MAXIMAL EXERCISE CAPACITY AND OXYGEN-CONSUMPTION OF LAMBS WITH AN AORTOPULMONARY LEFT-TO-RIGHT SHUNT

We determined maximal exercise capacity and measured hemodynamics in 10 6-wk-old lambs with an aortopulmonary left-to-right shunt [S, 57 +/- 11%, (SD)] and in 9 control lambs (C) during a graded treadmill test 8 days after surgery. Maximal exercise capacity (3.7 +/- 0.2 km/h and 10 +/- 5% inclination vs. 4.0 +/- 0.9 km/h and 15 +/- 0% inclination, P less than 0.02) and peak oxygen consumption (25 +/- 7 vs. 34 +/- 8 ml O2.min-1.kg-1, P less than 0.02) were both lower in the shunt than in the control lambs. This was due to a lower maximal systemic blood flow in the shunt lambs (271 +/- 38 vs. 359 +/- 71 ml.min-1.kg-1, P less than 0.01). Despite their high maximal left ventricular output, which was higher than in the control lambs (448 +/- 87 vs. 359 +/- 71 ml.min-1.kg-1, P less than 0.05), the left-to-right shunt could not be compensated for during maximal exercise because of a decreased reserve in heart rate (S: 183 +/- 22 to 277 +/- 38 beats/min; C: 136 +/- 25 to 287 +/- 29 beats/min) and in left ventricular stroke volume (S: 1.8 +/- 0.3 to 1.6 +/- 0.4 ml/kg; C: 1.0 +/- 0.3 to 1.3 +/- 0.2 ml/kg). We conclude that exercise capacity of shunt lambs is lower than that of control lambs, despite a good left ventricular performance, because a part of the reserves for increasing the left ventricular output is already utilized at rest. </jats:p

Effects of body position and clinical signs on L7-S1 intervertebral foraminal area and lumbosacral angle in dogs with lumbosacral disease as measured via computed tomography

Objective—To measure effects of dog position on L7-S1 intervertebral foraminal area and lumbosacral (LS) angle by means of computed tomography (CT) and determine whether changes in values between positions are associated with clinical signs in dogs with LS disease. Animals—86 dogs examined via a positional CT protocol that included flexion and extension scans of L7-S1. Procedures—Archived CT images and medical records were reviewed. Included dogs had good-quality flexion and extension CT scans of L7-S1 and no evidence of fractures, neoplasia, or previous LS surgery. One person who was unaware of CT findings recorded clinical status with regard to 3 signs of LS disease (right or left hind limb lameness and LS pain) at the time of CT evaluation. One person who was unaware of clinical findings measured L7-S1 foraminal areas and LS angles, with the aid of an image-analysis workstation and reformatted parasagittal planar CT images. Results—Intraobserver variation for measurements of L7-S1 foraminal area ranged from 6.4% to 6.6%. Mean foraminal area and LS angle were significantly smaller when vertebral columns were extended versus flexed. Percentage positional change in L7-S1 foraminal area or LS angle was not significantly different among dogs with versus without each clinical sign. There was a significant correlation between percentage positional change in L7-S1 foraminal area and LS angle in dogs with versus without ipsilateral hind limb lameness and LS pain. Conclusions and Clinical Relevance—Positional CT is a feasible technique for quantifying dynamic changes in L7-S1 intervertebral foraminal morphology in dogs with LS disease.Jeryl C. Jones, Sarah E. Davies, Stephen R. Werre, Kristen L. Shackelfor