100 QUESTIONS IN CARDIOLOGY

81 What do I do about non-sustained ventricular

tachycardia on a 24 hour tape?

Simon Sporton

The term non-sustained ventricular tachycardia (VT) is used

conventionally to describe salvos lasting a minimum of four

consecutive ventricular beats and a maximum of 30 seconds in the

absence of intervention. The concerns are that the non-sustained

VT may itself cause symptoms of palpitation, presyncope or

syncope and that the arrhythmia may persist or degenerate into

ventricular fibrillation. The finding of non-sustained VT on a 24

hour tape should prompt the following questions: firstly, is there

evidence of underlying heart disease; secondly, what is the

morphology of the VT; thirdly, what are the patient’s symptoms?

An arrhythmia is usually although not invariably a sign of

underlying heart disease. This is an important consideration

because treatment of the underlying condition, where possible, is

likely to be more effective than antiarrhythmic drug therapy both

in terms of preventing the arrhythmia and improving prognosis.

Conversely, if treatable underlying heart disease remains untreated

then antiarrhythmic drug therapy is unlikely to be successful.

The morphology of the VT may help to guide management: for

example if torsade de pointes is observed then management will

focus on adjustment of drug regimes and treatment of electrolyte

deficiencies and bradycardia. The finding of monomorphic VT

might suggest the presence of a re-entrant circuit or automatic

focus that may be amenable to mapping and modification or

ablation. Non-torsade polymorphic VT is typically seen in the

context of heart failure and is seldom reliably induced by electro-

physiological study or amenable to radiofrequency ablation.

There is little evidence that antiarrhythmic drug therapy alters

prognosis in patients with non-sustained VT. This may reflect a

lack of efficacy and/or toxicity of currently available anti-

arrhythmic agents. Another explanation is that non-sustained VT

is frequently a marker of underlying heart disease, which itself

determines prognosis. There is evidence that implantable

cardioverter-defibrillators (ICDs) may improve the prognosis of

patients with poor left ventricular function, asymptomaticnon-

sustained VT and inducible, non-suppressible VT following

myocardial infarction. However, many important questions