Myocardial ischemia (second of three parts)

The combined transduction of copper, zinc-superoxide dismutase and catalase mediated by cell-penetrating peptide, PEP-1, to protect myocardium from ischemia-reperfusion injury

Background

Our previous studies indicate that either PEP-1-superoxide dismutase 1 (SOD1) or PEP-1-catalase (CAT) fusion proteins protects myocardium from ischemia-reperfusion-induced injury in rats. The aim of this study is to explore whether combined use of PEP-1-SOD1 and PEP-1-CAT enhances their protective effects.

Methods

SOD1, PEP-1-SOD1, CAT or PEP-1-CAT fusion proteins were prepared and purified by genetic engineering. In vitro and in vivo effects of these proteins on cell apoptosis and the protection of myocardium after ischemia-reperfusion injury were measured. Embryo cardiac myocyte H9c2 cells were used for the in vitro studies. In vitro cellular injury was determined by the expression of lactate dehydrogenase (LDH). Cell apoptosis was quantitatively assessed with Annexin V and PI double staining by Flow cytometry. In vivo, rat left anterior descending coronary artery (LAD) was ligated for one hour followed by two hours of reperfusion. Hemodynamics was then measured. Myocardial infarct size was evaluated by TTC staining. Serum levels of myocardial markers, creatine kinase-MB (CK-MB) and cTnT were quantified by ELISA. Bcl-2 and Bax expression in left ventricle myocardium were analyzed by western blot.

Results

In vitro, PEP-1-SOD1 or PEP-1-CAT inhibited LDH release and apoptosis rate of H9c2 cells. Combined transduction of PEP-1-SOD1 and PEP-1-CAT, however, further reduced the LDH level and apoptosis rate. In vivo, combined usage of PEP-1-SOD1 and PEP-1-CAT produced a greater effect than individual proteins on the reduction of CK-MB, cTnT, apoptosis rate, lipoxidation end product malondialdehyde, and the infarct size of myocardium. Functionally, the combination of these two proteins further increased left ventricle systolic pressure, but decreased left ventricle end-diastolic pressure.

Conclusion

This study provided a basis for the treatment or prevention of myocardial ischemia-reperfusion injury with the combined usage of PEP-1-SOD1 and PEP-1-CAT fusion proteins.

Protective effect of total flavones of rhododendra on ischemic myocardial injury in rabbits

This study was to investigate the effect of total flavones of rhododendra (TFR) on ischemic myocardial injury in rabbits. Rabbit ischemic myocardial injury was induced by occluding the anterior descent of the left artery (LAD). The ECG was recorded; the plasma creatine kinase (CK), nitric oxide (NO) and endothelin-1 (ET-1) levels were measured using spectrophotometry, Griess method and radioimmunoassay, respectively. The myocardial ischemic size and infarction size were determined by dual staining with Evan's blue and Nitroblue tetrazolium reductionest (N-BT). A typical ECG S-T segment elevation and an increase of plasma CK activity were observed 6 and 24 hours after the induction of ischemia. These changes were inhibited in rabbits treated with either TFR (30, 60 mg/kg) or ginkgo biloba extract (EGB) for 7 days, indicating a protective effect of TFR on ischemic myocardial injury. The myocardial ischemic size and infarction size were 40.7 +/- 3.6% and 36.8 +/- 3.6% respectively in the control group, while TFR (60 mg/kg) pretreatment for 7 days significantly reduced both myocardial ischemic size (32.40 +/- 5.38%, p < 0.05) and infarction size (28.7 +/- 5.8%, p < 0.05). In addition, the occlusion of LAD resulted in an increase of ET-1 and a decrease of NO levels in the plasma, effects that were inhibited by TFR treatment, suggesting a possible mechanism for the protective effect of TFR against myocardial ischemic injury.

