To examine the effects of coronary collateral development on thallium-201 (201Tl) distribution the left circumflex coronary artery was ligated in eight @entity235 . Three days later these animals ran on a treadmill, and 201-thallous @entity2865 was injected into the right atrium at peak exercise. Scintigraphic scanning was begun within 10 min and continued for 3 hr. Scanning was repeated weekly for 6 weeks. In the last week radioactive microspheres were injected into the left atrium at peak exercise to measure regional myocardial blood flow. The scintigraphically determined disparity between perfusion of the @entity63 and normal myocardium was most marked at 3 days after ligation. This difference gradually lessened over the first 4 weeks until there was no difference in 201Tl distribution to normally perfused myocardium and tissue distal to the ligation. Concomitant with the improvement in the scintigrams, exercise hemodynamics also improved over this 4 week period with significant increases in cardiac output and decreases in left atrial pressure. Serial coronary angiographic studies in two animals demonstrated the appearance of collaterals in the initial weeks after @entity1563 , and by 4 weeks the left circumflex artery distal to the obstruction was completely opacified by collateral flow. The ratio of directly measured exercise blood flow to the left circumflex and normally perfused tissues was 0.89 +/- 0.08 at 6 weeks after ligation. Scintigraphic 201Tl redistribution after 3 hr also changed over the weeks after ligation. Three days after ligation washout from the @entity63 area was significantly slower than that from the normal myocardium. By 6 weeks loss of 201Tl from the two regions occurred at nearly equal rates. Thus myocardial perfusion and function during exercise after @entity1563 are dynamic events that change with time. It is likely that coronary collateral development is responsible for these phenomena. Therefore coronary collaterals do have salutary effects in the @entity235 .

Exercise thallium-201 scintigraphy in XXXX : effects of long-term @entity1563 and collateral development on early and late scintigraphic images.

@entity235 :: ('9615', 'Species') :: ['dog', 'dogs'] @entity63 :: ('MESH:D007511', 'Disease') :: ['ischemic'] @entity1563 :: ('MESH:D054059', 'Disease') :: ['coronary occlusion'] @entity2865 :: ('CHEBI:17996', 'Chemical') :: ['chloride']
@entity235 :: (9615,Species) :: ['dogs']
