• Sinoatrial Node
• Frequency and Sinus Rhythm
• Sinus Tachycardia
• ECG and Sinus Tachycardia
• Most Common Causes of Sinus Tachycardia

Sinoatrial Node

• Automaticity
• Every part of the conduction system and the working myocardium
• Has the ability to spontaneously generate impulses
  
  
• Overdrive Suppression
• Impulses propagate through the conduction system from the focus
• which generates impulses with the highest frequency
• The focus with the highest frequency deactivates foci
• with lower frequency (overdrive suppression)
  
  
• Sinoatrial Node (SA Node)
• Spontaneously generates impulses at a frequency of 60 - 100/min.
• Other foci generate impulses at a lower frequency

Sinus Tachycardia

• Sinus Tachycardia is a sinus rhythm with a frequency >100/min.
• In children, this means a frequency above the upper limit of normal
• The SA node is intact, only generating impulses at a higher frequency (increased automaticity)
• Sinus tachycardia is a secondary symptom - a sign of something else
• The primary disease stimulates the SA node, increasing its frequency
• In sinus tachycardia, one should always search for the primary cause
• For example: a patient may primarily have angina with a fever, and secondarily (due to the fever) have sinus tachycardia
  
  
• Maximum frequency of sinus tachycardia is 220 - age.
• A 30-year-old patient has a maximum sinus tachycardia of 190/min. (220 - 30)
• Sinus tachycardia rarely exceeds a frequency of 170/min.
• Treatment of sinus tachycardia is causal, addressing the underlying cause of the sinus tachycardia (primary disease)

Sinus Tachycardia

• Frequency: 150/min. (>100/min.)
• P waves are less visible because they overlap with T waves
• QRS alternans: changes in the amplitude of QRS complexes
• Heart rate is regular (RR interval remains constant)

Sinus Tachycardia

• Frequency: 150/min. (>100/min.)
• P waves are less visible because they overlap with T waves
• P and T waves create two peaks, similar to the humps of a bactrian camel
• This EKG pattern in sinus tachycardia is sometimes referred to as a "camel hump" in English

Sinus Tachycardia

• Frequency: 150/min.
• Physiological P wave
• Positive (I, II)
• Negative (aVR)
• P waves merge closely with T waves and together form "two humps"
• QRS alternans - changes in the amplitude of QRS complexes

Sinus Rhythm

• Frequency: 75/min.
• If the frequency were > 100/min., it would be sinus tachycardia
• Physiological P wave
• Positive (I, II)
• Negative (aVR)