All these patients need to be managed in a monitored bed equipped for cardiopulmonary resuscitation, defibrillation and airway management.The first question is whether the patient is stable or unstable…
Signs of instability:
- Hypotension
- Loss of consciousness
- Chest pain
- Acute heart failure
Unstable patients require immediate synchronised DC cardioversion. Starting energy is 100 J (monophasic) or 70 J (biphasic), with titration of energy settings upwards as required.
In stable patients, consider whether SVT with aberrancy is likely.
- Previous similar episodes
- Young, fit patient with structurally normal heart
- No family history of sudden death or cardiomyopathy
In these cases, a trial of adenosine or vagal manoeuvres (Valsalva manoeuvre or carotid sinus massage) is a reasonable next step. The starting dose of adenosine is 6mg rapid IV push, preferably through a proximally-sited large-bore cannula, followed by incremental doses at 12mg and 18mg.
Beware that adenosine may occasionally provoke degeneration to VF (particularly in patients with coronary artery disease) so the patient should have defibrillator pads attached during this procedure.
If adenosine is unsuccessful, or if VT is the likely diagnosis, then the options for treatment are as follows:
- Procedural sedation and DC cardioversion – this would be the treatment of choice in a fasted patient with no significant cardio-respiratory comorbidities
- Amiodarone 150 mg IV over 10 mins (first-line antiarrhythmic)
- Lignocaine 1-1.5 mg/kg over 2-3 minutes
- Procainamide 100mg every 5 minutes up to a maximum dose of 10-20mg/kg
Serum electrolytes (potassium and magnesium) should be corrected to normal and associated conditions such as hypoxia, myocardial ischaemia and drug toxicities (e.g. poisoning with sodium-channel blocking drugs) should be treated.
Remember that overall, VT accounts for:
- 80% of cases of BCT
- 95% of cases of BCT in patients with structural heart disease
So if in doubt, treat as VT!