[Hemodynamic effects of the nitroprusside test in chronic congestive heart failure treated with long-term beta...

In patients with congestive heart failure (CHF) sympathetic reflexes are attenuated because of down regulation of beta receptors. Many Authors suggest that betablockers therapy can be useful in selected patients. We wanted to test if betablockers therapy could modify sympathetic reflex during nitroprusside test. We studied 20 patients: 10 were healthy volunteers and 10 were affected by CHF of different origin. They were divided in 4 groups in relation to therapy. During nitroprusside infusion we evaluated the following parameters: heart rate (HR), mean arterial pressure (MAP), mean pulmonary arterial pressure (MPAP), pulmonary capillary wedge pressure (PCWP), right atrial pressure (RAP), cardiac index (CI), systemic vascular resistance (SVR), pulmonary vascular resistance (PVR). In normal subjects we observed that the heart rate increased and the PAM and SVR decreased significantly. Betablockers therapy did not modify hemodynamic response of PAM and SVR, while we did not find any modification of the heart rate. In patients with CHF we observed a decrease of PAM, MPAP, SVR and PVR. Betablockers therapy in CHF did not modify the hemodynamic response to nitroprusside test. This effect is probably due to beta adrenergic receptor down regulation that decrease the responsiveness to sympathetic stimulation evoked by vasodilatation.