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Biomedical subjects

C B Moschos

Publications and source records attributed to C B Moschos.

At least 19 recordsLinked to original sources
PubMed1981

Evaluation of thallium-201 imaging in nontransmural ischemia and infarction.

To assess the validity of thallium-201 myocardial imaging in the diagnosis of nontransmural ischemia and infarction, the proximal left anterior descending coronary artery was partially occluded for 60 minutes with a balloon-tip catheter in intact anesthetized dogs in a basal state or during atrial pacing. In vivo scintigrams of myocardium were compared with those obtained in the isolated heart and in the incised ventricle spread flat. None of the animals with partial occlusion with or without pacing demonstrated abnormal scintiscans in vivo. Removal of background by isolating the heart increased positive images to 30%; positive images were associated with an isotope count ratio between ischemic and normal muscle of less than 0.67. Removal of superimposed nonischemic muscle in the heart enface increased image detection after pacing to 11 of 15. Since animals with subendocardial scar failed to demonstrate a "cold area" in vivo, unfavorable geometry as well as extent and degree of ischemia appear to be important. Thus, thallium radioactivity in superimposed and adjacent myocardium, as well as background, may limit the detection of nontransmural ischemia and scar.

Animals↗
PubMed1981

Effect of sulfinpyrazone on ventricular fibrillation during acute myocardial ischemia.

In patients treated with sulfinpyrazone, an apparent reduction in the incidence of sudden death and presumed ventricular fibrillation has been reported. Using an intact animal model without microcirculatory thrombosis, we studied the effects of sulfinpyrazone on ischemic myocardium in 58 anesthetized dogs divided into three groups: control untreated (n =24), group 1 (n = 16), treated daily with 300 mg of sulfinpyrazone for 7 days, and group 2 (n = 18), treated daily with 300 mg of sulfinpyrazone for 7 days but omitting treatment on day 8. Although consistent hemodynamic differences were not apparent, the degree of injury determined by ECG mapping was significantly lower in group 1. The incidence of fibrillation was 54% for control and 0% in group 1. Group 2 had a 44% incidence, suggesting a limited duration of action. The apparent absence of microcirculatory thrombosis in this model suggests other mechanisms of action. A significantly smaller increase in tissue water and Na+ and smaller loss of K+ in group 1 may have contributed to the lower incidence of fibrillation, perhaps through selective prostaglandin inhibition.

Acute Disease↗
PubMed1978

Relation of platelets to catecholamine induced myocardial injury.

To test the thesis that myocardial injury, induced by catecholamines, is ischaemic in origin due to platelet accumulation in the coronary microvasculature, sustained left intracoronary and systemic infusion of catecholamines in toxic dosage was given to dogs previously infused with autologous 51Cr-labelled platelets. Subsequent determination of tissue radioactivity and electrolytes, as well as electronmicrography, indicated that the induced myocardial injury was not related to microvascular occlusion by platelets.

Animals↗
PubMed1978

Antiarrhythmic effects of aspirin during nonthrombotic coronary occlusion.

To study the action of aspirin upon the myocardium per se, independent of thrombosis, coronary occlusion with a balloon catheter was induced in 53 anesthetized dogs divided into two groups. One group (N = 20) was treated daily with aspirin (600 mg/dog) for seven days and another (N = 33) was untreated. Left ventricular hemodynamics and precordial ECG mapping were used to assess the influence of myocardial ischemia over a four hour period. There were no significant differences in left ventricular function or extent of injury as judged by ECG mapping between the two groups. However, there was a significant decrease in the incidence of ventricular fibrillation in the treated dogs (5% vs 39%). Serial plasma samples for free fatty acid determination showed a significant rise in the untreated group. Aspirin blocked the FFA increment in the treated animals. Tissue samples from the ischemic area of left ventricle exhibited a significant reduction of the sodium and water increments, as well as a lesser potassium loss in the treated animals compared to the controls and may have been the basis for the lower incidence of arrhythmias. Since infusion of 51Cr labelled platelets showed no myocardial accumulation of platelets in either group, microthrombi did not appear to contribute to the observed differences.

Animals↗
PubMed1977

Myocardial function and coronary blood flow response to acute ischemia in chronic canine diabetes.

