Impact of concomitant medication use on myocardial ¹²³I-mIBG imaging results in patients with heart failure

Introduction Medications that interfere with sympathetic neuronal norepinephrine uptake and storage, such as neuropsychiatrics (NP) and sympathomimetic amines, are most likely to affect cardiac uptake of iodine-123 metaiodobenzylguanidine (¹²³I-mIBG). The present study examined these and other medications reported to affect ¹²³I-mIBG uptake using measurements of cardiac ¹²³I-mIBG uptake on the heart failure (HF) patients in the ADMIRE-HF extension (X) study. Methods Baseline concomitant medications taken by the 961 HF patients were categorized into five groups: calcium channel blockers, NP medications, β agonists and sympathomimetics, α antagonists, and other antihypertensives. NP medications were further subcategorized into those expected to have high and low impact on norepinephrine transporter (NET) function. Myocardial ¹²³I-mIBG heart/mediastinum (H/M) uptake ratios on 4 h planar images were compared among the groups. Impact of medication group on the prognostic value of the H/M ratio for all-cause (AC) and cardiac death during a median 2-year follow-up was also examined. Results A total of 283 (29%) patients were using at least one calcium channel blocker, NP medication, or β agonist or sympathomimetic. These patients had a lower mean H/M ratio than the other study patients (1.42 ± 0.20 vs. 1.45 ± 0.20; P=0.022). However, the 2-year AC mortality rates in the two groups were the same [11.3% (95% confidence interval: 7.5 15.2%) vs. 11.8% (95% confidence interval: 9.2 14.4%)]. In terms of medication categories, there were no significant differences in the mean H/M ratios between patients who did and did not use NP medications, β agonists, calcium channel blockers, and α antagonists. Across all categories, patients with H/M ratio greater than or equal to 1.60 had lower AC and cardiac mortality. Patients using higher potency (for NET inhibition) NP medications had significantly lower H/M ratio values, but the prognostic significance of H/M ratio greater than or equal to 1.60 was unchanged. Conclusion Only a small number of higher potency NETinhibiting NP medications have a measurable effect on the results of ¹²³I-mIBG myocardial imaging. There appears to be no basis for restricting the use of calcium channel blockers and β agonist respiratory medications in HF patients referred for cardiac ¹²³I-mIBG imaging.