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Chapter 2: Cardiac arrhythmias 55

compromise of cardiac output overt cardiac failure or Torsades de pointes
loss of consciousness may occur. The presenting pic-
Definition
ture is dependent on the rapidity of the tachycardia and
Torsades de pointes or ‘twisting of the points’ is a con-
the function of the left ventricle, as well as general con-
dition in which there is episodic tachycardia and a pro-
dition of the patient (e.g. hypovolaemia, anaemia, is-
longed Q–T interval when in sinus rhythm.
chaemic heart disease, etc). On examination during an
acute episode the rapid regular pulse is felt and as the
atria are dissociated from the ventricles they may con-
Aetiology
tract against a closed AV valve resulting in cannon ‘a’
Itariseswhenventricularrepolarisationisprolongeddue
waves in the JVP. Carotid sinus massage may help to
to congenital cause, hypokalaemia, hypocalcaemia, anti-
distinguish ventricular tachycardia, which does not re-
arrhythmic drugs, tricyclic antidepressants or bradycar-
spond, from supraventricular tachycardia with bundle
dia from the sick sinus syndrome. It may also occur in
branch block, which may respond.
overdose of drugs that prolong the Q–T interval.
Investigations
The ECG shows a broad complex tachycardia, AV disso- Pathophysiology
ciation (independent P wave activity). Low serum potas- It is thought that the long Q–T interval allows adjacent
sium or magnesium may predispose to arrhythmias, so cells, which are repolarising at slightly different rates,
levels should be checked. to trigger one another in a knock-on effect. The Q–T
interval is prolonged by biochemical abnormalities and
Complications drugs, and is also prolonged in bradycardic states.
Cardiac arrest due to pulseless ventricular tachycardia or
ventricular fibrillation. Pulmonary oedema or syncope
may also occur. Clinical features
It typically recurs in frequent short attacks, causing pre-
syncope, syncope or heart failure.
Management
Any underlying electrolyte disturbance should be

identified and managed.
Investigations
If the patient has low cardiac output and is hypoten-

Repetitive bursts of rapid regular, polymorphic, QRS
sive, intravenous amiodarone or emergency synchro-
complexes, the axis of which undergoes cyclical change.
nised DC cardioversion is used.
During periods of sinus rhythm a prolonged Q–T inter-
Anti-arrhythmic drugs such as amiodarone and β-

val is seen.
blockers often in combination with other drugs are
used to prevent further episodes. Implantable car-
dioverterdefibrillators,whichautomaticallydetectVT
Complications
and VF and terminate the arrhythmia with overdrive
The major risk of torsades de pointes is progression to
pacing or DC shock, may be used.
ventricular fibrillation.
Patients require treatment of any underlying condi-

tion such as ischaemic heart disease.
Pulseless VT is treated as per cardiac arrest with ba- Management

sic and advanced life support. Early defibrillation is Anyunderlyingcauseshouldbeidentifiedandcorrected.
needed to restore sinus rhythm. Overdrive pacing at 90–100 bpm may terminate the ar-
rhythmia and is the best method for preventing recur-
Prognosis rences, alternatively an infusion of isoprenaline may be
Recurrent VT has a worse prognosis, particularly in the used.IfcardiacoutputiscompromisedsynchronisedDC
context of myocardial infarction. cardioversion is used.