title: Standardization of plasma brain natriuretic peptide concentrations in older Japanese-relationship to latent renal dysfunction and ischemic heart disease.
abstract: OBJECTIVE
  To determine the contributors to elevating plasma brain natriuretic peptide (BNP) concentrations in older people with normal systolic function. To investigate the relationship between cyclic guanosine monophosphate (cGMP) and BNP in older people with and without ischemic heart disease (IHD).
  
  
  METHODS
  Observational study.
  
  
  METHODS
  Hospitalized patients in Nagoya University Hospital from November 1997 to May 2000.
  
  
  METHODS
  Younger patients (<65) without IHD (n = 31), older patients (> or=65) without IHD (n = 37), and older patients with stable IHD (n = 32). All participants showed 45% or greater of their left ventricular ejection fraction (LVEF).
  
  
  METHODS
  LVEF, peak atrial velocity/peak early velocity (A/E) ratio at the mitral valve, and left ventricular mass volume were measured using transthoracic echocardiogram. Plasma BNP level, cGMP, and serum creatinine (Scr) were measured. Creatinine clearance (CLcr) was calculated based on 24-hour urine collection.
  
  
  RESULTS
  Plasma BNP levels in older people with and without IHD were significantly greater than in younger patients (mean +/- standard deviation = 76.4 +/- 96.0 (P <.001), 165.2 +/- 200.6 (P <.001), and 8.1 +/- 7.0, respectively). By simple regression analysis, in the groups without IHD, the logarithm of plasma BNP (Log BNP) concentrations had a significant positive relationship with age (R = 0.657, P <.001), Scr (R = 0.449, P <.001), and A/E ratio (R = 0.326, P =.003) and a significant negative relationship with CLcr (R = -0.663, P <.001). A stepwise multiple regression analysis with Log BNP level as the dependent variable and age, Scr, CLcr, and A/E ratio as independent variables showed that CLcr was a significant independent contributor in groups without IHD (R = -0.766, P <.001). In this analysis, the regression coefficient of the intercept was 2.006, and that of CLcr was -0.010. The cGMP/BNP ratio in older subjects with stable IHD tended to be lower than in those without IHD (P =.063).
  
  
  CONCLUSIONS
  Elevated BNP levels in older patients with normal systolic function may be in part due to latent renal dysfunction, despite normal Scr levels. In healthy older people, it is important to exclude the effects of latent renal function in assessing cardiac function according to BNP level. In older subjects with stable IHD, the cGMP/BNP ratio tended to be lower than in those without IHD. This may be a reflection of a poor response of cGMP to BNP.
authors.affiliation: Department of Internal Medicine, Chubu Hospital, Obu, Aichi, Japan. h-nomura@za2.so-net.ne.jp
authors.forename: Hideki
authors.initials: H
authors.lastname: Nomura
authors.forename: Toshio
authors.initials: T
authors.lastname: Hayashi
authors.forename: Teiji
authors.initials: T
authors.lastname: Esaki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kanda
authors.forename: Hatsuyo
authors.initials: H
authors.lastname: Kano
authors.forename: Ayako
authors.initials: A
authors.lastname: Hattori
authors.forename: Akihisa
authors.initials: A
authors.lastname: Iguchi
mesh_terms: D000368:Aged; D003404:Creatinine / Q000097:blood / Q000378:metabolism; D006152:Cyclic GMP / Q000097:blood*; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000097:blood*; D008297:Male; D017202:Myocardial Ischemia / Q000097:blood*; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D013318:Stroke Volume
chemical_list: D020097:Natriuretic Peptide, Brain; D003404:Creatinine; D006152:Cyclic GMP