Bradycardia and Tachycardia Algorithms
Bradycardia
Decide first whether the patient is unstable - hypotension, altered mental status, ischemic chest pain, acute heart failure, or shock. If stable, monitor and identify the cause. If unstable: atropine 1 mg IV every 3–5 minutes, maximum 3 mg. If atropine fails, move to transcutaneous pacing (rate 60–80, confirm both electrical and mechanical capture, sedate if conscious) and/or a dopamine 5–20 mcg/kg/min or epinephrine 2–10 mcg/min infusion. High-grade blocks - Mobitz II and third-degree - often do not respond to atropine; go to pacing early. Consider hyperkalemia, beta-blocker or calcium-channel-blocker overdose, and ischemia.
Tachycardia with a pulse
Ask two questions: is the patient unstable? and is the QRS narrow or wide? Unstable means synchronized cardioversion.
- Narrow and regular (SVT): adenosine 6 mg rapid IV push with a flush, then 12 mg; if it fails, a beta-blocker or calcium-channel blocker.
- Narrow and irregular (AFib): rate control; adenosine is not the answer.
- Wide and regular (presumed VT): amiodarone 150 mg over 10 minutes, procainamide, or synchronized cardioversion if unstable.
- Wide and irregular (polymorphic VT/torsades): unsynchronized defibrillation and magnesium 1–2 g.
Traps
Using adenosine for an irregular or wide-complex rhythm. Forgetting that if synchronization fails, you deliver an unsynchronized shock. Treating stable VT with a rapid amiodarone push rather than a 10-minute infusion.
Rule of thumb
Unstable = electricity; stable = 12-lead and drugs. Narrow-regular answers adenosine; anything wide answers VT.