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Biomedical subjects

T Yipintsoi

Publications and source records attributed to T Yipintsoi.

At least 37 records · Page 2Linked to original sources
PubMed1981

Restoration of cardiac function and myocardial flow by collateral development in dogs.

Hemodynamics of instrumented beagles with 75-85% stenoses of the left circumflex (LCf) coronary artery were evaluated before and during transient LCf balloon occlusion at rest and during treadmill running. Studies were done after surgery and 3 mo later. Myocardial blood flow was measured with radioactive microspheres during the LCf occlusions. Nine dogs (group I) had patent LCf arteries at the second study, and six (group II) had occluded vessels. Transient LCf occlusion during running in group I at weeks 1 and 12 and in group II at week 1 caused significant left ventricular failure, whereas the same protocol in group II dogs at week 12 produced minimal hemodynamic changes. Left ventricular failure precipitated by coronary occlusion during exercise diminished from week 1-12 in those animals with increasing LCf collateral flow, but actually increased in the animals with diminishing collateral flow. In group II dogs after chronic LCf occlusion total flow to LCf myocardium as well as inner-to-outer layer ratios were normal both at rest and during exercise. Thus coronary collaterals do preserve myocardial function, limit adverse hemodynamic responses to myocardial ischemia, and restore postocclusion tissue flows to normal even during the stress of exercise.

Animals↗
PubMed1981

Quantitative thallium-201 redistribution with a fixed coronary stenosis in dogs.

The redistribution of thallium-201 (201Tl) after coronary vasodilation was studied in 14 dogs with a proximal stenosis of the left circumflex coronary artery that did not reduce basal flow but attenuated reactive hypermia. During an 8-10-minute i.v. infusion of adenosine, radioactive microspheres and 201Tl were injected into the left atrium. Sequential cardiac scintiscans and microsphere injections permitted subsequent determination of coronary blood flow during the redistribution of 201Tl. After 15-220 minutes of observation, the dogs were killed and the hearts removed for the measurement of the activity of 201Tl and the radioactive microspheres in the normal (left anterior descending coronary artery [LAD]) and flow-restricted (left circumflex coronary artery [LCX]) regions. The ratios of the activity in LAD/LCX for microspheres (TRmic) and for 201Tl (RT1) were compared with the activity ratio determined from the scintiscan (Rscan). Rmic for the microsphere simultaneously injected with 201Tl can be compared with the initial Rscan, which showed a significant hourly decrease from an initial value of 1.26 +/- 0.12 to a mean final value of 1.02 +/- 0.09 by 3-4 hours. The final Rscan (mean 1.07 +/- 0.10) in each experiment also correlated significantly (r = 0.854) with the final true myocardial RT1 (mean 1.26 +/- 0.25). Rscan underestimated Rmic (average 2.25 +/- 0.48) when both 201Tl and microspheres were simultaneously injected; Rscan also underestimated RT1, but the directional changes were similar. A further analysis of the Rmic, Rscan and RT1 in two groups of dogs with either relatively high or low coronary flow during adenosine infusion suggests that the net loss of cellular 201Tl from the normal scintigraphic area is the mechanism underlying the resolution of these initial defects.

Adenosine↗
PubMed1981

Production of left ventricular cavitary obliteration in normal man.

To determine whether left ventricular cavitary obliteration (a finding previously described only in hypertrophic states) can be induced in normal subjects, 16 patients without coronary artery disease or clinical evidence of hypertrophic obstructive cardiomyopathy were studied during cardiac catheterization. Resting left ventricular and aortic pressures and left ventriculography were repeated during the strain phase of Valsalva maneuver after administration of amyl nitrite. Cavitary obliteration during normal sinus rhythm was defined as disappearance of the sinus portion of the left ventricle during systole, and graded as absent, partial or total. Patients were placed into two groups on the basis of qualitative analysis of the resting left ventriculogram: the 10 patients in group A had normal left ventriculograms and the six patients in group B had hyperkinetic left ventricles. During the left ventriculogram done with amyl nitrite and Valsalva, left ventricular volumes in both decreased dramatically, from 69 ml/m2 to 43 ml/m2 (p less than 0.001) and ejection fraction increased from 70% to 82% in group A (p less than 0.01). None of the patients in group A had evidence of cavitary obliteration at rest, but eight developed total and two developed partial cavitary obliteration with the second ventriculogram. Three patients in group B had partial or complete cavitary emptying at rest and all developed total cavitary obliteration with provocation. Pressure gradients between left ventricle and aorta were produced in two group A patients and three group B patients. Thus, cavitary obliteration can be produced in normal left ventricles by manipulation of loading conditions.