To examine the influence of preexistent diabetes mellitus on left ventricular performance and coronary blood flow responses to acute ischemia, mild normoglycemic diabetes was induced in nine mongrel dogs after three doses of alloxan, (20 mg/kg, iv), at monthly intervals. Hemodynamic measurements and coronary blood flow (85Kr clearance) were obtained before and after the onset of ischemia. This was produced by occlusion of the proximal left anterior descending coronary artery via a balloon-type catheter in nine intact anesthetized diabetic dogs and 10 nondiabetic dogs. During the 1st hour of ischemia in the diabetic group, the end-diastolic pressure rose from 7 +/- 1.1 (mean +/- SE) mm Hg to 23.8 +/- 2.3 without a significant increase of end-diastolic volume. In controls end-diastolic pressure rose from 8.6 +/- 1.1 mm Hg to 15.3 +/- 1.4, and end-diastolic volume was significantly increased, so that the ratio of end-diastolic pressure and volume was significantly higher in the diabetic group (P less than 0.005). Although indices of contractility did not differ, stroke volume and work reductions were significantly greater in diabetics, despite the fact that coronary blood flow was reduced to a similar extent. Size of the ischemic areas appeared comparable as judged by distribution of dye injected distal to the occlusion. Since potassium loss and sodium gain in the inner and outer layers of ischemic tissue did not differ between the two groups, the intensity of ischemia seemed similar. Glycogenolysis was unimpaired in the diabetic ischemic muscle but triglyceride levels remained elevated. Morphologically the diabetic myocardium was characterized by a diffuse accumulation of periodic acid-Schiff-positive glycoprotein in the interstitium, which was thought to limit diastolic filling of the ischemic ventricle and to contribute to the substantial reduction of ventricular performance.

Animals↗
PubMed1976

Cardiovascular effects of long-term cigarette smoking and nicotine administration.

The nature of the cardiovascular risk in cigarette smokers has not been characterized. To compare the relative effects of long-term smoking and nicotine administration on the cardiovascular system, 18 month old beagle littermates were prepared with a permanent tracheostomy. They were classified into three groups: I, seven control dogs; II, nine dogs that smoked seven cigarettes/day; and III, eight dogs that received an equivalent amount of nicotine. After a period of up to 22 months, the animals were catheterized under anesthesia for assessment of left ventricular function and volumes by indicator-dilution technique. Heart rate, stroke volume, left ventricular end-diastolic pressure and volume and intraventricular conduction times did not differ significantly in the three groups. Left ventricular ejection fraction was 44 +/- 3 percent (mean +/- standard error of the mean) in the control group, 35 +/- 3 percent in the dogs that smoked cigarettes (P less than 0.05) and 27 +/- 3 percent in those given nicotine (P less than 0.01) despite similar values for end-diastolic variables in the three groups. The first derivative of left ventricular pressure (dP/dt) normalized for pre- and afterload was 2.4 +/- 0.2 cm/sec -1 in the control group, 1.41 +/- 0.12 in the cigarette-smoking group (P less than 0.005) and 1.34 +/-0.08 in the nicotine group (P less than 0.01). Although mean aortic pressure was significantly elevated in both the smoking (127 +/- mm Hg) and nicotine (127 +/- 10 mm Hg) groups, there was no significant correlation with the contractility indexes. Reduction of afterload to normal levels did not affect the abnormal ventricular performance. Hypertrophy, inflammation and abnormalities of cell ultrastructures were not present, and myocardial lipid and cation composition were normal. Since interstitial fibrosis was evident in both experimental groups, an alteration of elastic elements may be operative. These cardiovascular abnormalities appear to be predominantly dependent on the nicotine of cigarettes.

Animals↗
PubMed1976

Evaluation of potassium-43 scintillation images during early myocardial ischemia in an animal model.

To assess the validity of myocardial imaging with potassium-43 (43K) early after the onset of ischemia, the left anterior descending artery was occluded with a baloon tip catheter in 32 intact anesthetized dogs. 99mTechnetium ventriculograms localized the left ventricle. 43K was administered intravenously and serial images were obtained in four views using an Anger camera with a pinhole collimator. The heart was arrested after 60 minutes and removed for imaging and tissue counts to ascertain extracardiac and geometric factors. In normals (group 1) left ventricular images were relatively homogeneous, except for the thin walled apex, both in vivo and in the isolated heart. Equilibration with 43K prior to ischemia (group 2) gave similar images to group 1, associated with a small reduction in tissue count after one hour of ischemia. Group 3 was infused with 43K after initiation of ischemia. Despite a reduction of 43K counts in the ischemic area to less than one-fourth of the nonischemic site (P less than 0.001), demonstration of a "cold area" in vivo was inconstant, occurring in only 34% of studies. Lead shielding did not improve accuracy. In the isolated heart the ability to detect the cold area was improved to 73%. However, when the left ventricle was incised and spread flat, so that low and high activity areas were contiguous rather than superimposed, a widespread area of ischemia was present without exception in the anterior wall. Use of a rectilinear scanner in seven animals failed to improve diagnostic yield; areas of reduced radioactivity were seen at the apex in normals by both techniques. Thus, while detection of low flow areas in the isolated heart is feasible by isotopic imaging early after the onset of ischemia, both extracardiac and geometric factors can contribute to qualitative and quantitative errors in vivo.

