Effects of angiotensin II receptor antagonists on [¹²³I]metaiodobenzylguanidine myocardial imaging findings and neurohumoral factors in chronic heart failure

Abstract

 Previous studies have not investigated the ef-ficacy of angiotensin II (AII) receptor antagonists against cardiac sympathetic overactivity in patients with chronic heart failure (CHF) using [¹²³I]metaiodobenzylguanidine (MIBG) myocardial imaging. We studied 34 CHF patients with fractional shortening of the left ventricular (LV) diameter ≦25% or LV ejection fraction ≦45% in echocardiograms. An AII receptor antagonist (losartan or candesartan) was administered. Before and 6 months after the administration, MIBG myocardial imaging and echocardiography were performed, and neurohumoral factors were investigated. MIBG imaging revealed that the antagonist did not significantly change the heart-to-mediastinum ratio. However, the washout rate fell significantly (from 32.6% ± 7.6% to 28.2% ± 7.5%; P < 0.001). No significant changes occurred in LV diameter, fractional shortening, or LV ejection fraction. Circulating atrial (ANP) and brain natriuretic peptides (BNP), and aldosterone fell significantly. Changes in the MIBG washout rate correlated positively with changes in BNP (r = 0.35, P < 0.05). In 19 patients also being treated with angiotensin-converting enzyme (ACE) inhibitors, the MIBG washout rate also fell significantly with AII antagonists, as did BNP and aldosterone. The decreased MIBG washout and BNP in patients with CHF induced by the AII receptor antagonists suggests the efficacy of these agents in modifying cardiac sympathetic function and neurohumoral factors, even with ACE inhibition. Combination therapy with AII receptor antagonists and ACE inhibitors appears effective for CHF.