title: Myocardial 123I-MIBG scintigraphy predicts an impairment in myocardial functional reserve during dobutamine stress in patients with idiopathic dilated cardiomyopathy.
abstract: OBJECTIVE
  We investigated whether myocardial (123)I-metaiodobenzylguanidine ((123)I-MIBG) scintigraphy predicts impairment of myocardial functional reserve in response to dobutamine stress in patients with idiopathic dilated cardiomyopathy (DCM).
  
  
  METHODS
  Forty DCM patients (LVEF 39 ± 12 %) underwent myocardial (123)I-MIBG scintigraphy, echocardiography, and cardiac catheterization. Myocardial (123)I-MIBG uptake was quantified as the delayed heart to mediastinum (H/M) ratio and washout rate (WR). Local denervation was evaluated on polar map images. LV dP/dt (max) and T(1/2) were determined from left ventricular pressure curves at baseline and during dobutamine infusion (15 μg/kg /min). Patients were classified into two groups as follows: group A comprised 21 patients showing a delayed H/M ratio of <1.9 (median value); group B comprised 19 patients showing a delayed H/M ratio of ≥ 1.9.
  
  
  RESULTS
  The percentage change in heart rate (%HR), LV dP/dt (max) (%LV dP/dt (max)), and T (1/2) (%T (1/2)) from baseline to dobutamine stress were significantly more reduced in group A than in group B (39.3 ± 20.2 %, 55.2 ± 24.1 %, p < 0.01; 102.3 ± 46.3 %, 152.0 ± 72.3 %, p < 0.05; 38.7 ± 15.3 %, 46.9 ± 15.4 %, p < 0.05, respectively). No significant differences between the two groups were observed in the echocardiographic parameters or baseline cardiac catheterization parameters. Significant correlations were found between delayed H/M ratio and %HR (r = 0.35, p < 0.05), %LV dP/dt (max) (r = 0.45, p < 0.05) and %T (1/2) (r = 0.34, p < 0.05). Significant inverse correlations were also found between WR and %HR (r = -0.37, p < 0.05), %LV dP/dt (max) (r = -0.60, p < 0.0001), and %T (1/2) (r = -0.34, p < 0.05). SPECT images revealed enhanced denervation from the inferoposterior to anterior wall in accordance with the advancement of global denervation.
  
  
  CONCLUSIONS
  Reduced (123)I-MIBG uptake and increased washout were related to impairment in adrenergic myocardial functional reserve in idiopathic DCM.
authors.affiliation: Department of Cardiology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466-8550, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Ohshima
authors.forename: Satoshi
authors.initials: S
authors.lastname: Isobe
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hayashi
authors.forename: Shinji
authors.initials: S
authors.lastname: Abe
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kato
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Murohara
mesh_terms: D000328:Adult; D006328:Cardiac Catheterization; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging*; D004280:Dobutamine / Q000378:metabolism; D004452:Echocardiography / Q000379:methods; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006339:Heart Rate; D006352:Heart Ventricles; D006801:Humans; D007457:Iodine Radioisotopes / Q000494:pharmacology*; D008297:Male; D008482:Mediastinum / Q000473:pathology; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D011877:Radionuclide Imaging / Q000379:methods*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism
chemical_list: D007457:Iodine Radioisotopes; D011943:Receptors, Adrenergic, beta; D004280:Dobutamine