Clinicopathologic correlates of acute ischemic heart disease syndromes

Pathobiology of myocardial and cardiomyocyte injury in ischemic heart disease: Perspective from seventy years of cell injury research

This review presents a perspective on the pathobiology of acute myocardial infarction, a major manifestation of ischemic heart disease, and related mechanisms of ischemic and toxic cardiomyocyte injury, based on advances and insights that have accrued over the last seventy years, including my sixty years of involvement in the field as a physician-scientist-pathologist. This analysis is based on integration of my research within the broader context of research in the field. A particular focus has been on direct measurements in cardiomyocytes of electrolyte content by electron probe X-ray microanalysis (EPXMA) and Ca2+ fluxes by fura-2 microspectrofluorometry. These studies established that increased intracellular Ca2+ develops at a transitional stage in the progression of cardiomyocyte injury in association with ATP depletion, other electrolyte alterations, altered cell volume regulation, and altered membrane phospholipid composition. Subsequent increase in total calcium with mitochondrial calcium accumulation can occur. These alterations are characteristic of oncosis, which is an initial pre-lethal state of cell injury with cell swelling due to cell membrane dysfunction in ATP depleted cells; oncosis rapidly progresses to necrosis/necroptosis with physical disruption of the cell membrane, unless the adverse stimulus is rapidly reversed. The observed sequential changes fit a three-stage model of membrane injury leading to irreversible cell injury. The data establish oncosis as the primary mode of cardiomyocyte injury in evolving myocardial infarcts. Oncosis also has been documented to be the typical form of non-ischemic cell injury due to toxins. Cardiomyocytes with less energy impairment have the capability of undergoing apoptosis and autophagic death as well as oncosis, as is seen in pathological remodeling in chronic heart failure. Work is ongoing to apply the insights from experimental studies to better understand and ameliorate myocardial ischemia and reperfusion injury in patients. The perspective and insights in this review are derived from basic principles of pathology, an integrative discipline focused on mechanisms of disease affecting the cell, the organizing unit of living organisms.

Innovators in atherosclerosis research: A historical review

This review presents a retrospective analysis of the significance of the contributions of pathologists and kindred investigators in the latter half of the twentieth century to the advancement of understanding of atherosclerosis, a major disease and affliction of humankind. These outstanding investigators contributed importantly to the development of a large body of evidence encompassing population-based autopsy studies, experimental animal studies and cell biological investigations that, coupled with insights from epidemiological studies, serve as the underpinning for the current dominant response to injury theory of atherogenesis. Their collective contributions have been highly meritorious and will remain seminally important into the future.

A review of neuroimaging studies of stressor-evoked blood pressure reactivity: emerging evidence for a brain-body pathway to coronary heart disease risk

An individual's tendency to show exaggerated or otherwise dysregulated cardiovascular reactions to acute stressors has long been associated with increased risk for clinical and preclinical endpoints of coronary heart disease (CHD). However, the 'brain-body' pathways that link stressor-evoked cardiovascular reactions to CHD risk remain uncertain. This review summarizes emerging neuroimaging research indicating that individual differences in stressor-evoked blood pressure reactivity (a particular form of cardiovascular reactivity) are associated with activation patterns in corticolimbic brain areas that are jointly involved in processing stressors and regulating the cardiovascular system. As supported empirically by activation likelihood estimates derived from a meta-analysis, these corticolimbic areas include divisions of the cingulate cortex, insula, and amygdala--as well as networked cortical and subcortical areas involved in mobilizing hemodynamic and metabolic support for stress-related behavioral responding. Contextually, the research reviewed here illustrates how behavioral medicine and health neuroscience methods can be integrated to help characterize the 'brain-body' pathways that mechanistically link stressful experiences with CHD risk.

