Term
| what does the rate of phase 0 of ventricular action potential depend on and what affect does extracellular potassium concentration have on the rate? |
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Definition
the rate depends on the extent of depolarization
hyperkalemia causes the cells to be less polarized and the rate is more gradual
hypokalemia causes the cells to be more polarized and the rate is more rapid |
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Term
| list the different parts of normal sinus rhythm. |
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Definition
heart rate between 60-100 bpm
equal spacing between R waves
P to QRS ratio of 1:1
PR interval b/w 0.12 and 0.2 sec
QRS complex width less than 0.12 sec |
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Term
| what does positive deflection of a P wave in leads I and aVF tell you? |
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Definition
| that the impulse is being generated from the SA node and traveling right to left, superior to inferior |
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Term
| what are the differences between primary, secondary, and tertiary AV block? |
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Definition
primary - has a longer PR interval, but P : QRS = 1:1
secondary - some p waves are conductive but not all
P : QRS not = 1:1
tertiarty - P wave and QRS have separate rates |
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Term
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Definition
the heart rate varies with respiration,
HR increases with inspiration (sympathetic) and decreases with exhalation (parasympathetic) |
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Term
| define overdrive suppression. |
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Definition
| says that the SA node has the fastest impulse rate, and the other pacemaker cells of the heart have incrementally slower rates. as the heart rate slows the next pacemaker takes over control of HR |
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Term
| what is the difference between regular and irregular arrhythmias? |
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Definition
regular involves a consistant dropped or added beat
irregular has no consistency |
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Term
| what is the difference between escape and premature beats? |
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Definition
escape beats involve overdrive suppression and are usually preceded by a pause between beats
whereas premature beats usually occur early in the rhythm and are often followed by a pause |
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Term
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Definition
| a rate disturbance associated with heart rates over 100 bpm. |
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Term
| what are some irregular rhythms and what do they look like on an EKG? |
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Definition
wandering pacemaker - irregular rhythm, varying P waves (but all conductive), rate < 100. means that different parts of atria initiate contraction
multifocal atrial tachycardia - irregular rhythm, varying P waves (but all conductive), rate > 100. similar to wandering, but faster rate
atrial fibrillation - continuous chaotic atrial spikes with irregular ventricular rhythm
ventricular fibrillation - continuous chaotic ventricular spikes that vary in width and amplitude, no discernable P waves |
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Term
| describe the difference between escape rhythm and escape beat. |
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Definition
rhythm involves escape from overdrive suppression and a new heart rate is established
beat involves escape from overdrive suppression for only one beat and then a return to normal rhythm |
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Term
| list some common escape rhythms and how do they appear on an EKG? |
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Definition
atrial escape rhythm - reduced heart rate with regular QRS, different P waves from sinus rhythm
junctional escape rhythm - lack of P wave (or inverted), regular QRS, reduced rate
ventricular escape rhythm - wide QRS, P wave is consistent but not conductive, QRS is slower and regular |
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Term
| define atrial bigeminy and trigeminy. |
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Definition
they involve premature atrial beats occurring at regular rhythms, QRS is normal in duration
bigeminy has a premature beat every second beat
and trigeminy has a premature beat every third beat |
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Term
| what are the signs of a premature ventricular contraction on an EKG? |
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Definition
| an early beat with a wide QRS that is not preceded by a P wave |
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Term
| what are the signs of a premature junctional beat on an EKG? |
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Definition
| an early beat with a QRS of normal duration that is not preceded by a P wave, but instead contains an inverted P wave after the QRS |
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Term
| what is paroxysmal tachycardia and what does it look like on an EKG? |
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Definition
| it is a very irritable automaticity focus that suddenly paces rapidly, it is characterized by a normal rhythm and then a premature beat that results in tachycardia |
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Term
| what are the three types of paroxysmal tachycardia and how do they appear on an EKG? |
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Definition
atrial - sudden tachycardia with productive P waves and normal QRS durations
junctional - sudden tachycardia with no P waves (or retrograde P waves) and normal QRS durations
ventricular - sudden tachycardia with no P waves and wide QRS complexes |
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Term
| what is torsades de pointes and what is it indicative of? |
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Definition
it is characterized by an EKG rhythm that has a ribbon like appearance with increasing and decreasing amplitudes
it indicates drug toxicity |
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Term
| describe atrial and ventricular flutter. |
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Definition
atrial flutter is characterized by very rapid and weak atrial contraction, producing many P waves with a slower and consistent ventricular response
ventricular flutter is characterized by very rapid and weak ventricular contractions that produce rapid and wide QRS waves |
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Term
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Definition
| occurs when multiple foci of the atria or ventricles discharge rapidly |
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