Dichloroacetate as metabolic therapy for myocardial ischemia and failure

This article critically reviews the pharmacologic effects of the investigational drug dichloroacetate (DCA), which activates the mitochondrial pyruvate dehydrogenase enzyme complex in cardiac tissue and thus preferentially facilitates aerobic oxidation of carbohydrate over fatty acids. The pharmacologic effects of DCA are compared with other interventions, such as glucose plus insulin, inhibitors of long chain fatty acid oxidation and adenosine, that are also thought to exert their therapeutic effects by altering myocardial energy metabolism. Short-term clinical and laboratory experiments demonstrate that intravenous DCA rapidly stimulates pyruvate dehydrogenase enzyme complex activity and, therefore, aerobic glucose oxidation in myocardial cells. Typically these effects are associated with suppression of myocardial long chain fatty acid metabolism and increased left ventricular stroke work and cardiac output without changes in coronary blood flow or myocardial oxygen consumption. Although long-term studies are lacking, short-term parenteral administration of DCA appears to be safe and capable of significantly improving myocardial function in conditions of limited oxygen availability by increasing the efficient conversion of myocardial substrate fuels into energy.

Hyperlactatemia and increasing metabolic acidosis in hepatorenal failure treated by hemofiltration

We report a case of increasing hyperlactatemia in the course of repeated treatment by machine hemofiltration (MHF) using a lactate-buffered replacement solution. The hyperlactatemia was associated with a reduction in mean arterial pressure, and in the majority of treatments a metabolic acidosis developed. Hyperlactatemia due to exogenous lactate may not be as benign as previously discussed.

Psychiatric management of acute myocardial infarction in the coronary care unit

Failure to recognize and treat the psychiatric complications of myocardial infarction (MI) may aggravate the underlying cardiac condition and interfere with its treatment. The timing and manifestations of several distinct psychiatric conditions that commonly accompany the acute phase of MI (anxiety, depression, delirium, and behavioral abnormalities secondary to a person's premorbid character style) will be reviewed. In addition, the importance of psychological risk factors for the development of coronary artery disease (e.g., life stress and the Type A behavior pattern) and the impact of denial on the cardiac patient's condition will be discussed. Management strategies that include nonpharmacologic (i.e., support, reassurance, brief psychotherapy and cardiac rehabilitation) and psychopharmacologic interventions (e.g., the rational use of benzodiazepines, antidepressants and neuroleptic agents) for psychiatric conditions in the MI patient will be provided. Postdischarge issues that occur in both the patient and his or her family are outlined, and the enrollment in cardiac rehabilitation programs is encouraged.

The influence of adenosine triphosphate on left ventricular function and blood flow distribution during aortic crossclamping in dogs

To evaluate the influence of adenosine triphosphate (ATP)-induced vasodilation on myocardial performance and blood flow during aortic crossclamping (XC), ten dogs were instrumented to measure left ventricular (LV) pressure and dimensions. Regional LV function was assessed from the percentage of systolic shortening, whereas the slope of the linear regression of the LV end-systolic pressure-diameter relationship was used as an index of overall contractility. The regional blood flow distribution was measured from sequential injections of radioactive microspheres. Following XC, systemic arterial pressure proximal to the clamp (SAPa), LV end-diastolic pressure (LVEDP), LV end-systolic meridional wall stress (WS), and central venous pressure (CVP) increased significantly, whereas the cardiac index (CI) and heart rate did not change. After 30 minutes of ATP infusion (1 mg/kg/min) SAPa, LVEDP, WS, and CVP returned to control levels, CI increased significantly compared with XC alone, and vascular resistance fell below the control level. ATP produced a threefold increase in myocardial blood flow and shifted the intramural distribution in favor of the endocardial layer. In conclusion, our investigation of the effect of ATP on aortic XC in a canine model showed the drug to produce a smooth, predictable, and rapid reduction in left ventricular preload and afterload. This was accomplished with minimal changes in distal organ perfusion, some improvement in measured cardiac performance, and a large increase in myocardial blood flow.