Animals↗
PubMed1976

Effect of coronary thrombus age on fibrinogen uptake.

A study was carried out to define the time limits during which an experimental coronary thrombus remains capable of incorporating fibrinogen. 131I-fibrinogen was given to intact anesthetized dogs at different time intervals, up to 67 hours, following the formation of a coronary thrombus by catheter-electrode. Radioactivity of the recovered thrombi as a whole and segmentally divided, was determined following variable time intervals of exposure to circulating fibrinogen and was expressed as thrombus/blood ratio. The results indicate that coronary thrombi formed in a normal coronary vessel remain capable of incorporating fibrinogen for at least eighteen hours, with no significant differences in the segmental distribution of radioactivity. These findings do not support the view that the recovery of isotopic fibrinogen, which was given after the onset of coronary symptoms, in thrombi from patients with myocardial infarction establishes that the thrombus was initiated after the ischemic process.

Animals↗
PubMed1975

Effects of experimental coronary thrombosis upon regional and systemic plasma chromatographic patterns.

An evaluation of changes in the plasma chromatographic pattern was carried out in dogs with experimental coronary thrombosis. Sequential samples were taken simultaneously from the aorta and coronary sinus over a two, four and twenty-four hour period. In addition to gel-chromatography, immunodiffusion and electrophoresis were also employed to identify the protein components of the elution fractions. The results showed that there was a shift of the normal chromatographic pattern to the left from the control within two hours following thrombotic occlusion of the coronary artery and it was maintained over a twenty-four hour period. The shift to the left was presumably due to the earlier elution of the heavy molecular weight components forming as a result of the thrombotic process. The early appearance of the altered chromatographic pattern constitutes an important advantage worthy of further exploration for possible diagnostic application in the human subject.

Animals↗
PubMed1975

Hemodynamic effects of staged hematocrit reduction in patients with stable cor pulmonale and severely elevated hematocrit levels.

Patients with cor pulmonale and high hematocrit levels are often subjected to phlebotomy in the belief that the adverse effects of high viscosity may outweigh the benefit of increased oxygen carrying capacity. To evaluate this, 12 patients with stable cor pulmonale and hematocrit values greater than 55 per cent were studied before and after a series of venesections. Right heart and aortic pressures, cardiac output and blood gases were measured at three mean hematocrit levels, 61 per cent (stage I), 50 per cent (stage II) and 44 per cent (stage III), with blood volume unchanged. From stages I to II, there were significant decreases in both man pulmonary artery pressure and total pulmonary resistance. Oxygen transport fell but not oxygen consumption. Right ventricular end-diastolic pressure and cardiac output did not change. Right ventricular work either fell or was maintained by increased output. Frank-Starling performance (supine exercise) improved. No significant changes occurred with further reduction in hematocrit to normal levels (stage III). The findings of this study support the concept of overcompensating erythrocytosis in cor pulmonale, and the effects of moderate hematocrit reduction should not be overlooked in these severely ill patients.

Adult↗
PubMed1975

Acute myocardial infarction in toxic cardiomyopathy without coronary obstruction.

Confluent left ventricular scar without significant coronary obstruction has been found in alcoholic subjects at autopsy. To evaluate the pathogenesis, 12 patients with chronic alcoholism and severe precordial pain persisting 4-24 hours were observed clinically. Cardiac isoenzymes of lactic dehydrogenase rose in serum. ST segment was elevated in anterior or posterior ECG leads, and abnormal Q waves appeared. Hypertnesion and hypercholesterolemia were present in two (group B) but not in the ten (group A). The latter exhibited no significant obstructive disease, based on coronary angiography in seven survivors and postmortem examination of the remaining three. Clinical evidence, as well as the quantitative assessment of platelets, made arterial thromboembolism an unlikely cause for the symptoms. Neither hemotologic or systemic disease affecting myocardium was present. The morphology of the left ventricle in three autopsies was compared with that of patients with alcoholism who had no cardiac disease, cardiomyopathy, or an asymptomatic scar. All had accumulation of Alcian positive glycoprotein in the interstitium. The patients with cardiac disease also had interstitial fibrosis which was characterized, particularly in the acute infarction group, by concentric periarterial fibrosis. Restriction of coronary vasodilation by this process during periods of high blood flow requirements was postulated as a basis for infarction.

Adult↗