Atrial and ventricular myocardial blood flows in horses at rest and during exercise.
Abstract: Right atrial, pulmonary artery, pulmonary capillary, pulmonary artery wedge, and systemic blood pressures of strenuously exercising horses increase markedly. As a consequence, myocardial metabolic O2 demand in exercising horses must be high. Experiments were, therefore, carried out on 9 healthy, exercise-conditioned horses (2.5 to 8 years old; 481 +/- 16 kg) to ascertain the regional distribution of myocardial blood supply in the atria and ventricles at rest and during exercise. Blood flow was measured, using 15-micron-diameter radionuclide-labeled microspheres that were injected into the left ventricle while reference blood samples were being withdrawn at a constant rate from the thoracic aorta. Myocardial blood flow was determined at rest and during 2 exercise bouts performed on a high-speed treadmill at 8 and 13 m/s (0% grade). The sequence of exercise bouts was randomized among horses, and a 60-minute rest period was permitted between exercise bouts. There was considerable heterogeneity in the distribution of myocardial perfusion in the atria and the ventricles at rest; the right atrial myocardium received significantly (P < 0.05) less perfusion than did the left atrium, and these values were significantly (P < 0.05) less than those for the respective ventricular myocardium. The right ventricular myocardial blood flow also was significantly less than that in the left ventricle. With exercise, myocardial blood flow in all regions increased progressively with increasing work intensity and marked coronary vasodilation was observed in all cardiac regions. During exercise at 8 or 13 m/s, right and left atrial myocardial blood flows (per unit weight basis) were not different from each other.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1994-10-01 PubMed ID: 7998705
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The researcher examined how the myocardial blood flow changes in the hearts of horses at rest and during intense exercise. Using radionuclide-labeled microspheres as markers in nine fit horses, differences in perfusion between the atria and ventricles were analysed.
Research Methodology
- The study involved nine healthy, exercising horses, aged between 2.5 to 8 years old with an average weight of approximately 481 kg.
- The researchers induced an increase in myocardial oxygen demand by making the horses exercise intensively. This occurs naturally as the heart needs to work harder during exercise, which in turn creates a requirement for higher oxygen levels.
- They measured the blood flow by injecting radionuclide-labeled microspheres into the left ventricle of the horse’s heart. These microspheres were used as markers to trace the blood flow through the organ while maintaining withdrawal of blood samples at a steady rate from the thoracic aorta.
- The blood flow was calculated during rest and two different periods of exercise, with the horses subjected to running on a high-speed treadmill at two different speeds, 8 m/s and 13 m/s.
- There was a randomized sequence of exercise bouts among the horses, with an allowed 60-minute rest interval in between.
Findings
- At rest, there was a significant variation in the distribution of myocardial perfusion across the chambers of the heart; the right atrial myocardium received less blood flow than the left atrium, which was in turn less perfused than the ventricles.
- The right ventricular myocardium blood flow was significantly lower compared to the blood flow in the left ventricle.
- During exercise, all heart regions experienced an increase in blood flow that was proportional to the intensity of the exercise. Additionally, notable vasodilation was observed in all cardiac regions, suggesting a physiological response to the increased oxygen demands.
- Under exercise conditions (8 or 13 m/s), there were no significant differences between right and left atrial myocardial blood flows on a unit weight basis.
Cite This Article
APA
Manohar M, Goetz TE, Hutchens E, Coney E.
(1994).
Atrial and ventricular myocardial blood flows in horses at rest and during exercise.
Am J Vet Res, 55(10), 1464-1469.
Publication
Researcher Affiliations
- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign 61801.
MeSH Terms
- Animals
- Coronary Circulation / physiology
- Female
- Heart Atria
- Heart Ventricles
- Horses / physiology
- Male
- Physical Exertion / physiology
Citations
This article has been cited 2 times.- Reichlin T, Lockwood SJ, Conrad MJ, Nof E, Michaud GF, John RM, Epstein LM, Stevenson WG, Jarolim P. Early release of high-sensitive cardiac troponin during complex catheter ablation for ventricular tachycardia and atrial fibrillation. J Interv Card Electrophysiol 2016 Oct;47(1):69-74.
- Joyner MJ, Casey DP. Regulation of increased blood flow (hyperemia) to muscles during exercise: a hierarchy of competing physiological needs. Physiol Rev 2015 Apr;95(2):549-601.
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