1. Sinus Bradycardia

2. Sinus Bradycardia
• Sinus rate below 60 beats/minute
• Regular rhythm
• Occurs normally during sleep
– Decreased metabolic demands
• Occurs normally in a person with a well-
conditioned heart
– Athlete
• Well-conditioned hearts can maintain a normal stroke
volume with less-than-normal effort

3. Sinus Bradycardia
• How it happens
– Normal response to a reduced demand for blood
flow
• Vagal simulation increases and sympathetic stimulation
decreases
– Automaticity in the SA node diminishes

4. Sinus Bradycardia
• A tolerable condition?
– Most adults can tolerate a sinus bradycardia of 45-
59 beats/minute
– Less tolerant of a rate below 45 beats/minute

5. Sinus Bradycardia
• Causes
– Non-cardiac disorders
– Conditions producing excess vagal stimulation or
decreased sympathetic stimulation
– Cardiac diseases
– Certain drugs

6. Sinus Bradycardia
• No symptoms? No problem
• Symptoms? PROBLEM
– Prompt attention is critical
– Can lead to more serious problems
• Hypotension and dizziness
• Ventricular tachycardia and ventricular fibrillation

7. Symptomatic Bradycardia
• If a patient can’t tolerate bradycardia, he may
develop these signs and symptoms:
– Hypotension
– Cool, clammy skin
– Altered mental status
– Dizziness
– Blurred vision
– Crackles, dyspnea
– Chest pain
– Syncope

8. Symptomatic Bradycardia
• When to call for help and what to do until help
arrives
– Look at the patient and ask how they are doing
– Call for help if heart rate is too slow and/or
symptomatic
• Compare it their normal heart rate and rhythm
– Stay with the patient
– If the patient is not breathing and does not respond
• Call code
• ABCs/CPR

9. Sinus Bradycardia
• Atrial & ventricular rhythms are regular, as are
their rates, except that they’re both under 60
beats/minute

10. Sinus Bradycardia
• Normal
– P wave preceding each QRS complex
– PR interval
– QRS complex
– T wave
– QT interval

11. Sinus Bradycardia
• P wave
– rounded, smooth, and upright in lead II, signaling
that a sinus impulse has reached the atria

12. Sinus Bradycardia
• PR interval
• Normal indicating that the impulse is following
normal conduction pathways
– 0.12-0.20 seconds

13. Sinus Bradycardia
• QRS complex
• Normal duration representing normal
ventricular impulse conduction and recovery
– Less than 0.12 seconds

14. Sinus Bradycardia
• T wave
– Upright in lead II, confirming that normal
repolarization has taken place

15. Sinus Bradycardia
• QT interval
– Within normal limits
• 0.36 to 0.44 seconds