Bradyarrhythmias

Watch ▶Approach to bradycardia: Clinical sciences

Atrial Bradyarrhythmias Overview

Sinus Bradycardia

Causes

• Benign ⇒ Sleep, well-conditioned athletes.

• Drugs ⇒ Beta-blockers, calcium channel blockers (CCBs).

• Pathologic ⇒ SA node disease, increased intracranial pressure (ICP), obstructive sleep apnea (OSA), hypothyroidism.

  <aside> 💡 Increased ICP → Cushing triad

  1. Bradycardia
  2. Hypertension
  3. Irregular respiration </aside>

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Severe bradycardia and AV block during laparoscopy directly after Co2 insufflation is due to peritoneal stretching → Vagal stimulation → ↓↓ HR

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Clinical Presentation

• Generally asymptomatic until heart rate < 45 bpm.
• Possible symptoms include fatigue, dizziness, syncope.

Diagnosis

• Electrocardiogram (ECG) showing sinus origin of P waves and heart rate < 60 bpm [A].

[A] Sinus bradycardia

• Details

Management

• Hemodynamically Stable

  • Investigate and address underlying cause.

• Hemodynamically Unstable

  • Give atropine 1 mg IV (can repeat every 3-5 min up to 3 mg total)
  • If preseitent
    • Transcutaneous or transvenous pacing
    • OR IV infusion of dopamine

  <aside> ☠️

  Hemodynamically Unstable

  • Bradycardia causing any of the following
    • Congestive heart failure (CHF)
    • Altered mentation
    • Shock
    • Hypotension
    • Chest pain </aside>

Sick Sinus Syndrome

General

• Inability of the sinoatrial node to generate an adequate heart rate.
• SA nodal dysfunction leading to a spectrum of abnormal heart rhythms, including sinus pauses and tachy-brady syndrome.

Etiology

• Most common cause → age-related degeneration of the cardiac conduction system with fibrosis of the sinus node.
• Other potential causes:
  • Ischemia.
  • Infiltrative cardiac disease (e.g., sarcoidosis, amyloidosis).

Sinus bradycardia with sinus pause and junctional escape rhythm

• Details

Clinical Presentation

• Bradycardia leading to
  • Fatigue, dizziness, lightheadedness.
  • Dyspnea on exertion.
  • Confusion.
  • Syncope or presyncope.
• Paroxysmal atrial arrhythmias (e.g., atrial fibrillation).
• Bradycardia-tachycardia syndrome (alternating bradycardia with supraventricular tachycardia).

Diagnosis

<aside> 💡 Preferred initial diagnostic study ⇒ 12-lead ECG

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• Telemetry monitoring reveals [A,B]
  1. Sinus bradycardia
  2. Sinus pauses (delayed P waves)
  3. Dropped beats (sinus arrest)
  4. Junctional escape beats
  5. Alternating tachycardia/bradycardia [C]

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Chronotropic incompetence

• One of the rhythm abnormalities of Sinus node dysfunction
• Typically defined as reaching < 80% of the expected age-predicted maximal heart rate.
  • The heart rate is unable to increase sufficiently in response to increased activity or demand.
• Exercise ECG testing inadequate heart rate response to exercise) </aside>

Management

• Symptomatic Patients ⇒ Permanent pacemaker implantation.
• Address reversible causes if identified (ischemia, drugs, vagal tone) before considering pacemaker insertion.
• After pacemaker placement
  • Rate-control medications (beta blockers) for patients with persistent paroxysmal tachyarrhythmias.

[A]

[B]

[C]

• UWT - Sick Sinus Syndrome

Atrioventricular Block