Cardiovascular Performance of Alaska Sled Dogs during Exercise

Citters, Robert L. Van; Franklin, Dean

doi:10.1161/01.res.24.1.33

Cited by 136 publications

(63 citation statements)

References 8 publications

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“…Here, the lowest hematocrit is 20% and maximal value for v/D is five times 0.565 which results in Pe = 18. This maximal value for v/D is chosen since for different species, the coronary flow can increase about five times for heavy work (Honig, 1981;Lochner, 1971;Van Citters and Franklin, 1969).…”

Section: Resultsmentioning

confidence: 99%

Reconsidering the Effect of Local Plasma Convection in a Classical Model of Oxygen Transport in Capillaries

Bos

Hoofd

Oostendorp

1996

Microvascular Research

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Please be advised that this information was generated on 2018-05-09 and may be subject to change. m f c r o v a s c u l a r r e s e a r c h 51, 39-50 (1996) In 1970, Aroesty and Gross investigated the influence of local plasma convection in between two successive red blood cells (RBC) in a capillary on the local oxygen transfer into tissue by combining convectional and diffusional oxygen transport, They concluded that the effect of local plasma convection on oxygen transport in the capillaries was insignificant. Here it is shown that this result was due to their choice of flat oxygen concentration profiles as boundary conditions. In fact, the plasma motion can be of importance when more realistic oxygen concentrations are used as boundary conditions. The fluxes of oxygen through the capillary wall could be up to 50% larger as compared to those of Aroesty and Gross, especially for low hematocrit values and for maximally working muscle. Since the boundary concentrations in the model of the current paper are fixed, chosen not to be influenced by the transport processes, calculations will not show to what extent motion really enhances the oxygen transport, and should be considered as rough indications of the effect of plasma motion. The results in this investigation indicate that in capillaries motion has to be taken into account under conditions of low hematocrit or high RBC velocity.

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Section: Resultsmentioning

confidence: 99%

Reconsidering the Effect of Local Plasma Convection in a Classical Model of Oxygen Transport in Capillaries

Bos

Hoofd

Oostendorp

1996

Microvascular Research

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“…It is worth noting that the heart rates reached at the time of the circumflex arterial occlusion (198 + 22 to 211 ± 17 beats/min for the control and postinfarction dogs) rep-796 resent 70% of maximum heart rate for dogs. 17,18 As an example, the heart rate reached by postinfarction patients during a normal and necessary physical activity such as sexual intercourse is 117 ± 14 beats/min, 9 which corresponds to 65% of maximum heart rate for healthy men.…”

Section: Discussionmentioning

confidence: 99%

Autonomic mechanisms in ventricular fibrillation induced by myocardial ischemia during exercise in dogs with healed myocardial infarction. An experimental preparation for sudden cardiac death.

Schwartz¹,

Billman²,

Stone³

1984

Circulation

429

186

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The relationship between activity of the autonomic nervous system, myocardial ischemia, and malignant arrhythmias has been investigated in a new experimental preparation for sudden death. Fifty-seven dogs were chronically instrumented and studied under control conditions (n = 15) and 1 month after production of an anterior myocardial infarction (n = 42). The protocol consisted in occluding the left circumflex coronary artery for 2 min, commencing at the last minute of an exercise stress test and extending through the first minute after cessation of exercise. With this protocol, ventricular fibrillation was observed in 40% of normal dogs and 66% of dogs with infarction. In 14 dogs.with infarction, left stellectomy reduced the incidence of ventricular fibrillation to zero (p < .001). The reflex changes in heart rate elicited within the first minute of ischemia during exercise in the animals that survived (from 204 ± 14 to 198 ± 31 beats/min, -6) were opposite those in animals that had ventricular fibrillation (from 208 24 to 229 30 beats/min, + 21) (p < .05). The ischemiainduced reduction in heart rate despite continuation of exercise suggests the presence in the dogs that survived of active vagal reflexes that may have played an important role in the maintenance of cardiac electrical stability. This preparation has the potential to induce ventricular fibrillation consistently in conscious animals by the interaction of a few clinically relevant factors (acute myocardial ischemia, submaximal exercise and its cessation, sympathetic and vagal reflexes, and heart rate) and offers the possibility of acquiring further insights into the mechanisms of malignant arrhythmias and evaluating novel strategies for targeted prevention. Circulation 69, No. 4, 790-800, 1984. TARGETED prevention of sudden cardiac death depends on an adequate understanding of the mechanisms of and the factors leading to ventricular fibrillation, as well as an understanding of their relative roles. Basic electrophysiologic experiments, usually performed in isolated hearts or in open-chest preparations, are designed to identify these factors and their probable modes of action, but comprehension of their relative roles in the clinical setting requires experiments in unanesthetized animals.Necessary to achieve this goal are the identification of the most critical factors, the capability of controlling

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“…Heavy exercise was the level of exercise necessary to achieve heart rates greater than 220 beats/min. Mean (1)(2)(3)(4). Heart rate, mean arterial pressure, and mean left atrial pressure were measured directly from the recording during rest and each level of exercise.…”

Section: Methodsmentioning

confidence: 99%

“…Received for publication 12 June 1974 and in revised form 29 August 1974. ercise (1)(2)(3)(4), regional myocardial blood flow has not been measured previously during exercise. Since perfusion of the subendocardial myocardium occurs principally during diastole, uniform transmural myocardial perfusion requires a gradient of coronary vascular resistance during diastole with resistance lower in the subendocardium than the subepicardium.…”

Section: Introductionmentioning

confidence: 99%

Regional myocardial blood flow during graded treadmill exercise in the dog.

Ball¹,

Bache²,

Cobb³

et al. 1975

J. Clin. Invest.

101

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A B S T R A C T Regional myocardial blood flow was measured in nine dogs at rest and during three levels of treadmill exercise by using left atrial injections of 7-10-,um radioactive microspheres. At rest, heart rate was 76±3 beats/min (mean+SEM), mean left ventricular myocardial flow was 0.94±0.09 ml/min/g and endocardial flow (endo) exceeded epicardial flow (epi) in all regions (endo/epi = 1.12-1.33). When treadmill exercise was regulated to increase heart rates from 152±3 to 190±3 to 240±6 beats/min, myocardial blood flow (MBF) to all regions of the left ventricle increased linearly with heart rate (HR) from 1.83±f-0.11 to 2.75± 0.22 to 3.90±0.26 ml/min/g (MBF = 0.0175HR -0.523 ±0.614, r = 0.87). Exercise abolished the gradient of blood flow favoring the left ventricular endocardium at rest, so that the endo/epi flow ratios were not significantly different from 1.00. Right ventricular flows were consistently less than corresponding left ventricular flows, but showed a similar linear increase with heart rate. Right ventricular endo/epi ratios were not different from 1.00 either at rest or during exercise. Thus, exercise resulted in increased myocardial blood flow to all regions of the left and right ventricles with maintenance of subendocardial flow equal to subepicardial flow.

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Cardiovascular Performance of Alaska Sled Dogs during Exercise

Cited by 136 publications

References 8 publications

Reconsidering the Effect of Local Plasma Convection in a Classical Model of Oxygen Transport in Capillaries

Reconsidering the Effect of Local Plasma Convection in a Classical Model of Oxygen Transport in Capillaries

Autonomic mechanisms in ventricular fibrillation induced by myocardial ischemia during exercise in dogs with healed myocardial infarction. An experimental preparation for sudden cardiac death.

Regional myocardial blood flow during graded treadmill exercise in the dog.

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