Myocardial ischemia (first of three parts)

Natural history and prognostic implications of left ventricular end-diastolic pressure in reperfused ST-segment elevation myocardial infarction: an analysis of the thrombolysis in myocardial infarction (TIMI) II randomized controlled trial

Background

The aim of the current study is to assess the natural history and prognostic value of elevated left ventricular end-diastolic pressure (LVEDP) in patients with ST-segment elevation myocardial infarction (STEMI) after reperfusion with thrombolysis; we utilize data from the Thrombolysis in Myocardial Infarction (TIMI) II study.

Methods

A total of 3339 patients were randomized to either an invasive (n = 1681) or a conservative (n = 1658) strategy in the TIMI II study following thrombolysis. To make the current cohort as relevant as possible to modern pharmaco-invasively managed cohorts, patients in the invasive arm with TIMI flow grade ≥ 2 (N = 1201) at initial catheterization are included in the analysis. Of these, 259 patients had a second catheterization prior to hospital discharge, and these were used to define the natural history of LVEDP in reperfused STEMI.

Results

The median LVEDP for the whole cohort was 18 mmHg (IQR: 12–23). Patients were divided into quartiles by LVEDP measured during the first cardiac catheterization. During a median follow up of 3 (IQR: 2.1–3.2) years, quartile 4 (highest LVEDP) had the highest incidence of mortality and heart failure admissions. In the cohort with paired catheterization data, the LVEDP dropped slightly from 18 mmHg (1QR: 12–22) to 15 mmHg (IQR: 10–20) (p = 0.01) from the first to the pre-hospital discharge catheterization.

Conclusions

LVEDP remains largely stable during hospitalisation post-STEMI. Elevated LVEDP is a predictor of death and heart failure hospitalization in STEMI patients undergoing successful thrombolysis.

Graphic abstract

The Importance of Intra-aortic Pulse Pressure After Anterior ST-segment Elevation Myocardial Infarction

Objective

To evaluate the association of pulse pressure (PP) with mortality and major adverse cardiac events (MACE) in one-year period after anterior ST-elevation myocardial infarction (A-STEMI).

Methods

A total of 261 consecutive patients whose blood pressure was measured with the aid of a catheter before primary percutaneous coronary intervention (PPCI) between August 2016 and February 2017 were included in the study. The patients were divided into three groups according to pulse pressure (PP) (Group 1, PP<35 mmHg; Group 2, 35≤PP≤50 mmHg; Group 3, PP>50 mmHg).

Results

The mean age of the patients was 63.4±14.1 years, and 206 of them were male. The groups were similar in terms of age and diastolic blood pressure (DBP). The ratio of female patients in Group 1 was higher, and their systolic blood pressure (SBP) was lower than those from the other groups (P=0.005 vs. P=0.042). The rates of MACE and mortality were higher in Group 1. The predictive PP values were calculated to be 42.5 mmHg for development of MACE and 41.5 mmHg for mortality. One-year survival ratio was worse in Group 1 than in the others according to Kaplan-Meier analysis (P<0.001).

Conclusion

The values of PP which was measured intra-aortically in patients with A-STEMI were associated with mortality and MACE in the one-year follow-up period.

Prognostic Value of Left Ventricular End-Diastolic Pressure in Patients With Non-ST-Segment Elevation Myocardial Infarction

Background

Elevated left ventricular end-diastolic pressure (LVEDP) has been reported to predict an increased mortality in patients with ST-segment elevation myocardial infarction. However, its prognostic value in patients with non-ST-segment elevation myocardial infarction (NSTEMI) remains unclear.

Methods

We performed a retrospective analysis of NSTEMI patients who underwent coronary angiography between January 2013 and June 2014. We excluded patients who did not undergo LVEDP measurements. Baseline and angiographic characteristics, in-hospital heart failure as well as in-hospital mortality were recorded.

Results

After exclusion, 367 patients were included in the final analysis. The median (interquartile range) LVEDP was 19 mm Hg (14 - 24 mm Hg). By receiver operating characteristic curve analysis, the optimal cutoff value for predicting in-hospital mortality was 22 mm Hg (area under the curve 0.80, sensitivity 80%, and specificity 71%). Of 367 patients, 109 patients (29.7%) had LVEDP > 22 mm Hg. Patients with LVEDP > 22 mm Hg had a greater number of comorbidities. There was no statistically significant difference in the rate of multi-vessel disease. Patients with LVEDP > 22 mm Hg had a significantly higher rate of in-hospital heart failure (22.0% vs. 13.2%, P = 0.03) and in-hospital mortality (3.7% vs. 0.4%, P = 0.03) than those with LVEDP ≤ 22 mm Hg.

Conclusion

Elevated LVEDP was significantly associated with a higher in-hospital mortality in patients with NSTEMI.

Prognostic implications of left ventricular end-diastolic pressure during primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: Findings from the Assessment of Pexelizumab in Acute Myocardial Infarction study

BACKGROUND

Left ventricular end-diastolic pressure (LVEDP) is frequently measured during primary percutaneous coronary intervention (PCI). However, little is known of this measurement's utility in predicting outcomes or informing treatment decisions. We sought to determine the prognostic value of LVEDP measured during primary PCI for ST-segment elevation myocardial infarction (STEMI).

