Biomedical subjects

T Yipintsoi

Publications and source records attributed to T Yipintsoi.

58 records · Page 4Linked to original sources

PubMedDate not supplied

Coronary collaterals: role in restoration of blood flow and preservation of cardiac function during exercise.

Chronically instrumented dogs were studied at rest and during exercise on two occasions 10--12 weeks apart. The left circumflex coronary artery (LCf) was initially constricted in all dogs. By the time of the second study the LCf was still patent in 9 dogs and had become occluded in 6. In the dogs with chronic coronary occlusion, collaterals restored myocardial flow to normal both at rest and during exercise, and there were no adverse hemodynamic effects when running. Conversely, in dogs with constricted but patent LCfs collateral development was inadequate to return ischemic flows to normal following transient coronary occlusion, and occlusion during exercise produced significant myocardial failure. Thus coronary collaterals can compensate for decreased antegrade coronary flow.

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PubMedDate not supplied

Cardiac tamponade in dogs with normal coronary arteries. I. Effect of changing intravascular volume on hemodynamics and myocardial blood flow.

Intravascular volume expansion has been shown to improve cardiac output in experimental cardiac tamponade. To determine the limitations of intravascular volume manipulation, acute tamponade was created in 20 anesthetized, spontaneously breathing dogs. The intrapericardial volume causing tamponade was determined for each animal, and kept constant. Hemodynamics were recorded with and without tamponade at multiple levels of intravascular volume. During cardiac tamponade, intravascular volume expansion increased cardiac output only in animals which were initially volume-depleted. Volume expansion of normovolemic or hypervolemic animals caused minimal changes in cardiac output, but increased atrial and aortic pressures. Intravascular volume depletion of the normovolemic animal caused a significant decline in cardiac output, in contrast to the trend towards an increased output following phlebotomy of the volume-expanded animals. In general, the benefit of intravascular volume expansion during cardiac tamponade could only be demonstrated when atrial pressures were below 12 mm Hg.

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PubMedDate not supplied

Cardiac tamponade in dogs with normal coronary arteries. II. Myocardial flow and metabolism with moderate and severe hemodynamic impairment.

To determine the effects of cardiac tamponade on myocardial blood flow and its distribution, dogs were prepared with indwelling pericardial catheters. Hemodynamic, myocardial blood flow, and myocardial metabolic data were collected in 5 closed-chest, spontaneously breathing animals with normal blood volumes and hemoglobin concentrations and 6 with acute anemia. Instillation of an average of 89.0 +/- 14.9 ml of modified Normosol into the pericardial space in dogs with normal hemoglobin levels produced mild tamponade with a modest decline in aortic pressure (119.5 +/- 14.3 to 96.8 +/- 12.1 mm Hg) and significant rises in left and right atrial and pericardial pressures to 7-8 mm Hg. Increasing the pericardial volume to 124.0 +/- 13.6 ml produced hypotension (mean aortic pressure 86.2 +/- 10.5 mm Hg) and rises in the left and right ventricular filling pressures and pericardial pressure to 10-11 mm Hg. Total myocardial blood flow fell from 1.19 +/- 0.18 to 0.73 +/- 0.17 ml/min/g (p less than 0.02) during mild tamponade, and fell further to 0.56 +/- 0.17 ml/min/g (p less than 0.05) with more severe tamponade. Despite these declines, the left ventricular wall inner/outer flow ratio and left ventricular flow as a proportion of total cardiac output were unchanged. In dogs with anemia more severe tamponade was created, with consequently more marked hemodynamic abnormalities. However, the relative changes in myocardial blood flow and inner/outer flow ratio were similar. Myocardial metabolic parameters could be evaluated only in the dogs with less severe tamponade.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMedDate not supplied

Nonlinear model for capillary-tissue oxygen transport and metabolism.

Oxygen consumption in small tissue regions cannot be measured directly, but assessment of oxygen transport and metabolism at the regional level is possible with imaging techniques using tracer 15O-oxygen for positron emission tomography. On the premise that mathematical modeling of tracer kinetics is the key to the interpretation of regional concentration-time curves, an axially-distributed capillary-tissue model was developed that accounts for oxygen convection in red blood cells and plasma, nonlinear binding to hemoglobin and myoglobin, transmembrane transport among red blood cells, plasma, interstitial fluid and parenchymal cells, axial dispersion, transformation to water in the tissue, and carriage of the reaction product into venous effluent. Computational speed was maximized to make the model useful for routine analysis of experimental data. The steady-state solution of a parent model for nontracer oxygen governs the solutions for parallel-linked models for tracer oxygen and tracer water. The set of models provides estimates of oxygen consumption, extraction, and venous pO2 by fitting model solutions to experimental tracer curves of the regional tissue content or venous outflow. The estimated myocardial oxygen consumption for the whole heart was in good agreement with that measured directly by the Fick method and was relatively insensitive to noise. General features incorporated in the model make it widely applicable to estimating oxygen consumption in other organs from data obtained by external detection methods such as positron emission tomography.

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