Improvement of cardiac neuronal function after carvedilol treatment in dilated cardiomyopathy:: A 123I-MIBG scintigraphic study

Carvedilol can induce important clinical and hemodynamic improvements in patients with chronic heart failure resulting from severe left ventricular (LV) dysfunction. This study examines the impact of carvedilol on cardiac neuronal function using I-123-metaiodobenzylguanidine (MIBG) scintigraphy in dilated cardiomyopathy. Methods: Twenty-two patients with chronic heart failure (19 men, 3 women; mean age, 54 y; age range, 34-64 y) assessed as New York Hospital Association (NYHA) class II or III and with initial resting radionuclide LV ejection fractions (LVEF) < 0.40 were enrolled in the study. Patients had long histories of symptomatic LV dysfunction despite optimal diuretics and angio tensin-converting enzyme inhibitor treatment. Over a 6-mo period, 50 mg/day carvedilol was administered to these patients. Planar I-123-MIBG scintigraphy provided measurements of cardiac neuronal uptake (as heart-to-mediastinum count activity ratio [HMR]), 4h after intravenous injection of 185 MBq MIBG. Hemodynamic, clinical, radionuclide LVEF and HMR data measured at the outset and after 6 mo of carvedilol were compared. Results: Resting heart rate decreased from 81 +/- 13 to 71 +/- 9 bpm (P = 0.003). After carvedilol therapy NYHA functional classification for these patients improved from 2.6 +/- 0.5 to 2.3 +/- 0.5 (P = 0.04), LVEF improved from 22% +/- 9% to 30% +/- 13% (P = 0.005), and HMR improved from 145% +/- 23% to 170% +/- 25% (P = 0.0001). Conclusion: Carvedilol induces improvements of clinical symptoms and cardiac neuronal and systolic functions in patients with dilated cardiomyopathy and chronic optimal treatment.