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Path Pharm Arrythmias

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xibocutie's version from 2017-03-19 21:53

Section

Question Answer
Delayed afterdepolarizations occur in what phase?Phase 4
What causes delayed afterdepolarizations?Calcium overload, such as with digoxin toxicity or when cardiac cells are metabolically stressed. Here SR overloaded with Ca and may release some sponatenously following repolarization. This causes extrusion of Ca by Na-Ca and an inward positive current. This current can generate a new action potential if threshold is reached.
Another common cause of cardiac arrythimias is reentry. Explain reentry. occurs when an impulse travels through one location and the returns via a pathway that is not part of the normal cardiac conduction system.
What triggers reentry?A premature beat usually that blocks one of the pathways
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Vaughan-Williams Classification of Anti-Arrhythmic Drugs

Question Answer
Class ISodium Channel Block- sodium channel blockers
Class IIB-adrenergic receptor block - B-Blockers (especially B1 sensitive)
Class IIIProlongation of the AP - potassium channel blockers
Class IVCalcium Channel block- Calcium blockers/antagonists
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