ACLS | Bradycardia and Tachycardia Extended

Core Assessment & Stability Hallmarks

Prioritize identifying whether the rhythm causes hemodynamic instability [1]. Symptomatic bradycardia occurs at HR <50/min [1][4], and symptomatic tachycardia at HR ≥150/min [5][6].

• 5 Instability Signs: Hypotension, altered mental status, signs of shock, ischemic chest discomfort, acute heart failure [2].
• First Actions: Patent airway, assist ventilation/O2 if hypoxemic, monitor/BP/oximetry, IV access, 12-lead ECG [2]. Never delay electrical therapy for a 12-lead ECG in unstable patients [8].

2. Bradycardia Algorithm (HR <50/min)

• Stable: Monitor and observe [2][4].
• Unstable:
  1. Atropine (1st Line): 1 mg IV bolus every 3–5 min (max total: 3 mg) [4][9]. Doses <0.5 mg may slow HR [9].
  2. Atropine Gotchas: Avoid in Mobitz II 2nd-degree or 3rd-degree AV block with wide QRS [9], acute MI [9], or heart transplant patients (Class III: Harm; use TCP/dopamine/epinephrine) [9].
  3. 2nd Line (If Atropine Fails):
  • TCP: Rate 60–80/min; output 2 mA above capture threshold [10]. Sedate conscious patients if possible [11][12]. Contraindicated in severe hypothermia [12]. Don't check carotid pulse for capture [12].
  • Infusions: Dopamine IV (5–20 mcg/kg/min) [2] or Epinephrine IV (2–10 mcg/min) [2].

3. Tachycardia Algorithm (HR ≥150/min)

• Unstable: Immediate Synchronized Cardioversion (consider sedation) [3]. For regular narrow complex, consider Adenosine 6 mg IV [3][6].
• Stable Narrow QRS (<0.12 s):
  1. Regular (SVT): Vagal maneuvers → Adenosine 6 mg IV push + flush [6][14]. If unconverted in 1–2 min, give 12 mg IV [6][14]. Follow with β-blockers or CCBs [6][14]. (Use 3 mg Adenosine in heart transplants/central lines; avoid in asthma/COPD) [14].
  2. Irregular (Afib/Flutter): Rate control with β-blockers or CCBs [14][15].
• Stable Wide QRS (≥0.12 s):
  1. Regular & Monomorphic: Adenosine 6 mg IV only if regular and monomorphic [6][16].
  2. Antiarrhythmic Infusions: Procainamide (20–50 mg/min, max 17 mg/kg; avoid in prolonged QT/CHF) [6][16], Amiodarone (150 mg IV over 10 min) [6][16], or Sotalol (100 mg over 5 min) [6][16].

4. Electrical Therapy & Critical Traps

• Defibrillation (Unsynchronized): Pulseless (VF/pVT), polymorphic VT, or severe deterioration [13].
• Cardioversion (Synchronized): Unstable tachycardia with pulse [13]. Reactivate sync mode after each shock [17].
• AV Nodal Blocker Trap: Do NOT give AV nodal blockers (adenosine, CCBs, β-blockers, digoxin) in pre-excited Afib/flutter (WPW), as it risks triggering VF [14][15]. Avoid combining CCBs and β-blockers due to severe bradycardia [15].