Adult↗
PubMed1980

The effect of diabetes on performance and metabolism of rat hearts.

To explore the effects of diabetes on myocardial function and metabolism we injected male rats with streptozotocin and studied their hearts 8 weeks later. Blood sugar levels in the treated rats were about 600 mg/100 ml. Body and heart growth rates were diminished. When studied in an isolated working rat heart apparatus using 5.5 mM glucose, hearts of diabetic animals showed diminished cardiac output and stroke work at high filling pressures. There also were significant depressions in peak left ventricular systolic pressure, peak aortic flow rate, maximum negative dP/dt, myocardial oxygen extraction, myocardial lactate production, and effluent lactate:pyruvate ratios. Myocardial glycogen stores, calculated glycogen utilization, and pyruvate production were increased in hearts of diabetics, and myocardial oxygen consumption was the same as in control hearts. The end-diastolic pressure-volume relationship was shifted to the right in hearts of diabetics. Most of the abnormalities observed in hearts of diabetic rats persisted when insulin and 15 mM glucose were included in the perfusion medium. Hearts from young rats or from age-matched food-restricted rats with heart weights similar to those of diabetics did not show depressed function or a pressure-volume shift. Our findings indicate that streptozotocin diabetes in rats results in abnormal myocardial performance. This is not due to restrictions in coronary flow or myocardial oxygenation and is not correctable by the provision of high glucose plus insulin in the perfusion medium.

Animals↗
PubMed1979

Myocardial performance and collateral flow after transient coronary occlusion in exercising dogs.

Fourteen dogs with prior constriction of the left circumflex (LCf) coronary artery were studied at rest and during treadmill running. Hemodynamics were measured before and after a 1-min LCf occlusion. Coronary and collateral flows were quantitated during occlusion both at rest and during exercise. Group I consisted of 4 dogs with resting collateral flow exceeding one-half (average 78%) of normal flow, and group II consisted of 10 dogs with collateral flows less than one-half (average 30%) of normal. At rest LCf occlusion caused no hemodynamic changes in group I, but stroke volume fell significantly in group II. During running, collateral flow after LCf occlusion doubled in group I, and there was only a small rise in left atrial pressure to 18 mmHg. In group II, collateral flow increased by 50% during running and actually decreased in 4 dogs. Significant cardiac failure developed as stroke volume halved, and left atrial pressure rose to an average 30 mmHg. Therefore exercise-induced depression of left ventricular function in the ischemic heart can be correlated to the amount of coronary collateral flow.

Animals↗
PubMed1979

Thallium-201 myocardial scintigraphy in patients with triple-vessel disease and ischemic exercise stress tests.

Thirty patients with triple-vessel coronary artery disease proven by angiography, symptomatic angina and a positive ECG stress test were evaluated with thallium-201 (201TI) scintigraphy. Twenty patients also had aortocoronary saphenous vein bypass surgery; 15 of them had repeat noninvasive evaluation. Seventy percent of these patients showed ischemia by 201TI scintigraphy, of which one-half returned to normal after surgery. Postoperative reversion of the ECG stress test together with 201TI stress/reperfusion imaging correlated well with the completeness of surgical revascularization. We could not explain the prevalence (80%) of infarcts detected by 201TI in this group, of which 76% could be anatomically correlated to epicardial scars. The positivity of infarcts by 201TI exceeded that predicted by previous history of infarction, Q waves on resting ECG or ventriculographic akinesis. These observations suggest that 201TI scintigraphy is a useful noninvasive tool in the follow-up and understanding of patients with coronary heart disease. These conclusions also support the concept that 201TI stress imaging need not have the identical connotation as the ECG stress test.

Adult↗
PubMed1979

Differential lung blood flows in experimental unilateral emphysema: nonvalidity of perfusion scans.

As part of an evaluation of the effects of left lung transplantation in dogs with papain emphysema of the right lung, differential lung blood flows were estimated by in vivo scintiscan of 99Mc-macroaggregated albumin (99mTc-MAA) and, after sacrifice, by direct counting of isotopically labeled carbonized microspheres. In six dogs, percentage flow to the right lung was calculated at the following four times: before and after induction of papain emphysema and 2 and 6 weeks after left lung autotransplantation. After the induction of right lung emphysema, the right lung in four of six animals continued to receive more than 50 percent of the total pulmonary blood flow. No correlation could be established between right lung blood flow determined by carbonized microsphere distribution (true right lung blood flow) and the flow determined by anterior and posterior scintiscans (apparent right lung blood flow). This discrepancy was caused by gross distortion of the right, emphysematous lungs, which had herniated into the left hemithoraces. This herniation was demonstrated by coronal slices taken through the thoraces of two additional dogs with right lung emphysema that were given radiolabeled carbonized microspheres and 99Tc-MAA and frozen after sacrifice. These results indicate that external scintiscans for which the particulate distribution technique are used are invalid in circumstances of altered lung geometry.

