ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

A digital computer program for automatic recognition of electrocardiographic waves has been described. First, a filtering procedure was applied in order to eliminate extraneous noise. Consequently, the spatial velocity derived from three orthogonal electrocardio-graphic leads was determined for an entire cardiac cycle. It was found that a critical value of 3 μV per msec, was never exceeded during T-P intervals, P-R segments, and S-T segments. This limit for the spatial velocity could be used to indicate the beginning and end of electrocardiographic waves. The method was tested in a series of 395 records. The computer failed in 1.3 per cent of all expected measurements. "With one exception, failures were encountered only in eases with cardiac arrhythmias but not with regular sinus rhythm. Comparison between computed and visual time measurements showed close agreement, especially when limits of visual accuracy and beat-to-beat variations in wave duration were taken into account. The described procedure can serve as the basis for a complete electrocardiographic analysis by digital computer.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Toxic doses of ouabain were injected in animals which were subsequently cooled. The mortality- in this group was compared to that of similarly treated controls. Lowering of body- temperature by 8 to 12 C. reduced the arrhythmias produced by the toxic doses of ouabain but did not alter the overall incidence of mortality from ventricular fibrillation when compared to the controls. However, cooled animals survived for considerably longer periods of time than the normothermic controls. It is concluded that subsequently induced hypothermia does not afford an effective protection from digitalis toxicity, even though arrhythmias are reduced and survival is prolonged. These results support the hypothesis that partial protection from ventricular arrhythmias is not necessarily associated with, protection from lethal ventricular fibrillation.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

In the modified heart-lung preparation of the dog, sudden increases in outflow resistance were imposed during the diastolic interval between two beats. The changes in cardiac performance which were recorded during the first beat at higher resistance represent the response to augmented resistance per se, since there was no change in the initial length or initial tension of the ventricular myocardial fibers. Increased resistance elicited an immediate elevation of the peak aortic systolic pressure. This pressure rise was a direct function of the magnitude of the outflow resistance, and the effect was enhanced at higher left atrial pressures. Peak aortic flow and stroke volume were inversely related to the magnitude of the outflow resistance. At slight to moderate increases of resistance, stroke work was relatively unaffected; with more severe augmentations of resistance, however, stroke work varied inversely with outflow resistance. Arterial compliance played an important role in the ventricular response. For any given increase of resistance, the reductions of peak aortic flow and ventricular power were more severe when the arterial system was more rigid.It is concluded that the limits of cardiac performance are determined by the initial conditions, such as fiber length or tension, previous activity, temperature, and nervous and humoral factors. Within these limits, however, ventricular performance is determined by the afterload, of which the outflow impedance is an integral component.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

A series of eighteen experiments have been carried out on the heart-lung perfused dog kidney, and the results have defined the role of the intrarenal veins in the autoregulation phenomenon. It was found that there are a variety of intrarenal venous pressures which differ greatly according to (a) anatomical location and (b) the prevailing renal-artery pressure.Findings have pointed out the importance of correct techniques in establishing the changes occurring in the intrarenal venous segment in response to an increase in renal artery pressure.An increase in ureteral pressure results in a significant decrease in renal blood flow and an increase in overall renal vascular resistance, which further supports the role of extra-vascular pressure increases in renal-flow regulation.The findings of the present study corroborate previous reports from this laboratory indicating that autoregulation is primarily accounted for on the basis of changes in renal extravascular pressure. Evidence has been provided for the absence of the “myogenie reflex” as a causal factor in autoregulation.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

