title: Function of natural internal mammary-to-coronary artery bypasses and its effect on myocardial ischemia.
abstract: BACKGROUND
  The function of naturally existing internal mammary (IMA)-to-coronary artery bypasses and their quantitative effect on myocardial ischemia are unknown.
  
  
  RESULTS
  The primary end point of this study was collateral flow index (CFI) obtained during two 1-minute coronary artery balloon occlusions, the first with and the second without simultaneous distal IMA occlusion. The secondary study end point was the quantitatively determined intracoronary ECG ST-segment elevation. CFI is the ratio of simultaneously recorded mean coronary occlusive pressure divided by mean aortic pressure both subtracted by mean central venous pressure. A total of 180 pairs of CFI measurements were performed among 120 patients. With and without IMA occlusion, CFI was 0.110±0.074 and 0.096±0.072, respectively (P<0.0001). The difference of CFI obtained in the presence minus CFI obtained in the absence of IMA occlusion was highest and most consistently positive during left IMA with left anterior descending artery occlusion and during right IMA with right coronary artery occlusion (ipsilateral occlusions): 0.033±0.044 and 0.025±0.027, respectively. This CFI difference was absent during right IMA with left anterior descending artery occlusion and during left IMA with right coronary artery occlusion (contralateral occlusions): -0.007±0.034 and 0.001±0.023, respectively (P=0.0002 versus ipsilateral occlusions). The respective CFI differences during either IMA with left circumflex artery occlusion were inconsistently positive. Intracoronary ECG ST-segment elevations were significantly reduced during ipsilateral IMA occlusions but not during contralateral or left circumflex artery occlusions.
  
  
  CONCLUSIONS
  There is a functional, ischemia-reducing extracardiac coronary artery supply via ipsilateral but not via contralateral natural IMA bypasses.
  
  
  BACKGROUND
  http://www.clinicaltrials.gov. Unique identifier: NCTO1676207.
authors.affiliation: From the Department of Cardiology, University Hospital, Bern, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Stoller
authors.affiliation: From the Department of Cardiology, University Hospital, Bern, Switzerland.
authors.forename: Stefano F
authors.initials: SF
authors.lastname: de Marchi
authors.affiliation: From the Department of Cardiology, University Hospital, Bern, Switzerland. christian.seiler@insel.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Seiler
mesh_terms: D000368:Aged; D000792:Angiography; D001794:Blood Pressure / Q000502:physiology; D003097:Collateral Circulation / Q000502:physiology*; D017023:Coronary Angiography; D054059:Coronary Occlusion / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000502:physiology*; D004562:Electrocardiography; D023381:Endpoint Determination; D005260:Female; D006801:Humans; D008297:Male; D008323:Mammary Arteries / Q000000981:diagnostic imaging / Q000502:physiology*; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology* / Q000517:prevention & control*; D011446:Prospective Studies; D016896:Treatment Outcome
keywords: collateral circulation; coronary circulation; mammary arteries; thoracic arteries