Evaluation of response to dopamine in idiopathic dilated cardiomyopathy by echocardiography and thallium-201 myocardial scintigraphy.

Twenty-six patients with idiopathic dilated cardiomyopathy (DCM) underwent thallium-201 myocardial scintigraphy. Nine patients (group A) showed a perfusion defect in the interventricular septum (IVS) and 7 patients (group B) showed a defect in the left ventricular posterior wall (LVPW). Hemodynamic responses and catecholamine levels were compared between 16 patients (DCM group) and 6 control subjects (control group) following dopamine infusion (6 micrograms/Kg/min). The end-diastolic thickness of the IVS and LVPW, and the percentage wall thickening were assessed by echocardiography. Plasma dopamine and norepinephrine concentrations in the DCM group were not different from those of the control group at rest. During the dopamine infusion, however, norepinephrine increased only in the control group. There were significant differences in the thickness of the IVS among the 3 groups [7.3 +/- 1.4 mm for group A (p less than 0.001 vs control and p less than 0.05 vs group B), 8.9 +/- 1.5 mm for group B (p less than 0.01 vs control), 10.2 +/- 1.5 mm for the control group]. The percentage thickening of the IVS increased during the dopamine infusion in group B only and the thickening of the LVPW increased in group A only. Thus, in the myocardium of DCM patients with thallium perfusion defects, the degree of thickening did not change during dopamine infusion, but in the myocardium of DCM patients with normal thallium uptake the percentage thickening increased more than in the control group.