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Antiarrhythmic drug therapy in the Multicenter UnSustained Tachycardia Trial (MUSTT): drug testing and as-treated
D G Wyse1, M Talajic, G E Hafley
1Division of Cardiology, University of Calgary, Health Science Center, Alberta, Canada. dgwyse@ucalgary.ca
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.
Insights
Programmed ventricular stimulation (PVS)-guided antiarrhythmic drug therapy did not improve outcomes in patients with coronary artery disease and unsustained ventricular tachycardia. Mortality rates were similar between PVS-guided therapy and control groups, regardless of PVS endpoints.
Area of Science:
- Cardiology
- Clinical Electrophysiology
- Pharmacology
Background:
- The Multicenter UnSustained Tachycardia Trial (MUSTT) investigated programmed ventricular stimulation (PVS) to guide antiarrhythmic therapy.
- Patients in MUSTT had coronary arteriosclerosis, left ventricular dysfunction, and asymptomatic, unsustained ventricular tachycardia (VT).
- Trial outcomes may be influenced by the selection criteria for antiarrhythmic drug therapy.
Purpose of the Study:
- To examine factors influencing antiarrhythmic drug selection in MUSTT.
- To assess the impact of PVS-guided antiarrhythmic therapy on patient outcomes.
- To evaluate the effectiveness of PVS endpoints in guiding therapy.
Main Methods:
- Comparison of patient subgroups with inducible sustained VT randomized to PVS-guided therapy (n=351) versus no antiarrhythmic therapy (controls, n=353).
- Specific analysis of patients receiving PVS-guided antiarrhythmic drug therapy (n=142).
- Assessment of PVS endpoints: noninducibility versus hemodynamically stable induced VT.
Main Results:
- "Effective" antiarrhythmic drug therapy, defined as noninducible or hemodynamically stable VT, was achieved in 43% of patients (142/351), often within the first two PVS sessions.
- Mortality rates did not differ between the PVS-guided therapy group and the control group.
- No significant difference in mortality was observed between PVS noninducibility and stable VT endpoints, though arrhythmias were more frequent in the latter group.
Conclusions:
- PVS-guided antiarrhythmic drug therapy showed no benefit in patients with clinical unsustained VT and inducible sustained VT.
- These findings remained consistent regardless of the PVS endpoint used or the specific antiarrhythmic drugs considered.
- The study suggests that PVS-guided therapy does not improve outcomes in this specific patient population.
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