Cardiac emergencies and arrhythmias

Bradycardia, heart block and temporary pacing

Reviewed Nov 2026·2 references
New· views rounded down, updated weekly

Look for adverse features and reversible causes (drugs, K+, ischaemia, hypothermia, hypothyroidism, raised ICP). Atropine first; if it fails or the block is infranodal, adrenaline or isoprenaline infusion and transcutaneous then transvenous pacing.

At the bedside

Timed steps
  1. 1

    Assess

    0 min

    Shock, syncope, ischaemia, heart failure, pauses > 3 s, Mobitz II, complete heart block with wide QRS, ventricular standstill.

  2. 2

    Atropine

    0-5 min

    0.5-1 mg IV every 3-5 min to 3 mg (ineffective after heart transplant and in infranodal block).

  3. 3

    Chronotropes

    5-15 min

    Adrenaline 2-10 mcg/min or isoprenaline 1-10 mcg/min (dopamine 5-20 mcg/kg/min alternative).

  4. 4

    Transcutaneous

    Pacing

    Rate 60-70, increase output until capture; confirm with femoral pulse; analgesia/sedation. Bridge to transvenous.

  5. 5

    Transvenous

    Pacing

    Right internal jugular or left subclavian with ultrasound; ventricular capture threshold < 1 mA, output 3 × threshold.

  6. 6

    Treat

    Reversible causes

    Beta-blocker (glucagon), calcium-channel blocker (calcium, high-dose insulin), digoxin (Fab fragments), hyperkalaemia (calcium), inferior MI (often resolves after reperfusion), hypothermia, hypothyroidism, raised ICP, Lyme or infiltrative disease.

First-line

Atropine

IV push
Dose
0.5-1 mg every 3-5 min (max 3 mg)
Preparation
0.6 mg/mL: 1 mg ≈ 1.7 mL

Bridge to pacing

Isoprenaline (isoproterenol)

IV infusion
Dose
1-10 mcg/min
Red flag · call your senior now
Complete heart block with broad escape or pauses: pace early.
Red flag
Bradycardia with hypertension and irregular breathing: Cushing response (raised ICP).
Pitfall
Repeated atropine for infranodal block.
Pitfall
Assuming electrical capture means mechanical capture.
Pearl
Yellow oleander (Thevetia) poisoning in South India causes digoxin-like bradyarrhythmias; anti-digoxin Fab is effective but rarely available (module 28).

References

  1. 1

    Glikson M, Nielsen JC, Kronborg MB, et al. 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Eur Heart J. 2021;42(35):3427-3520

  2. 2

    Part 9: Adult Advanced Life Support: 2025 American Heart Association Guidelines for CPR and ECC. Circulation. 2025

Test yourself

Module quiz · score 70% to complete the module

Previous

Ventricular tachycardia, wide-complex tachycardia and electrical storm

Next

Hypertensive emergencies

Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.