123I-mIBG and 99mTc-tetrofosmin SPECT for prediction of arrhythmic risk in ischemic heart failure patients

Objectives While an abnormal heart/mediastinal (H/M) ratio on planar cardiac 123I-mIBG imaging is associated with increased risk for adverse outcomes in heart failure (HF) patients (pts), the significance of SPECT image findings is less clear. The present study examined the potential utility of mIBG SPECT in combination with rest 99mTc-tetrofosmin perfusion SPECT for prediction of arrhythmic events (ArE) in pts with ischemic HF.

Methods Of 635 ischemic HF pts (NYHA II/III, LVEF≤35%) in the ADMIRE-HF study, 546 had assessable 4-hour planar (for H/M ratio determination) and SPECT mIBG and rest tetrofosmin SPECT studies. SPECT images were read together by 2 experienced readers and scored by consensus using a standard 17-segment/4-point scoring system. Total mIBG defect and mIBG/tetrofosmin mismatch scores were analyzed using Cox proportional hazard ratios (HR) and Kaplan Meier survival analyses vs. occurrence of ArE (sustained VT, resuscitated cardiac arrest, appropriate ICD activation).

Results During a 2-year median follow-up, 41 pts (7.5%) had ArE. Independent predictors for ArE were NYHA class (HR: 0.36, 95%CI: 0.16-0.83), LVEF (HR: 0.92, 95%CI: 0.87-0.98), and mIBG defect score (HR: 0.97, 95%CI: 0.94-0.99). The lowest risk for ArE was for subjects with mIBG SPECT defect scores <14 while the highest risk was for subjects with intermediate scores (14-28). In relation to pts with scores>28, the HR for this group was 2.34 (95%CI: 1.06-5.12). Intermediate mIBG SPECT score pts at particularly high-risk for ArE were those with NYHA II and LVEF<30% (HR 3.17; 95%CI: 1.13-8.85) and those with H/M 1.30-1.59 (Figure).

Conclusions mIBG SPECT defect but not the mIBG/tetrofosmin mismatch score was a predictor of ArE. Highest risk was in patients with intermediate mIBG SPECT scores, adding to H/M findings on planar imaging.

Research Support The study was supported by an unconditional grant from GE Healthcare.