During prolonged electrical stimulation of the stellate ganglion in the dog, blood pressure, and more specifically systolic pressure, is significantly elevated. The amount of augmentation in pulse pressure is related to the frequency of stimulation, as is the duration of the sustained pressor response. Postmortem examination of the hearts revealed a distinctive pattern of subendocardial hemorrhages distributed along the long axis of the papillary muscles and the trabeculae carneae. They also frequently marked the endocardium at the base of the mitral valve. These lesions appeared in the left ventricle in 29 of 33 animals in which the left stellate ganglion was stimulated at a frequency of three to ten per second. They were found in only five instances in the right ventricles of these animals. The incidence of lesions in the ventricular wall was low during stimulation of the right stellate ganglion, although the mitral valve became involved in about 50 per cent of the animals. The similarity of the lesions to those induced during hemorrhagic hypotension, elevated intracranial pressures, and infusion of large quantities of the catecholamines suggests the possibility of a similar etiology. A satisfactory explanation of the lesion, however, is not yet available.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Plasma samples taken from the renal veins of rabbits hypertensive following renal-artery constriction were examined for evidence of increased renin content. No increase in the activity of the renal-vein samples was found as compared with plasma obtained from other sites in these rabbits, or with samples taken from unoperated animals. By contrast, renin infused into the renal veins of rabbits to give comparable elevation of the arterial pressure was, in all cases, detected. The experimental findings are discussed in relation to current views of the role of renin in experimental hypertension in the rabbit.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Mephentermine increased maximum breathing capacity in emphysema patients due to partial relief of existing bronehospasm. Small variations occurred in tidal volume, arterial-blood saturation, O2uptake and CO2removal per liter ventilation, and in respiratory quotient. There was an increase in expiratory minute volume, alveolar ventilation, frequency of respiration, O2consumption, CO2elimination, and arterial-blood pH; a decrease occurred in physiological dead space, physiological dead space/tidal volume ratio, and CO2content and tension in arterial blood. These changes were marked in normal individuals and in mitral stenosis patients, in contrast to the minimal effects obtained in emphysema cases. Bronehodilatation in emphysema, reduction of the physiological dead space and physiological dead space/tidal volume ratio, and changes in both direction in arterial-blood saturation as well as circulatory effects suggest that mephentermine affects the ventilation-perfusion relationships throughout the lung. The disproportionate increase in expiratory minute volume and frequency of respiration, while arterial-blood findings showed a significant decrease in CO2tension and a significant increase in pH, suggests an important central effect. In normal and in mitral stenosis patients, mephentermine produced an increase in heart rate, a decrease in mean right-atrial pressure, and an increase in cardiac output as a result of myocardial stimulation. Changes in pulmonary-artery pressure were variable. Pulmonary arteriolar resistance decreased in all three normal controls and in the majority of mitral stenosis cases, while wedge pressure changed very slightly. These changes are interpreted as pulmonary vaso-dilatation. Systemic pressure increased, while total systemic resistance decreased or remained essentially unchanged. Arteriovenous O2difference decreased in most eases with increased cardiac output, and vice versa. Increased cardiac output, associated with unchanged or falling systemic resistances and decreased arteriovenous O2difference, suggests vasodilatation with, increased peripheral blood flow. The fact that systemic resistance increases slightly in some cases must mean that vasocon-striction with decreased peripheral blood flow occurred in other vascular areas as a probable compensatory reaction. These effects led to an increase in arteriovenous O2difference and a reduction in cardiac output.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Indicator-dilution curves were recorded simultaneously from the left atrium and the femoral artery during injections of indocyanine green into the left ventricle in normal dogs and in dogs with chronic mitral regurgitation. A study was made-without the use of thoracotomy-of the effect of the following factors on the amount of early appearing indicator detected in the left atrium: (a) the timing of the injection of indicator in relation to the cardiac cycle, (b) the position of the injecting catheter in the left ventricle, and (c) the position of the sampling catheter in the left atrium. It was found that the time and site of the injection into the left ventricle had little effect on the amount of early appearing dye detected in the left atrium and that, although the position of the sampling catheter in the left atrium was important, reproducible results were attained when the sampling site was restricted to a region in close proximity to the mitral valve. A close correlation was demonstrated between the volume of regurgitation determined independently on a hydraulic basis and the volume estimated from the fraction of early appearing indicator detected in the left atrium. It is concluded that further work with this upstream-sampling technique is justified in order to study its possibilities as a practical method for detecting and quantitating mitral regurgitation in human beings.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The distribution, metabolism, and excretion of intravenously administered I131-labeled components of the fibrinolysin system were studied in dogs. lodination of plasmin tended to decrease slightly its in vitro fibrinolytie activity. Inaetivation appeared to depend on degree of iodination. Todination of strepto-kinase or urokinase did not decrease their plasminogen activator potential. All plasmins and plasminogen, regardless of the position of the iodine tag, adsorbed to preformed clots in the dog. Spontaneously activated human and chloroform-activated bovine plasmin adsorbed to a lesser extent than streptokinase-or urokinase-activated human plasmin. Clots removed from piasmin-treated dogs lysed in vitro within 24 hours. However, streptokinase or urokinase alone, on the basis of radioactivity measurements, did not exhibit any affinity for clots, nor did they cause any clot lysis. Plasma clearance curves revealed the presence of at least two processes in all preparations: a fast one (average half-life four minutes) responsible for the removal of over 60 per cent of the injected radioactivity and a slower process with a biological half-life greater than four hours. Pour hours after the injection of labeled compounds, the thyroid and stomach were the only organs which contained significant percentages of the injected radioactivity. Major excretory routes for the radioactivity were the urinary and biliary systems. Persistence of circulating radioactivity at a time when no free fibrinolytie activity could be determined in the blood was interpreted as complex formation between plasmin and antiplasmin.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID