The Sinus Rhythms

Sinus Rhythm

• Normal rhythm and rate
• P Waves present- originating in SA node.

Sinus Tachycardia

• Sinus Rhythm, >100bpm
  • Expected with exercise
  • Expected with fear/ pain
  • Normal in children
• Can be caused by:
  • Hypoxia
  • Hypercarbia
  • Pulmonary Embolism
  • ß- Agonists
• Can occur without obvious stimuli. (More common in young females)
• Tachycardia at rest suggests a pathology
• Could represent atrial tachycardia or atrial flutter

Sinus Bradycardia

• Sinus rhythm, <60bpm
  • Normal during sleep
  • Normal in athletes
•  Can be caused by:
  • Sinus Node disease
  • Anorexia nervosa (pictured)
  • Hypothermia
  • ß- Blockers
  • Hypothyroidism
  • Hyperkalaemia
• Can be mistaken for Sinoatrial Block Type II

Sinus Arrhythmia

• Sinus Rhythm, varying HR
  • Normal in young individuals
• RR interval increases and decreases with respiratory cycle
  • SA node firing rate is increased
• Constant PR interval
  • Excludes Mobitz I

Sinus Arrest

• A pause >3s

Sinoatrial Block Type I

• Lengthened impulse generation/ transmission interval. Results in transmission failure
• P waves pushed closer together
• PP interval gets progressively shorter
  • PQRS complex is then absent

Sinoatrial Block Type II

• Sporadic dropped P waves. Interval between atrial depolarisation and prior impulse generation
• Fragmentary ‘dropping out’ of P waves from rhythm.
  • Followed by regular P wave

Ref:

http://www.lifeinthefastlane.com

Luthra, A. (2007) ECG Made Easy. Third edition. Tunbridge Wells: Anshan