Clinical Progress Series Current Status of Antitachycardia Devices

M anagement of hemodynamically significant supraventricular and ventricular tachyarrhythmias is often a difficult problem for the practicing cardiologist. Not only is there considerable controversy regarding the appropriate technique to guide the selection of therapy (i.e., noninvasive versus invasive techniques), but the available therapeutic options continue to expand. Antitachycardia therapy now includes not only pharmacological agents but also ablative techniques (surgical or catheter) and implanted devices. It is this latter antitachycardia treatment modality that forms the basis for this review. Much of the impetus for the development of effective antitachycardia device therapy has risen from the limitations of the other therapeutic options available. Pharmacological antiarrhythmic therapy, whether guided by empirical trial or invasive electrophysiological testing, identifies an agent capable of suppressing tachycardia occurrence in a minority of patients. Of considerable concern in patients with life-threatening arrhythmias is the occurrence of arrhythmia recurrence despite predicted success during rigorous testing before discharge.1-5 The problem of serious proarrhythmic effects of antiarrhythmic drugs, most recently raised by the CAST trial,6 also may limit this option in addition to less serious but frequent side effects. For sustained ventricular tachyarrhythmias, amiodarone has been perceived as the most efficacious pharmacological option, but its use has been limited by its significant side-effect profile and the 30-40% recurrence rate in 1-2-year follow-up studies, which cannot be predicted.7-10 Although catheter ablation techniques are promising for patients with circus movement tachycardias, particularly those using posteroseptal bypass tracts" and dual atrioventricular (AV) nodal pathways,12 they carry some risk and appear to be limited in usefulness for ventricular tachycardia (VT).13 Similarly, surgical ablative techniques have become accepted therapy in patients with supraventricular tachycardia (SVT) us-