title: The collateral circulation of the heart in coronary total arterial occlusions in man: systematic review of assessment and pathophysiology.
abstract: BACKGROUND
  Anatomical and functional assessment of the collateral circulation of the heart in total arterial occlusions is challenging, and this is particularly true of the microcirculation. The pathophysiology of the collateral circulation has historically been and remains of considerable research focus but with diverging and sometimes conflicting results. Our purpose was to conduct a systematic review on the assessment and pathophysiology of the collateral circulation of the heart in total coronary arterial occlusions.
  
  
  METHODS
  We extracted data from Pubmed, Ovid, EMBASE, and Cochrane database from 1966 to December 2012. Two investigators independently reviewed the identified articles for eligibility and extracted the data.
  
  
  RESULTS
  Seventy-seven studies met inclusion criterion. An invasive assessment of the collateral circulation with pressure and/or Doppler wires is the gold standard in the assessment of collateral physiology and anatomy, although this can only be undertaken after successful passage of the sensor in the true lumen of the occluded vessel. A collateral circulation can provide resting metabolic requirements for the heart but invariably cannot meet demands on stress irrespective of the degree of collateralization as assessed by coronary angiography. In the case of myocardium subtending a totally occluded epicardial artery coronary collateral grading systems or physiological assessment of collateral flow is only moderately sensitive and poorly specific at predicting viability. Regression of collaterals seems more profound in totally occluded arteries versus nonoccluded lesions postrevascularization.
  
  
  CONCLUSIONS
  Key controversies in the assessment and pathophysiology of the collateral circulation of the heart in total coronary arterial occlusions are systematically evaluated.
authors.affiliation: University Hospital Aintree NHS Foundation Trust, Liverpool, United Kingdom; Liverpool Heart and Chest Hospital, Liverpool, United Kingdom. Electronic address: akhand31@aol.com.
authors.forename: Aleem
authors.initials: A
authors.lastname: Khand
authors.forename: Michael
authors.initials: M
authors.lastname: Fisher
authors.forename: Julia
authors.initials: J
authors.lastname: Jones
authors.forename: Bilal
authors.initials: B
authors.lastname: Patel
authors.forename: Raph
authors.initials: R
authors.lastname: Perry
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Mitsudo
mesh_terms: D003097:Collateral Circulation / Q000502:physiology*; D017023:Coronary Angiography; D003326:Coronary Circulation / Q000502:physiology*; D054059:Coronary Occlusion / Q000175:diagnosis / Q000503:physiopathology*; D003331:Coronary Vessels; D006801:Humans; D055414:Myocardial Perfusion Imaging