ACLS Provider: Course

Bradycardia Recognition and Management

Bradycardia is defined as a heart rate less than 50 beats per minute (bpm). While some individuals, such as well-trained athletes, may have resting heart rates below 60 bpm without experiencing any symptoms, bradycardia becomes clinically significant when it causes symptoms related to inadequate tissue perfusion. The management of bradycardia depends on the patient's clinical presentation and whether they are experiencing symptoms (symptomatic bradycardia).

Key ECG Rhythms Associated with Bradycardia

Several different ECG rhythms can present with bradycardia:

  • Sinus Bradycardia: A slow sinus rhythm (originating from the sinoatrial node) with a heart rate less than 60 bpm. All other ECG characteristics (P waves, QRS complexes, T waves) are typically normal.
  • First-Degree AV Block: Characterized by a prolonged PR interval (greater than 0.20 seconds), indicating a delay in conduction through the AV node. The heart rate may be slow if the underlying rhythm is sinus bradycardia.
  • Second-Degree AV Blocks:
    • Mobitz Type I (Wenckebach): Progressive lengthening of the PR interval until a QRS complex is dropped. This pattern repeats cyclically. The ventricular rate will be slower than the atrial rate.
    • Mobitz Type II: Intermittent non-conducted P waves without progressive PR interval lengthening. This is a more serious type of AV block and can progress to complete heart block.
  • Third-Degree (Complete) AV Block: Complete dissociation between the atria and ventricles. The atria and ventricles beat independently of each other. The ventricular rate is typically slow (often less than 40 bpm).

Management of Symptomatic Bradycardia

Symptomatic bradycardia, characterized by symptoms such as hypotension, altered mental status, chest pain (angina), acute heart failure, or other signs of poor perfusion, requires prompt intervention:

  • Atropine: Atropine is the first-line pharmacologic treatment for symptomatic bradycardia. It is an anticholinergic medication that blocks the effects of the vagus nerve, which normally slows the heart rate. The recommended dose is 0.5 mg IV every 3–5 minutes, with a maximum total dose of 3 mg.
  • Transcutaneous Pacing (TCP): If atropine is ineffective in improving the patient's condition or if the patient is experiencing high-degree AV block, transcutaneous pacing (TCP) should be initiated. TCP involves placing pacing pads on the patient's chest and delivering electrical impulses to stimulate the heart to contract.
  • Dopamine or Epinephrine Infusion: If TCP is unavailable or ineffective, or while preparing for TCP, consider an infusion of dopamine (2–20 mcg/kg/min) or epinephrine (2–10 mcg/min). These medications increase heart rate and improve cardiac contractility.