title: Various clinical scenarios leading to development of the string sign of the internal thoracic artery after coronary bypass surgery: the role of competitive flow, a case series.
abstract: BACKGROUND
  The left internal mammary artery (LIMA) is the choice for grafting of the left anterior descending coronary artery (LAD). One possible mechanism of the rare graft failure involve the presence of competitive flow.
  
  
  METHODS
  105 patients who had undergone coronary bypass grafting between 1998 and 2000 were included in this observational study. The recatheterizations were performed 28 months after the operations. The rate of patency the LIMA grafts was determined, and the cases with graft failure were analyzed.
  
  
  RESULTS
  The LIMA graft was patent in 99 patients (94%). Six patients (6%) exhibited diffuse involution of the graft (string sign). The string sign was always associated with competitive flow as the basis of the LIMA graft involution. In one case quantitative re-evaluation of the preoperative coronary angiography revealed merely less than 50% diameter stenosis on the LAD with a nonligated side-branch of the LIMA. At recatheterization in two patients the pressure wire measurements demonstrated only a non-significant decrease of the fractional flow reserve (0.83 and 0.89), despite the 53% and 57% diameter stenosis in the angiogram. Another patient displayeda significant regression of the LAD lesion between the pre- and postoperative coronary angiography (from 76% to 44%) as the cause of the development of the competitive flow. In one instance, a radial artery graft on the LAD during a redo bypass operation resulted in competitive flow in the radial graft due to the greater diameter than that of the LIMA. In a further patient, competitive flow developed from a short sequential part of the LIMA graft between the nonsignificantly stenosed diagonal branch and the LAD, with involution of the main part of the graft to the diagonal branch.
  
  
  CONCLUSIONS
  The most common cause of the development of the string sign of a LIMA graft due to competitive flow is overassessment of the lesion of the LAD. Regression of a previous lesion or some other neighboring graft can also cause the phenomenon.
authors.affiliation: Department of Cardiology, University of Debrecen, Debrecen, Hungary. rudlinghealth@yahoo.com
authors.forename: Rudolf
authors.initials: R
authors.lastname: Kolozsvari
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Galajda
authors.forename: Tamas
authors.initials: T
authors.lastname: Ungvari
authors.forename: Gabor
authors.initials: G
authors.lastname: Szabo
authors.forename: Ildikó
authors.initials: I
authors.lastname: Racz
authors.forename: Tamás
authors.initials: T
authors.lastname: Szerafin
authors.forename: István
authors.initials: I
authors.lastname: Herzfeld
authors.forename: István
authors.initials: I
authors.lastname: Edes
authors.forename: Arpad
authors.initials: A
authors.lastname: Peterffy
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Koszegi
mesh_terms: D000368:Aged; D001157:Arterial Occlusive Diseases / Q000209:etiology* / Q000503:physiopathology*; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008323:Mammary Arteries / Q000503:physiopathology* / Q000637:transplantation*; D008875:Middle Aged; D012039:Regional Blood Flow