Management of Patients With Dysrhythmias and
Conduction Problems Med-Surg Study Guide
, Normal Sinus Rhythm
Normal sinus rhythm occurs when the electrical impulse starts at a regular rate and rhythm in the SA node and
travels through the normal conduction pathway the AV node and bundle of His, bundle branches and Purkinje
fibers.
EKG Strip
Normal sinus rhythm has the following characteristics:
Ventricular and atrial rate: 60 to 100 bpm in
the adult.
Ventricular and atrial rhythm: Regular
QRS shape and duration: Usually normal, but
may be regularly abnormal.
P wave: Normal and consistent shape; always
in front of the QRS.
PR interval: Consistent interval between 0.12
and 0.20 seconds.
P:QRS ratio: 1:1.
Depolarization and repolarization of the atria and ventricles show up as 3 distinct waves on ECG.
A unique labelling system is used to identify each wave.
Although the diagram shows 5 waves, we will concentrate on 3 waves. You will not always see a Q
wave or an S wave on an ECG.
This is why only 3 waves are emphasized when you are learning from scratch.
Waveforms
, P wave:
Reflects conduction of an electrical impulse
starting in the SA node and spreading through the
atria.
represents atrial depolarization.
QRS Complex:
Presents depolarization or contraction of the
ventricles.
Not all QRS complexes have all three waveforms.
Q wave
First negative or downward deflection of this
large complex
R wave
First upward or positive deflection following the
P wave (tallest waveform)
S wave
3 things to look for in P waves in a rhythm strip
The sharp, negative or downward deflection that
are:
follows the R wave
T wave: Are there P waves before each QRS
Produced by ventricular repolarization or complex?
relaxation. Are there any P waves that do not have a
Commonly seen as the first upward or positive QRS complex that follows?
deflection following the QRS complex. Do all the P waves look the same / have the
same shape?
U Wave:
Usually not visible on EKG strips.
If visible, typically follows the T wave.
Appears much smaller than T wave, rounded,
upright, or positive deflection is they are present.
although this wave is rare, it sometimes appears in
pt’s w/ hypokalemia (low K levels), hypertension,
or heart disease.
Intervals
PR:
measured from the beginning of the P wave to the
beginning of the QRS complex
represents the time needed for sinus node
stimulation, atrial depolarization, and conduction
through the AV node before ventricular
depolarization
RR interval:
the duration between the beginning of one QRS
complex and the beginning of the next QRS
complex; used to calculate ventricular rate and
rhythm
QT:
represents the total time for ventricular
depolarization and repolarization
measured from the beginning of the QRS complex
to the end of the T wave.
The QT interval varies with heart rate, gender, and
age; therefore, the measured interval needs to be
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