Tachyarrhythmias

Management— do this, in order

• Unstable, any rhythm — synchronised DC cardioversion. Sedate or anaesthetise the conscious patient, because cardioversion is intensely painful, and confirm the synchronisation markers before every shock, since most defibrillators revert to unsynchronised mode after each discharge.Doctor / NurseNot available at your setup — Defibrillator.
• Cardioversion energies (biphasic): regular narrow-complex SVT 100 J (70–120 J) escalating; atrial flutter 100–200 J; atrial fibrillation 200 J escalating to 360 J or the machine maximum; pre-excited AF treated as AF with high energy from the outset; VT with a pulse 100–200 J escalating with each shock; paediatric 1 J/kg for the first shock, then 2 J/kg.Doctor / NurseNot available at your setup — Defibrillator.
• Up to three synchronised shocks are given. If three fail, give amiodarone 300 mg intravenously over 10–20 minutes and repeat the shock, followed by amiodarone 900 mg over 24 hours; failure is most often uncorrected potassium or magnesium, or high thoracic impedance, and an anteroposterior pad position may succeed where anterolateral failed.Doctor / NurseNot available at your setup — Defibrillator.
• Stable, narrow, regular — vagal manoeuvres first, which terminate 20–50% of episodes. Modified Valsalva: semi-recumbent at 45 degrees, blow into a 10 mL syringe hard enough just to move the plunger (about 40 mmHg of intrathoracic pressure) for at least 15 seconds, then lie flat with both legs passively raised to 45 degrees for a further 15 seconds; conversion typically occurs during the leg raise. In infants use the diving reflex — an iced flannel over forehead, eyes and bridge of the nose for up to 15 seconds.
• Carotid sinus massage: firm but gentle pressure over the right carotid sinus for 10–20 seconds with the ECG running, then the left if unsuccessful — never both sides simultaneously, never if a bruit is present, never after stroke or transient ischaemic attack or with known carotid disease, and not in children.Doctor / Nurse
• Adenosine is the first-line drug and terminates AVNRT and AVRT in approximately 90% of cases. Adult: 6 mg by rapid intravenous push over 1–2 seconds, immediately followed by a 20 mL sodium chloride 0.9% flush and arm elevation; if no effect after 1–2 minutes, 12 mg; if still none, a further 12 mg (Davidson's expresses this as 3–12 mg in rapid incremental doses). Start at 3 mg if the line is central, or the patient takes dipyridamole or has a transplanted heart.Doctor / Nurse
• Adenosine, paediatric: 0.1 mg/kg (maximum first dose 6 mg), then 0.2 mg/kg (maximum 12 mg), then 0.3 mg/kg (maximum 12 mg), each with a rapid 5–10 mL flush.Doctor / Nurse
• Give adenosine properly or not at all: use the largest, most proximal vein — adenosine given into a small hand or foot vein is metabolised before reaching the heart — push drug and flush as one continuous movement, and warn the patient of about ten seconds of chest heaviness, flushing, breathlessness and a sense of dread, which passes and is harmless.Doctor / Nurse
• If adenosine fails or is contraindicated, choose one AV nodal blocking class and stay within it: verapamil 5–10 mg IV over 5–10 min, or 2.5 mg boluses every 1–3 min to a total of 20 mg over 20 min; diltiazem 0.25 mg/kg IV over 2 min, a second bolus of 0.35 mg/kg after 15 min if inadequate, then a 5–15 mg/hour infusion; metoprolol 5 mg IV every 5 min up to 3 doses (15 mg total), orally 25–200 mg daily; esmolol 500 micrograms/kg IV over 1–2 min then 50–300 micrograms/kg/min; propranolol 1–3 mg IV every 5 min to a total of 5 mg.Doctor / Nurse
• Stable, broad, regular — treat as VT with amiodarone 300 mg intravenously over 20–60 minutes, then 900 mg over 24 hours (Kumar and Clark: 900–1200 mg per 24 hours; CMDT and Harrison's: 150 mg over 10 minutes, then 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours). In the peri-arrest patient give the 300 mg over 10–20 minutes; dilute in 5% dextrose and give through the largest available vein or a central line. Paediatric dose 5 mg/kg over 20–60 minutes.Doctor / NurseNot available at your setup — Infusion pump.
