Cardiac sympathetic activity estimated by 123I-MIBG myocardial imaging in patients with dilated cardiomyopathy after beta-blocker or angiotensin-converting enzyme inhibitor therapy.

Abstract

Impaired cardiac sympathetic activity can be evaluated by 123I-metaiodobenzylguanidine (MIBG) imaging. We studied the significance of MIBG imaging for 24 patients (age 58+/-12 y) with dilated cardiomyopathy (DCM). We compared 12 patients (group A) treated with metoprolol (dose from 30-60 mg/d) with 12 patients treated with angiotensin-converting enzyme (ACE) inhibitors. Patients were studied before treatment, after 5 mo of treatment (only in group A) and after 1 y of treatment. Cardiac MIBG uptake was assessed as the heart-to-mediastinum activity ratio (H/M) and total defect score (TDS) from anterior planar and SPECT MIBG images, which were acquired in 4 h after tracer injection. New York Heart Association (NYHA) class and left ventricular ejection fraction (LVEF) calculated by echocardiography were also assessed. TDS decreased in both groups (in group A, from 30+/-7 through 23+/-9 to 18+/-10; P < 0.01, in group B, from 30+/-6 to 24+/-8; P < 0.01) and H/M was increased in both groups (in group A, from 1.87+/-0.31 through 2.03+/-0.28 to 2.14+/-0.29; P < 0.01, in group B, from 1.82+/-0.28 to 1.94+/-0.26; P < 0.05). But TDS and H/M were more improved in group A than in group B (P < 0.05). LVEF was significantly increased in only group A (from 38+/-6 through 43+/-8 to 49%+/-9%; P < 0.01). NYHA improved in both groups (in group A, from mean 2.5 through 2.1 to 1.8; P < 0.01, in group B, from mean 2.6 to 2.1; P < 0.05) but was more improved in group A than in group B (P < 0.05). Cardiac function, symptom and cardiac sympathetic activity evaluated by MIBG images improved after the beta-blocker therapy more than with the treatment that used ACE inhibitors.