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SA Node rate...
AV Node rate...
Bundle of HIS rate...
QT Interval. Normal range?
From beginning of Q to the end of the T wave. Represents total ventricular activity. Normal range= 0.44 or >
represents ventricular repolarization
End of the S wave, beginning of the T wave
R & S waves represent?
R & S waves represent the depolarization of the L & R ventricles.
Negative waveform that follows the R wave.
First positive deflection following the P Wave or Q wave (if present). Always appears as a positive waveform.
a negative deflection following the P wave. Always appears as a negative waveform.
QRS Complex. Normal range?
- Represents the depolarization of the ventricles and HR.
- Normal range= 0.06- 0.12
PR Interval. What is the normal range?
- From the beginning of the P wave to the beginning of QRS Complex. Reflects the impulse travel time from the SA node through the AV node, HB, R & L bundles, and into the Purkinje fibers.
- Normal range= 0.12- 0.20
P wave represents...
atrial depolarization and spread of impulse across the L & R atria
EKG paper: Small squares?
Small square: 1mm x 1mm, 0.04 sec
EKG paper: Large squares?
Large square: 5mm x 5mm, 0.2 sec
Relative Refractory Period
"Vulnerable Period" because cells are repolarizing and can be stimulated (if stimulus is strong enough) thus possibly resulting in ventricular chaos. Downslope of T wave.
Absolute Refractory Period
From the onset of QRS to approximately the peak of T wave. Cells are depolarized and cannot be stimulated.
- Normal electrical activity.
- Impulse originates in the SA node & follows the normal pathway of conduction, resulting in atrial & ventricular depolarization
SA node discharges impulses fewer than 60 beats/min. Originates in the SA node and follows the normal pathway of conduction.
Occurs when the SA node discharges irregularly
Junctional Escape Rhythm
- Originates from the AV junction & is considered an SV rhythm.
- 40-60 bpm
- Usually regular.
Accelerated Junctional Rhythm
- An ectopic rhythm caused by altered automaticity in the Bundle of His.
- 60-100 bpm
- Usually initiated by a few PJCs.
Three or more sequential PJCs occurring at 100/min or more is considered JT (100-180 bpm).
Paroxysmal junctional tachycardia (PJT)
- When JT starts & ends suddenly, it is called paroxysmal junctional tachycardia (PJT) & is often initiated by a PJC.
- When JT is >150 bpm, often difficult to distinguish JT from AT since P waves are not easily seen - then rhythm is called supraventricular tachycardia (SVT)
Multifocal Atrial Rhythm (MFAR)
P waves vary in size, shape, & direction across the rhythm strip. Need to identify 3 different P wave shapes in the same lead to call the rhythm MFAR.
SVT & Atrial Tachycardia (AT)
SVT can be called atrial tachycardia if a visible P wave (atrial activity) is present.
Paroxysmal Supraventricular Tachycardia(PSVT)
Describes an SVT that starts & stops suddenly.
Atrial Flutter (A Flutter)
- An irritable atrial site depolarizes regularly at an extremely rapid rate (250-350 bpm).
- Results in waveforms that resemble the teeth of a saw or a picket fence.
Atrial Fibrillation (A Fib)
- Multiple atrial ectopic sites initiate rapid impulses (350-600 bpm) which causes ineffectual atrial contraction or quiver (fibrillate).
- Results in subsequent decrease in CO, loss of “atrial kick”, & risk of clot formation.