Cardiomyocyte death and renewal in the normal and diseased heart

During post-natal maturation of the mammalian heart, proliferation of cardiomyocytes essentially ceases as cardiomyocytes withdraw from the cell cycle and develop blocks at the G0/G1 and G2/M transition phases of the cell cycle. As a result, the response of the myocardium to acute stress is limited to various forms of cardiomyocyte injury, which can be modified by preconditioning and reperfusion, whereas the response to chronic stress is dominated by cardiomyocyte hypertrophy and myocardial remodeling. Acute myocardial ischemia leads to injury and death of cardiomyocytes and nonmyocytic stromal cells by oncosis and apoptosis, and possibly by a hybrid form of cell death involving both pathways in the same ischemic cardiomyocytes. There is increasing evidence for a slow, ongoing turnover of cardiomyocytes in the normal heart involving death of cardiomyocytes and generation of new cardiomyocytes. This process appears to be accelerated and quantitatively increased as part of myocardial remodeling. Cardiomyocyte loss involves apoptosis, autophagy, and oncosis, which can occur simultaneously and involve different individual cardiomyocytes in the same heart undergoing remodeling. Mitotic figures in myocytic cells probably represent maturing progeny of stem cells in most cases. Mitosis of mature cardiomyocytes that have reentered the cell cycle appears to be a rare event. Thus, cardiomyocyte renewal likely is mediated primarily by endogenous cardiac stem cells and possibly by blood-born stem cells, but this biological phenomenon is limited in capacity. As a consequence, persistent stress leads to ongoing remodeling in which cardiomyocyte death exceeds cardiomyocyte renewal, resulting in progressive heart failure. Intense investigation currently is focused on cell-based therapies aimed at retarding cardiomyocyte death and promoting myocardial repair and possibly regeneration. Alteration of pathological remodeling holds promise for prevention and treatment of heart failure, which is currently a major cause of morbidity and mortality and a major public health problem. However, a deeper understanding of the fundamental biological processes is needed in order to make lasting advances in clinical therapeutics in the field.

Inflammation and immune system response against unstable angina and its relationship with coronary angiographic findings

The aim of this study was to assess the relations between inflammation, immune response, and coronary angiographic findings in patients with unstable angina pectoris (UAP). Recent studies suggest a role for inflammation in the pathophysiology of UAP. Although activation of neutrophils, monocytes and lymphocytes has been shown in UAP, no studies have correlated the activation findings with clinical and angiographic features of patients with UAP. Seventy-three patients undergoing coronary angiography were classified according to their ischaemic syndrome, stable angina pectoris (SAP) (n = 25) and UAP (n = 48). Patients with UAP were classified using the Braunwald classification; UAP class I (n = 15), UAP class II (n = 15), and UAP class III (n = 18). Patients with UAP were also classified into a progression to myocardial infarction (MI (+)) group (n = 15) and a non-progression to myocardial infarction (MI(-)) group (n = 33). Venous blood samples were taken from all patients. Cell surface receptors (CD4, CD8, CD3, CD14, CD45, CD56+16, and HLA-DR) were detected by flow cytometry using monoclonal antibodies tagged with fluorescent markers and serum levels of C-reactive protein (CRP) were measured. The serum levels of CRP and the percentages of HLA-DR, CD14, and CD16+56 were higher in UAP than SAP. The serum levels of CRP and percentages of HLA-DR, CD14, and CD16+56 were higher in UAP class II than UAP class I. The serum levels of CRP and percentages of HLA-DR, CD14, and CD16+56 were higher in UAP class III than UAP class II and UAP class I. The serum levels of CRP and percentages of CD16+56 were higher in the MI(+) group than the MI(-) group. The CRP levels in serum and the percentages of cell surface antigens had no correlation with extent of coronary artery disease (no differences among one, two or three vessels) but Type C lesion had significantly higher percentages of HLA-DR, CD14, CD16+56 and the serum levels of CRP than Type A and Type B lesions. This investigation shows that inflammatory and immunologial components may be detectable in UAP and were correlated with the clinical severity, progression to myocardial infarction, and lesion morphology, but were not correlated with the extent of coronary artery disease.

