BACKGROUND: We hypothesized that increased myocardial @entity26 demand resulting from @entity551 and reflex @entity591 unmasking a reduced endocardial @entity296 ( @entity296 ) reserve is the mechanism of @entity4341 -induced regional dysfunction in chronic @entity453 . METHODS AND RESULTS: Ameroid constrictors were placed around the proximal coronary arteries and their major branches in 15 @entity235 to create chronic @entity3979 . Seven days later, radiolabeled microsphere-derived @entity296 and 2-dimensional echocardiography-derived percent wall thickening (%WT) were measured at rest and after 0.56 mg/kg @entity4341 . @entity4341 caused an increase (mean, 21%) in the rate-pressure product secondary to reflex @entity591 resulting from mild systemic @entity551 . %WT in @entity296 with an endocardial @entity296 reserve ( @entity4341 /resting @entity296 ) of 1.5 to 2.5 (n=35) did not change after @entity4341 , whereas it decreased in segments with an endocardial @entity296 reserve of <1.5 (n=30) and increased in those with an endocardial @entity296 reserve of > or =2.5 (n=45) (P<0.05). Most (80%) segments with endocardial @entity296 reserve of <1.5 and 14% with an endocardial @entity296 reserve of 1.5 to 2.5 showed inducible dysfunction after @entity4341 , whereas none of the segments with an endocardial @entity296 reserve of > or =2.5 showed this finding. A sigmoid relation (y=-6.74/[1+exp (19.9. [x-1.84])]+1.35. x, r=0.93, P<0.0001) was noted between endocardial @entity296 reserve and Delta%WT. In contrast, neither the epicardial @entity296 reserve nor the @entity296 ratio during @entity450 was associated with inducible regional dysfunction. CONCLUSIONS: Increased myocardial @entity26 demand resulting from @entity551 and reflex @entity591 unmasking a reduced endocardial @entity296 reserve is the primary mechanism of @entity4341 -induced regional dysfunction in chronic @entity453 .

Mechanism of inducible regional dysfunction during XXXX stress.

@entity296 :: ('MESH:D009202', 'Disease') :: ['MBF', 'myocardial segments', 'endocardial/epicardial MBF', 'myocardial blood flow'] @entity235 :: ('9615', 'Species') :: ['dogs'] @entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity4341 :: ('MESH:D004176', 'Chemical') :: ['dipyridamole', 'Dipyridamole'] @entity450 :: ('MESH:D006940', 'Disease') :: ['hyperemia'] @entity591 :: ('MESH:D013610', 'Disease') :: ['tachycardia'] @entity3979 :: ('MESH:D023921', 'Disease') :: ['coronary stenosis'] @entity453 :: ('MESH:D003324', 'Disease') :: ['coronary artery disease'] @entity551 :: ('MESH:D007022', 'Disease') :: ['hypotension']
@entity4341 :: (MESH:D004176,Chemical) :: ['dipyridamole']
