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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.

The iron absorption from heme, ferritin and vegetable foods was tested in 63 humans (10 males and 53 females). The iron absorption from heme in beef exposed to prolonged heating was markedly reduced, following the degree of denaturation of the heme. The iron absorption from ferritin was about 31% of the absorption of the reference dose when administered with meat alone, falling to 11% of the reference dose when administered in a meal containing meat and vegetable foods. The absorption of ferritin iron was less than half that of vegetable iron. The data confirm a previous proposal that ferritin forms part of a subgroup of the non-heme iron pool.