Albumins↗
PubMed1978

Effect of exercise on collateral development in dogs with normal coronary arteries.

To determine the effects of chronic exercise on the coronary collateral circulation of dogs with normal coronary arteries, 1-yr-old purebred beagles were divided into sedentary control and exercising groups. The latter were trained to run on a treadmill. A lower maximal heart rate during a standardized exercise test protocol after a 10- to 12-week training period and a higher gastrocnemius cytochrome oxidase activity in the runners attested to the presence of cardiovascular and skeletal muscle training effects. However, left ventricular weights, left ventricle/body weight ratios, myocardial myofibrillar and myosin ATPases, and hemodynamics were similar in sedentary and exercising dogs except for a significantly higher resting cardiac output in the runners. After occlusion of the left anterior descending coronary artery, both collateral conductance (retrograde flow/aortic pressure) and collateral flow measured with microspheres tended to be lower in the trained dogs, but differences were not significant. The endocardial/epicardial flow ratio in the ischemic area after coronary occlusion did not distinguish between exercisers and controls. Thus treadmill running in the dog with normal coronary arteries produced a training effect, but had no effect on coronary collateral vessels.

Adenosine Triphosphatases↗
PubMed1977

Cardiac responses to moderate training in rats.

Left ventricular (LV) performance was studied in 30 rats conditioned by swimming and in 27 sedentary controls. Hearts were studied in the open chest both during sinus rhythm and during atrial pacing. Afterload was increased by occlusion of the aorta. Sinus rates were 328 beats/min in sedentary and 300 in conditioned animals (P less than 0.01). During ejection (E), peak left ventricular systolic pressure (PLVSP) and maximum LV dP/dt were significantly higher in conditioned than in sedentary animals. When data from hearts matched for similar heart rates were compared, increased LV performance was still seen during aortic obstruction in conditioned animals. Performance at pacing rates up to 400 beats/min was similar in hearts from conditioned and sedentary animals. At pacing rates above 400 beats/min cardiac performance was less in sedentary than in the conditioned animals. These data illustrate that although base-line cardiac performance may be the same in rats conditioned by a moderate swimming program and in sedentary animals, cardiac reserve is improved by the swimming program.

Animals↗
PubMed1976

Single-passage extraction and permeability estimation of sodium in normal dogs lungs.

Bolus injections of 24NaCl, 131I-albumin, and indocyanine green dye were made into the right atria of anesthetized, ventilated dogs. Blood was sampled from the femoral artery, and from the dilution curves, instantaneous extractions, E2(t), and area averaged extractions, E3(t), were calculated for sodium at various plasma flows (Fp). Flow reduction was produced by transient inferior vena cava obstruction. E2(t) and E3(t) within any dilution curve generally started off with a high value, then decreased with time. The E3 that occurred at the peak of the albumin-dilution curve were about 0.11 for plasma flow of 0.75 liter/min and tended to decrease as flow increased. Parallel study of the sodium extravascular space at equilibrium gave values of 0.3-0.4 g of plasma sodium per g of tissue, suggesting that this volume is not infinitely small. Since the E was low it is unlikely that the high initial E(t) and the decreasing E(t) were due to early back flux. Calculation of capillary permeability surface area product [PS = Fp loge (1 - E)] showed an increasing PS with plasma flows. The injection of 9-mum microspheres at low and high total blood flow gave evidence supporting a decrease of capillary surface area (S) with decreasing total blood flow. Regional pulmonary blood flow also showed marked heterogeneity. Because of the low average extraction of sodium in the lung, insensitivity of the method in normal lungs cannot be excluded.

Animals↗
PubMed1976

131I-fibrinogen in the detection of pulmonary allograft rejection.

The uptake of 131I-fibrinogen in canine pulmonary allografts was compared to that in lung autografts or lungs with papain-induced unilateral hemorrhagic pneumonia. In addition to serial lung scans and the postmortem measurement of tissue radioactivity, all dogs had serial chest roentgenograms and histologic study of their lungs. All four animals in the allografted group had increased radioactive uptake on the side of the allograft lung at the same time as or slightly before radiographic abnormalities were evident. However, increases in lung radioactivity also occurred in animals with pneumonia or autografts at the time infiltrates were present. Thus the presence of increased lung scan activity, which occurs in rejecting lung allografts after the injection of 131I-fibrinogen, is not a specific index of pulmonary rejection.

Animals↗