Myeloperoxidase activity as a quantitative assessment of neutrophil infiltration into ischemic myocardium

The infiltration of neutrophils into ischemic myocardium exacerbates myocardial damage upon reperfusion, whereas drugs that inhibit neutrophil activity or function reduce infarct size. Consequently, it is important to accurately assess the myocardial neutrophil content. Histologic sections and radiolabeled cells have been used, but have major limitations. We have developed a method to measure the neutrophils present in cardiac tissue by utilizing a spectrophotometric assay for the neutrophil-specific myeloperoxidase enzyme (MPO) (Bradley et al., 1982a). Coronary artery occlusion and reperfusion in the anesthetized dog induces neutrophil accumulation into the ischemic heart, which shows a linear relationship with time. An increase in activity from 0.014 +/- 0.001 units (u) MPO/100 mg tissue to 0.091 +/- 0.02 u MPO/100 mg is already apparent at the end of the 90-min occlusion period. This activity increases over 5 hr reperfusion to 0.32 +/- 0.018 u MPO/100 mg tissue. Histologic analyses confirmed the temporal association of neutrophil accumulation. Moreover, there is a correlation between infarct size and tissue MPO activity. Measuring the MPO content in preparations of canine neutrophils, which is directly correlated with cell number, allows units of MPO activity to be converted into a tissue neutrophil content. This assay is simple, sensitive, and provides a quantitative index of myocardial neutrophil accumulation that can be used to study the relationship between leukocyte infiltration and myocardial injury.

Effects of verapamil in patients with acute myocardial infarction: hemodynamics and function of normal and ischemic left ventricular myocardium

We evaluated the effects of intravenous verapamil, a calcium antagonist, on hemodynamics and regional left ventricular (LV) performance in patients with acute myocardial infarction (AMI). Twenty patients having uncomplicated infarction or moderate heart failure were randomized to receive either verapamil or placebo and were studied a mean of 12 hours after onset of symptoms. Verapamil, 7.5 mg intravenously, acutely reduced systolic arterial pressure (p less than 0.0005), systemic vascular resistance, and LV stroke work (p less than 0.005) and rate-pressure product (p less than 0.05); the heart rate did not alter. The Frank-Starling relationship by Swan-Ganz catheter did not change for 1 hour. Segmental wall motion amplitudes were recorded from eight standardized segments around the left ventricle by a multidirectional M-mode echocardiographic technique. The systolic wall motion of the uninvolved LV segments and LV cavity size did not change after verapamil. Verapamil improved mechanical performance in the ischemic segments (p less than 0.005). Therefore, the overall regional contractile function of the left ventricle improved as well (by 11% to 13%, p less than 0.05). This echocardiographic improvement continued after the acute vasodilatory response of intravenous verapamil subsided and was preserved for 1 week, the patients having had oral verapamil, 240 mg daily. Chest pain was relieved in five of the six patients having ongoing slight pain before verapamil injection. No sequential hemodynamic or echocardiographic changes occurred in the placebo-treated patients. Thus, in patients with uncomplicated AMI, verapamil improve contractile function of the acutely ischemic LV segments by hemodynamic unloading and/or by direct myocardial effect, without manifest depression of the uninvolved myocardium.

Alpha- and beta-blockade in angina pectoris

Angina pectoris encompasses a clinically diverse group of syndromes in which the common factor is myocardial ischaemia resulting from an imbalance between oxygen requirement and delivery. Anginal pain is most frequently precipitated by exercise, but may occur without any apparent cause at rest. Fixed obstructions in the coronary vessels, often attended by thickening of the overlying coronary artery media, are the most frequent cause of ischaemic cardiac pain. The resulting myocardial fibrosis impairs efficient filling and emptying of the ventricles, further aggravating the functional embarrassment resulting from the reduced coronary blood flow. In stable coronary heart disease the increased energy demands during exercise are associated with the rapid development of a haemodynamic profile characteristic of acute left ventricular failure. This results in further substantial increases in pressure work, wall stress and oxygen consumption of the left ventricle. The reflex sympathoadrenal consequences of these primary haemodynamic changes lead to further mechanical and electrical embarrassment of the ischaemic heart. Increased stimulation of beta 1- and beta 2-receptors in the heart increases heart rate and contractility and thereby myocardial oxygen demand. Increased stimulation of alpha-receptors in the peripheral veins and arteries indirectly increases left ventricular oxygen demand still further by increasing preload and afterload, respectively. The reduced blood flow to the endocardium enhances its sensitivity to increased sympathoadrenal stimulation and facilitates initiation of arrhythmias. Blockade of all adrenergic activity, particularly in the myocardium, coronary arteries and peripheral blood vessels should, therefore, help alleviate the myocardial ischaemia. There is a rational argument for the use of alpha-blockade in coronary heart disease, particularly in conjunction with beta-blockade. Attenuation of the risk of coronary spasm and ventricular arrhythmias and reduction of pressure work and left ventricular afterload are amongst the potential attributes of alpha-blockade. Alone, however, their utility is severely limited by the risks of hypotension and reduction in coronary perfusion pressure and reflex oxygen-wasting tachycardia. Alone, alpha-adrenoceptor antagonists have no place in the treatment of angina pectoris. beta-Adrenoceptor blocking drugs competitively inhibit catecholamines at both cardiac and peripheral vascular beta-adrenergic receptors. Their main advantage is that they reduce many of the important determinants of myocardial oxygen consumption, particularly by reducing the heart rate during exercise.(ABSTRACT TRUNCATED AT 400 WORDS)