The use of antiplatelet agents in acute cardiac care

Antiplatelet therapy with aspirin has long been established as standard therapy in the management of conditions such as ST-elevation myocardial infarction and the acute coronary syndromes (unstable angina and non-ST-elevation myocardial infarction). Recently, several more potent platelet inhibitors have been developed and tested in randomized clinical trials. This article reviews the current state of the art of antiplatelet therapy.

Cardiologic problems in the post acute ventilated patient

Chronically critically ill patients who develop acute respiratory failure commonly have complicating cardiac pathology that may or may not be evident at initial evaluation. The acute coronary syndromes should be excluded in all patients presenting with respiratory failure. Cardiac rhythm disturbances are common and should be actively investigated and treated in all critically ill patients. Heart failure is common in the chronically critically ill patient but usually responds to early diagnosis and prompt treatment. Finally, cardiogenic shock carries a poor prognosis in most patient subsets except when it is caused by cardiac tamponade. The intensivist must be vigilant for cardiac pathology complicating the recovery of patients with acute respiratory illness and initiate the search for correctable problems that may precipitate further episodes of respiratory insufficiency.

Elevated levels of soluble intercellular adhesion molecule-1 in the coronary circulation of patients with coronary organic stenosis and spasm

The cell surface expression of intercellular adhesion molecule-1 (ICAM-1) is upregulated following activation during inflammatory responses, mediating both cell migration and activation. The involvement of inflammation in unstable angina is suggested by the presence of activated circulating leukocytes. To examine whether plasma soluble ICAM-1 (sICAM-1) levels increase in the coronary circulation of patients with coronary organic stenosis and coronary spasm, plasma sICAM-1 levels were measured in the coronary sinus (CS) and the aortic root (Ao) simultaneously in 10 patients with 90% or more coronary narrowing and coronary spasm (coronary spastic angina (CSA) with organic stenosis), in 11 patients with coronary spasm and no significant coronary narrowing (CSA without organic stenosis), in 16 patients with stable exertional angina, and in 13 control subjects. The plasma sICAM-1 levels (ng/ml) in the CS increased in CSA with organic stenosis (230+/-26) as compared with CSA without organic stenosis (158+/-14), stable exertional angina (130+/-9) and control subjects (121+/-10) (p<0.01). The levels in the Ao also increased in CSA with organic stenosis (208+/-24) as compared with CSA without organic stenosis (149+/-13), stable exertional angina (130+/-11) and control subjects (121+/-10) (p<0.01). Furthermore, the plasma sICAM-1 levels were higher in the CS than in the Ao only in CSA with organic stenosis. These results suggest that activation of leukocytes occurs through the induction of ICAM-1 in the coronary circulation in the patients with CSA with organic stenosis.

Plasma soluble intercellular adhesion molecule-1 levels in coronary circulation in patients with unstable angina

It has been suggested that active inflammation plays an important role in the pathogenesis of acute coronary syndromes, including unstable angina. Intracellular adhesion molecule-1 (ICAM-1) is a major ligand on the endothelial cells for adherence of the activated polymorphonuclear leukocytes. Recently, it has been demonstrated that the soluble form of ICAM-1 has been detected in human serum and has been increased in many other inflammatory or autoimmune disorders. To evaluate the involvement of ICAM-1 in unstable angina, we examined plasma soluble ICAM-1 (sICAM-1) levels in coronary circulation. The plasma sICAM-1 levels in the coronary sinus and aortic root were simultaneously examined in 20 patients with unstable angina, 19 patients with stable exertional angina, and 16 control subjects. The plasma levels of sICAM-1 were measured by enzyme-linked immunosorbent assay. The mean plasma sICAM-1 levels (nanograms per milliliter) both in the coronary sinus and aortic root were significantly higher (p <0.01) in patients with unstable angina than in those with stable exertional angina and in control subjects (217+/-14 vs 126+/-8; 120+/-10 in the coronary sinus, 202+/-13 vs 125+/-9; 123+/-10 in the aortic root). Furthermore, the mean value was higher in the coronary sinus than in the aortic root in patients with unstable angina. There were no significant differences in the values between in the coronary sinus and aortic root in patients with stable exertional angina and control subjects. Thus, sICAM-1 release is increased, especially in coronary circulation in unstable angina.

