Difference between revisions of "Electrocardiography"

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* Prolongation can be a normal variant: 67,00 healthy airmen studied and .52% found to have a prolonged PR. 80% of the PR prolongations ranged from .21 to .24 (4).  In a second study 59 of 19,000 (.31%) airmen had a PR of .24 or more (5). <br>
 
* Prolongation can be a normal variant: 67,00 healthy airmen studied and .52% found to have a prolonged PR. 80% of the PR prolongations ranged from .21 to .24 (4).  In a second study 59 of 19,000 (.31%) airmen had a PR of .24 or more (5). <br>
 
* In healthy middle aged men, a prolongation of the PR in the presence of a normal QRS does not affect prognosis and is not related to ischemic heart disease (6). <br>
 
* In healthy middle aged men, a prolongation of the PR in the presence of a normal QRS does not affect prognosis and is not related to ischemic heart disease (6). <br>
* PR prolongation often signifies a delay in the AV node but may reflect intra atrial or His Purkinje disease. <br><br>
+
* PR prolongation often signifies a delay in the AV node but may reflect intra atrial or [[His Purkinje disease]]. <br><br>
 
=== Differential Diagnosis of the Shortened PR Interval: ===  
 
=== Differential Diagnosis of the Shortened PR Interval: ===  
 
* AV junctional and low atrial rhythms. <br>
 
* AV junctional and low atrial rhythms. <br>
* Wolff Parkinson White syndrome. <br>
+
* [[Wolff Parkinson White syndrome]]. <br>
* Lown Ganong Levine syndrome. <br>
+
* [[Lown Ganong Levine syndrome]]. <br>
* Glycogen storage disease. <br>
+
* [[Glycogen storage disease]]. <br>
* Hypertension. <br>
+
* [[Hypertension]]. <br>
 
* Normal variant. <br>
 
* Normal variant. <br>
* Fabry's disease. <br>
+
* [[Fabry's disease]]. <br>
* Pheochromocytoma. <br><br>
+
* [[Pheochromocytoma]]. <br><br>
 
=== Differential Diagnosis of a Prolonged PR Interval: ===  
 
=== Differential Diagnosis of a Prolonged PR Interval: ===  
* AV block due to coronary artery disease, rheumatic disease.  
+
* AV block due to [[coronary artery disease]], [[rheumatic disease]].  
* Hyperthyroidism. <br>
+
* [[Hyperthyroidism]]. <br>
 
* Normal variant. <br><br>
 
* Normal variant. <br><br>
 
=== Differential Diagnosis of the Depressed PR Interval: ===
 
=== Differential Diagnosis of the Depressed PR Interval: ===
* Acute pericarditis. <br>
+
* [[Acute pericarditis]].]] <br>
* Atrial infarction. <br><br>
+
* [[Atrial infarction]]. <br><br>
 
=== References ===
 
=== References ===
 
1.  Chou's Electrocardiography in Clinical Practice.
 
1.  Chou's Electrocardiography in Clinical Practice.

Revision as of 21:56, 6 January 2006

Electrocardiography

The PR Interval

Background

  • Shortens up to a rate of 140 to 150 beats per minute through a withdrawal of parasympathetic tone (1,2).
  • PR may increase with increasing rate in the presence of digoxin or if the conducting system is diseased.
  • If the atria are artificially paced the PR increases as the paced rate increases (3).
  • Children have shorter PR intervals (.11 at 1 year).
  • Prolongation can be a normal variant: 67,00 healthy airmen studied and .52% found to have a prolonged PR. 80% of the PR prolongations ranged from .21 to .24 (4). In a second study 59 of 19,000 (.31%) airmen had a PR of .24 or more (5).
  • In healthy middle aged men, a prolongation of the PR in the presence of a normal QRS does not affect prognosis and is not related to ischemic heart disease (6).
  • PR prolongation often signifies a delay in the AV node but may reflect intra atrial or His Purkinje disease.

Differential Diagnosis of the Shortened PR Interval:

Differential Diagnosis of a Prolonged PR Interval:

Differential Diagnosis of the Depressed PR Interval:

References

1. Chou's Electrocardiography in Clinical Practice.

2. Atterhog, J. Electrocardiol. 1977:10,331.

3. Lister,J., Am.J. Cardiol 1965:16,516.

4. Johnson, R, Am. J. Cardiol. 1960:6,153.

5. Manning, G., Am. J. Cardiol.1962:9,558.

6. Erikssen, J.,Clin.Card. 1984:7,6.

The QRS Interval

Adapted from Chou's Electrocardiography in Clinical Practice.

Duration

  1. The precordial leads are approximately .01 or .02 seconds longer than the standard leads.


Amplitude

  1. Definitions of low voltage:
    • If the total amplitude above and below the isoelectric line is < 5 mm in all 3 standard leads.
    • An average voltage in the limb leads of < 5 mm with an average of < 10 mm in the chest leads (1).
    • Should be at least 5 mm in V1 and V6 , 7 mm in V2 and V5 and 9 mm in V3 and V4.

  2. Differential diagnosis of low voltage:
    • Diffuse coronary artery disease.
    • Congestive heart failure.
    • Pericardial effusion.
    • Myxedema.
    • Amyloidosis.
    • Emphysema.
    • Obesity.

  3. Maximal acceptable voltage: can be up to 20 to 30 mm in lead 2 and can be up to 25 to 30 mmm in the precordial leads.


References

1. Unverferth, Chest 1979: 75, 157.

The QT Interval

References

The T Wave

References

The U Wave

References

Specific Electrocardiographic Abnormalities

Ventricular Tachycardia

References


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