Quantification of experimental myocardial infarction using nuclear magnetic resonance imaging and paramagnetic ion contrast enhancement in excised canine hearts

Determination of myocardial infarct size is important for clinical management of patients with ischemic heart disease and for research on limiting infarct size. Nuclear magnetic resonance (NMR) imaging permits tomographic depiction of the distribution of mobile tissue protons. NMR images have demonstrated high spatial resolution and contrast. To evaluate the potential of this technique in measuring myocardial infarct size, NMR imaging was performed in six canine hearts excised 24 hours after circumflex coronary artery ligation. Before sacrifice, the dogs received i.v. manganous chloride (0.05 mmol/kg). After NMR imaging, the heart were sectioned and the myocardial slices were stained with triphenyl tetrazolium chloride. The pathologically determined infarct size was compared with the infarct size measured by NMR imaging. The correlation was good (regression line slope 1.06; r = 0.94). We conclude that NMR imaging with paramagnetic contrast agents can be used to determine infarct size in excised hearts.

Estimation of infarct size by myocardial emission computed tomography with thallium-201 and its relation to creatine kinase-MB release after myocardial infarction in man

We evaluated emission computed tomography (ECT) for thallium-201 (201TI) myocardial imaging in estimating infarct size (IS). In 18 patients in whom IS was estimated enzymatically at the time of the acute episode, planar 201TI perfusion scintigraphy and ECT with a rotating gamma camera were performed 4 weeks after the first myocardial infarction. From the size of 201TI perfusion defects, the infarct area in planar images and the infarct volume in reconstructed ECT images were measured by computerized planimetry. When scintigraphic IS was compared with the accumulated creatine kinase-MB isoenzyme release (CK-MBr), infarct volume determined from ECT correlated closely with CK-MBr (r = 0.89), whereas infarct area measured from planar images correlated less satisfactorily with the enzymatic IS (for an average infarct area from three views, r = 0.69; for the largest infarct area, r = 0.73). Although conventional scintigraphic evaluation is useful for detecting and localizing infarction, quantification of ischemic injury with this two-dimensional technique has a significant inherent limitation. The ECT approach can provide a more accurate three-dimensional quantitative estimate of infarction, and can corroborate the enzymatic estimate of IS.

Serum myoglobin, creatine kinase and creatine kinase-MB as mutually supportive indices of myocardial infarction and infarct size

A comparison was made between the appearance of serum myoglobin and creatine kinase in 22 patients with acute myocardial infarction who were admitted to a coronary-care unit within four hours of onset of chest pain. The MB isoenzyme of creatine kinase was measured in 12 patients. The more rapid appearance and disappearance of myoglobin relative to creatine kinase and creatine kinase-MB was confirmed, as was the correspondence between their respective peak values. A significant correlation was also obtained between the area under the myoglobin time-course and the respective peak levels. Whereas creatine kinase activity declined exponentially from a single peak, myoglobin appeared in multiple episodes inadequately represented by a single peak value and having no clear clinical correlation. The role of myoglobin as a diagnostic aid in myocardial infarction is probably limited to its ability to support creatine kinase and creatine kinase-MB as indices of infarct size.

