PHARMACOLOGICAL TREATMENT OF VENTRICULAR- TACHYCARDIA

Pharmacological antiarrhythmic therapy is the treatment of first inten tion for the prevention of ventricular tachycardia (VT). In sustained VT, electrophysiological investigations without treatment enable the i nduction of VT, the demonstration of its reproductibility, the confirm ation of diagnosis (if necessary), the determination of its mechanism and the choice of treatment. In an effort to standardise the technique , a minimum acceptable protocol of stimulations was agreed upon : at l east 2 cycles (600 milliseconds and 400 milliseconds) and 3 extrastimu li (S2, S3, S4). The percentage of inducibility (sensitivity) depends on the underlying heart disease and is of the order of 90-95 % in coro nary artery disease with a history of infarction. Serial electrophysio logical studies show noninducibility of VT with treatment in 20-60 % o f cases. This result is influenced by the ejection fraction, the type of ventricular arrythmia (fibrillation or tachycardia) and the antiarr ythmic agent tested. A Class IA, then a Class IC antiarrhythmics or so talol (if the ejection fraction is over 40 %) are evaluated by this te chnique. Empiric therapy has no place in the management of malignant p oorly tolerated arrhythmias. In recurrent, well tolerated arrhythmias which are non-inducible, treatment may be guided by the results of Hol ter monitoring, providing the patient has a sufficient number of extra systoles. Exercise stress tests may be useful in effort or catecholami ne-induced tachycardias. There is no consensus about the management of non-sustained VT. When these arrhythmias are associated with syncope or cardiac arrest, programmed ventricular stimulation seems indicated. The choice of antiarrhythmic drugs and their results are reviewed. Al though the value of serial testing with amiodarone is debatable, non-i nducibility with amiodarone therapy remains a good prognostic indicato r. Recently reported results with Sotalol are worthnoting. In the choi ce of pharmacological treatment, whether a monotherapy or a combinatio n proarrhythmia, hemodynamic status and the patient's general conditio n must be taken into consideration.