title: Impact of scar on SPECT assay of left ventricular contraction dyssynchrony.
abstract: OBJECTIVE
  Many patients presently receiving cardiac resynchronization therapy (CRT) do not respond. A disproportionate number of nonresponders have ischemic cardiomyopathy, with significant left ventricular (LV) scar burden. Current selection criteria, such as electrocardiography or echocardiography, may not reliably portray the magnitude of CRT-remediable LV contraction dyssynchrony. Although phase analysis of gated single photon emission computed tomography (SPECT) image data is increasingly appreciated as a tool for quantifying dyssynchrony, its use in the setting of scar has not been adequately evaluated.
  
  
  METHODS
  Consecutive patients with ischemic (ICM, n = 50) or nonischemic (NICM, n = 39) cardiomyopathy underwent SPECT imaging prior to receiving CRT. In each patient, phase analysis of the raw images was performed to yield a phase standard deviation (PSD), an index which varies directly with the magnitude of dyssynchrony. ICM patient image data were also reanalyzed after scarred segments were stripped away.
  
  
  RESULTS
  Raw image analysis demonstrated that PSD was significantly larger among ICM (57 ± 17°) than NICM (35 ± 13°, p < 0.001) patients. Among ICM patients, PSD after stripping of scarred segments was significantly decreased (40 ± 13°, p < 0.001). Signals emanating from scarred segments were of low amplitude and presented a random pattern, suggestive of noise rather than indicating contraction.
  
  
  CONCLUSIONS
  PSD values may be spuriously increased by scar. These findings may be important when using SPECT in selecting ischemic cardiomyopathy patients for CRT.
authors.affiliation: Heart, Lung, and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Ludwig
authors.forename: Mati
authors.initials: M
authors.lastname: Friehling
authors.forename: Erik B
authors.initials: EB
authors.lastname: Schelbert
authors.forename: David
authors.initials: D
authors.lastname: Schwartzman
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy; D002921:Cicatrix / Q000000981:diagnostic imaging*; D017023:Coronary Angiography; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000628:therapy; D015899:Tomography, Emission-Computed, Single-Photon; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging*