INCREASED MYOCARDIAL [I-123] METAIODOBENZYLGUANIDINE UPTAKE AFTER ENALAPRIL TREATMENT IN PATIENTS WITH CHRONIC HEART-FAILURE

Objective - To assess non-invasively the effect of enalapril on cardia c sympathetic neuronal uptake function in patients with congestive hea rt failure, by using [I-123]-metaiodobenzylguanidine (MIBG), which is a noradrenaline analogue. Cardiac MIBG uptake was visualised by single photon emission tomography (SPET). In addition, plasma noradrenaline concentration, indicating systemic sympathetic activity, was measured to see whether it was related to cardiac MIBG uptake. Design - Consecu tive patients were treated with enalapril and served as their own cont rols. Setting - Cardiac unit of a tertiary care centre. Patients - 23 Patients with chronic, mild to moderate, stable congestive heart failu re, and a left ventricular ejection fraction less than 40%. Heart fail ure was caused by ischaemic heart disease or was idiopathic. Intervent ions - Cardiac MIBG SPET was performed and plasma noradrenaline concen tration was measured before and after 6 weeks treatment with enalapril . Main outcome measures - Cardiac uptake of MIBG was measured by using the left ventricular cavity and a venous blood sample as a reference. Results - Cardiac uptake of MIBG increased significantly after enalap ril treatment, indicating improved cardiac neuronal uptake function. P lasma noradrenaline concentration did not decrease significantly. Card iac MIBG uptake was not related to plasma noradrenaline concentration. Conclusions - Cardiac MIBG SPET can be used to assess changes in card iac sympathetic neuronal uptake function caused by pharmacological int ervention. Enalapril seemed to improve cardiac sympathetic neuronal up take function but did not significantly affect plasma noradrenaline co ncentrations in a group of patients with predominantly moderate heart failure. These results accord with the hypothesis that restoration of cardiac neuronal uptake of noradrenaline is one of the beneficial effe cts of enalapril in such patients.