Patients with
coronary artery disease, depressed left ventricular ejection fraction, and
nonsustained ventricular tachycardia (VT) have a high mortality rate due to arrhythmic (arrhythmic
death/cardiac arrest) and other cardiac causes. The Multicenter UnSustained
Tachycardia Trial (MUSTT) investigated whether electrophysiologic study (EPS) was helpful in choosing
drug or
defibrillator therapy in patients induced into sustained VT. The events committee attempted to categorize follow-up events in patients in MUSTT and to present a detailed breakdown of events. A derivative of the Hinkle-Thaler classification was used, incorporating lessons from other multicenter studies. The committee was blinded to results of EPS and
implantable cardioverter-defibrillator (ICD) or other antiarrhythmic
therapy status of patients. The primary end point was
cardiac arrest or death from
arrhythmia. Secondary end points were death from all causes, cardiac causes, and spontaneous sustained VT. Classifications were death and
cardiac arrest. Each was similarly divided as arrhythmic with 14 subcategories, e.g., unwitnessed or related to EPS and nonarrhythmic with 10 subcategories, e.g.,
ischemia. Terminal VF in progressive
heart failure was considered nonarrhythmic. Events were reviewed by 2 members. Disagreements were resolved by the 2 members or, if needed, by the full committee. Of the 2,202 patients in MUSTT, there were 902 deaths. Sustained VT requiring
cardioversion occurred in 182 patients. An additional 94 patients had resuscitated cardiac arrests. Events occurred in 1,027 patients, and all were reviewed. The 3 leading events were deaths that were classed as sudden/unwitnessed (23% of 902), due to progressive
heart failure (22%), or due to noncardiovascular causes (18%). Arrhythmic deaths or cardiac arrests were highest in inducible patients randomized to no antiarrhythmic
therapy; next were inducible patients receiving an ICD; and lowest were in patients who were noninducible. In conclusion, the classification system provided a detailed breakdown of events in consistent categories, showing utility for event analysis and interpretation and development of therapeutic strategies. The classifications assigned by the committee were used in all MUSTT outcomes reports, thus affecting all reported outcomes and overall interpretations of the MUSTT.