NURS 3375 Critical Care Exam 2 notes NURSING OF
ADULTS WITH COMPLEX NEEDS University of Texas at
Arlington
Critical Care Exam 2
Dysrhythmias
Basic Heart Information
- Purpose of the heart is to “beat on and on”. Any cell can initiate depolarization & the rest of the
cardiac cells may follow (like the wave)
o SA node: primary pacemaker -> 60-100
o AV node: secondary pacemaker -> 40-60
o Purkinjie fibers: can pace at 15-40 if upstream conduction is compromised
- Depolarization: electrical charge changes -> cells goes to work
- Repolarization: electrical charge returns to “normal” -> cell is resting
- The first heart cell depolarizes -> goes to work -> stimulates the next cell to depolarize -> in a wave of
electrical activity -> this electrical wave can be seen on the monitor -> each “blip/bump” on the
ECG/EKG paper means electrical activity of a given group of cardiac cells
- SA node fires -> impulse travels thru the atria (atrial depolarization) -> pauses at the AV node to allow
atria to contract (PRI) -> impulse sent down from the AV node/junction to the ventricles -> impulse travel
thru the ventricles (ventricular depolarization = QRS) -> ventricle contraction (pulse) -> ventricular relax (T
wave)
o Key point: AV node/junction is the messenger between the atria & the ventricles. WITHOUT
the AV node, the impulse will NOT go to the ventricles
- P wave: atrial depolarization -> if you see an
upright P wave -> the beat originated from the SA
node -> the first name of your rhythm will be
“sinus”
- QRS: ventricular depolarization -> ventricle ready
to work = beat/bump
o Normal QRS: ≤12 seconds
o If narrow, rhythm first name is atrial
o If wide, rhythm first name is ventricular
- T wave: ventricular repolarization -> ventricle
is resting
- PR interval (PRI): the time interval for the atria to…
o Contract (pump the last bit of blood into the ventricles from the atria)
o Allows the electrical impulse (electrical wave) to be sent on down to the ventricle
o Normal PR: 0.12-0.20 seconds
- Rate: <60 bradycardia; >100 tachycardia
o 6 second strip: count the Rs in the strip & multiply by 10
o Count the number of little bitty boxes between the Rs and divide by 1500
ECG Interpretation:
1. Are the P waves upright? Yes, the impulse most likely originated in the SA node, the first name of
the rhythm will be sinus
2. Is there a P wave before each QRS complex & QRS for every P wave? No, consider a block
3. What is the PR interval? Normal PRI is 0.12-0.20 seconds
4. What is the width of the QRS? Normal QRS is ≤12 seconds. If narrow, rhythm name is atrial. If
, wide, rhythm name is ventricular
5. What is the rate? <60 brady, >100 tachy
a. Easy way: count the R waves & multiply by 10. Works if you have a 6 second strip
b. Not sure you have a 6 second strip. Count small squares between R waves & divide by 1500
6. Regular or irregular?
7. What is the rhythm?
, Sinus Rhythm
- Sinus rhythm: rhythm originating from the SA node
- Normal sinus rhythm (NSR): normal
o Rate: 60-100
o Rhythm: regular
o P wave: upright, round, consistent in shape, seems paired with QRS complex
o PR interval: 0.12-0.20 seconds
o QRS: ≤12 seconds
- Sinus bradycardia: SA node fires at slower rate resulting in slower rhythm
o Rate: <60
o Rhythm: regular
o P wave: upright, rounded, consistent in shape, seems paired with QRS complex
o PR interval: 0.12-0.20 seconds
o QRS: ≤12 seconds
- Sinus tachycardia: increase in the rate of firing of the SA node, resulting in faster rhythm
o Rate: >100
o Rhythm: regular
o P wave: upright, rounded, consistent in shape, seems paired with QRS complex
o PR interval: 0.12-0.20 seconds
o QRS: ≤12 seconds
Atrial Rhythm
- Atrial rhythm: rhythm originating in the atria, but NOT from the SA or AV nodes
- Atrial fibrillation: totally irregular rhythm may be rapid or slow, depending upon the ventricular
response rate. The P waves cannot be identified, only the chaotic electrical activity referred to as the “f”
(fibrillatory) waves is occurring in the atria
o P waves: N/A, just looks like wavy base. Idk if it’s P or T waves
o PR interval: N/A, unable to calculate
o QRS: usually normal
- Atrial flutter: kinda looks like shark teeth or ocean waves
o P wave: N/A, looks like shark teeth or ocean waves
o PR interval: N/A
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