Abstract 1664: Impact of Ischemic Burden and Revascularization on Outcomes among Patients Receiving Drug Therapy Versus an Implantable Cardioverter Defibrillator in MUSTT: Evidence for Ischemia Induced Proarrhythmia
Background. ICD implantation for primary prevention of sudden death in patients with ischemic cardiomyopathy and left ventricular dysfunction is well established. However debate exists between the relationship between ischemia and the proarrhythmic state. Persistent ischemia may counter antiarrhythmic (AA) drug and/or device efficacy. Furthermore, the extent to which revascularization mitigates this influence of ischemia on efficacy is unknown.
Methods. 704 patients enrolled in the MUSTT trial were studied. Ischemia was determined by the presence of angina within 6 weeks of enrollment and ≥ 2 reversible thallium defects. Revascularization was characterized as CABG or PTCA within 1 year of enrollment or the use of thrombolytics with the sentinal myocardial infarction (MI). We compared groups who were randomized to background medical treatment (BG Rx) verses those who were randomized to AA drug therapy in addition to EP testing (EP AARx).
Results. 507 (81%) patients had ≤2 vessel CAD, whereas the remaining 19% had 3 vessel disease. 268 patients reported angina within 6 weeks of study enrollment. Thallium imaging revealed 0–1 defects in 458 (65%) and ≥2 in another 246 (35%). Those with ≥ 2 defects on Thallium and angina within 6 weeks of device implant had a significantly lower 5-year freedom from mortality in the EP AARx and BG Rx cohorts (Table⇓). Patients with EP AARx had an 8% lower mortality than those with BG Rx therapy alone if they received thrombolytics. However, if they did not receive thrombolytics, their mortality rate was 5% higher than the BG Rx group.
Conclusion. Outcomes are worse in patients on antiarrhythmic therapy with ischemic factors compared to those on background therapy alone, particularly in the setting of recent angina. A proarrhythmic effect from antiarrhythmic drug therapy in patients with ischemia may underlie the higher mortality. ICD therapy mitigates the negative long-term effect of ischemia on mortality in those treated with AA therapy.