title: Myocardial perfusion imaging (MPI) is superior to the demonstration of distal collaterals in predicting cardiac events in chronic total occlusion (CTO).
abstract: BACKGROUND
  In chronic total occlusion (CTO), the evidence for revascularization is less robust than for stable angina. A medical therapy strategy is common and often based on distal collateralization, regardless of the presence of ischemia.
  
  
  OBJECTIVE
  The aim of this study was to examine the correlation between distal collateralization, myocardial perfusion imaging (MPI), and hard cardiac events (HCE) in CTO.
  
  
  METHODS
  Retrospective analysis of consecutive patients undergoing coronary angiography revealed 21 non-revascularized patients with CTO and MPI, over a 24-month period. Blinded review of patient charts, MPI, and angiography was undertaken. HCE of death, myocardial infarct, and unstable angina were assessed. Mean follow up was 23 months.
  
  
  RESULTS
  Summed difference scores were calculated on a 17-segment model and collaterals graded on the Rentrop scale. 43% of patients had HCE, and 62% had collaterals. Ischemia on MPI accurately predicted HCE in CTO (60% vs 0%, P = .01). Distal collateralization failed to predict freedom from ischemia on MPI (31% vs 25%, P = .53) or HCE (31% vs 62%, P = .15).
  
  
  CONCLUSIONS
  MPI in patients with CTO accurately predicted HCE. This allows for accurate triage of patients by MPI for consideration of revascularization. Patients without ischemia can be safely managed with optimal medical therapy. The presence of collateralization did not predict either ischemia or HCE.
authors.affiliation: Department of Nuclear Medicine, Royal Melbourne Hospital, Parkville, VIC, Australia. dr.samuel.wright@gmail.com
authors.forename: Samuel
authors.initials: S
authors.lastname: Wright
authors.forename: Meir
authors.initials: M
authors.lastname: Lichtenstein
authors.forename: Leeanne
authors.initials: L
authors.lastname: Grigg
authors.forename: Dinesh
authors.initials: D
authors.lastname: Sivaratnam
mesh_terms: D000328:Adult; D000368:Aged; D000789:Angina, Unstable / Q000000981:diagnostic imaging*; D003251:Constriction, Pathologic / Q000000981:diagnostic imaging; D017023:Coronary Angiography / Q000379:methods*; D054059:Coronary Occlusion / Q000150:complications* / Q000000981:diagnostic imaging*; D005260:Female; D005500:Follow-Up Studies; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging*; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D009206:Myocardium / Q000473:pathology; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012306:Risk; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*