Sympathetic Activation and Loss of Reflex Sympathetic Control in Mild Congestive Heart Failure

Abstract

Background Baroreflex control of sympathetic activity is impaired in severe congestive heart failure (CHF), probably causing the marked sympathetic activation typical of this condition. Little information exists, however, as to whether baroreflex impairment and related sympathetic activation also occur in mild CHF. Methods and Results We studied 19 patients (age, 57.5±2.2 years, mean±SEM) with CHF in New York Heart Association (NYHA) class III or IV and with a marked reduction in left ventricular ejection fraction (LVEF, 30.1±1.5% from echocardiography) and 17 age-matched patients with CHF in NYHA class I or II and with an only slightly reduced LVEF (44.9±3.3%) that never was P <.05 and P <.01, respectively). Heart rate and MSNA were progressively reduced by phenylephrine infusion and progressively increased by nitroprusside infusion. Compared with control subjects, the responses were strikingly impaired in severe CHF patients, but a marked impairment also was seen in mild CHF patients. On average, baroreflex sensitivity in mild CHF patients was reduced by 59.1±5.5% (MSNA) and 64.8±4.8% (heart rate). In contrast, reflex responses to the cold-pressor test were similar in the three groups. Conclusions These results demonstrate that in mild CHF patients the baroreceptor inhibitory influence on heart rate and MSNA is already markedly impaired. This impairment may be responsible for the early sympathetic activation that occurs in the course of CHF.