Elevated coronary vascular resistance in the presence of reduced resting blood flow distal to a severe XXXX .

@entity1 @entity1707 @entity859 @entity450 @entity51 @entity3979 @entity850
Vascular reserve in underperfused myocardium has recently been described. This seemingly paradoxical observation conflicts with older concepts of the coronary circulation which hold that @entity51 do not develop until reserve is fully exhausted. To examine this phenomenon in greater detail in an animal model mimicking a fixed @entity1 @entity3979 , we analysed the records of 25 carefully selected, sedated @entity1707 all instrumented with a rigid @entity3979 (82% lumenal diameter reduction). Each animal satisfied the following criteria: 1) perfused myocardial mass beyond the @entity850 was within a narrow weight range (16 to 24 g); and 2) post @entity850 (distal) epicardial (Epi) and @entity450 were less than or equal to 90% of respective flows in a region perfused by the non-stenosed circumflex (CX) coronary artery. Accordingly, distal flow was reduced compared to circumflex zone flow (p less than 0.01) in the Epi (173 +/- 51 to 113 +/- 32 ml . 100g-1 . min-1), Endo (146 +/- 39 to 116 +/- 27) and transmural (Tm) regions (164 +/- 45 to 124 +/- 31). Despite a flow deficit and constant severity of @entity850 , distal zone Tm resistance (0.55 +/- 0.21 mmHg/ml . 100 g-1 . min-1) exceeded the minimum level achievable with intravenous infusion of @entity859 (0.25 +/- 0.07) in a separate group of eight animals without a @entity850 . Distal transmural resistance also varied over a five fold range (0.27 to 1.33) and in 20/25 animals exceeded the highest level (0.37) seen in non- @entity850 animals during @entity859 infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