2,4,5-T effects on cardiac and serum lactic dehydrogenase (LDH) and creatine kinase (CK) isozymes. I. Maternal enzyme activities and isozyme profiles

Pregnant mice were exposed to 100 mg/kg 2,4,5-T, IG, on gestation days 6 through 17, and sacrificed on postpartum day 1 or 21. Toxicologic evaluation showed no changes in body weight, heart weight, heart to body weight ratio, or cardiac supernate protein between corn oil control and 2,4,5-T treated mice on days 1 or 21 postpartum (pp). There were no effects of 2,4,5-T treatment on the total LDH enzyme activity of cardiac supernate on day 1 or 21pp. Serum LDH total activity was depressed on day 1pp and comparable to control values on day 21pp. Cardiac CK total activity was elevated on day 1pp, but not on day 21pp. Serum CK total activity on day 1 was comparable to control values; however, on day 21, a significant decrease in activity was observed. Cardiac LDH and CK isozyme profiles were normal on days 1 and 21pp. The serum LDH isozyme profile was normal at both times. The serum CK isozyme profile on Day 1 was markedly altered by athe appearance of two aberrant isozyme bands while on day 21, there was a profile shift with an increase in the BB band and a compensatory decrease in the MM band. These changes in creatine kinase suggest metabolic or pathologic changes in the cardiac muscle.

Metabolic basis for disorders of purine nucleotide degradation

Purine nucleotide degradation refers to a regulated series of reactions by which human purine ribonucleotides and deoxyribonucleotides are degraded to uric acid in humans. Two major types of disorders occur in this pathway. A block of degradation occurs with syndromes involving immune deficiency, myopathy or renal calculi. Increased degradation of nucleotides occurs with syndromes characterized by hyperuricemia and gout, renal calculi, anemia or acute hypoxia. Management of disorders of purine nucleotide degradation is dependent upon modifying the specific molecular pathology underlying each disease state.

Fluorocarbons reduce myocardial ischemic damage after coronary occlusion

Open-chest, anesthetized dogs with occlusions of the left anterior descending coronary artery breathed 100 percent oxygen while they were bled to a hematocrit of 25 percent and infused with an approximately equal volume (40 milliliters per kilogram) of fluorocarbon preparation or Ringer solution. Dogs breathing room air and receiving no treatment served as controls. After undergoing 6 hours of coronary occlusion, animals bled and treated with fluorocarbons developed smaller infarctions than those receiving Ringer solution or no treatment.

Estimation of myocardial involvement in patients with acute myocardial infarction by two-dimensional echocardiography

To determine whether real-time two-dimensional echocardiography (2-D echo) can estimate the extent of myocardial involvement in patients with acute myocardial infarction (MI), regional wall motion on serial short-axis 2-D echo recordings was analyzed and the summed scores were compared with estimates of infarct involvement by thallium-201 reperfusion (Tl) and technetium-99m stannous pyrophosphate (99mTc-PYP) scintigraphy. Thirty-two consecutive male patients admitted with their first MI were studied; 10 patients had anterior, 16 had inferior and six had subendocardial MIs. Two patients were technically unsuitable for 2-D echo studies. Twenty patients had Tl scintigrams and 29 had 99MTc-PYP scintigrams. Summed 2-D echo scores correlated closely with estimates of infarct involvement by Tl (r = 0.87) and with estimates of infarct size by 99mTc-PYP (r = 0.74). The location of MI by 2-D echo agreed with the electrocardiographic location in 26 of 29 patients; discrepancies occurred in one inferior and two subendocardial MIs. Predischarge 2-D echo failed to identify extension of transmural infarction. However, two patients whose subendocardial MIs progressed to transmural MIs were identified. This study shows that 2-D echo is a valid method for the early estimation of the extent of myocardial involvement in patients with acute MI, especially transmural MIs. In particular, 2-D echo correlates closely with Tl reperfusion scintigraphy because both detect areas of ischemia and infarction.

