title: Effects of stretch or distention on phenylephrine-induced constriction of human coronary artery bypass grafts.
abstract: OBJECTIVE
  To determine the effects of grafting saphenous veins into the arterial circulation and to compare the responsiveness of saphenous veins and mammary arteries to vasoconstrictors (phenylephrine or potassium) and a vasodilator (the calcium antagonist isradipine).
  
  
  METHODS
  Prospective, controlled, in vitro study.
  
  
  METHODS
  Laboratory facility in a university teaching hospital.
  
  
  METHODS
  Small excess segments of internal mammary arteries or saphenous veins obtained from patients undergoing coronary artery bypass graft surgery.
  
  
  METHODS
  Vessel segments were cut into rings to measure isometric tension development in isolated tissue chambers. The law of LaPlace for a cylinder was applied to determine tensions in vitro corresponding with arterial or venous tensions in vivo or distending pressures ex vivo.
  
  
  RESULTS
  Stretching saphenous vein rings from venous to arterial tensions reduced maximal phenylephrine-induced constriction but did not alter their dose response to phenylephrine, potassium, or isradipine. At arterial tensions, potassium, but not phenylephrine, was more potent in constricting mammary artery than saphenous vein; isradipine was more potent as a vasodilator of potassium-constricted mammary artery than saphenous vein. Maximal phenylephrine-induced or potassium-induced constriction was no different for either vessel at arterial tensions; however, prior distention of veins to tensions corresponding with pressures of 200 or 300 mmHg significantly (p < 0.01, Dunnett's test) reduced subsequent constriction.
  
  
  CONCLUSIONS
  Phenylephrine may be more likely to constrict native internal mammary arteries than distended autogenous saphenous vein grafts in vivo because high-pressure distention of veins markedly inhibits their vasoreactivity.
authors.affiliation: Department of Anesthesiology, Section of Cardiac and Thoracic Surgery, Temple University Hospital, 3401 North Broad Street, Philadelphia, PA 19140, USA..
authors.forename: W W
authors.initials: WW
authors.lastname: Wendling
authors.forename: L J
authors.initials: LJ
authors.lastname: Krasner
authors.forename: S C
authors.initials: SC
authors.lastname: Cooper
authors.forename: D
authors.initials: D
authors.lastname: Chen
authors.forename: C
authors.initials: C
authors.lastname: Harakal
authors.forename: V P
authors.initials: VP
authors.lastname: Addonizio
authors.forename: N W
authors.initials: NW
authors.lastname: Brister
authors.forename: C
authors.initials: C
authors.lastname: Carlsson
mesh_terms: D001026:Coronary Artery Bypass; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D017275:Isradipine / Q000494:pharmacology; D008323:Mammary Arteries / Q000187:drug effects* / Q000502:physiology / Q000637:transplantation; D010656:Phenylephrine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D012501:Saphenous Vein / Q000187:drug effects* / Q000502:physiology / Q000637:transplantation; D013314:Stress, Mechanical; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D010656:Phenylephrine; D011188:Potassium; D017275:Isradipine