Myocardial 123I-MIBG scintigraphy predicts an impairment in myocardial functional reserve during dobutamine stress in patients with idiopathic dilated cardiomyopathy

Abstract

We investigated whether myocardial (123)I-metaiodobenzylguanidine ((123)I-MIBG) scintigraphy predicts impairment of myocardial functional reserve in response to dobutamine stress in patients with idiopathic dilated cardiomyopathy (DCM). Forty DCM patients (LVEF 39 ± 12 %) underwent myocardial (123)I-MIBG scintigraphy, echocardiography, and cardiac catheterization. Myocardial (123)I-MIBG uptake was quantified as the delayed heart to mediastinum (H/M) ratio and washout rate (WR). Local denervation was evaluated on polar map images. LV dP/dt (max) and T(1/2) were determined from left ventricular pressure curves at baseline and during dobutamine infusion (15 μg/kg /min). Patients were classified into two groups as follows: group A comprised 21 patients showing a delayed H/M ratio of <1.9 (median value); group B comprised 19 patients showing a delayed H/M ratio of ≥ 1.9. The percentage change in heart rate (%HR), LV dP/dt (max) (%LV dP/dt (max)), and T (1/2) (%T (1/2)) from baseline to dobutamine stress were significantly more reduced in group A than in group B (39.3 ± 20.2 %, 55.2 ± 24.1 %, p < 0.01; 102.3 ± 46.3 %, 152.0 ± 72.3 %, p < 0.05; 38.7 ± 15.3 %, 46.9 ± 15.4 %, p < 0.05, respectively). No significant differences between the two groups were observed in the echocardiographic parameters or baseline cardiac catheterization parameters. Significant correlations were found between delayed H/M ratio and %HR (r = 0.35, p < 0.05), %LV dP/dt (max) (r = 0.45, p < 0.05) and %T (1/2) (r = 0.34, p < 0.05). Significant inverse correlations were also found between WR and %HR (r = -0.37, p < 0.05), %LV dP/dt (max) (r = -0.60, p < 0.0001), and %T (1/2) (r = -0.34, p < 0.05). SPECT images revealed enhanced denervation from the inferoposterior to anterior wall in accordance with the advancement of global denervation. Reduced (123)I-MIBG uptake and increased washout were related to impairment in adrenergic myocardial functional reserve in idiopathic DCM.