Antiarrhythmic drug therapy in the Multicenter Unsustained Tachycardia Trial (MUSTT): Drug testing and as-treated analysis

OBJECTIVES: Using data from the Multicenter UnSustained Tachycardia Trial (MUSTT), we examined the factors used to select antiarrhythmic drug therapy and their impact on outcomes. BACKGROUND: The MUSTT examined the use of programmed ventricular stimulation (PVS) to guide antiarrhythmic therapy in patients with coronary arteriosclerosis, left ventricular dysfunction and asymptomatic, unsustained ventricular tachycardia (VT). Trial outcomes may reflect factors used to select antiarrhythmic drug therapy. METHODS: We compared subgroups of patients with inducible sustained VT randomized to PVS-guided antiarrhythmic therapy (n = 351), in particular those receiving PVS-guided antiarrhythmic drug therapy (n = 142) versus no antiarrhythmic therapy (controls, n = 353). RESULTS: "Effective" antiarrhythmic drug therapy (i.e., the term "effective" was used to denote therapy that resulted in noninducible VT or hemodynamically stable induced VT) was found for 142 of the 351 patients (43%), most often at the first or second PVS session (125/142, 88%). Mortality among the 142 patients did not differ from that among control patients. Of these 142 patients, the PVS end point was noninducibility in 91 patients and stable VT in 51 patients. Mortality did not differ between these two groups either, but arrhythmia was numerically more frequent in the PVS-induced stable VT group. Mortality was greatest in the few patients receiving propafenone (unadjusted p = 0.07, adjusted p = 0.14 vs. controls), but mortality with all agents did not differ from that of controls, even after adjustment. CONCLUSIONS: Even when presenting the results as favorably as possible, we found no benefit with PVS-guided drug therapy in patients with clinical unsustained VT who had inducible sustained VT. These findings are unaltered by using different end points for PVS or considering the response to individual drugs.