Extension of myocardial necrosis differently affects MIBG retention in heart failure caused by ischaemic heart disease or by dilated cardiomyopathy

Purpose: This study aims to investigate the relationship between cardiac sympathetic nervous function (CSNF) and myocardial perfusion/function in patients with heart failure (HF) due to dilated cardiomyopathy (DCM) or ischaemic heart disease (CAD). Methods: Twenty patients (10 DCM, 10 CAD, 17 males, age 69±5 years) with NYHA class IIIb HF were studied. CSNF was evaluated by early/delayed 123I-metaiodobenzylguanidine (MIBG) uptake and regional washout (WO). Myocardial perfusion and function were evaluated by 99mTc-tetrofosmin gated single-photon emission tomography (G-SPECT) using a 20-segment model for 400 segments. In each segment, regional MIBGWOwas computed as (count density in early images-count density in delayed images/count density in early images)×100. Results: DCM and CAD showed similar summed rest perfusion score (6.7±5 vs 9.5±5, p=NS) and mean ejection fraction values (29±7% vs 30±9%, p=NS). By contrast, the summed thickening score was higher in DCM than in CAD patients (26±7 vs 17±6, p<0.05). QGS analysis identified akinesis/dyskinesis in 129/137 (94%) severely hypoperfused segments which were considered as damaged. According to the underlying aetiology of HF, marked differences in regional MIBGWOwere observed. In fact, within theCAD group, regional MIBG WO was lower in reference than in damaged segments (38±21% vs 46±19%, p<0.05). By contrast, in DCM patients, regional MIBG WO was faster in reference than in damaged segments (49±18% vs 41±30%, p<0.05). When the two groups were directly compared, regional MIBG WO from damaged areas was similar irrespective of the underlying disease, while it was faster in DCM than in CAD patients from reference segments. Conclusion: These data confirm the hypothesis that the presence of myocardial necrosis in HF due to CAD and the consequent loss of neuronal endings cause alterations in regional MIBGWOdifferent from those observed in DCM.