular tachycardia • Unconsciousness, synkope, ventricular fibrilation, sudden death • SADH – sudden arrhytmia death syndrome

  17. Signs • Electrical • Changes in the ECG • Haemodynamic • Decreased preload • Decreased minute heart output • Clinical • Syncope • Palpitation • Sudden cardiac death

  18. Classification • Mechanism • Disorders of impulse generation • Disorders of impulse conduction • Combined • Site of origin • Supraventricular • Sinus • Atrial • Junctional • Ventricular • Rate • Tachycardia • Bradycardia

  19. Disorders of impulse generation

  20. Sinus arrhytmias • Sinus tachycardia • rate > 100 bites/min. (normal 60 – 100bites/min.) • physiological – newborns and children, physical activity, stress • drugs – catecholamines • diseases – hyperthyreosis, anaemia... • Sinus bradycardia • rate < 60 bites/min. • physiological – sportsmen • diseases – hypothyreosis...

  21. Sinus arrhytmias • Premature sinus contraction (Sinus extra beat) • Sinus arrhytmia • physiological – breathing • Sick sinus syndrome • inherited • coronary artery disease • hypertension • idiopathic • Sinus arrest

  22. Atrial arrhytmias • Premature atrial contraction (extra beat) • Atrial rhythm • Atrial (supraventricular) tachycardia • Atrial flutter • Atrial fibrilation

  23. Junctional arrhytmias • Premature junctional contraction (extra beat) • Junctional rhythm • Junctional (supraventricular) tachycardia

  24. Ventricular arrhytmias • Premature ventricular contraction (extra beat) • Accelerated idioventricular rhythm • Ventricular tachycardia • Polymorphic ventricular tachycardia • Ventricular fibrilation

  25. Disorders of impulse conduction

  26. Heart blocks (AV blocks) • 1st degree • 2nd degree • type 1 (Mobitz I, Wenckenbach) • type 2 (Mobitz II) • 3rd degree

  27. Left bundle branch block Right bundle branch block

  28. Wolff-Parkinson-White syndrome

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