• Lidocaine as an alternative that may be given peripherally: 1 mg/kg intravenously as a bolus (Kumar and Clark: 50–100 mg), then 1–4 mg/min by infusion; an intravenous beta-blocker (metoprolol 5 mg, or esmolol 50–300 micrograms/kg/min) is useful in ischaemic VT and electrical storm.Doctor / NurseNot available at your setup — Infusion pump.
• Torsades de pointes: magnesium sulphate 2 g (8 mmol of magnesium) intravenously over 10–15 minutes in every case, irrespective of the serum magnesium, followed by 72 mmol over 24 hours; paediatric 25–50 mg/kg, maximum 2 g, over 10–15 minutes. Stop every QT-prolonging drug and correct potassium to 4.0–4.5 mmol/L along with magnesium and calcium.Doctor / Nurse
• Torsades — raise the heart rate, because it is bradycardia- and pause-dependent: overdrive pacing at 90–120/min shortens the QT rate-dependently and is definitive, and isoprenaline 2–20 micrograms/min is the alternative where pacing is unavailable. If the pulse is lost, defibrillate immediately with an unsynchronised shock.Doctor / NurseNot available at your setup — Defibrillator. Where pacing is unavailable, isoprenaline 2–20 micrograms/min is the alternative to raise the rate.
• Pre-excited atrial fibrillation is an emergency and synchronised DC cardioversion is the treatment of choice. If the patient is genuinely stable and a drug is required, use procainamide (loading 10–17 mg/kg at 20–50 mg/min, stopping if the QRS widens by more than 50% or the blood pressure falls) or ibutilide 1 mg over 10 minutes, repeated once.Doctor / NurseNot available at your setup — Defibrillator.
• Atrial fibrillation, stable — rate control first, with metoprolol where there is ischaemia or infarction and diltiazem where blood pressure is low, never the two classes combined intravenously. Digoxin may be added: loading 0.5 mg intravenously over 20 minutes, then increments of 0.25 mg or 0.125 mg to a total of 1–1.5 mg over 24 hours (or the same total orally over 24–36 hours in divided doses); maintenance 0.125–0.5 mg daily, or 0.0625–0.25 mg daily in heart failure and the elderly. Rate targets: below 110/min suffices without symptoms or left ventricular dysfunction, below 80/min where symptoms persist.Doctor / Nurse
• The timing rule for cardioversion in stable AF: acceptable without prior anticoagulation if AF has been present less than 48 hours (Davidson's uses a more cautious 24-hour threshold, and the safer figure should be preferred); beyond 48 hours or where onset is unknown, either perform transoesophageal echocardiography to exclude left atrial thrombus or anticoagulate therapeutically for at least 3 weeks first, and continue anticoagulation for at least 4 weeks afterwards.Not available at your setup — Ultrasound. Where transoesophageal echocardiography is unavailable, anticoagulate therapeutically for at least 3 weeks before cardioversion and continue for at least 4 weeks afterwards.
• Pharmacological cardioversion: flecainide 2 mg/kg intravenously over 30 minutes, maximum 150 mg restores sinus rhythm in about 75% within 8 hours — but only in structurally normal hearts; use amiodarone where structural or ischaemic heart disease is present. In the unstable patient in whom 200 J then 360 J both fail, cardioversion may succeed after loading with ibutilide 1 mg intravenously over 10 minutes, repeated once.Doctor / Nurse
• Correct the substrate in parallel and treat the precipitant: potassium to 4.0–4.5 mmol/L, magnesium, calcium, hypoxia, acidosis and ischaemia — no antiarrhythmic drug and no shock works reliably in a hypokalaemic, hypomagnesaemic, hypoxic or acidotic patient. Wide-complex tachycardia in tricyclic antidepressant, diphenhydramine or class Ia overdose is treated with sodium bicarbonate 8.4%, 50 mmol (50 mL) intravenously, repeated as necessary, even without acidosis.Doctor / NurseNot available at your setup — Serum electrolytes.