Effects of right lateral decubitus position on plasma norepinephrine and plasma atrial natriuretic peptide levels in patients with chronic congestive heart failure

Abstract

P with chronic congestive heart failure (CHF) have fatigue and dyspnea with exercise intolerance and a poor prognosis. Fluid retention along with peripheral vasoconstriction and reduced skeletal muscle perfusion provide the physiologic basis for the symptoms. Neurohormonal modulation by norepinephrine (NE), atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) are heavily involved in the clinical manifestations of patients with CHF. We have recently reported that posture largely affects the autonomic nervous activity in patients with CHF. In the right lateral decubitus position, sympathetic tone decreased, whereas parasympathetic activity increased. In the present study, we hypothesized that neurohormonal environment of patients with CHF is ameliorated in the right lateral decubitus position because these patients prefer the position. • • • The study group consisted of 14 patients (8 men and 6 women, mean age 72 14 years) with CHF due to coronary artery disease (Table 1). Three patients had New York Heart Association functional class II CHF, 10 had class III, and 1 had class IV. The mean left ventricular ejection fraction was 39 18%. No patient had diabetes mellitus. A constant diuretic, digitalis, calcium antagonist, nitrate, angiotensin-converting enzyme inhibitor, and angiotensin II antagonist dosing regimen was continued. However, -blocking therapy had been withdrawn at least 7 days earlier. Eight ageand sex-matched New York Heart Association functional class I patients with normal left ventricular function (5 men, 3 women, mean age 69 13 years) were selected as the control group. In the early morning, each of the 3 positions (left lateral decubitus, supine, right lateral decubitus) was maintained for 1 hour before blood samples were drawn from a peripheral vein through an indwelling catheter. The order of each position was randomized. Plasma NE, ANP, and BNP levels were then measured by radioimmunoassay. All patients provided informed consent to the protocol, which was approved by the human subjects review committee of Takeda Hospital. Data are expressed as mean SD. Comparisons of variables between the 2 groups were conducted by Fisher’s exact test or unpaired Student’s t test. Multiple comparisons were performed by 2-way analysis of variance, followed by the Tukey-Kramer test for each parameter among the 3 recumbent positions of both groups of patients. Results were considered significant at p 0.05. Plasma NE concentrations were higher in patients with CHF than in those with normal LV function (Figure 1A). In addition, plasma NE concentrations were significantly lower in the right lateral decubitus position than those in the left lateral decubitus and supine positions. Plasma ANP and BNP concentrations were also higher in patients with CHF than in those with normal left ventricular function (Figures 1B and 1C). In addition, in patients with CHF, plasma ANP concentrations were higher in the right lateral decubitus position than those in the left lateral decubitus and supine positions, although plasma BNP levels did not significantly differ among the 3 recumbent positions. In patients with normal left ventricular function, there were no significant differences in these From the Departments of Cardiovascular Medicine and Cardiovascular Surgery, Kyoto University, Kyoto; Division of Cardiology, Takeda Hospital, Kyoto; Division of Cardiology, National Cardiovascular Center, Osaka; Department of Medicine, Division of Cardiology, Kitano Hospital, The Tazuke Kofukai Medical Research Institute, Osaka; Second Department of Internal Medicine, Kansai Electric Power Hospital, Kanasi; and College of Medical Technology, Kyoto University, Kyoto, Japan. Dr. Fujita’s address is: College of Medical Technology, Kyoto University, 53 Kawaharacho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan. E-mail: mfujita@kuhp.kyoto-u.ac.jp. Manuscript received June 29, 2001; revised manuscript received and accepted September 25, 2001. TABLE 1 Clinical Characteristics of Eight Patients With Normal Left Ventricular Function and 14 Patients With CHF