title: Baseline scintigraphic abnormalities by myocardial perfusion imaging predict echocardiographic response to cardiac resynchronization therapy in nonischemic cardiomyopathy.
abstract: BACKGROUND
  Significant myocardial scar in the posterolateral left ventricle (LV) has been associated with a diminished response to cardiac resynchronization therapy (CRT) in patients with coronary artery disease, but the effects of resting perfusion abnormalities in nonischemic cardiomyopathy (NICM) are yet to be described.
  
  
  OBJECTIVE
  We sought to characterize the effect of myocardial perfusion abnormalities upon echocardiographic outcomes of CRT in patients with NICM.
  
  
  METHODS
  Twenty-one patients (mean age 64.4 +/- 13.3; 71.4% male; mean left ventricular ejection fraction [LVEF] 20.2 +/- 6.9%) with NICM who underwent CRT implantation and Thallium-201 single positron emission computed tomography (SPECT) myocardial perfusion imaging (MPI) were included. MPI studies were read quantitatively, assigning each of 17 myocardial segments a perfusion score (0-4) and cumulatively generating a summed perfusion score (SPS). The LV lead position was determined by chest radiography. Echocardiograms were performed both before and after (median 12 mo) CRT in 15 patients.
  
  
  RESULTS
  Echocardiographic response, defined as > or = 15% relative increase in LVEF, was documented in 8 (53.3%) of 15 patients. All patients (5/5) with an SP < or =6 responded to CRT, whereas only 30.0% (3/10) with an SPS > or = 6 responded (odds ratio 3.33 [95% confidence interval {CI} 1.29-8.59]; p = 0.01). All nonresponders had inferior perfusion defects. Defect density adjacent to the LV lead tip had little demonstrable effect upon CRT efficacy.
  
  
  CONCLUSIONS
  The presence of significant myocardial perfusion defects negatively influences echocardiographic response to CRT in NICM. These findings warrant prospective confirmation and histopathological correlation with explanted hearts.
authors.affiliation: Cardiovascular Institute, Department of Medicine, University of Pittsburgh, Medical Center, Pittsburgh, PA 15213-2582, USA.
authors.forename: Evan C
authors.initials: EC
authors.lastname: Adelstein
authors.forename: Samir
authors.initials: S
authors.lastname: Saba
mesh_terms: D000368:Aged; D009202:Cardiomyopathies / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D015331:Cohort Studies; D003326:Coronary Circulation / Q000502:physiology; D017147:Defibrillators, Implantable; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging* / Q000628:therapy*; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D015899:Tomography, Emission-Computed, Single-Photon; D016896:Treatment Outcome; D014463:Ultrasonography