What do I do about non-sustained ventricular tachycardia on a 24 hour tape?

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 electrophysiological 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 antiarrhythmic 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, asymptomatic nonsustained VT and inducible, non-suppressible VT following myocardial infarction. However, many important questions remain about the prophylactic implantation of ICDs in such patients. The decision to implant is easier if there is a history of presyncope or syncope.