title: Magnetic resonance imaging is superior to cardiac scintigraphy to identify nonresponders to cardiac resynchronization therapy.
abstract: BACKGROUND
  Left ventricular (LV) postero-lateral scar and total scar burden are factors responsible for a poor response to cardiac resynchronization therapy (CRT). Contrast-enhanced magnetic resonance imaging (CMR) and (99m)Tc-2-methoxy isobutyl isonitrile single photon emission computed tomography (SPECT) perfusion imaging are widely used to detect myocardial scar tissue; however, their ability to detect regional scars and predict a positive response to CRT has not been fully evaluated.
  
  
  METHODS
  CMR and SPECT were performed in 17 patients with dilated cardiomyopathy (DCM) and seven patients with ischemic cardiomyopathy (ICM) before CRT. All images were scored, using a 17-segment model. To analyze the LV scar regions by CMR, we assessed the transmural delayed enhancement extent as the transmural score in each segment (0 = no scar, 4 = transmural scar). Similarly, a perfusion defect score was assigned to each segment by SPECT (0 = normal uptake, 4 = defect).
  
  
  RESULTS
  By both SPECT and CMR imaging, the total scar score was significantly higher in the ICM than in the DCM group. An LV postero-lateral wall scar region was detected using both imaging modes. By SPECT imaging, the percentage of regional scar score in the LV inferior wall was significantly higher in the DCM than in the ICM group.
  
  
  CONCLUSIONS
  By SPECT imaging in the DCM group, severe perfusion defects, due to attenuation artifacts, were frequently observed in the LV inferior wall, resulting in the overestimation of scar tissue. CMR identified nonresponders to CRT more reliably than SPECT in patients with DCM.
authors.affiliation: Division of Cardiology, Gunma Prefectural Cardiovascular Center, Maebashi, Gunma, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Yokokawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tada
authors.forename: Takuji
authors.initials: T
authors.lastname: Toyama
authors.forename: Keiko
authors.initials: K
authors.lastname: Koyama
authors.forename: Shigeto
authors.initials: S
authors.lastname: Naito
authors.forename: Shigeru
authors.initials: S
authors.lastname: Oshima
authors.forename: Koichi
authors.initials: K
authors.lastname: Taniguchi
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D002311:Cardiomyopathy, Dilated / Q000175:diagnosis* / Q000517:prevention & control*; D002921:Cicatrix / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D017682:Myocardial Stunning / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D017211:Treatment Failure; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000517:prevention & control