Effects of Short-term Carvedilol on the Cardiac Sympathetic Activity Assessed by 123I-MIBG Scintigraphy

Background: Autonomic alterations in heart failure are associated with an increase in morbimortality. Several noninvasive methods have been employed to evaluate the sympathetic function, including the Meta-Iodobenzylguanidine (I-123-MIBG) scintigraphy imaging of the heart. Objective: to evaluate the cardiac sympathetic activity through I-123-MIBG scintigraphy, before and after three months of carvedilol therapy in patients with heart failure and left ventricular ejection fraction (LVEF) < 45%. Patients and methods: Sixteen patients, aged 56.3 +/- 12.6 years (11 males), with a mean LVEF of 28% 8% and no previous use of beta-blockers were recruited for the study. Images of the heart innervation were acquired with I-123-MIBC, and the serum levels of catecholamines (epinephrine, dopamine and norepinephrine) were measured; the radioisotope ventriculography (RIV) was performed before and after a three-month therapy with carvedilol. Results: Patients' functional class showed improvement: before the treatment, 50% of the patients were FC II and 50% were FC III. After 3 months, 7 patients were FC I(43.8%) and 9 were FC II (56.2%), (p = 0.0001). The mean LVEF assessed by RIV increased from 29% to 33% (p = 0.017). There was no significant variation in cardiac adrenergic activity assessed by I-123-MIBC (early and late resting images and washout rate). No significant variation was observed regarding the measurement of catecholamines. Conclusion: The short-term treatment with carvedilol promoted the clinical and LVEF improvement. However, this was not associated to an improvement in the cardiac adrenergic activity, assessed by I-123-MIBC scintigraphy, as well as the measurement of circulating catecholamines. (Arq Bras Cardiol 2010; 94(3):308-312)