Introduction to Cardiac Arrythmias

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Introduction to Cardiac Arrythmias Arrythmia is a
generalized term used to denote disturbances in
the heart's rhythm. Normal sinus rhythm is
characterized by a regular rhythm and PR interval
duration range of 0.12 sec - 0.20 sec.  
Arrythmias can be recognized by evaluating the
EKG in a systematic manner. The following five
steps are offered as a guideline to assist you in
identifying arrythmias. It is important to
remember to treat the patient not the EKG. Find
out the Patient's history and use it in
conjunction with the EKG.    1.After finding
out the patient's medical history, begin by
labeling the P wave, PR interval, QRS complex, QT
interval and T wave. 2. Calculate
the atrial and ventricular heart rates.  A rate
of less than 60 beats per minute is slow (brady),
60-100 beats per minute is normal  and greater
than 100 beats per minute is fast (tachy) .
3. Determine if the rhythm is regular or
irregular. This is done by accessing whether the 
RR intervals and PP intervals are regularly
spaced.  Regular rhythm Irregular
rhythm If the rhythm is irregular,
determine if               i.   It is
occasionally irregular               ii.  
Regularly irregular (there is a pattern to the
irregularity)               iii.  Irregularly
irregular (there is no pattern to the
irregularity)
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4. Evaluate the waveform of the EKG in detail for
additional clues a. Determine the shape of the
P-wave. Normally, P-waves are upright and each P
wave is related to a QRS complex. If inverted,
the impulse is  spreading from the ventricles to
the atria in a retrograde manner.b. Determine if
the PR interval is of normal length (0.12-0.2
seconds).c. Examine the QRS complexes and
determine if the QRS complex is wide or narrow.
Narrow QRS complexes (less than 0.12 sec)
indicate that the rhythm is supraventricular
(originating from above the ventricles). Wide QRS
complexes (longer than 0.12 sec), indicate that
the rhythm is originating in the ventricles or
that there is an intraventicular
block.d. Determine if the ST segment is displaced
from the mid-line. 5. Review the patient's
medical history, assess the patient to ensure
that the assessment and rhythm agree. The
following EKG clues can be used to recognize
cardiac arrythmias in non sinus rhythm EKGs. If
the rhythm is regular but too fast or slow, it
could be an indication of either a. Sinus
bradycardia The rhythm is regular and looks
normal but is slower than 60 beats per minute.
The RR interval is longer, often more than one
second. P waves are present and regular and each
P-wave is followed by a QRS complex in a ratio of
11. b. Sinus tachycardia The  rhythm is
regular and looks normal but at a rate greater
than 100 beats per minute  The R-R interval is
shorter (usually less than 0.6 seconds). P waves
are present and regular and each P-wave is
followed by a QRS complex in a ratio of 11. If
the rhythm is irregular, check for the
following a. Atrial flutter. Atrial flutter
waves (F-waves) with a characteristic saw-tooth
form will also be observed at a rate of 200-350
BPM. b. Atrial fibrillation. No P-waves will
observable. Rather, a wavy base-line is recorded.
If there are no P-waves, it could be an
indication of either Sinus arrest with
junctional or ventricular escape. If P-waves are
not associated with QRS complexes, it could
indicate either 1. Ventricular tachycardia. 2.
Third degree AV block.