METHODS

We studied 1,909 (33.2%) of 5,745 STEMI patients in whom LVEDP was measured during primary PCI in the APEX-AMI trial. Cox regression analysis was used to evaluate whether LVEDP was an independent predictor of mortality and the composite of death, cardiogenic shock, or congestive heart failure (CHF) at 90 days.

RESULTS

The median (25th, 75th percentiles) LVEDP level was 22 mm Hg (16, 29); compared with patients with LVEDP ≤ 22 mm Hg, those with LVEDP > 22 mm Hg had higher rates of CHF (7.3% vs 3.1%, P < .001), cardiogenic shock (4.6% vs 1.7%, P < .001), and death (4.1% vs 2.2%, P = .014) at 90 days. After multivariable adjustment, LVEDP was associated with increased risk of mortality through 90 days (adjusted hazard ratio 1.22, 95% CI 1.02-1.46, per 5-mmHg increase, P = .044) and the composite of death, cardiogenic shock, or CHF within the first 2 days (adjusted hazard ratio 1.40, 95% CI 1.23-1.59, per 5-mm Hg increase, P < .001), but not from day 3 to 90 (P = .25).

CONCLUSIONS

Left ventricular end-diastolic pressure measured during primary PCI for STEMI is an independent predictor of inhospital and longer term cardiovascular outcomes. Measuring LVEDP may be useful to stratify patient risk and guide postinfarct treatment.

Usefulness of multiaxis echocardiography in assessment of the left ventricle in ischemic heart disease. A review

Echoventriculography, a multiaxis M-mode echocardiographic technique, was developed to examine in detail the regional wall motions of the left ventricle. The basic technical aspects and limitations are described, and experience is reviewed on 263 healthy subjects or patients with ischaemic heart disease. The reliability in detecting site and size of asynergic segments was excellent as related to electrocardiographic and thallium scintigraphic sites of acute infarction, and with left ventricular cineangiograms in chronic coronary heart disease. The correlation with pathologic anatomic size of infarct in 24 consecutive patients was r = 0.88 (p less than 0.001) when expressed by a percentage of the left ventricular horizontal circumference. 94% of 111 infarcted segments were correctly detected by echo; only the posteroseptal and the most lateral regions remain out of the methodological range. The method separated old infarct scars from fresh necrosis. Decreasing echo contraction index correlated with increasing severity of coronary obstructions in 43 patients studied for coronary artery surgery. In 15 infarct patients the M-mode technique was more sensitive than two-dimensional echocardiography in recording asynergic segments or endocardial echoes. The multiple segmental echoventriculographic index decreased parallel with clinical severity of acute infarction (r = -0.79, p less than 0.001; 30 patients). There was a 88% (p less than 0.01) concordance between the reduction of the ST segments (-30%) and the recovery of the mechanical function in the ischaemic myocardial segments (+26%) after beta blockade with pindolol in 22 patients with acute infarction. Methylprednisolone showed no improvement. With dopamine the left ventricular size decreased markedly (p less than 0.0005). Echoventriculography thus seems to be very informative in evaluation of chronic or acute left ventricular dysfunction, despite the rather demanding nature of the technique in practice.

BM-573, a dual thromboxane synthase inhibitor and thromboxane receptor antagonist, prevents pig myocardial infarction induced by coronary thrombosis

The aim of this study was to characterize the effects of BM-573 [N-terbutyl-N'-[2-(4'-methylphenylamino)-5-nitro-benzenesulfonyl] urea], a novel dual thromboxane A2 receptor antagonist and thromboxane synthase inhibitor, on myocardial infarction induced by topical ferric chloride (FeCl3) application to the left anterior descending (LAD) coronary artery in anesthetized pigs. All control animals (n = 6) developed an occlusive thrombus in the LAD coronary artery. The mean infarct size, revealed by triphenyl tetrazolium chloride (TTC), and the area at risk, evidenced by Evans blue, corresponded to 35.3 +/- 2.2 and 36.9 +/- 2.1% of the left ventricular mass, respectively. In the BM-573-treated group (n = 6), a drug infusion (10 mg. kg-1. h-1) started 30 min before FeCl3 application and continued throughout the experimentation. Among the BM-573-treated group, four pigs did not develop coronary artery thrombus and their myocardium appeared healthy. Histopathological examination of FeCl3-injured coronary artery revealed an occlusive and adherent thrombus in control group, while pretreatment with BM-573 prevented thrombus formation. In infarcted zones, lack of desmin staining and muscle structure disorganization were obvious. Depletion of myocardial ATP content was observed in the myocardial necrotic region of the control group, but not in myocardial samples of BM-573-treated pigs that did not develop myocardial infarction. When BM-573 prevented LAD artery occlusion, the area under the curve of plasmatic troponin T was reduced by 77% over 6 h. These data suggest that BM-573 could be useful for the prevention of myocardial infarction.

Continuous perfusion improves preservation of donor rat hearts: importance of the implantation phase

BACKGROUND

Continuous hypothermic perfusion of donor hearts may provide extra protection for long ischemic times and suboptimal donors. The aim of three separate studies was to assess the effect of continuous hypothermic perfusion during simulated donor heart storage and implantation.

METHODS

In study 1 twelve isolated rat hearts underwent 10 minutes of normothermic ischemia to simulate the effect of brain death on the heart and 5 hours of cardioplegic arrest, using University of Wisconsin solution. Six hearts were statically stored in University of Wisconsin solution at 2 degrees C, and six were perfused with University of Wisconsin solution. To assess the effect of simulated implantation, in study 2 an additional 12 hearts were statically stored for 5.5 hours in University of Wisconsin solution, six of which were rewarmed to a mean of 16 degrees C over the last 30 minutes of arrest. To assess the effect of simulated perfusion, in study 3 during implantation 12 hearts were rewarmed to a mean of 16 degrees C over the last 30 minutes of arrest, during which time six were perfused with 2 degrees C solution.

RESULTS

Hearts perfused during storage demonstrated greater recovery of prearrest power, 85.8% +/- 1.8%, than hearts preserved by static storage, 72.7% +/- 3.0% (p < 0.01). The simulated warm implantation period reduced recovery of power from 68.3% +/- 5.1% to 40.2% +/- 2.0% (p < 0.001). Perfusion during warm implantation improved recovery to 61.8% +/- 3.9% (p < 0.01). In all experiments improved function was accompanied by improved metabolic energy status.

CONCLUSIONS

During the implantation period of heart transplantation the donor heart sustains injury that could amount to 50% of total ischemic injury. Continuous perfusion during the cold storage phase and during simulated implantation improves recovery of the donor heart.

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.

Delayed protection against ischaemia-induced ventricular arrhythmias and infarct size limitation by the prior administration of Escherichia coli endotoxin

1. Bacterial endotoxin (lipopolysaccharide derived from Escherichia coli) was injected intraperitoneally in conscious rats in doses ranging from 0.5 to 2.5 mg kg-1. At various times afterwards the animals were anaesthetized and subjected to a 30 min period of left coronary artery occlusion. 2. Under these conditions the severity of ventricular arrhythmias was markedly suppressed, in comparison with saline-injected controls, but this was particularly marked with the higher doses (1.5 and 2.5 mg kg-1); the number of ventricular premature beats was reduced from 1687 +/- 227 over the 0.5 h coronary artery occlusion period to 190 +/- 46 in those rats administered 2.5 mg kg-1 endotoxin 8 h previously (P < 0.05). The duration of ventricular tachycardia was also significantly reduced (138 +/- 26 s to 8.9 +/- 4.2 s; P < 0.01) and there was a reduction in the incidence of ventricular fibrillation (from 56% to 10%). 3. The time course of this protection was studied following the administration of a single dose of 2.5 mg kg-1 of endotoxin by anaesthetizing rats 4, 8 or 24 h later. Protection was apparent at each time but was particularly marked at 8 h. 4. No rat given the highest dose of endotoxin (32 in all) died as a result of ventricular fibrillation, or from any other cause, during an occlusion, in contrast to a 26% mortality in the controls (P < 0.01). 5. Infarct size, measured following a 30 min period of coronary artery occlusion followed by a 3 h reperfusion period, was reduced both 8 and 24 h after the administration of 2.5 mg kg-1 endotoxin (reductions of 24.3 and 23.1% respectively; P < 0.05). Endotoxin had no significant effect on the area at risk. 6. The beneficial effects of endotoxin on infarct size and on ventricular arrhythmias were markedly attenuated by the prior administration of dexamethasone, 3 mg kg-1 given 1 h prior to endotoxin administration. Dexamethasone itself reduced infarct size (P < 0.05) but had no direct effect on arrhythmia severity following coronary artery occlusion. 7. The mechanisms of this "cross-tolerance' induced by bacterial endotoxin against ischaemia-reperfusion injury remain to be elucidated but the most likely mechanisms appear to be the induction of protective enzymes or proteins (e.g. nitric oxide synthase, cyclo-oxygenase (COX) 2) probably mediated by cytokine release.

VEGF mRNA is reversibly stabilized by hypoxia and persistently stabilized in VEGF-overexpressing human tumor cell lines

Solid tumor growth is dependent upon angiogenesis, a process by which soluble factors released from a tumor induce the sprouting and growth of new blood vessels from nearby venules into the tumor. This process of tumor vascularization provides tumor cells with nutrients, oxygen, and an enhanced ability to establish metastasis at peripheral sites by migration through the circulatory system. Vascular endothelial growth factor is a potent angiogenic factor that is expressed at low levels by most normal cells, can be upregulated in normal cells by exposure to hypoxia or phorbol esters, and exhibits high levels of constitutive expression in some human tumors and tumor cell lines. The mechanism underlying the stable change that results in VEGF overexpression in tumors is unknown. Here, we demonstrate that both hypoxia and TPA induce stabilization of VEGF mRNA, that stabilization by hypoxia is rapidly reversible upon reexposure to normoxia, and that tumor cell lines exhibiting constitutive overexpression of VEGF also exhibit constitutive stabilization of VEGF transcripts. Stabilized VEGF transcripts in tumor cells are refractile or nearly refractile toward further stabilization by TPA or hypoxia, respectively. Furthermore, cycloheximide induces stabilization of VEGF mRNA in normal cells but has no effect on VEGF transcript stability in tumor cells that contain stabilized transcripts. These results suggest that normal signal transduction mechanisms mediate stabilization of the VEGF mRNA, and that mutations in this regulatory pathway in tumor cells may lead to chronic message stabilization, overexpression of VEGF proteins, and ensuing tumor vascularization.

Metabolism of 2,6-dinitro[3-3H]toluene by human and rat liver microsomal and cytosolic fractions

1. 2,6-Dinitrotoluene (2,6-DNT) metabolism by human liver and male Fischer F344 rat liver subcellular fractions under aerobic (100% oxygen) and anaerobic (100% nitrogen) incubation conditions was examined. Under aerobic conditions the major 2,6-DNT metabolite formed by hepatic microsomes was 2,6-dinitrobenzyl alcohol (2,6-DNBalc); under anaerobic conditions 2-amino-6-nitrotoluene (2Am6NT) was the major metabolite. 2. Rates of 2,6-DNBalc formation by human and rat liver microsomes under aerobic conditions were 247 and 132 pmol/min per mg protein, respectively. Rates of 2Am6NT formation by human and rat liver microsomes under anaerobic conditions were 292 and 285 pmol/min per mg protein, respectively. Anaerobic reduction of 2,6-DNT to 2Am6NT by rat and human liver microsomes was inhibited by carbon monoxide and metyrapone, which indicates that microsomal metabolism of 2,6-DNT to 2Am6NT is mediated by cytochrome P-450. 3. Liver cytosolic fractions also metabolized 2,6-DNT to 2Am6NT under anaerobic conditions. Formation of 2Am6NT by human and rat liver cytosols was supported by hypoxanthine, NADPH and NADH. Allopurinol inhibited the hypoxanthine-supported anaerobic metabolism of 2,6-DNT by rat, but not human, liver cytosol. Dicumarol inhibited the NADPH-supported anaerobic metabolism of 2,6-DNT by human, but not rat, liver cytosol. These results indicate that xanthine oxidase contributes to the hypoxanthine-supported anaerobic metabolism of 2,6-DNT by human liver cytosol.

Precordial ECG mapping in acute myocardial infarction (AMI) after intravenous infusion of streptokinase (s)

Repeated precordial ECG mapping (42 leads) and CK-MB serum measurements were done in 40 patients with anterior and/or anterolateral acute myocardial infarction. Twenty patients serving as controls, were treated with routine anticoagulant therapy. In 20 patients (the s group), randomly selected, a short-term IV infusion of 1,500,000 IU streptokinase was administered and followed by the same anticoagulant treatment as in controls. Ten subjects from each group underwent coronary arteriography one month later. From the analysis of ECG mapping the number of leads (N) and the sum of measurements (sigma) for each parameter were calculated. Before treatment there were no significant differences for all measured parameters between the two groups of patients. Seven days later, ST elevations were statistically different for NST and sigma ST with lower values for the s group. Higher values for NR and sigma R were also noted in this group. No statistically significant difference was found for NQ and sigma Q. CK-MB curve showed an earlier peak in the s group than in the control group. Five patients from the s group showed a patency of the infarct-related vessel. In conclusion, the results of this study show that patients receiving s have a significant benefit with ECG improvement. On the other hand, the CK-MB curve indicates an eventual recanalization to a certain degree in the obstructed coronary artery, which is the final goal.

Imaging of acute myocardial infarction by magnetic resonance tomography (MRT) using the paramagnetic relaxation substance gadolinium-DTPA

Twenty-six patients admitted to the Free University of Berlin University Hospital catheterization laboratory with acute myocardial infarction were studied. The diagnosis was confirmed by angiography, but acute revascularization was unsuccessful in every case. MR imaging was performed within 7 days of the acute event in 11 patients with uncomplicated clinical courses after acute infarction. Imaging was performed within 3 weeks in three additional cases, while the remaining 12 patients underwent studies more than 3 weeks after infarction. We determined signal intensity at three points within the area of infarction and at three other points in adjacent myocardial tissue. Decreased signal intensity within the area of infarction was found in native scans in 60% of all cases. Administration of gadolinium-DTPA 0.1 mmol/kg body weight was followed by a mean 70% increase in signal intensity within the zones of acute infarction, as compared to a 20% increase in surrounding myocardial tissue. In cases of subacute and chronic infarction, there was no significant signal enhancement after administration of gadolinium-DTPA. Uptake of the substance in the area of acute infarction may be a positive marker of acute myocardial necrosis and as such may prove useful in the clinical setting.

Atrial bioenergetic variations in moderate hypoxia: danger or protective defense?

The effects of hypoxia on contractile tension and on tissue adenylate pool content, nicotinamide adenine nucleotide, NAD, nicotinamide adenine dinucleotide phosphate, NADP, and creatine phosphate, CrP, were investigated in isolated, spontaneously beating, guinea pig atria. When two different degrees of hypoxia were induced by lowering oxygen tension from 95% O2 (control) to 40% (moderate hypoxia) and 20% (severe hypoxia) for 30 min, contractile tension slowly decreased to 60% and 40% of control, respectively. In 40% O2 hypoxic atria, ATP was not significantly decreased, AMP slightly increased, TAN (total adenylate nucleotides) and adenylate energy charge [(ATP + 0.5 ADP)/(ATP + ADP + AMP)] did not change and creatine phosphate was decreased down to 53%. Hypoxic atria in 20% O2 showed a significant decrease of 26% in ATP, while ADP and AMP increased four and seven times, respectively. The adenylate energy-charge value was reduced from 0.93 to 0.70. Creatine phosphate decreased to below the analytical detection limit. Moderate hypoxia (40% O2), which induced a significant decrease of contractile tension but only minor changes of energetic tissue metabolism, was further investigated 2, 5, and 10 min after low oxygen tension was applied. Two stages of variations were evident during 30 min of experimental hypoxia. Within the first 10 min, concomitantly with atrial tension decrease, ATP, NAD, NADP, ATP/AMP, ATP/ADP, and TAN decreased, CrP began to decrease, inosine and xanthine showed no significant change. During the following 20 min of hypoxia, all parameters returned to the control levels with the exception of creatine phosphate. Adenylate energy charge did not change. The electrophysiological analysis of atrial cells did not show any major change in action potential configuration and resting potential, during 40% O2 hypoxia. The differences at metabolic level between moderate and more severe hypoxia suggest that the energetic state may be extremely unbalanced, in atrial tissue, as long as hypoxia is aggravated. Moreover, the time-course study, during 30 min of 40% O2, suggests that the early decrease of contractile tension does not depend on lowered energy availability, instead it might be, at least in part, a preventive measure to maintain energy balance in myocardial tissue to counteract hypoxic damage and, in this mechanism of defense, creatine phosphate shuttle seems to play a relevant role.

Dobutamine: ten years later

Dobutamine is a commonly used positive inotrope for the short-term management of heart failure. It is commercially available as a 50:50 mixture of two isomers with unique effects on alpha- and beta adrenergic receptors. In dosages of 2-15 micrograms/kg/minute, dobutamine has been shown to increase cardiac output (mainly through stroke volume), reduce systemic vascular resistance, lower central venous and pulmonary artery wedge pressures, improve renal blood flow, and relieve signs and symptoms of congestive heart failure. At higher dosages it can increase heart rate and induce arrhythmias. Recent evidence indicates that effects of dobutamine last long after the drug has been eliminated from the plasma, and some work has been done on ambulatory use of this agent. Dobutamine has been used successfully in several circumstances, such as after cardiac surgery, in patients with myocardial infarction, and in various shock states. An understanding of the pathophysiology of the underlying disorder is important in deciding which catecholamine to use. With this in mind, monotherapy or combination therapy with inodilators such as dobutamine, or inopressors like dopamine will follow logically.

Profile of an ideal antianginal agent

Many antianginal agents are available for the treatment of coronary artery disease. These agents act by influencing the determinants of myocardial oxygen supply and demand. The 3 main classes of agents are the nitrates, beta-adrenergic blocking agents and the calcium entry blockers. Agents from all 3 classes have shown efficacy in treating both symptomatic and asymptomatic myocardial ischaemia. However, some patients cannot be treated with these agents because of side effects or contraindications. An ideal antianginal drug should effectively treat both angina and silent ischaemia. Additionally, it should be free of side effects, allow for maintenance of physical performance and be metabolically neutral. New agents are being developed which strive for this goal.

Studies on oxygen and volume restriction in cultured cardiac cell: possible rearrangement of sarcolemmal lipid moieties during anoxia and ischemia-like states

Cultured heart cells have been shown useful for investigating states of oxygen and volume restrictions, simulating anoxia and ischemia-like states at cellular levels. The sarcolemma has been implicated as one of the early sites of ischemic damage; therefore, lactoperoxidase catalyzed radioiodination was used to study accessibility of the sarcolemmal lipid moieties to this enzymatic probe, reflecting their exposure to the extracellular environment, hence the biophysical state of the sarcolemma. These studies have shown that within one hour of 'ischemic' injuries: (1) The degree of labelling in the total phospholipid fraction is considerably increased; and (2) Profound changes in the relative extent of labelling of different phospholipid classes were observed. The PE/PC labelling ratio increases dramatically with the progress of ischemia-like state. We suggest that early during ischemic injury, reorganization of the cell surface phospholipids occurs and discuss possible relations to the energy charge of the cell.

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.

Myocardial surface oxygen pressure across the border zone in the pig during acute coronary artery occlusion. A comparison of pretreatment with metoprolol or isoprenaline

Tissue oxygen pressure was measured in the pig heart during repeated coronary artery occlusions. ptO2 was measured with an array-multiwire-electrode across the border zone, i.e. the transition zone between normal and ischaemic myocardium. The LAD was occluded three times, each lasting 5 min and with 55 min of reperfusion between the occlusions. Three groups of animals were studied: Group 1 served as controls; Group 2 were given metoprolol 0.3 mg/kg i.v. after the first LAD occlusion; Group 3 were given isoprenaline in a continuous infusion, started after the first LAD occlusion and continued throughout the rest of the experiment. Heart rate differed as expected between the two treated groups. The pattern of ptO2 values across the border zone repeated itself for each animal. No change in the pattern of ptO2 values was seen in either treatment group. In conclusion, there were no indications that it was possible to change the ptO2 of the border zone in the pig heart either with metoprolol or isoprenaline in the doses used.

Verapamil crystalloid cardioplegia: an experimental evaluation of dose-response relationships

Calcium channel blockers have been advocated as agents which enhance myocardial protection during ischemia and reperfusion. Unfortunately, while cellular integrity is preserved, myocardial function is depressed as a result of the negative inotropic effects of these agents. In order to assess the efficacy of verapamil cardioplegia, 25 isolated perfused rabbit hearts were studied. A model of normothermic ischemic arrest was utilized, employing either verapamil-free crystalloid cardioplegia or cardioplegia containing verapamil in concentrations of 0.5, 1.0, or 5.0 mg/liter. All three verapamil-treated groups demonstrated increased postischemic left ventricular developed pressure and improved postischemic compliance when compared with the untreated group (P less than 0.05). However, myocardial function was significantly depressed at 15 min of reperfusion in the 1.0 and 5.0 mg/liter verapamil-treated groups when compared with the 0.5 ml/liter group (P less than 0.05). These data suggest that the addition of verapamil to crystalloid cardioplegia results in enhanced myocardial function while minimizing the early reperfusion depression associated with higher dose therapy.

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.

Reduction in myocardial acidosis using blood cardioplegia

The composition of the ideal cardioplegic solution is controversial. Blood cardioplegia is an attractive alternative to standard crystalloid solutions, though its superiority in preserving myocardial metabolism has not been demonstrated. Using a new pH electrode system, this study contrasts the effects of blood and crystalloid solutions upon the generation of myocardial acidosis during global ischemia. Thirty-eight mongrel dogs underwent a 120-min period of aortic cross clamping using systemic hypothermia. To maintain myocardial temperature below 15 degrees C, 19 dogs received multiple doses of a bicarbonate containing crystalloid cardioplegic solution (Group I), while 19 dogs received multiple doses of blood cardioplegia (Group II). Myocardial pH and temperature were continuously monitored in the subendocardial region of the left ventricle. There was no difference in baseline pH between Group I (7.13 +/- 0.05) and Group II (7.17 +/- 0.05, P:NS). With systemic cooling and the initial bolus of cardioplegia, myocardial pH rose to 7.42 +/- 0.04 in Group I and 7.42 +/- 0.06 in Group II (P:NS). After 120 min of global ischemia, myocardial pH decreased to 6.61 +/- 0.05 in Group I and 7.07 +/- 0.05 in Group II (P less than 0.001). Blood cardioplegia was most effective during the first hour of aortic cross clamp when myocardial pH rose by 0.13 +/- 0.04 pH units. In contrast, myocardial pH in Group I during the first hour of global ischemia fell -0.35 +/- 0.08 pH units (P less than 0.001 compared to Group II). During the second hour of cross clamp, myocardial pH declined both in Group I (0.26 +/- 0.03 pH units) and in Group II (0.24 +/- 0.05 pH units, P:NS). However, the accumulation of hydrogen ion during the second hour was significantly greater in Group I (+128.0 +/- 21.4 nm/liter) than in Group II (+36.6 +/- 9.0 nm/liter, P less than 0.001). Thus, myocardial acidosis was reduced during the administration of blood cardioplegia when compared to a bicarbonate-buffered crystalloid solution. The salutary effects of blood cardioplegia on myocardial metabolism stem from blood's significant buffering capacity and its ability to deliver oxygen.

Effect of perfluorochemical (Fluosol-DA) on infarct morphology in dogs

To assess the effect of Fluosol-DA treatment on infarct morphology, detailed histologic examination was performed in 17 dogs with permanent proximal left anterior descending coronary artery occlusion. Two of the three groups of dogs received an equal blood volume exchange (40 ml/kg i.v.) with either Fluosol-DA (F) or heparinized autologous blood (H) 30 min post occlusion while being ventilated with 100% oxygen. A third group received no therapy (C). Animals were sacrificed 3 days post occlusion and sections were obtained for light and electron microscopy. Histologic studies showed that infarct size was statistically smaller in dogs treated with F 54 +/- 7% versus heparin 64 +/- 10% treatment or no therapy 79 +/- 6%. Fluosol-DA animals demonstrated decreased inflammatory infiltrate, larger viable subepicardial zones and greater endocardial sparing in the area surrounding the central zone of necrosis. By electron microscopy, perfluorochemical particles were found within endothelial and inflammatory cells in subepicardial zones of infarction. In midmyocardial zones, Fluosol-DA particles were present in capillaries, extracellular spaces and necrotic myocytes. In the normal myocardium Fluosol-DA particles were rarely seen within endothelial cells and never within the interstitium or myocytes. Thus, Fluosol-DA reduces infarct size and alters infarct morphology in the 3 day post permanent coronary occlusion model.