Coronary artery constriction in rats: necrotic and apoptotic myocyte death

The purpose of this study was to determine whether coronary artery narrowing was associated with the activation of necrotic and apoptotic myocyte cell death in the myocardium and whether these 2 forms of cell death were restricted to the left ventricle, or involved the other portions of the heart. Coronary artery narrowing was surgically induced in rats, and the animals were killed from 45 minutes to 12 days after surgery. Myocyte apoptosis was detected by the terminal deoxynucleotidyl transferase assay, confocal microscopy, and deoxyribonucleic acid (DNA) agarose gel electrophoresis. Myocyte necrosis was identified by myosin monoclonal antibody labeling of the cytoplasm. A separate group of animals was treated with trimetazidine in an attempt to interfere with tissue injury. Coronary artery narrowing was characterized by myocyte apoptosis in the left ventricle and interventricular septum, which progressively increased from 45 minutes to 6 days. However, apoptosis was not observed at 12 days. Conversely, myocyte necrosis reached its maximum value at 1 day and was still present at 12 days. This form of cell death affected not only the left ventricular free wall and interventricular septum, but also the right ventricle. Cell necrosis markedly exceeded apoptosis at all intervals. At the peak of cell death, myocyte necrosis was 52-fold and 33-fold higher than apoptosis in the left ventricle and septum. In conclusion, necrotic myocyte cell death is the prevailing form of damage produced by coronary artery narrowing, but apoptotic cell death contributes to the loss of myocytes in the ischemic heart. Trimetazidine treatment attenuated the extent of myocardial damage produced by global ischemia.

Increased coronary vasomotor tone in acute myocardial infarction patients with spontaneous coronary recanalization

To clarify the role of coronary spasm or dynamic coronary obstruction in the development of acute myocardial infarction (AMI) with spontaneous recanalization (SR), symptoms in 296 patients with AMI admitted within 24 h after the onset of chest pain were analyzed just before and after onset, and coronary angiograms were analyzed soon after onset. Patients were divided into 3 groups according to the initial angiographic findings in the infarct-related coronary artery (IRCA): group 1 comprised 172 patients with total occlusion (TIMI O); group 2 comprised 57 patients with subtotal occlusion (TIMI 1,2); and group 3 comprised 67 patients with SR (TIMI 3). The incidence of SR was 20.3% at 0-4 h after onset, 22.2% at 4-6 h, 19.7% at 6-12 h, 24.0% at 12-24 h, and 36.0% at 24 h or later. The incidence of SR did not increase significantly as time elapsed. The incidence of angina at rest and variable-threshold angina before the onset of infarction was only 16.2% in group 1, but was significantly higher in groups 2 (64.3%) and 3 (61.9%). The incidence of intermittent chest pain at onset in group 1 (8.4%) was significantly lower than in groups 2 (54.5%) and 3 (38.8%). Vasodilation of the proximal normal segment adjacent to the stenotic site of the IRCA induced by intracoronary nitroglycerin was significantly higher in groups 2 (11.7 +/- 1.2%) and 3 (20.7 +/- 2.6%) than in group 1 (4.0 +/- 0.6%). These results suggest that coronary spasm or dynamic obstruction may be involved in the pathogenesis of thrombus formation or coronary obstruction causing AMI in many Japanese patients.

Acute T-cell activation is detectable in unstable angina

BACKGROUND

Recent studies suggest a role for inflammation in the pathophysiology of unstable angina. This study was designed to investigate whether circulating lymphocytes are involved in the inflammatory reaction associated with the episodes of unstable angina.

