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K W Scheel

Publications and source records attributed to K W Scheel.

36 records · Page 2Linked to original sources
PubMed1981

Effects of exercise on the coronary and collateral vasculature of beagles with and without coronary occlusion.

The purpose of this study was to determine if exercise stimulates coronary collateral vessel growth and if exercise after coronary occlusion can promote additional collateral growth. One group of 10 beagles served as control. The second group considered of 10 normal beagles exercised at 50% of maximum O2 consumption 7 days/week for 6 weeks. In the third group, the circumflex was occluded (Ameroid method) in eight beagles for 5 months. In the fourth group, seven beagles were exercised for 8 weeks following 3 months of circumflex occlusion. The coronary and collateral circulation was assessed, using an isolated heart preparation. It was found that exercise did not stimulate collateral growth in normal beagles. However, exercise after coronary occlusion doubled collateral conductance to be impaired vascular bed compared to animals with only coronary occlusions. Our study shows that, in beagles with coronary occlusion, exercise after a 3-month convalescent period promotes epicardial and intramyocardial (septa) collateral growth. Coronary reserve in the trained animals returned to 52% of initial capacity vs. 34% for the untrained animals.

Animals↗
PubMed1980

Reduced coronary collateral resistances after chronic ventricular sympathectomy.

Previous work has suggested that chronic ventricular sympathectomy causes a reduction in coronary collateral resistances. In the present experiments an isolated dog heart procedure was used to directly measure directional collateral resistances in 12 acutely denervated controls and 8 hearts that had undergone ventricular sympathectomy 2 wk earlier. In the procedure, the major coronary arteries were perfused separately but simultaneously during maximum vasodilation, and collateral resistances supplying the vascular beds of the arteries were determined by the double retrograde flow method. In the sympathectomized hearts, all collateral resistances were 47--65% less than in the controls (P less than 0.05). Also, in all hearts, minimum antegrade coronary resistances were determined from pressure-flow relationships in the major coronary arteries. Minimum coronary resistances in the 2 groups were not significantly different (P greater than 0.05). These results indicate that 2 wk of ventricular sympathectomy indeed causes a reduction in coronary collateral resistances, but has no effect on coronary resistances.

Animals↗
PubMed1980

The septal artery and its collaterals in dogs with and without circumflex occlusion.

The purpose of this investigation was to study myocardial perfusion and the collateral circulation of the septal artery in dogs without occlusion and to determine the magnitude and time course of septal collateral development with gradual circumflex occlusion. After the dogs with circumflex occlusion for 1 and 3 mo were allowed to develop a prolific collateral circulation under normal physiological conditions, coronary and collateral resistances were determined on an isolated heart preparation with maximal vasodilation. It was found that the septal artery contributes about 25% to the collateral circulation of the major coronary arteries (right, circumflex, and anterior descending). Septal collateral growth increased up to 15 times with circumflex occlusion. Due to the anatomic location of the septal artery, this collateral growth was intramyocardial in contrast to epicardial collaterals. Although there was collateral proliferation to all major coronary vessels, the most significant growth was toward the circumflex, the ischemic vascular bed. Although primary collateralization in the dog is via epicardial collaterals, the septal artery participates in collateral development.

Animals↗
PubMed1977

Directional coronary collateral growth with chronic circumflex occlusion in the dog.

The object of this study was to determine whether coronary collateral resistances were dependent on the direction of perfusion and to investigate whether a pattern of collateral growth with gradual circumflex occlusion could be discerned. In 12 dogs an Ameroid occluder was placed on the circumflex for 1 month, and six dogs for 3 months; 12 dogs served as controls. The circumflex, left anterior descending, and right coronary arteries were separately but simultaneously perfused in an isolated heart preparation in which the vasculature was maximally dilated with dipyridamole. Collateral flows were determined by measuring retrograde flows for two vessels simultaneously. The results showed that collateral flows from the right to the left coronaries in control dogs were 3.5-fold larger than when these collateral beds were perfused in the opposite direction. This difference in the 1- and 3-month Ameroid groups was approximately 20-fold. Relative to the control group, the collateral resistances from right to left coronary vessels were an average of 10-fold less in the 1- and 3-month groups, but there was no significant differences in resistance in the collaterals perfused from the left to the right. The results strongly suggest that collateral proliferation occurs in response to hypoxia rather than to a pressure gradient, and that collateral development is toward the hypoxid area.

Animals↗
PubMed1976

Effects of chronic anemia on the coronary and coronary collateral vasculature in dogs.

