title: Prognostic value of myocardial MIBG scintigraphy findings in patients with cardiomyopathy--importance of background correction for quantification of MIBG activity.
abstract: OBJECTIVE
  To assess the prognostic value of I-123 metaiodobenzylguanidine (MIBG) scintigraphy findings, and establish the most appropriate method for calculating myocardial MIBG activity in patients with left ventricular dysfunction due to cardiomyopathy (CM).
  
  
  METHODS
  Predictors of cardiac death related to progressive heart failure (HF) were examined in 150 patients with CM (80 patients with idiopathic CM and 70 patients with ischemic CM). All patients underwent MIBG scintigraphy at rest and other hemodynamic studies when their clinical status was stable. MIBG scintigrams were obtained 15 minutes and 4 hours after the injection of the isotope. The parameters for quantification of myocardial MIBG activity were heart/mediastinal activity ratio (H/M) and myocardial washout rate (WR). The WR was calculated with and without background (BG) correction.
  
  
  RESULTS
  The WR showed better correlation with plasma norepinephrine and left ventricular ejection fraction after BG correction. During a mean follow-up period of 33 +/- 9 (7 to 54) months, 12 patients died due to HF; 7 patients due to progressive HF and 5 patients due to sudden cardiac death. Cox regression analysis indicated, the H/M and the WR with and withoutBG correction, were significant predictors of cardiac death (Wald chi-squared value: H/M [ 15 min] = 9.7, H/M [4 hr] = 19.5, WR with BG correction = 29.9, WR without BG correction = 12.6). WR prognostic value was better after BG correction, and a high WR with BG correction was the only independent predictor of cardiac death (relative risk [RR] = 1.174, p < 0.0001).
  
  
  CONCLUSIONS
  Accelerated WR is a powerful predictor of the patient's prognosis and BG correction is essential for calculating WR.
authors.affiliation: Department of Cardiology, Matsuyama Red Cross Hospital, Ethime, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Imamura
authors.forename: Takaya
authors.initials: T
authors.lastname: Fukuyama
mesh_terms: D019797:3-Iodobenzylguanidine; D016477:Artifacts; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000000981:diagnostic imaging* / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology / Q000401:mortality*
chemical_list: D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine