Internal thoracic artery flow competition: studies in a XXXX H-graft model.

@entity101 @entity63 @entity235 @entity1854 @entity591 @entity2647 @entity8108 @entity551
OBJECTIVE: Internal thoracic artery (ITA) flow competition is a diversion of graft flow through intact ITA branches with a net decrease in perfusion to the grafted coronary. Although a widely acknowledged phenomenon, the conditions under which flow competition occurs have not been established. This is examined in a @entity235 H-graft model. METHODS: Eight @entity235 had a right ITA segment interposed (H-graft) between their in situ left ITA (LITA) and the snared left anterior descending (LAD) coronary artery. Proximal LITA and H-graft flows were measured at baseline and during pacing-induced @entity591 , @entity2647 -induced @entity101 , and @entity1854 -induced @entity551 . Flows were measured with the distal LITA open and occluded. Two additional animals were subjected to eight separate 2-min periods of @entity63 , after which post- @entity63 H-graft flow measurements were obtained with and without distal LIMA occlusion. RESULTS: During baseline conditions, proximal LITA flow was greater when the distal LITA was open rather than occluded (46+/-15 versus 35+/-12 ml/min, respectively; P=0.002), but H-graft flow did not change significantly (32+/-18 versus 35+/-18 ml/min, respectively; P=0.21). Similarly, occlusion of the distal LITA had no impact on H-graft flow during @entity591 , @entity101 , or @entity551 . Only in animals subjected to transient @entity63 did H-graft flow increase with distal LITA occlusion, albeit marginally (65+/-7-70+/-9 ml/min, occluded versus open, respectively; P=0.04). CONCLUSIONS: Mild diversion of flow from the LAD was demonstrated during immediate post- @entity63 coronary reperfusion only, and could not be elicited under any other physiologic condition. These data suggest that flow competition is unlikely to constitute a clinically significant limitation to the use of @entity8108 -grafts or other modalities that leave ITA branches patent.