We compared coronary resistances and collateral (retrograde) flows for a group of normal dogs (hematocrit 40) to values for a group of dogs with severe chronic anemia (hematocrit 17). We used an isolated heart preparation in which the vessels were maximally dilated by dipyridamole. All data were compared for a hematocrit of 40. The results showed a significant decrease in coronary resistances with anemia; average resistances (+/-SE) of the anterior descending, circumflex, and right coronary arteries of the control dogs were 1.04 +/- 0.09,0.74 +/- 0.01, and 2.63 +/- 0.17 mm Hg/[(ml/min)/100 g], respectively, and 0.6 +/- 0.04,0.41 +/- 0.05,and 1.17 +/- 0.15 for the anemic dogs. Average coronary collateral flows increased in anemia but statistical significance could not be shown. We conclude that increased vascularity is a long-term regulatory mechanism in response to a hypoxic stimulus.

Anemia↗
PubMed1976

Changes in coronary and collateral flows and adequacy of perfusion in the dog following one and three months of circumflex occlusion.

We investigated changes in circumflex, left anterior descending (LAD), and right coronary artery flows as well as changes in collateral flows to these vessels after long-term circumflex occlusion. Coronary and collateral flows of each vessel were determined simultaneously in an isolated heart preparation in which the vasculature was maximally dilated with dipyridamole. The resistances as related to total heart weight of the circumflex, LAD, and right coronary arteries of 16 control dogs were found to be 0.59 +/- 0.06, 0.93 +/- 0.09, and 2.37 +/- 0.17 (mean +/- SEM) mm Hg/[(ml/min)/100 g], respectively. Total minimal coronary resistance was 0.21 +/- 0.01. In 10 dogs subjected to occlusion for 1 month no significant change in circumflex coronary resistance was observed, but the resistance of the unimpaired vessels decreased significantly. The resistances of the LAD and right coronary arteries were 0.66 +/-0.04 and 1.72 +/- 0.13, respectively. Both values were considerably less (P less than 0.01) than control. In nine dogs subjected to occlusion for 3 months the resistance of the unimpaired LAD and right arteries, as well as the circumflex coronary resitance, were not significantly different from control. We also found that retrograde flows for all vessels increased 7-fold after 1 month and 10.5-fold (relative to control) after 3 months of occlusion. From these data we conclude that vascular adaptations, which occurred in response to an ischemic stimulus, are responsible for the long-term regulation of the metabolic needs of the myocardium.

Animals↗
PubMedDate not supplied

Relationship between coronary collateral growth in the dog and ischemic bed size.

Two models of gradual coronary occlusion (Ameroid method) were compared in this study: 3 months circumflex and 3 months right coronary occlusion. Following coronary occlusion, the collaterals developed in intact, normally active dogs. The collateral flows were assessed in an isolated heat preparation. The results indicated a pattern for collateral development. Collateral flow was directed primarily toward the left heart with circumflex occlusion, and toward the right heart with right occlusion. Although dominant collateralization was via epicardial collaterals, intramyocardial septal collaterals strongly participated in growth development of both models. Collateral growth to the circumflex with circumflex occlusion was 6.54 fold greater than collateral growth to the right coronary artery with right occlusion. The data suggest a relationship between collateral growth and ischemic bed size.

Animals↗
PubMedDate not supplied

Reduced resistances of septal artery collateral channels after cardiac sympathectomy.

We have shown that chronic cardiac sympathectomy reduces coronary collateral resistances. The present experiments in isolated dog hearts delineated the role of intramyocardial collateral channels from the septal (SEP) to the circumflex (CIRC), left anterior descending (LAD), and right (RT) coronary arteries in this phenomenon. In 11 controls and 8 2-wk sympathectomized hearts, a retrograde flow technique was used to determine collateral resistances between the epicardial arteries (CIRC, LAD, RT). Collateral resistances between the CIRC and LAD and between the LAD and RT were 42-68% less in sympathectomized hearts (P less than 0.05). Collateral resistances from the SEP to each epicardial artery were determined from retrograde flows simultaneously collected on each epicardial artery when the SEP was the only vessel perfused. Collateral resistances from the SEP to the CIRC and LAD were 51-59% less in the sympathectomized hearts (P less than 0.05). Thus, intramyocardial channels from the SEP to the left coronary arteries show reduced resistances after sympathectomy and can provide a substantial portion of the increased collateral flow to these vessels.

Animals↗