Coronary steal-induced increase in myocardial infarct size after pharmacologic coronary vasodilation

This study was performed to determine if maximal coronary arterial vasodilation of nonischemic areas would produce an increase in myocardial infarct size through a "steal" of collateral flow from an ischemic region. Myocardial infarction was produced by a 2 hour occlusion and reperfusion of the distal left anterior descending coronary artery in anesthetized dogs. Five minutes after occlusion, 7 dogs were given saline solution, and in 12 dogs the coronary vasodilator chromonar (8 mg/kg, intravenously) was administered. Chromonar produced a significant increase (p less than 0.05) in blood flow to nonischemic regions and a concomitant decrease in flow to ischemic areas. Associated with these changes in flow was an elevation in total release and peak plasma creatine kinase compared with values in saline-treated control dogs. Myocardial infarct size determined with nitroblue tetrazolium stanining was significantly increased (p less than 0.05). These demonstarte that maximal coronary vasodilation of nonischemic areas can result in an extension of myocardial infarction by a steal of collateral flow away from the ischemic region.

Reduction of cell injury in hypoxic cultures of rat myocardial cells by methylprednisolone

An in vitro model to study myocardial cell injury was developed with primary monolayer cultures of rat myocardial cells. Two important conditions associated with myocardial ischemia were simulated by depriving the cultures of oxygen and glucose for a specified period of time. Cellular injury caused by hypoxia and glucose deprivation resulted in significant leakage of lactate dehydrogenase (LDH) from the cells into the culture medium. The cells were not lethally injured by treatments as reflected by a lack of change in cell viability and protein content when compared to controls. Pretreatment of cultures with methylprednisolone for 24 hr provided protection to the cells when challenged by hypoxia and glucose deprivation. Methylprednisolone exhibited a dose-response effect in reducing LDH leakage in cultures, which were subsequently deprived of oxygen and glucose for 4 hr. Similar pretreatment with hydrocortisone had no effect in limiting cellular injury in hypoxic and glucose-deprived cultures.

Quantification of thallium-201 scintigrams in acute myocardial infarction

A method has been developed for measurement of myocardial infarct size from thallium-201 scintigrams that depends on computer measurement of levels of radioactivity in the myocardium. In 16 dogs, thallium-201 scintigrams were obtained in the left lateral and left anterior oblique projections 48 hours after ligation of the left anterior descending coronary artery. Scintigraphic results were obtained by two independent observers and were compared with tissue measurements of infarct volume calculated from thallium autoradiograms and nitro-blue tetrazolium (NBT)-stained tissue slices. Infarct volumes derived from tissue measurements were used to develop criteria for the computer scintigraphic technique. There was no significant difference in the scintigraphic measurements made by the two observers. Scintigraphic infarct size in the left lateral and left anterior oblique projections correlated with tissue infarct size with r values of 0.88 and 0.75, respectively, for thallium autoradiography and 0.71 and 0.70, respectively, for NBT tissue staining. The range of infarct volume was 3.3 to 14.8 percent of the left ventricular mass. Results of this study suggest that scintigraphic quantitation of infarct size is feasible in this dog model.

Effect of acute ischemia, nitroglycerin and nitroprusside on regional myocardial thickening, stress and perfusion. Experimental echocardiographic studies

The purposes of this study were to demonstrate that echocardiography can be used to demonstrate the systolic wall thinning of acutely ischemic myocardium, and to compare the effects of nitroglycerin and nitroprusside on systolic thinning, wall stress and perfusion of ischemic myocardium. In 37 dogs, the ratio of end-systolic-to-end-diastolic posterior wall thickness fell from 1.30 +/- 0.02 to 0.88 +/- 0.01 ((p less than 0.001) after circumflex coronary occlusion; perfusion of the area supplied by the occluded artery fell from 98.2 +/- 7.5 ml/100 g/min to 36.5 +/- 2.9 ml/100 g/min (p less than 0.001). Nitroglycerin and nitroprusside were given to lower mean arterial pressure by 7% and 15%. Despite the reduction in coronary perfusion pressure, transmural perfusion, endocardial/epicardial perfusion ratio and systolic thinning remained constant. Both drugs reduced the ischemic "wall stress index" (ventricular pressure x ventricular diameter/wall thickness) by almost 50%. Thus, both nitroglycerin and nitroprusside were equally beneficial in this model of acute myocardial ischemia.

