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Biomedical subjects

F L Abel

Publications and source records attributed to F L Abel.

At least 55 records · Page 3Linked to original sources
PubMed1984

Modified Starling heart-lung preparation for measuring coronary vascular resistance.

A simplified in situ heart-lung preparation has been developed for measuring coronary vascular resistance and left ventricular performance. It provides the ability to observe the direct, cardiac effects of an agent independent of the central nervous system and circulating hormones. It eliminates the need for cross-matched blood or the use of colloidal solutions and permits direct control of coronary driving pressure and heart rate, and partial control of myocardial compression. The preparation shows relative long-term stability with readily alterable acid-base and blood gas content. Total coronary flow and resistance may be measured and the systolic and diastolic components calculated. Measurement of the various parameters of ventricular performance, total cardiac oxygen consumption, and cardiac efficiency is readily accomplished with an appropriate data acquisition system.

Animals↗
PubMed1984

Influence of aortic compliance on coronary blood flow.

The influence of a change in aortic compliance on the systolic/diastolic filling of the coronary vascular system was investigated in a canine heart-lung preparation. Changes in compliance were produced by opening and closing a Windkessel attached to the ascending aorta and a reservoir system. The percentage of total coronary flow occurring during systolic ejection increased significantly with a decrease in aortic compliance, whereas isovolumetric and diastolic coronary flow decreased. These effects were also present when cardiac work was changed by altering either afterload or bypass flow. The hypothesis was also tested in whole animal experiments in which left circumflex coronary flow was divided into systolic and diastolic components while the ascending aorta was partially constricted. A similar increase in the proportion of systolic flow was seen even at the same total circumflex flow, cardiac output, heart rate, and mean aortic pressure levels. It is suggested that this finding may have important implications in human disease.

Animals↗
PubMed1983

The effects of systole on left ventricular blood flow.

Coronary artery flow is complex. Flow in this system is divided into systolic and diastolic. However, systolic flow should be divided into two phases, isovolumetric and the ejection phase, since these two components are determined by completely different parameters. Flow through the myocardium is affected by the close mechanical coupling between myocytes and capillaries effected by the array of collagen struts and their disposition. This latter provides the anatomic arrangement that makes possible the integrated "massaging" effect postulated by Wiggers (26).

Animals↗
PubMed1983

Action of glucagon on canine left ventricular performance and coronary hemodynamics.

The effects of glucagon on coronary resistance and myocardial performance were evaluated in a canine heart-lung preparation in which changes in left ventricular compression of the coronary vessels, due to inotropic effects, could be largely prevented. Glucagon (0.2 mg) caused an increase in left ventricular performance as evaluated by maximal dp/dt, time to peak ventricular pressure, and end diastolic pressure. Although coronary flow increased slightly, the increase was significant only when heart rate was allowed to increase and followed the same time course as the change in heart rate. It therefore appeared to be the result of an indirect metabolic effect. The increase in flow involved only the systolic component. This effect was not blocked by propranolol. No redistribution of coronary flow was demonstrated using microspheres. Myocardial efficiency, as evaluated by cardiac work versus oxygen consumption, increased slightly after glucagon injection.

Animals↗
PubMed1981

Maximal negative dP/dt as an indicator of end of systole.

The maximal negative peak of the first derivative of left ventricular pressure was examined as an index of the end of ventricular ejection by comparing it with the end of aortic flow. Under varying heart rate and afterload situations in anesthetized dogs, a correlation coefficient of 0.982 was obtained with a mean error of less than 0.4 ms. This may be a useful end point for determining systolic time where only ventricular pressure is available.

Animals↗
PubMed1980

Direct effects of ethanol on myocardial performance and coronary resistance.

Ethanol has been infused into an isolated heart-lung type preparation in which the "isotonically" contracting left ventricle pumps blood and does work at a lower than normal value while afterload is maintained constant. The isotonic contraction permits observation of the influence of a drug or other agent on the coronary vasculature independent of the compressive effects of the musculature. Infusions of ethanol to concentrations of approximately 210 mg/100 ml over a 30- to 60-min period resulted in significant increases in coronary blood flow, decreases in coronary vascular resistance and depression of myocardial performance. Cardiac work increased concomitantly with the increase in coronary blood flow and cardiac output without significant alterations in tension-time index and oxygen consumption. A second group of animals received a smaller amount of ethanol over a 5-min period, accompanied by injection of 86Rb and 125I for nutritional flow measurements and of radioactive microspheres for flow distribution. Extraction increased slightly after alcohol but flow distribution was not significantly altered. Small concentrations of ethanol are concluded to have a direct vasodilating effect on the coronary vasculature.

