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29 Cards in this Set

  • Front
  • Back
Myocardial cells with Na+ dependent tissue
atria, ventricles, purkinje fibers
Myocardial cells with Ca++ dependent tissue
sinus node, AV noda
The heart's dominant center of automaticity and pacemaker that initiate cardiac electrical impulse during a normal cardiac cycle; generates a sinus rhythm
SA node
Defined as <50bpm caused by parasympathetic excess
sinus bradycardia
Defined as >100bpm caused by sympathetic stimulation
sinus tachycardia
Innervates and distributes depolarization to the left atrium
Interatrial tract (bachman's bundle)
Increases conduction rate and enhances transmission of impulses
sympathetic stimulation
Decreases conduction rate and prolongs the refractory period
parasympathetic stiumulation
Has highest conduction velocity
purkinje fibers
Represents atrial depolarization
p wave
Measures AV conduction time (0.12-0.20s)
P-R interval
Represents ventricular depolarization (0.06-0.1s)
QRS complex
Represents ventricular repolarization
T wave
Time between successive QRS complexes; measures the heart rate
R-R interval
Measures duration of repolarization (men=0.39s; women=0.41s)
Q-T interval
Rate <50bpm; R-R wave interval lengthened
Rate >100bpm; R-R wave interval shortened
Increases slope of phase 4 depolarization
1) chemicals: catecholamines, digitalis glycosides
2) hypoemia or ischemia
3) hypokalemia
4) fiber stretch (cardiac dilatation)
Causes early afterdepolarization (EAD) during repolarization (phase 3)
1) hypokalemia
2) antiarrhythmic drugs
Cause of drug-induced torsades de pointes
antiarrhythmic agents
Precipitates delayed afterdepolarization (DAD) that occurs after repolarization but prior to phase 4 of AP
1) catecholamines
2) digitalis glycosides
Requirements for a formation of a reentrant focus
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
Precipitates atrial premature complexes
alcohol, tobacco, adrenergic stimulation
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
atrial flutter
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
Atrial fibrillation
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
Clinical presentation varies with the:
1)ventricular rate
2)underlying functional state of heart
3)duration of condition
Atrial fibrillation
What patients have highest recurrence rates of Afib?
1)>1 year AF
2) larget left atrial size (>65mm)
3) multiple previous drug failures
Symptoms of rapid ventricular rate
hypotension, HF, and angina due to decrease in CO