Magnetic resonance imaging (MRI) in different stages of myocardial infarction using the contrast agent gadolinium-DTPA

We investigated 26 patients admitted to our catheterization laboratory with a diagnosis of acute myocardial infarction. In each case acute revascularization was unsuccessful, but the diagnosis was confirmed by angiography. In 11 patients with an uncomplicated course of acute myocardial infarction magnetic resonance imaging was carried out within 7 days of the acute event. In three additional cases imaging was performed within 3 weeks, while a remaining 12 patients underwent studies more than 3 weeks after the onset of symptoms. We determined signal intensity at three points within the area of infarction and at three other points in adjacent myocardial tissue. Decreased signal intensity within the area of infarction was present in native scans in 60% of all cases. Application of 0.1 mmol/kg body weight gadolinium-DTPA was followed by an average 70% increase in signal intensity within zones of acute infarction, as compared to a 20% increase in surrounding myocardial tissue. In cases of subacute and chronic infarction there was no significant signal enhancement after administration of gadolinium-DTPA. Uptake of gadolinium-DTPA in the area of acute myocardial infarction may be a positive marker of acute myocardial necrosis, which may be of potential clinical benefit.

Elevated CK-MB with normal total creatine kinase in suspected myocardial infarction: associated clinical findings and early prognosis

To test the hypothesis that patients with normal serum levels of creatine kinase (CK) but elevated percentages of MB isoenzyme fractions in suspected myocardial infarction may have sustained clinically significant events, we studied the hospital course of 347 consecutive patients admitted with suspected myocardial infarction. Two hundred twenty-three patients had normal CK levels (182 +/- 44 IU) and normal MB percentages (normal group), 68 had elevated levels of both CK (1395 +/- 178 IU) and MB percentage (10.5 +/- 0.6) (macroinfarction group), and 40 had normal CK levels (96 +/- 7 IU) but elevated MB percentages (9.6 +/- 0.5) with typical enzyme curves (microinfarction group). Compared to the normal group, microinfarction patients were older, had more congestive heart failure, required more intensive monitoring and therapy during longer stays, and sustained a higher in-hospital mortality rate. Thus, these microinfarction patients are at increased risk and therefore warrant aggressive treatment and further evaluation.

Effects of pindolol therapy on the size of experimentally induced myocardial infarction in the pig

The effect of pindolol on experimental myocardial infarction was studied in a pig model. Intravenous application of 0.05 mg pindolol per kg body weight was initiated one hour after coronary ligation and repeated at 12-hour intervals for five days. No significant difference in infarct size could be found between pindolol-treated animals (20.4 +/- 0.6% SEM of whole ventricular mass, n = 6) and untreated controls (20.5 +/- 1.2% SEM, n = 9). Hemodynamic data did not change significantly throughout the experiment. These results differ in part from those reported by other investigators: The disagreement may be due to the specific pharmacological properties of the applied drug, to variations in the dosages of beta blockers, as well as to differences in the study design.

Genetic differences in the resistance of rats to isoprenaline-induced heart lesions

Two strains of rats were obtained by selective breeding: the IR strain, resistant to isoprenaline-induced myocardial lesions and the IS strain, sensitive to this damage. The IR rats grew more slowly, the weight of their adipose tissue was higher and the weight of m. soleus was less than that of the IS rats. The IR rats had a higher content of triglycerides in the serum and a lower isoprenaline-stimulated lipolytic activity of adipose tissue in vitro. The basal NEFA level in the serum and its rise after the administration of isoprenaline in vivo did not differ between the strains. The IR rats had a higher content of glycogen in the heart and in the muscle. After the administration of isoprenaline the glycogen content decreased more slowly in IR rats. The findings indicate a considerable importance of the glycogen stores in the heart for the resistance of myocardium to damage.

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.

Effect of nifedipine in hypothermic cardioplegia: a phosphorus-31 nuclear magnetic resonance study

The ability of nifedipine to enhance myocardial protection was assessed on isolated perfused rat hearts subjected to 180 min of hypothermic (20 degrees C), global ischemia, followed by 45 min of normothermic reperfusion. Intracellular pH, ATP, Pi and phosphocreatine content were serially measured at 4 min intervals by phosphorus-31 nuclear magnetic resonance spectroscopy and correlated with simultaneously recorded hemodynamic parameters. Addition of nifedipine (0.075 mumol/l and 0.5 mumol/l) to Saint Thomas' cardioplegic solution reduced Pi accumulation during ischemic arrest and increased phosphocreatine levels during reperfusion. Post-ischemic functional recovery was not improved at a drug concentration of 0.075 mumol/l and was depressed at 0.5 mumol/l. These results clearly show that the presence of nifedipine in Saint Thomas' cardioplegic solution does not provide significant additional myocardial protection under hypothermic conditions.

Studies on oxygen and volume restrictions in cultured cardiac cells. I. A model for ischemia and anoxia with a new approach

A novel incubation unit is described that is highly suitable for thorough studies of oxygen deprivation states. Its application with cultured heart cells is experimentally demonstrated. The release of enzymes, taken as a marker for cell damage, has clearly shown that restriction of the volume of extracellular medium combined with oxygen plus glucose deprivation caused greatest cellular damage. It may be considered as an experimental ischemia-like state. Furthermore, the onset of cellular damage followed a time table very much like that occurring in vivo under similar conditions, more so than any other previously described studies. A time lag between the release of cytoplasmic enzymes and lysosomal enzymes and other observations made in the present study suggests a sequential order of events in which the release of cytoplasmic enzymes occurs at a stage of reversible damage due to oxygen deprivation, whereas the release of lysosomal enzymes may point at irreparable damage.

