Tachyarrhythmias — the structured approach and the dangerous traps

The structured approach:

1. Stability first: the unstable tachyarrhythmia (the shock, the ischaemic chest pain, the acute heart failure, the altered consciousness) receives the synchronised DC cardioversion, regardless of the rhythm.
2. QRS width: the narrow (below 120 ms) is the supraventricular; the broad (above 120 ms) is the ventricular or the aberrant.
3. Regularity: within each, the regular versus the irregular narrows the differential.
4. The specific rhythm and the drug follow.

The narrow-regular: the AVNRT and the AVRT — the vagal manoeuvres (the modified Valsalva) then the IV adenosine 6-12-12 mg.^[3] The atrial flutter at around 150 — the adenosine unmasks, the cardioversion or the rate control terminates.

The narrow-irregular: the atrial fibrillation — the rate versus the rhythm control, the 48-hour rule (the rhythm control reasonable under 48 hours; the rate control and the anticoagulation beyond, with the three-week anticoagulation or the TOE before the cardioversion), and the CHA2DS2-VASc for the long-term anticoagulation.^[4]

The broad-regular: the ventricular tachycardia — the IV amiodarone (stable) or the cardioversion (unstable). Treat as VT if uncertain.^[2]

The broad-irregular: the torsades (the IV magnesium bolus, the potassium, withdraw drug) and the atrial fibrillation with the Wolff-Parkinson-White (no AV-node blockers; cardiovert or a pathway drug).^[2][3]

The dangerous traps:

• The verapamil or the adenosine in the broad-complex tachycardia (treat as the VT — the verapamil kills in the VT).^[2]
• The AV-node blocker in the atrial fibrillation with the WPW (the varying QRS, the irregular broad — the blocker diverts the conduction down the accessory pathway, the VF).^[3]
• The adenosine in the asthma (avoid — the bronchospasm).^[3]
• The cardioversion of the AF beyond 48 hours without the anticoagulation or the TOE (the stroke).^[4]
• The unsynchronised shock on the cardioversion (the VF).^[3]