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Introduction ⬇

What Causes It ⬆ ⬇

  • Cardiomyopathy
  • Heart block
  • Inferior-wall MI
  • Myocardial ischemia
  • Myocarditis
  • Sinoatrial (SA) node disease
  • Conditions that increase vagal stimulation or decrease sympathetic stimulation
  • Carotid sinus massage
    • Deep relaxation
    • Sleep
    • Valsalva maneuver
    • Vomiting

Recognizing sinus bradycardia

Rhythm

  • Regular

Rate

  • Less than 60 beats/min

P wave

  • Normal size
  • Normal configuration
  • P wave before each QRS complex

PR interval

  • Within normal limits
  • Constant

QRS complex

  • Normal duration
  • Normal configuration

T wave

  • Normal size
  • Normal configuration

QT interval

  • Within normal limits
  • Possibly prolonged


  • Glaucoma
  • Hyperkalemia
  • Hypothermia
  • Hypothyroidism
  • Increased ICP
  • Drugs
    • Antiarrhythmics (amiodarone [Cordarone], propafenone [Rythmol], quinidine, sotalol [Betapace])
    • Beta-adrenergic blockers (metoprolol [Lopressor], propranolol [Inderal])
    • Calcium channel blockers (diltiazem [Diltiazem], verapamil [Calan])
    • Digoxin (Lanoxin)
    • Lithium (Lithobid)
  • Normal in well-conditioned athletes

What to Look for ⬆ ⬇

  • Pulse rate less than 60 beats/min
  • Regular rhythm
  • Possibly bradycardia-induced syncope (known as a Stokes–Adams attack)

If Patient Can Compensate for Decreased Cardiac Output

  • No symptoms

If Patient Can't Compensate

  • Altered mental status
  • Palpitations
  • Chest pain
  • Dizziness
  • Crackles, dyspnea, and S3 indicative of heart failure
  • Hypotension
  • Cool clammy skin
  • Syncope

How It's Treated ⬆

  • Usually, no treatment is needed if the patient has stable vital signs and no symptoms.
  • Continue to observe the patient's heart rhythm and monitor the progression and duration of bradycardia.
  • Evaluate the patient's tolerance for the rhythm at rest and with activity.
  • Review the patient's drug regimen for drugs that depress SA node.
  • If the patient has symptoms of reduced cardiac output, identify and correct the underlying cause. Notify the practitioner. Prompt attention is critical. The heart of a patient with underlying cardiac disease may not be able to increase stroke volume to compensate for a decrease in rate.

  • Prepare the patient for treatments as needed (ACLS Bradycardia algorithms) such as drug administration (atropine, dopamine, epinephrine); transvenous or transcutaneous pacing; or permanent pacemaker insertion for a chronic, symptomatic condition.
Memory jogger

To remember the bradycardia (slow heart rate) algorithm, just SLOW down:

Survey the ABCs

Look for serious symptoms

Observe if symptoms aren't serious and no AV block is present

OR

Weigh in (intervene) if symptoms are serious.