Chapter I Physiology of the Heart and Circulation System

Chapter II The Electrocardiogram and the Normal EKG

Chapter III Arrhythmia Determination

Chapter IV Arrhythmias and Select Disease Conditions

Chapter V The 12-Lead EKG

Conclusion

References

Course Exam

Arrhythmias

The normal EKG consists of repetitive series of P, Q, R, S, and T Waves, which conform to established standards for size and shape and occur 60 – 100 times each minute.  If these conditions prevail, the heart is in normal sinus rhythm.  When either the rate of the contour of any of the individual waves is abnormal, the disorder is called an arrhythmia.

Classifications of Arrhythmias:

There are several ways in which arrhythmias may be classified.  Perhaps the most logical method involves classification, first, by the site of the arrhythmia and secondly by the type of mechanism responsible for the disorder.

Sites

Mechanisms

SA Node (sinus rhythms)

Tachycardia (rate over 100 bpm)

Atrial (atrial rhythms)

Bradycardia (rate under 60 bpm)

AV node (nodal rhythms)

Premature beats

Ventricles (ventricular rhythms)

Flutter
Fibrillation
Defects in conduction.

Arrhythmias can also be classified in a general way according to their seriousness or prognosis.  This is a meaningful method for nurses caring for patients with acute Myocardial Infarction and the one we have found useful.

Using this division, arrhythmias may be considered as:

  1. Minor – these arrhythmia are not of the immediate concern and generally do not affect circulation.  They are important because they frequently reflect irritability of the heart.
  2. Major – these disturbances reduce the efficiency of the heart of warn of impending danger and require prompt treatment.
  3. Death Producing – Immediate resuscitation is needed to prevent death.

Identifying ECG Features – Sinus Arrhythmias

  1. Rate  (In Sinus Arrhythmias)

The heart rate per minute is normal (60-100); however, the rate increased during inspiration and then slows during expiration.

  1. Rhythm (In Sinus Arrhythmias)
    Irregular rhythm; there is a variation of at least 0.12 seconds between the longest and shortest R-R intervals.
  2. P Waves (In Sinus Arrhythmias)
    P Waves are normal.
  3. PR Interval (In Sinus Arrhythmias)
    Normal; each P Wave is followed by a normal QRS complex.
  4. QRS (In Sinus Arrhythmias)
    QRS is normal width

Sinus Arrhythmia:

Rate:

About 80/minute.

Rhythm:

There is a variation in R-R intervals of more than 0.12 seconds.

P Waves:

Normal

PR Interval:

Normal (0.12 second).

QRS:

Normal (0.04 second).

Comments:

The short R-R intervals occur during inspiration and the long R-R intervals during expiration.

Sinus Bradycardia

Sinus Bradycardia is an arrhythmia defined as a rate below 60 BPM with all beats remaining normal.  The SA node is still the pacemaker and the conduction pathway is still normal.  This rhythm can be normal during sleep, for athletes, for persons on certain medications and other reasons.  It can be an abnormal rhythm in certain conditions such as myocardial infarction or congestive heart failure, or if the rate falls so low as to cause clinical symptoms such as fainting of dizziness, etc.

Sinus Bradycardia Indentifying ECG Features

Rate:

Usually 40 – 50 /minute, but may be slower.

Rhythm:

Regular.

P. Waves:

Normal.

PR Interval:

Normal and each P wave are followed by a normal QRS complex.

QRS:

Normal

Example Sinus Bradycardia

Rate:

About 50/minute

Rhythm:

Regular.

P Waves:

Normal.

PR Interval:

Normal (0.16 second).

QRS:

Normal (0.08 second).

Comments:

The inverted T waves are not related to the arrhythmia; they result from myocardial ischemia.

Sinus Tachycardia

Sinus tachycardia is another sinus arrhythmia.  Causes of this condition are exercise, anxiety, fear, fever, and others.  If the tachycardia is secondary to another factor, such as above, usually no treatment is needed, as these conditions are usually temporary.  However, if clinical signs are seen, such as dizziness, fainting, or others, treatment may be indicated and perhaps more than just simple sinus tachycardia is present.

Sinus Tachycardia Identifying ECG Features

Rate:

Usually 100-150/minute.

Rhythm:

Regular.

P Waves:

Normal. (If the rate is very rapid, the P waves may not be clearly identified because they may encroach on the preceding T Waves.)

PR Interval:

Normal, indicating that conduction from the SA node through the ventricles is not disturbed.

QRS:

Normal

Example: Sinus Tachycardia

Interpretation of ECG

Rate:

About 120/minute

Rhythm:

Regular.

P Waves:

Normal.

PR Interval:

Normal (0.16 second), and each P wave is followed by a normal QRS complex.

QRS:

Normal (width is 0.06 second).

Comments:

Other than the rapid rate there are no abnormalities.

Example 2 Sinus Tachycardia

Next: Part II: Abnormal Rhythms