title: Does perfusion pattern influence stress-induced changes in left ventricular mechanical dyssynchrony on thallium-201-gated SPECT myocardial perfusion imaging?
abstract: BACKGROUND
  The relationship between perfusion pattern and stress-induced changes in left ventricular mechanical dyssynchrony (LVMD) on stress-rest thallium-201-gated SPECT myocardial perfusion imaging (Tl-201 SPECT MPI) is not clear. The aim of the study is to assess the relation of perfusion pattern with stress-induced changes in LVMD on Tl-201 MPI.
  
  
  METHODS
  Data of 194 patients who underwent exercise-rest Tl-201 MPI between January to December 2012 at our institute was retrospectively evaluated. Institute Ethical committee approval was obtained. Fifty patients who underwent Tl-201 MPI for suspected CAD and had normal LV perfusion and function on MPI were taken as normal group. Patients with perfusion abnormalities (n = 144) were divided into three groups: ischemia (n = 66), infarct (n = 32), and mixed group (n = 46; ischemia and infarct both). Summed stress score, summed rest score, summed difference score (SDS), and LV ejection fraction (EF) were evaluated. Two LVMD parameters, phase standard deviation (PSD) and phase histogram bandwidth (PHB), were assessed in post-stress and rest MPI images. ΔPSD (post-stress PSD - rest PSD) and ΔPHB (post-stress PHB - rest PHB) were calculated to measure stress-induced changes in LVMD.
  
  
  RESULTS
  In all the groups, mean post-stress LVMD parameters were lower as compared to LVMD parameters at rest. Post-stress PSD was significantly lower than rest PSD in all groups. Similar trend was noted with PHB values also, but it was statistically significant in the normal and ischemia group only. Post-stress worsening of at least one of the LVMD parameters was noted in 28 patients and all these patients had perfusion abnormalities. But on subgroup analysis, no difference was found in proportion of patients showing post-stress worsening of LVMD between ischemia (13.6%), infarct (25%), and mixed (23.6%) groups. No significant correlation was found between ΔPSD/ΔPHB and ΔLVEF/SDS in any group.
  
  
  CONCLUSIONS
  LV mechanical dyssynchrony parameters are smaller in post-exercise stress as compared to rest on Tl-201 MPI, regardless of perfusion pattern. Stress-induced worsening of LV dyssynchrony was observed only in patients with perfusion abnormalities, but this is not related to the type of perfusion abnormality.
authors.affiliation: Department of Nuclear Medicine, All India Institute of Medical Sciences, B-54, South Extension Part-1, New Delhi 110049, India.
authors.forename: Harmandeep
authors.initials: H
authors.lastname: Singh
authors.forename: Chetan D
authors.initials: CD
authors.lastname: Patel
authors.forename: Punit
authors.initials: P
authors.lastname: Sharma
authors.forename: Nitish
authors.initials: N
authors.lastname: Naik
authors.forename: Sandeep
authors.initials: S
authors.lastname: Singh
authors.forename: Rajiv
authors.initials: R
authors.lastname: Narang
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D058406:Cardiac Resynchronization Therapy; D055426:Cardiac-Gated Single-Photon Emission Computer-Assisted Tomography; D002921:Cicatrix / Q000473:pathology; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000473:pathology; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000473:pathology; D055414:Myocardial Perfusion Imaging; D010477:Perfusion; D000091402:Prohibitins; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013794:Thallium Radioisotopes / Q000737:chemistry*
chemical_list: C000717328:PHB protein, human; D000091402:Prohibitins; D013794:Thallium Radioisotopes