ECG Level 2 Tutorial: Rhythm Diagnostic Criteria
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Tutorial: Rhythm Diagnostic Criteria
This module will list the basic rhythms, their diagnostic criteria, and their clinical significance .
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Tutorial: Rhythm Diagnostic Criteria Normal Sinus Rhythm
Lessons
42
Times Practiced
1284
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Progress
Accuracy
Efficiency
Accuracy
Efficiency
Current lesson 1 Normal Sinus Rhythm Normal Sinus Rhythm
2 Sinus Bradycardia Sinus Bradycardia
3 Sinus Tachycardia Sinus Tachycardia
4 Re-entry Re-entry
5 Atrial Fibrillation Atrial Fibrillation
6 Atrial Flutter Atrial Flutter
7 Heart Block - First degree Heart Block - First degree
8 Heart Block - Second degree Type 1 Heart Block - Second degree Type 1
9 Heart Block - Second degree Type 2 Heart Block - Second degree Type 2
10 Heart Block - Third degree Heart Block - Third degree
11 Junctional Rhythm Junctional Rhythm
12 SVT (supraventricular tachycardia) SVT (supraventricular tachycardia)
13 VT (Ventricular Tachycardia) VT (Ventricular Tachycardia)
14 Ventricular Fibrillation Ventricular Fibrillation
Normal Sinus Rhythm
Normal Sinus Rhythm
 


Diagnostic criteria:
  • Rate: 60-100
  • Rhythm: regular
  • P waves: upright, all same size and shape
  • PR interval: normal (3-5 little squares)
  • QRS: narrow (< 3 little squares)
 
Normal sinus rhythm is a rhythm that starts in the sinus node (which is why we have the word "sinus" in the title). If you checked your heart rate right now and it was between 60-100, you are most likely in normal sinus rhythm.

Normal sinus rhythm is frequently "combined" with other diagnoses, such as:
  • heart blocks (1st, 2nd and 3rd degree)
  • abnormal axes
  • bundle branch blocks
  • chamber enlargement, such as atrial enlargement or left ventricular hypertrophy
  • myocardial ischemia or infarction
  • and many others
Electrophysiology:

The sinus node action potential dictates the frequency of firing of the sinus node. The most important component of the action potential is phase 4. Notice that it is upsloping, always moving toward the action potential threshold (the dotted line). The fact that phase 4 is upsloping means that these cells have the ability to create their own heart rate. This is called automaticity.


In particular, the slope of phase 4 is the most important component of the action potential for determining the heart rate. A steep phase 4 will shorten the time between action potentials and thus increase the heart rate. Increased sympathetic nervous system (SNS) activity or decreased parasympathetic nervous system (PNS) activity increase the slope of phase 4 and increase the sinus heart rate. The opposite is also true: decreased SNS or increased PNS will reduce the heart rate.

Clinical Significance:

Normal sinus rhythm is completely normal.

Examples:

normal sinus rhythm

normal sinus rhythm

normal sinus rhythm

normal sinus rhythm