[Increase of force of concentration under hypoxic conditions by glucose-insulin. Experiments in isolated papillary muscles of the guinea pig (author's transl)]

The minimally remaining force of contraction under the influence of hypoxia was measured in isolated right-ventricular papillary muscles of the guinea-pig, incubated in hypoxic (pO2 90 mm Hg) and oxygenated (pO2 630 mm Hg) buffer solution. With insulin (0.05 IE/ml) and elevated glucose (300 mg% compared to 100 mg%) the force of contraction fell to only 70 +/- 9% minimally instead of 38 +/- 11% (control, p less than 0,001). Elevated glucose or insulin alone had less pronounced effects which were not statistically significant for insulin. The results show an increase of tolerance against hypoxia of isolated papillary muscles under the influence of glucose and insulin.

Acute hemodynamic effects of intravenous fat emulsion in dogs

An intravenous infusion of Intralipid-10% was observed to exert a negative inotropic effect on left ventricular performance in a canine isovolumetric left heart preparation. There was no effect on diastolic compliance, however. Intravenous fat emulsion also produced significant decreases in systemic vascular resistance. The mechanism of these actions has not been elucidated, but it is postulated that free fatty acid (FFA) components or their metabolites directly affect the contractile properties of both myocardium and smooth muscle. These results suggest that until suitable clinical studies can be obtained, caution should be exercised in administering intravenous fat emulsions, particularly at maximum rates of infusion or in conjunction with sodium heparin in patients with known cardiac dysfunction.

Lack of effect of methylprednisolone on lysosomal and microsomal enzymes after two hours of well-defined canine myocardial ischemia

Myocardial ischemia was produced for 2 hours by coronary ligation in 11 dogs pretreated with methylprednisolone (MP, 30 mg/kg). Myocardial blood flow (MBF) was measured with microspheres (15 micrometer) in each tissue sample used for enzymatic analysis. Homogenates of these tissue samples were separated by ultracentrifugation into lysosome-rich and microsomal fractions and were analyzed for N-acetyl-beta-glusosaminidase (NAGA), beta-glucuronidase (beta-gluc), rotenone-insensitive-NADH-cytochrome c reductase (RINCR), and cytochrome oxidase. The enzymatic data from centrifugal fractions were grouped according to MBF values for statistical analysis of inter-group effects of ischemia. Significant losses (P less than 0.001) of NAGA and beta-gluc were seen in all MP-treated lysosome-rich particulate fractions that were isolated from zones demonstrating MBF values less than 25% of control (L-ischemia). Similar significant losses (P less than 0.001) of RINCR were seen in microsomal fractions from L-ischemia zones. Samples with MBF values greater than 25% but less than 75% of control (M-ischemia) also demonstrated significant decreases of lysosomal and microsomal enzymatic activity in specific fractions. When the data of the above MP-treated group were compared with the untreated control group, no significant intergroup effects of treatment with MP were observed. In addition, enzymatic data (NAGA, RINCR) were normalized prior to performing linear regression analyses; percent loss of particulate enzymatic activity was plotted against percent decrease in MBF. The effects of 2 hours of ischemia on the above biochemical parameters were comparable between untreated and MP-treated groups. Finally, when myocardial samples were grouped according to similar levels of MBF, statistical analysis using the general linear models procedure revealed no beneficial effect of MP treatment on changes in lysosomal hydrolases, microsomal RINCR, or latency of lysosomes.

Evaluation of regional myocardial function in ischemic heart disease by echocardiography

Echocardiography can display motion abnormalities of acutely or chronically ischemic myocardium. In experimental studies, this permits the evaluation of the effect on regional dyskinesis of potentially therapeutic interventions. In clinical studies, the demonstration of segmental dyskinesis has been primarily useful for diagnostic purposes. As more experience is gained with the newer two-dimensional cross-sectional ultrasound techniques, it appears likely that these will afford a major advance in the diagnosis of ischemic heart disease by permitting the routine noninvasive demonstration of segmental ventricular dyskinesis and assessment of regional myocardial function.

The measurement and control of myocardial infarct size

Direct, chemical, electrocardiographic and radio-isotopic methods are described for the estimation of myocardial infarct size in animals and man. Their relative points and failings are discussed. The effects of interventions, physical, metabolic and pharmacological, upon the size of myocardial infarcts, are examined and work attempting to reduce myocardial infarct size in man reviewed.