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Arrhythmias Chapter 20

Arrhythmias Chapter 20. Arrhythmias. Result when disturbance of rate and/or rhythm occur - leads to abnormal contraction Proper function depends on movement of ions across cell membrane (K, Na, Ca, Cl). Action Potential ( Fig. 20-1). O-ventricular depolarization (Na enters), QRS

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Arrhythmias Chapter 20

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  1. Arrhythmias Chapter 20

  2. Arrhythmias • Result when disturbance of rate and/or rhythm occur - leads to abnormal contraction • Proper function depends on movement of ions across cell membrane (K, Na, Ca, Cl)

  3. Action Potential ( Fig. 20-1) • O-ventricular depolarization (Na enters), QRS • 1- “overshoot” contraction occurs (Ca enters) • 2 - “plateau” (slow Na and Ca in and K out) • 3 - Repolarization T wave • 4 - Na moves out of cell and k into cell, some cells stay this way until next impulse (e.g. ventricles), other cells reach threshold and then spontaneously depolarize all over again (e.g. sinoatrial node)

  4. Automaticity • Ability of cells to depolarize spontaneously (AKA pacemaker cells) • SE and AV nodes and His-Purkinje system (HPS) are examples of pacemakers • SA is dominant -reaches threshold faster than others, depolarizes 60-100/minute • AV and HPS - ~ 40-60/minute, these are over-ridden by SA node in healthy heart

  5. Classification of Arrhythmias • Above bundle of HIS are supraventricular • includes sinus bradycardia, sinus tachycardia, paroxysmal supraventricular tachycardia, atrial flutter, atrial fibrillation, Wolff-Parkinson-White (WPW) and premature atrial contractions (PACs) • The QRS is normal (ventricular depolarization is normal), unless there is a block • Sinus bradycardia -can be from athletic conditioning, tachycardia - during exercise these are arrhythmias but not pathologic • Below bundle of His -ventricular arrhythmias • PVC (premature Ventricular contractions), Ventricular tachycardia (VT), ventricular fibrillation (VF)

  6. Classification of Arrhythmias continued • Conduction blocks -classified by site - supraventricular (1st, 2nd, 3rd degree ) ventricle (right or left bundle branch) • < 60 BPM - bradyarrhythmia • > 100 BPM - tachyarrhythmia

  7. Antiarrythmics (Table20-3) • 4 drug classes • Class I - Na channel blockers • Ia - intermediate • Ib - quick • Ic - long • Class II B-blockers • Class III - K channel blockers • Class IV- calcium channel Blockers

  8. Arrhythmias • Result when disturbance of rate and/or rhythm occur -> leads to abnormal contraction

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