1. Abnormal cardiac rhythms can originate from the atria, AV node region, or ventricles. Rhythms originating above the ventricles have narrow QRS complexes, while those from the ventricles have wide complexes. 2. Abnormal rhythms can be categorized as tachycardias, extrasystoles, bradycardias, or fibrillation depending on whether they are fast/slow and sustained or isolated beats. 3. Examples of abnormal rhythms discussed include atrial escape, junctional escape, ventricular escape, sinus arrhythmia, sinus pause, SA block, and extrasystoles.

1. Dr. Abdulkadir Insi, MD

2. Abnormal rhythm
• Abnormal cardiac rhythms can begin in one of
three places:
1. The atrial muscle
2. The region around the AV node (this is called
junctional)
3. Ventricular muscle
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4. • These regions can be divided into:
1. Supraventricular: sinus rhythm, atrial rhythm
and junctional rhythm
2. Ventricular rhythm
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5. • In the supraventricular rhythms, the
depolarization wave spreads to the ventricles in
the normal way via the His bundle and its
branches.
• Therefore the QRS complex is normal, and is
the same whether depolarization was initiated by
the SA node, then atrial muscle, or the junctional
region.
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7. • In the ventricular rhythms, the depolarization
wave spreads through the ventricles by an
abnormal, and therefore slower, pathway through
the purkinje fibers.
• So the QRS complex is wide and abnormal.
• Repolarization is also abnormal, so the T wave is
of abnormal shape.
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9. Remember!
1. SV rhythms have narrow QRS complexes
2. Ventricular rhythms have wide QRS
complexes
3. The only exception to this rule occurs when
there is SVR with RT or LT BBB
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10. oAbnormal rhythms arising in the atrial muscle,
the junctional region or the ventricular muscle
can be categorized as:
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11. 1. Tachycardias: fast and sustained
2. Extrasystoles: occur as early single beats
3. Bradycardias: slow and sustained
4. Fibrillation: activation of the atria or ventricles
is totally disorganized.
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12. Atrial escape
• Def.: rate of depolarization of the SA node
slows down and a focus in the atrium takes
over control of the heart.
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13. oAfter one sinus beat the SA node fails to
depolarize
oAfter a delay, an abnormal P wave is seen
because excitation of the atrium has begun
somewhere away from the SA node
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14. oThe abnormal P wave is followed by a normal
QRS complex, because excitation has spread
normally down the His bundle.
oThe remaining beats show a return to sinus
arrhythmia
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16. Junctional escape
• Starts with sinus rhythm,
• Then sudden loss of P waves (indicates either
no atrial contraction or P wave lost in QRS
complex)
• Normal QRS complexes
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18. Ventricular escape
• Most commonly seen when conduction between
the atria and ventricles is interrupted by
complete heart block.
• It can occur without complete heart block and
can be single.
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19. Ventricular escape with complete HB
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20. Ventricular escape without comp. HB
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21. Sinus Arrhythmia
• The SA node discharges irregularly.
• The R-R interval is irregular.
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22. ♥ Clinical Tip
• The pacing rate of the SA node varies with respiration,
especially in children and elderly people.
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23. Sinus Pause (Sinus Arrest)
■ The SA node fails to discharge and then resumes.
■ Electrical activity resumes either when the SA
node resets itself or when a lower latent pacemaker
begins to discharge.
■ The pause (arrest) time interval is not a multiple
of the normal P-P interval.
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25. ♥ Clinical Tip
• Cardiac output may decrease, causing syncope
or dizziness.
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26. Sinoatrial (SA) Block
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The block occurs in some multiple of the P-P
interval.
After the dropped beat, cycles continue on time.

27. ♥ Clinical Tip
• Cardiac output may decrease, causing syncope
or dizziness.
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28. Extrasystoles
• Atrial extrasystoles have abnormal P waves.
• Junctional extrasystole either is no P wave at all, or
it appears immediately before or immediately after
the QRS complex.
• QRS complexes of atrial and junctional
extrasystoles are the same as those of sinus rhythm.
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29. • Ventricular extrasystoles, however, have
abnormal QRS complexes, which are typically
wide but can be of almost any shape.
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32. • The effect of SV and ventricular extrasystoles on the
following P wave are as follows:
SV extrasystole resets the P wave cycle
Ventricular extrasystole does not affect the SA node,
so the next P wave appears at the predicted time.
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33. SV extrasystole
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34. Ventricular extrasystole
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35. Tachycardia
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36. ♥ Clinical Tip
SVT may be related to caffeine intake, nicotine, stress,
or anxiety in healthy adults.
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