Effects of infusions of different doses of dopamine in dilated cardiomyopathy. Observations during and after treatment with beta-blockers

It is well known that there are abnormalities of the sympathetic nervous system in chronic congestive heart failure. The aim of our study was to verify the effects on heart rate, blood pressure and some echocardiographic parameters of performance and inotropic state of iv infusion of dopamine at different dosages in 14 patients affected by dilated cardiomyopathy. The patients were divided into 3 groups: the first one of patients on standard treatment, the second of subjects on standard treatment and beta blockers, the third of patients who stopped beta blocker therapy and remained on standard therapy. In the first group dopamine at low dosage did not significantly modify heart rate, blood pressure, performance and contractile state, while it did decrease end systolic wall stress. In the second group the same dosage significantly decreased blood pressure and stress, maintaining unchanged the other indexes; the same behaviour was presented by the third group. At high dosage dopamine in the first group significantly increased blood pressure, ejection fraction, contractility and stress. No modifications were observed in the second group, probably because of a pharmacological inhibition of beta receptors. The third group showed a significant increase in blood pressure, stress and inotropic state. From our data it appears that dopamine treatment in chronic congestive heart failure may reveal the presence of the so-called "down regulation" phenomenon