Emergency Medicine

CARDIAC ARRHYTHMIAS

62 General Medical Emergencies

3 Provide pain relief if needed with GTN 150–300 g sublingually for

coronary ischaemic pain, or morphine 2.5–5 mg i.v. with an antiemetic, e.g.

metoclopramide 10 mg i.v., for more severe pain, including non-ischaemic.

4 Correct any electrolyte abnormality. See page 131.

5 Tachycardia

This may be sinus with normal preceding P waves, narrow-complex or broad-

complex.

(i) Look urgently for and treat underlying causes such as hypoxia,

hypovolaemia, fever, anaemia, pain, etc. if it is definitely a sinus

tachycardia.

(ii) Give a synchronized DC shock, if the patient is unstable with

hypotension and a systolic BP <90 mmHg, is confused, has chest

pain or heart failure (see p.75)

(a) start with 120–150 J biphasic or 200 J monophasic and repeat

up to three times, with stepwise increases in joules

(b) a senior doctor with airway experience must first give a short-

acting general anaesthetic or i.v. midazolam in the conscious

patient

(c) give amiodarone 300 mg i.v. over 10–20 min if three attempts

at synchronized DC cardioversion failed, then repeat the DC

shock and follow by an infusion of amiodarone 900 mg over

24 h.

(iii) Broad-complex tachycardia

When regular this may be due to ventricular tachycardia (VT) or

supraventricular tachycardia with aberrant conduction (block):

(a) give amiodarone 5 mg/kg i.v. over 20–60 min if the patient is

stable, followed by an infusion of amiodarone 900 mg over

24 h

(b) consider AF with bundle branch block if the rhythm is

irregular, or AF with ventricular pre-excitation as in Wolff–

Parkinson–White syndrome:

• seek expert help if not already involved


• give flecainide 2 mg/kg over 10 min, or amiodarone 5 mg/
  kg i.v. followed by an infusion


• avoid adenosine, verapamil, digoxin and diltiazem, as they
  block the atrioventricular (AV) node and may worsen pre-
  excited AF leading to VT or even ventricular fibrillation
  (VF).

Tip: frequent ventricular ectopic beats (VEBs) do not require treatment,

unless they are multi-focal, in runs or arrive on the T wave of the

preceding complex.

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