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P wave
- Represents time for the passage of the electrical impulse through the atrium causing atrial depolarization (contraction)
- should be upright
- 0.06-0.12 seconds
- Disturbance in conduction within atria
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PR interval
- Measured from beginning of P wave to beginning of QRS complex
- represents time taken for impulse to spread through the atria, AV node and bundle of His, the bundle branches, and Purkinje fibers, to a point immediately preceding ventricular contraction
- 0.12-0.20 seconds
- Disturbance in conduction usually in AV node, bundle of His, or bundle branches but can be in atria as well
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QRS complex
- Measured from beginning to end of QRS complex
- represents time taken for depolarization (contraction) of both ventricles (systole)
- <0.12 seconds
- Disturbance in conduction in bundle branches or in ventricles
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ST segment
- Measured from the S wave of the QRS complex to the beginning of the T wave
- represents the time between ventricular depolarization and repolarization (diastole)
- should be isoelectric (flat)
- 0.12 seconds
- Disturbances usually caused by electrolyte imbalances, ischemia, or infarction
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T wave
- Represents time for ventricular repolarization
- should be upright
- 0.16
- Disturbances usually caused by electrolyte imbalances, ischemia, or infarction
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How to calculate heart rate
- count the number of R waves in a 6-second strip and multiply by 10.
- PVCs are not counted on rhythm strip
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Analyze Rhythms
- Rate: 60-100 (WNL) <60 (brady) >100 (tachy) do atrial (P wave) and ventricle (QRS) rates match?
- Rhythm: regular, irregularly irregular
- P wave: present, one uniform infront of every QRS
- PR interval: 0.12-0.20
- QRS complex: <0.12
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Normal Sinus Rythm
- Rate: 60-100 bpm
- Rhythm: regular
- P waves: present; one uniform infront of every QRS complex
- PR interval: 0.12-0.20 second and constant from beat to beat
- QRS duration: <0.12 second
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Sinus Arrhythmia
- Rate: Usually 60-100 bpm, but may be slower or faster
- Rhythm: R-R vary. Rate changes with respiration
- P waves: present; one uniform infront of every QRS complex
- PR interval: 0.12-0.20 second and constant from beat to beat
- QRS duration: <0.12 seconds
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Sinus Bradycardia
- Rate: Less than 60 bpm
- Rhythm: P-P interval regular, R-R interval regular
- P waves: present; one uniform infront of every QRS complex
- PR interval: 0.12-0.20 second and constant from beat to beat
- QRS duration: <0.12 second
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Sinus Tachycardia
- Rate: Greater than 60 bpm
- Rhythm: P-P interval regular, R-R interval regular
- P waves: present; one uniform infront of every QRS complex
- PR interval: 0.12-0.20 second and constant from beat to beat
- QRS duration: <0.12 second
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Atrial Fibrillation
- Rate: atrial rate is unmeasurable. Ventrical rate <100 "controlled" >100 "rapid ventricular response" / "RVR"
- Rhythm: atrial rhythm is unmeasurable; ventricular rhythm is grossly irregular
- P waves: none; "fibrillatory" waves
- PR interval: none
- QRS duration: <0.12 second
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Ventricular Tachycardia
- Rate: 150-250
- Rhythm: usually regular
- P wave: none
- PRI: none
- QRS: 0.12 or greater wide and bizarre
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Ventricular Fibrillation
- Rate: cannot be determined
- Rhythm: baseline is totally chaotic
- P wave: none
- PRI: none
- QRS: none discernible
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Asystole
No electrical activity; only straight line
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Premature Ventricular Contraction (PVC)
- Rate: do not count PVCs
- Rhythm: underlying can be regular or irregular
- P waves: PVC not preceded by P wave
- PRI: none w/ PVC
- QRS: wide and bizarre; at least 0.12 second T wave is frequently opposite direction from QRS
- Multi-focal or unifocal
- **more than 6 PVCs / minute typically requires treatment**
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- Couplet PVCs
- Two PVCs in a row
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S&S / Tx
Bradycardia
- S&S: syncope & CHF
- tx: Atropine; epinephrine/dopamine; pacemaker may be needed
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S&S / Tx
Sinus Bradycardia
- S&S: decreased CO (lightheadedness, chest pain, CHF)
- Treat Cause (pain, hypovolemia)
- Tx: betablockers, calcium channel blockers, digoxin, cardioversion
- (rarely treated in emergency situation, always treat underlaying cause)
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S&S / Tx
Atrial Fibrillation
- S&S: decreased CO ( dizziness, fatigue, dyspnea)
- tx: control rate (digoxin, beta blockers *lopressor*, calcium channel blockers *diltiazem/cardizem*) convert and maintain sinus rhythm (antidysrhythmics *amiodarone/cordarone*) Cardioversion if meds do not work. (anticoagulants if pt has been in A-fib >48 hours; anticoagulation therapy recommended 3-4 weeks BEFORE cardioversion)
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