title: Reduced septal glucose metabolism predicts response to cardiac resynchronization therapy.
abstract: BACKGROUND
  Up to 50% of patients do not respond to Cardiac Resynchronization Therapy (CRT). Recent work has focused on quantifying mechanical dyssynchrony and left ventricular scar. Septal reverse-mismatch (R-MM) (reduced FDG uptake vs perfusion) has been observed in patients with cardiomyopathy and prolonged QRS duration. We hypothesized that a greater quantity of septal R-MM would indicate a greater potential for reversibility of the cardiomyopathy, when the dyssynchrony is improved with CRT. Therefore, this study's objective was to assess whether greater septal R-MM pattern predicts response to CRT.
  
  
  RESULTS
  Forty-nine patients had pre-implant Rubidium-82 and Fluorine-18-fluorodeoxyglucose PET scanning. Total and regional left ventricular scar size and extent of R-MM were calculated. Response to CRT was defined as ≥10% improvement in left ventricular end-systolic volume or ≥5% absolute ejection fraction improvement. In the non-ischemic cardiomyopathy subset non-responders had significantly less septal R-MM than responders (13.1% compared to 27.1%, P = .012). There were correlations between the extent of septal R-MM and the increase in ejection fraction (r = 0.692, P = .0004) and reduction in left ventricular end-systolic volume (r = -0.579, P = .004). For each 5% absolute increase in extent of septal R-MM the odds ratio of being a responder was 2.17 (95% CI 1.15, 4.11, P = .017). Extent of septal R-MM displayed high sensitivity and specificity (area under curve = 0.855, P = .017) to predict response.
  
  
  CONCLUSIONS
  In patients with non-ischemic cardiomyopathy, greater extent of septal glucose metabolic R-MM pattern, predicted response to CRT. This parameter may be useful for identifying patients who benefit from CRT.
authors.affiliation: University of Ottawa Heart Institute, 40 Ruskin Road, Ottawa, ON K1Y 4W7, Canada. dbirnie@ottawaheart.ca
authors.forename: David
authors.initials: D
authors.lastname: Birnie
authors.forename: Rob A
authors.initials: RA
authors.lastname: de Kemp
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Tang
authors.forename: Terence D
authors.initials: TD
authors.lastname: Ruddy
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gollob
authors.forename: Ann
authors.initials: A
authors.lastname: Guo
authors.forename: Kathryn
authors.initials: K
authors.lastname: Williams
authors.forename: Kerry
authors.initials: K
authors.lastname: Thomson
authors.forename: Jean N
authors.initials: JN
authors.lastname: DaSilva
authors.forename: Rob S
authors.initials: RS
authors.lastname: Beanlands
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy; D009202:Cardiomyopathies / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000517:prevention & control*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006346:Heart Septum / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D008297:Male; D018579:Patient Selection; D011379:Prognosis; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18