Animals↗
PubMed1980

The effects of acetylstrophanthidin and glucocorticoids on canine left ventricular performance and coronary hemodynamics.

The effects of acetylstrophanthidin and methylprednisolone, individually and in combination, on coronary vascular resistance and left ventricular function were determined in an isolated dog heart preparation. The preparation permitted control of peak left ventricular pressure (and systolic tension) independent of inotropic actions by the drug and, thus, allowed direct measurements of its effect on coronary vascular resistance. The digitalis preparation initially increased coronary vascular tone and increased left ventricular performance; the increase in performance was followed by a decrease in coronary vascular resistance ascribed to metabolic effects. This response pattern was essentially unaltered when methylprednisolone was administered one hour before digitalis. Methylprednisolone itself depressed myocardial performance in this preparation, with a decrease in coronary vascular resistance after 30 minutes. Both agents also had a negative chronotropic action.

Animals↗
PubMed1978

Alterations in venous compliance in hemorrhagic shock.

Nine dogs and one primate were placed on total cardiopulmonary bypass and subjected to a simulated hemorrhagic shock procedure. Venous compliance was determined by occluding the venous outflow catheters; venous flow and pressure drop were used to calculate resistance. Individual measurements were made for the superior (SVC) and inferior vena caval (IVC) beds. During hypotension, compliance increased equally in the SVC and IVC; following reinfusion, IVC compliance was consistently lower than SVC compliance. Resistance of the sVC system increased slightly more rapidly during early hypotension than did that of the IVC, but SVC resistance then decreased and remained significantly below that of the IVC system throughout the posthypotension period. These results are interpreted as indicating a different response of the two vascular beds, particularly an increase in IVC arteriolar resistance with a decrease in venous tone. To the extent that the splanchnic bed contributes to the IVC system changes, they are contrary to the concept of a maintained venous tone and decreased arteriolar tone after hemorrhagic shock.

Animals↗
PubMed1977

Effects of glucocorticoids on ventricular performance and capillary permeability during hemorrhagic shock.

The effects of glucocorticoids on fluid uptake and myocardial performance was investigated in 14 dogs and two baboons. The animals were placed into stimulated hemorrhagic shock using a servocontrolled pump to maintain arterial pressure at desired levels. Ventricular function curves were generated by stepwise changes in afterload or by venous infusion and the resultant data were grouped by digital computer into similar preload, heart rate, and afterload groupings. Fluid uptake was monitored from the pump reservoir. Methylprednisolone was given intravenously, 30 mg/kg, approximately 3 hr after the postinfusion period. Fluid loss decreased and ventricular performance improved, as measured by maximal dp/dt, (maximal dp/dt)/developed pressure, and time to peak ventricular pressure. The improvements with steroid infusion were relatively small, however, and were not maintained for more than about 3 hr. Heart rate decreased markedly in response to the steroid, despite a general vasodilator response. The glucocorticoids appear to have mild beneficial effects on the myocardium and on capillary permeability in the presence of high circulating levels of catecholamines in the postinfusion phase of hemorrhagic shock.

Animals↗
PubMed1976

Comparative evaluation of pressure and time factors in estimating left ventricular performance.

Left ventricular and ascending aortic pressures were measured in open chest mongrel dogs under pentobarbital anesthesia. The data were digitized, averaged, and subgrouped by mean systolic aortic pressures (MSAP), end-diastolic pressure (EDP), and heart rate (HR). Seven raw and 32 derived variable from the pressure, as a function of time, wave forms were analyzed in each subgroup in the control state and following the infusion of catecholamines. A plot of control variability versus sensitivity to norepinephrine indicates that time to peak ventricular pressure (PVP time) is a more sensitive indicator of changes in the inotropic state than such other commonly used variables as max dP/dt, integrated isometric tension, and (max dP/dt)/developed pressure. PVP time also showed less variability with HR, EDP, and MSAP. Regression lines were also fit to the data using a second-order model. This permitted evaluation of experimentally varying either HR, EDP, or MSAP while maintaining the other two constant. PVP time was again one of the better variables in terms of sensitivity to HR, EDP, or MSAP. Vmax, fractional rate of change of power, preejection period, and systolic time were also analyzed and compared with PVP time using averaged data.

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