Arrhythmias, conduction disorders and electrophysiology
The exam tests rhythm recognition, safe acute management and long-term decisions about anticoagulation, ablation and devices.
Tachyarrhythmias
- Atrial fibrillation: use CHA2DS2-VASc; anticoagulate men with score 2 or more and women with 3 or more, and consider at 1 or 2 respectively. DOACs are preferred except in mechanical valves and moderate-to-severe mitral stenosis. Apply the ABC pathway: anticoagulation, better symptom control, comorbidity management.
- Atrial flutter: sawtooth waves, negative in II, III and aVF in typical counterclockwise flutter; CTI ablation is highly effective.
- AVNRT: most common paroxysmal SVT; regular narrow complex, retrograde P waves buried in or just after QRS; vagal manoeuvres then adenosine 6 mg, then 12 mg.
- WPW with pre-excited AF: avoid adenosine, verapamil, digoxin and beta-blockers; use procainamide or electrical cardioversion.
Bradyarrhythmias and wide-complex tachycardia
- Mobitz II and complete heart block need pacing; Mobitz I is usually benign in trained athletes.
- Wide-complex tachycardia: assume VT, especially with AV dissociation, capture or fusion beats, concordance. Unstable means synchronized cardioversion.
Drugs and devices
- Vaughan-Williams classes; amiodarone for refractory VT and AF; avoid QT-prolonging combinations in long QT syndrome.
- ICD for secondary prevention after VT or VF arrest, and for primary prevention in selected EF 35% or less.
Worked example
A 30-year-old with abrupt-onset palpitations has a regular narrow-complex tachycardia at 180 bpm with no visible P waves. Treat as AVNRT: vagal manoeuvres, then adenosine, and consider ablation for recurrence.
Traps
- Verapamil for a wide-complex tachycardia of uncertain origin.
- Adenosine in pre-excited atrial fibrillation.
- Anticoagulating with a DOAC in a mechanical mitral valve.