ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The effect of varying CBF and myocardial O2delivery on MVO2was studied in 23 experiments. In 14 of the experiments an isolated dog heart was perfused, while in the others the heart of a dog, whose systemic circulation was maintained on cardiopulmonary bypass, was studied. The ventricles were kept empty, developed no pressure and performed no external work, while their temperature was held constant. CBF and myocardial O2delivery were controlled by pumping blood into the coronary arteries, total coronary venous return was collected from the right side of the heart and MVO2, was calculated during a steady state by the Fick principle. Myocardial anoxia was avoided by maintaining the coronary venous O2content above 4 vol % and myocardial O2extraction below 78%.A comparison of MVO2at two levels of CBF (and O2delivery) was made in 42 instances, and in 32 of them 11 MV increased substantially as CBF was elevated, or vice versa. The ten exceptions all occurred when O2delivery greatly exceeded MVO2with O2extraction ratios below 35%. The fundamental mechanisms responsible for these findings are not clear, but a number of possible explanations are discussed.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The effects of varying coronary blood flow on the MVO2of a heart permitted to perform external work at a constant level were determined in 10 experiments. No consistent changes of MVO2occurred with alterations of coronary blood flow. These results were in contrast with those previously obtained when coronary blood flow was altered in a heart which performed no external work.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Experiments were done in the isolated supported heart preparation to ascertain whether a change in coronary blood flow would induce a change in myocardial O2consumption if the activity of the heart (aortic pressure, heart rate and stroke volume) was controlled. Over a wide range of coronary blood flows, the O2consumption did not vary under such circumstances. If the coronary flow was restricted to levels which produced an unequivocal deteriration of ventricular performance, a modest decrease in O2consumption was sometimes observed.Reciprocal type experiments were also performed. In these, coronary flow was held constant or nearly so while varying the activity of the heart markedly. Under these circumstances the myocardial O2consumption did vary directionally with the amount of ventricular myocardial tension developed insofar as this was indicated by the tension-time index.Data were also obtained suggesting that ventricular end diastolic fiber length is not of itself a major determinant of myocardial O2consumption.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

The influence of induced changes in coronary flow upon oxygen consumption and cardiac performance were observed in the in situ isovolumic left ventricle. This preparation was established with auxiliary pumps which bypass the dog's right and left heart and by inserting a balloon into the left ventricle so that the latter ejected no blood. Coronary flow was set or varied by a retrograde aortic perfusion pump. Oxygen consumption of the heart was found to be coronary flow dependent or independent, according to the conditions of the experiment. When it is coronary flow dependent there is usually a similar relationship between coronary flow and cardiac performance. In a single preparation, it was sometimes found that cardiac oxygen consumption was coronary flow dependent at lower rates of coronary flow and independent at higher flow rates. Possible explanations and clinical applications are given.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

High fat diets were givenad libitumorforce-fedto rats. The incidence of thrombosis in animals fed a cow butter diet was higher than in those fed a cocoa butter diet. No thrombosis was found in rats fed a diet containing peanut oil. Coagulation studies performed at weekly intervals on blood samples obtained from a tail vein of rats fed the dietsad libitumshowed that there was a gradual but marked increase in the levels of Factors II, VII, and X of animals fed a diet containing cow or cocoa butter, but not one containing peanut oil. Several weeks prior to death, however, the level of all coagulation factors, including Factors I and V, fell. A significant prolongation of the values for the partial thromboplastin time was found in animals killed at the time when levels of plasma coagulation factors decreased. The pattern of changes in concentration of plasma coagulation factors was similar in the groups of animals dying with proven thrombosis and in those in which thrombosis was not found. All rats force-fed the above two diets died within two weeks, showing a marked fall in all coagulation factors and no thrombosis. Weight loss was more pronounced in the groups of animals fed the diet containing cow butter and cocoa butter than in animals fed Purina chow. Autopsy findings were: intra-ventricular thrombi with myocardial infarction, lung hemorrhage, pneumonia, and rarely jaundice. No cause of death other than inanition was discernible in some of the animals. Marked fatty infiltration of the liver was a feature of all animals autopsied.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Three degrees of stenosis were produced in the femoral and carotid arteries of twenty-six adult dogs.Minimumstenosis caused neither proximal nor distal dilatation.Moderatestenosis, defined by the presence of a distal thrill and bruit, always produced post-stenotic dilatation.Severestenosis, with a marked decrease or absence of distal. pulsation caused temporary proximal dilatation.The arteries were painted with a radi-opaque paste which did not change their elastic properties and allowed daily measurements of arterial diameter. Radiograms showed that if turbulence was present, the artery usually started to dilate within twenty-four hours, reached a steady state within ten days, and then remained essentially unchanged for up to ten months. The dilatation was fusiform, and usually extended for 1.75 to 2.0 cm distal to the end of the band.Frequency analysisof the murmurs showed a wide frequency spectrum with no resonant points and no components over 1500 cycles/ sec. This type of sound is more likely to be produced by turbulence than by cavitation or vortex formation.Dye injectionin a model showed a random dye distribution starting a short distance distal to the constriction.Analysis of pressure-volume diagrams from these arteries35suggested that the dilatation was due to a weakness of the arterial wall in the poststenotic segment.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Transfer of blood from rats with acute renal hypertension to normal recipient rats demonstrated that a vasopressor substance was present in the circulation of the hypertensive animals. This is consistent with the view that a humoral mechanism plays a role in the origin of the hypertension. In contrast to the acute stage, no vasoactive material could be demonstrated in the blood after the second week of hypertension. Either the amount of pressor substance was too small to detect or none was being produced. In the latter case, chronic renal hypertension cannot be attributed to a humoral mechanism.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

1. The left pulmonary artery was ligated in day-old calves. All animals developed pulmonary arterial hypertension with restingmeanpressures as high as 114 mm Hg. This was associated with a reduction in the pulmonary arterial vascular bed of the right lung and right ventricular hypertrophy. The longest survival has been five months; death being associated with congestive heart failure.2. Pulmonary hypertension developed without concomitant rise of pulmonary arterial wedge pressure.3. Inhalation of 13% O2caused an average rise of 45 mm Hg in mean pulmonary arterial pressure, as compared with 21 mm Hg in normal calves and nine in yearling steers.4. Inhalation of 41% or 100% O2caused an average decrease of 29 mm Hg in pulmonary arterial pressure, as compared with 14 mm Hg in normal calves.5. Acetylcholine reduced the elevated pulmonary arterial pressure suggesting that vaso-constriction played an important role in the development of the pulmonary hypertension. Tolazoline was ineffective.6. The spectrum of reactivity of the pulmonary vascular bed among species as well as within a given species is illustrated.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID

摘要:

Since preparation of this paper, halothane (Fluothane) anesthesia has been substituted for ether, as suggested by McGrady et al., (Cardiovascular Bes. Center Bull. 1: 110, 1963). Results have been superior to ether. Using a plastic bag over the head, a high flow is used for induction; 2 liters oxygen, 2 liters nitrous oxide, and 400 cc halothane (about 4%). The calf is ready for intubation within three to five minutes and is maintained on about 1% halothane (25 cc to 50 cc halothane with 500 cc oxygen and 500 cc nitrous oxide). Recovery is rapid, usually within five to ten minutes.

ISSN:0009-7330    

出版商:OVID    

年代:1963

数据来源: OVID