Concordance between rest MIBG and exercise tetrofosmin defects: possible use of rest MIBG imaging as a marker of reversible ischaemia

Abstract

Perfusion imaging combined with pharmacological stress is the study of choice in patients with ischaemic heart disease who are incapable of exercising. Some medical conditions, however, can preclude the use of pharmacological stress. In these particular situations, availability of a diagnostic test which allows for the assessment of ischaemic territory at rest would be desirable. With the purpose of providing a marker of reversible ischaemia, we evaluated myocardial iodine-123 metaiodobenzylguanidine (MIBG) uptake in regions with fixed and reversible defects defined by exercise/rest perfusion study. Fifty-four male patients with ischaemic heart disease and previous myocardial infarction were studied by means of exercise/rest tetrofosmin and MIBG single-photon emission tomography (SPET). Regional tracer uptake was quantified and expressed as a percentage of maximum peak activity. Areas with denervated but perfused myocardium and areas with ischaemic myocardium were calculated. Regions with<75% of peak activity in the exercise perfusion study were divided into two groups according to whether the increase in peak activity in the respective rest study was >10% (reversible regional defect) or <10% (fixed regional defect). These percentages were compared with the percentages of the innervation study. The area of the innervation defect was significantly larger when the perfusion defect was reversible than when it was fixed. In regions with reversible perfusion defects, the size of the area of denervated but perfused myocardium was similar to the size of the area of ischaemic myocardium. In regions with reversible defects, the percentage of myocardial MIBG uptake was not significantly different from the percentage of tetrofosmin uptake at exercise, while it was significantly lower than the percentage of tetrofosmin uptake at rest. In regions with fixed defects, the percentage of myocardial MIBG uptake was significantly lower than the percentage of tetrofosmin uptake at exercise and at rest. In patients who developed angina during exercise test, the area of denervated but perfused myocardium was significantly larger than in patients without angina (4.1+/-2.4 vs 3.4+/-2.5, P=0.02). The same trend was observed with regard to the size of the innervation defect (8.6+/-2.4 vs 5.7+/-2.2, P=0.02). It is concluded that when the use of pharmacological stress is not possible in patients incapable of exercising, rest studies with MIBG combined with rest myocardial perfusion studies may be useful as a marker of reversible ischaemia.

Cardiac Sympathetic Imaging With mIBG in Heart Failure

“…This concordance suggests that resting imaging with 123 ImIBG combined with resting myocardial perfusion imaging (MPI) may be useful as a marker of reversible ischemia in patients unable to exercise and with contraindications to pharmacological stress (27). Another potential role of mIBG imaging at rest is the detection of transient ischemia, which has been shown with metabolic tracers of both fatty acid and glucose analogs, termed "ischemic memory," that may result in regional decrease in mIBG uptake (28 -32).…”

Ventricular Distribution Pattern of the Novel Sympathetic Nerve PET Radiotracer 18F-LMI1195 in Rabbit Hearts

“…Estorch et al . reported that in patients who developed angina during exercise test, the area of denervated but perfused myocardium was significantly larger than in subjects without angina 23 . Matsunari and coworkers reported similar findings: Sympathetic neuronal damage measured by 123 I-mIBG was larger than the infarct size assessed by perfusion imaging, suggesting higher susceptibility of sympathetic neurons compared to cardiac myocytes 21 .…”

123I-MIBG SPECT for Evaluation of Patients with Heart Failure

“…Although most of these studies relied primarily on planar imaging determinations of HMR and washout rate, some also included measurements from SPECT examinations because of the realization that SPECT may overcome the difficulties of planar imaging, including superposition of noncardiac structures and lack of segmental analysis (Fig. 1) 123 I-MIBG SPECT has been shown to be complementary to planar imaging in studies of coronary artery disease after an acute myocardial infarction (MI) (23,24). Viable but denervated myocardium has been shown to be supersensitive to the effects of infused catecholamines (25), which may provide a substrate for the genesis of ventricular arrhythmias.…”