Background: A minority of heart failure (HF) patients who undergo implantable cardioverter defibrillator (ICD) implantation for primary prevention of sudden cardiac death (SCD) receive device therapy. Whether the addition of mIBG scintigraphy to conventional markers of arrhythmic risk can provide incremental risk stratification in HF patients has not been investigated.
Methods: We identified 778 patients from the ADMIRE-HF study with LVEF < 35% and class II or III HF symptoms who did not have an ICD at the time of enrollment. Patients were followed up prospectively (median 5 17 months) for occurrence of arrhythmic events (ArE). Heart-to-mediastinum ratio (HMR) was determined as a measure of relative myocardial sympathetic nerve activity at baseline using 123I-mIBG. The primary endpoint was the first occurrence of ArE: a composite of SCD, appropriate ICD therapy, resuscitated cardiac arrest or sustained ventricular tachycardia. Multivariate regression was used to determine independent predictors of ArE and to derive a risk score for ArE prediction. The score was used to group patients according to their risk for ArE. Integrated discrimination improvement (IDI) was used to quantify improvement in risk assessment with addition of HMR.
Results: ArE occurred in 54 patients (6.9%). ArE predictors were:HMR < 1.6 (HR 3.5, 95%CI [1.52-8], P 5 .02), LVEF < 25% (HR 2.0, 95% CI [1.28-3.05], P 5 .04) and SBP < 120 (HR 1.2,95%CI [1.03-1.39], P 5 .02). Event rates in the low-, intermediate-, and high risk groups were 2, 10 and 16%, respectively (P 5 .001). The score significantly improved risk prediction(IDI 5 45%, P 0.03).
Conclusion: 123I-mIBG significantly provides incremental risk stratification for ArE in HF patients.