Hemodynamic and hormonal abnormalities in canine aortic coarctation at rest and during exercise

This study was designed to determine the hemodynamic and hormonal consequences of aortic coarctation at rest and during treadmill exercise. Twelve normal adult dogs served as controls. In eight dogs coarctation was created within 1 week of birth by banding the aorta just proximal to the ductus ligament, thereby fixing luminal diameter at 1 to 2 mm. Studies were performed 18 months after operation. Vascular pressures were monitored proximal and distal to the coarctation, cardiac output and regional blood flow were evaluated with radioactive microspheres and blood samples were collected for determination of hormone levels and blood gases. At rest, systolic pressure in the proximal aorta was 130 +/- 12 mm Hg (mean +/- SD) in the control group and 167 +/- 16 mm Hg in dogs with coarctation (p less than 0.01). During exercise at a level that doubled heart rate and cardiac index, mean aortic pressure increased by 11 and 31% (p less than 0.01) in the control and the coarctation group, respectively. Mean distal aortic pressure increased by 8% during exercise in control dogs but decreased by 29% in dogs with coarctation. Exercise decreased flow to the kidneys and the large intestine in the coarctation group. Plasma norepinephrine concentrations were greater in the coarctation group than in control dogs at rest; during exercise, plasma norepinephrine, epinephrine and renin activity increased in both groups, but to a greater degree in the group with coarctation. These results confirm an abnormality in renal and gut perfusion in experimental coarctation and suggest that this may be related to a decline in perfusion pressure.(ABSTRACT TRUNCATED AT 250 WORDS)