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29 Cards in this Set
- Front
- Back
Myocardial cells with Na+ dependent tissue
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atria, ventricles, purkinje fibers
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Myocardial cells with Ca++ dependent tissue
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sinus node, AV noda
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The heart's dominant center of automaticity and pacemaker that initiate cardiac electrical impulse during a normal cardiac cycle; generates a sinus rhythm
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SA node
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Defined as <50bpm caused by parasympathetic excess
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sinus bradycardia
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Defined as >100bpm caused by sympathetic stimulation
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sinus tachycardia
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Innervates and distributes depolarization to the left atrium
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Interatrial tract (bachman's bundle)
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Increases conduction rate and enhances transmission of impulses
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sympathetic stimulation
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Decreases conduction rate and prolongs the refractory period
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parasympathetic stiumulation
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Has highest conduction velocity
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purkinje fibers
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Represents atrial depolarization
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p wave
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Measures AV conduction time (0.12-0.20s)
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P-R interval
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Represents ventricular depolarization (0.06-0.1s)
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QRS complex
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Represents ventricular repolarization
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T wave
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Time between successive QRS complexes; measures the heart rate
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R-R interval
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Measures duration of repolarization (men=0.39s; women=0.41s)
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Q-T interval
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Rate <50bpm; R-R wave interval lengthened
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bradyarrhythmia
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Rate >100bpm; R-R wave interval shortened
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tachyarrhythmia
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Increases slope of phase 4 depolarization
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1) chemicals: catecholamines, digitalis glycosides
2) hypoemia or ischemia 3) hypokalemia 4) fiber stretch (cardiac dilatation) |
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Causes early afterdepolarization (EAD) during repolarization (phase 3)
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1) hypokalemia
2) antiarrhythmic drugs |
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Cause of drug-induced torsades de pointes
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antiarrhythmic agents
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Precipitates delayed afterdepolarization (DAD) that occurs after repolarization but prior to phase 4 of AP
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1) catecholamines
2) digitalis glycosides |
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Requirements for a formation of a reentrant focus
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1) 2 pathways for impulse conduction
a)area of uni block (prolonged refractoriness) in one of the pathways b)slow conduction of other pathway 2)premature impulse |
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Precipitates atrial premature complexes
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alcohol, tobacco, adrenergic stimulation
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Originates in atrial ectopic focus and causes rapid but regular atrial activation; P waves occur in rapid succession and each is identical to the next (saw tooth); 1/2 or 1/3 atrial depolarizations reaches the ventricles
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atrial flutter
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Characteristics include a continuous, rapid-firing of multiple foci in the atria; only an occasional impulse gets through the AV node to stimulate the ventricles producing an irregularly, irregular ventricular rhythm
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Atrial fibrillation
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ECG shows no P waves; continuous chaotic atrial spikes
ECHO shows LV dysfunction, valvular heart disease, atrial enlargement, presence of left atrial thrombus |
Atrial fibrillation
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Clinical presentation varies with the:
1)ventricular rate 2)underlying functional state of heart 3)duration of condition |
Atrial fibrillation
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What patients have highest recurrence rates of Afib?
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1)>1 year AF
2) larget left atrial size (>65mm) 3) multiple previous drug failures |
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Symptoms of rapid ventricular rate
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hypotension, HF, and angina due to decrease in CO
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