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Metabolic and physiological differences between zero-flow and low-flow myocardial ischemia: effects of L-acetylcarnitine

The metabolic and physiologic differences between low-flow and zero-flow ischemia of varying duration were compared in the isolated perfused rat heart. Hearts subjected to 60 and 90 minutes of zero-flow ischemia recovered less cardiac work than hearts subjected to low-flow ischemia. Low-flow ischemia caused a build-up of both myocardial long-chain acyl coenzyme A and acyl carnitine esters, while zero-flow ischemia produced no change in long-chain acyl carnitine and only a transient increase in long-chain acyl coenzyme A. High energy phosphate depletion was greater in zero-flow ischemia. Perfusion with excess free fatty acids decreased the recovery of cardiac work after low-flow ischemia but had no effect after repeated episodes of zero-flow ischemia. L-Acetylcarnitine improved the recovery of cardiac work after low-flow ischemia in hearts perfused with 0.4 and 1.2 mM palmitate. With zero-flow ischemia, L-acetylcarnitine had no effect on the recovery of cardiac work in hearts perfused with 0.4 mM palmitate and a slight but statistically significant effect with 1.2 mM palmitate. Possible protective mechanisms of L-acetylcarnitine against ischemic damage are discussed.

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.

Correction of intraoperative diastolic myocardial dysfunction with nifedipine

We report the case of a 62-year-old man with severe aortic stenosis and hypertrophic cardiomyopathy, who could not be weaned from cardiopulmonary bypass after aortic valve replacement until buccal administration of the calcium-blocking agent nifedipine led to achievement of adequate hemodynamics. These observations demonstrate the importance of diastolic dysfunction in patients with hypertrophic cardiomyopathy, and suggest an important peri- and intraoperative role for calcium-blocking agents in their management. Recent hemodynamic studies have shown the importance of diastolic myocardial dysfunction in patients with hypertrophic cardiomyopathy, and demonstrated that calcium-blocking agents may enhance myocardial performance by reducing this dysfunction (Goodwin, 1982; Lorell et al., 1980, 1982; Sanderson et al., 1977). Although this new class of drugs has been increasingly used as an adjunct to cardioplegia, there is little information thus far on their application as treatment of intraoperative diastolic abnormalities. We report the case of a 62-year-old man with severe aortic stenosis and hypertrophic cardiomyopathy, who could not be weaned from cardiopulmonary bypass after aortic valve replacement until buccal administration of the calcium-blocking agent nifedipine led to an increase in cardiac output and blood pressure.

Effects of flurbiprofen in altering the size of myocardial infarcts in dogs: reduction or delay?

Anti-inflammatory agents such as flurbiprofen have been claimed to reduce infarct size in a number of models of coronary artery occlusion. However, several of the studies are controversial and also do not allow the critical distinction between reducing and delaying injury. In the present study, a closed chest method of coronary occlusion was used to generate small areas of regional myocardial ischemia in dogs. The method involved cannulation of the coronary ostium by way of the carotid artery and coronary embolization with 2.5 mm diameter beads. Flurbiprofen (1 mg/kg) was given immediately after occlusion and thereafter every 6 hours. Groups of dogs were subjected to either 6 or 24 hours of elapsed ischemia, after which time the hearts were removed and sectioned. Frozen-tissue slices were stained with triphenyl tetrazolium in order to delineate infarct size. After staining the tissue slices were subjected to autoradiography in which microspheres given immediately after occlusion were visualized to delineate the perfusion bed served by the occluded coronary artery (zone at risk). Risk zone to infarct size ratios for drug treated and control animals revealed that flurbiprofen treatment had no effect upon infarct size as determined 24 hours after occlusion. Despite significant residual coronary flow in the ischemic area, virtually all of the risk zone deteriorated to necrotic tissue. By contrast, after 6 hours of elapsed ischemia, infarct size was considerably reduced in the flurbiprofen-treated group. With the proviso that the drug might have affected only the sensitivity to tetrazolium staining, these results indicate that in severe ischemia, flurbiprofen can greatly delay but not prevent tissue necrosis.

Intravenous short-term infusion of streptokinase in acute myocardial infarction

Short-term i.v. infusion of streptokinase was performed in 93 patients within 6 hours after the onset of acute myocardial infarction. Twenty-six patients underwent angiography in the acute phase (group A) and 52 underwent angiography in the fourth week only (group B); 15 patients had no angiography. Seven patients died during the hospital stay and six suffered nonfatal reinfarctions. There were no bleeding complications. In 11 of 21 group A patients, occluded coronary arteries were opened within 1 hour after the streptokinase infusion was started. In 84% of groups A and B, the infarct-related coronary artery was patent in the fourth week. In 75% of the patent arteries, the residual luminal diameter stenosis was less than 70%. According to serial serum CK-MB curves, recanalization was achieved mostly within 1-2 hours. Myocardial salvage was indicated by improvement in local contraction disorders in the recanalized group A patients and by the significant relationship between infarct size and time from symptom onset to treatment in group B. These data suggest that a high-dose, short-term, i.v. infusion of streptokinase is a safe and efficient method of restoring coronary blood flow. Expeditious initiation of i.v. streptokinase infusion is a critical determinant for early recanalization and salvage of myocardium. Patients with thrombotically subtotal occlusion probably receive the most benefit. Evaluation of the true impact on survival and myocardial function will require controlled clinical trials.