Long-term effects of the angiotensin-converting enzyme inhibitor enalaprilon chronic heart failure - Examination by I-123-MIBG imaging

To examine the long-term effects of the angiotensin-converting enzyme (ACE) inhibitor enalapril on chronic heart failure, 10 patients (7 men and 3 wom en, mean age: 62 +/- 11 years) with chronic stable heart failure, classifie d as New York Heart Association (NYHA) functional class 2-3 for more than 3 months, and a left ventricular ejection fraction less than 45% were treate d with 2.5-5.0 mg of enalapril once a day for 3-15 months (mean 7 months). The causes of heart failure were old myocardial infarction (n = 7), hyperte nsion (n = 2), and atrial fibrillation (n = 1). Radioiodinated metaiodobenz yl guanidine (I-123-MIBG) imaging, radionuclide angiography, and treadmill exercise test were performed before and after the treatment. With enalapril treatment, (1) left ventricular ejection fraction (LVEF) increased signifi cantly from 38.3 +/- 6.9% to 47.5 +/- 14.7%; (2) sub-maximal exercise time increased significantly from 205 +/- 112 to 272 +/- 120 seconds; (3) the he art to mediastinum (H/M) ratio of I-123-MIBG increased significantly (early image: 1.99 +/- 0.38 versus 2.20 +/- 0.50; delayed image: 1.86 +/- 0.44 ve rsus 2.09 +/- 0.51); and (4) the washout rate of I-123-MIBG decreased sligh tly from 29.1 +/- 9.1% to 25.4 +/- 7.0%. The improvement rate of LVEF was s ignificantly correlated with the improvement rates of the H/M ratio and was hout rate after treatment with enalapril. Thus, the long-term, effects of e nalapril can be observed in the cardiac sympathetic nervous system, and I-1 23-MIBG imaging appears to be useful for evaluating the therapeutic effects of enalapril on the cardiac sympathetic nervous system in patients with ch ronic heart failure.