METHODS AND RESULTS

Twenty-nine patients with proven unstable angina, 36 with stable angina, and 30 healthy subjects were studied. Both early and short-lived (interleukin-2 receptor [IL-2R], alpha-chain CD25, and transferrin receptor CD71) and late antigen (HLA-DR) expression were investigated by flow cytometric analysis. Soluble IL-2R (sIL-2R) was also measured in plasma by ELISA. Lymphocyte activation was studied at day 1 of hospital admission and after 7, 15, 30, 60, and 90 days. In patients with unstable angina, the number of HLA-DR+ CD3 lymphocytes and levels of sIL-2R were higher (P < .001) than in patients with stable angina and control subjects. Both CD4+ and CD8+ lymphocytes expressed HLA-DR antigens. No differences were found among the different groups of subjects in regard to the expression of CD25 and CD71. Lymphocyte activation was more marked in patients with urgent revascularization. No relationships were found between the number of HLA-DR+ lymphocytes and either the severity of coronary angiographic lesions or the number of ischemic episodes. Observations over time showed a gradual decrease in the number of HLA-DR+ lymphocytes and sIL-2R levels from weeks 3 through 8 to 12.

CONCLUSIONS

The present results indicate that (1) CD4+ and CD8+ circulating lymphocytes are activated in patients with unstable angina, and their activation state lasts 6 to 8 weeks; and (2) activation of lymphocytes is not a consequence of myocardial ischemia. These results support the immune system-mediated inflammatory nature of unstable angina.

Effects of cigarette smoking on the angiographic evolution of coronary atherosclerosis. A Canadian Coronary Atherosclerosis Intervention Trial (CCAIT) Substudy. CCAIT Study Group

BACKGROUND

Although smoking increases both the risk of developing coronary disease and the risk of coronary events in patients with known coronary atherosclerosis, the effect of smoking on the evolution of coronary atherosclerosis as assessed by serial angiography is poorly defined.

METHODS AND RESULTS

Ninety smokers with coronary atherosclerosis shown on a recent angiogram and with fasting cholesterol levels between 220 and 300 mg/dL were enrolled in a randomized, double-blind, placebo-controlled trial of cholesterol-lowering therapy, along with 241 nonsmokers and exsmokers. Lovastatin at a mean dose of 36 mg/d lowered total and LDL cholesterol by 21 +/- 11% and 29 +/- 11%, respectively, but these levels changed by < 2% in placebo-treated patients. Coronary arteriography was repeated after 2 years in 72 smokers and their 557 lesions were measured blindly with an automated quantitative system, along with 1752 lesions in 227 nonsmokers. Coronary change score, the per-patient mean of the minimal lumen diameter changes for all qualifying lesions, worsened by 0.16 +/- 0.16 mm in smokers and by 0.07 +/- 0.15 mm in nonsmokers in the placebo group (P < .001). Lovastatin-treated smokers had less worsening (0.07 +/- 0.15 mm) than placebo-treated smokers (P = .024). One or more coronary lesions progressed in 16 of 34 lovastatin-treated smokers and in 28 of 38 placebo-treated smokers (47% versus 74%, P < .001). In the placebo group, new coronary lesions developed in 21 of 38 smokers and in 28 of 115 nonsmokers (55% versus 24%, P < .001); fewer lovastatin-treated smokers developed new lesions (15% versus 55%, P < .001).

CONCLUSIONS

Smoking accelerates coronary progression and new lesion formation as assessed by serial quantitative coronary arteriography. Lovastatin slows the progression of coronary atherosclerosis and prevents the development of new coronary lesions in smokers.

Effects of cholesterol lowering on the progression of coronary atherosclerosis in women. A Canadian Coronary Atherosclerosis Intervention Trial (CCAIT) substudy

BACKGROUND

Although coronary disease is the leading cause of death in women and its clinical features differ from those in men, very few women have been included in angiographic trials of cholesterol lowering.

METHODS AND RESULTS

Sixty-two women with diffuse but not necessarily severe coronary atherosclerosis documented on a recent angiogram and with fasting serum cholesterol between 220 and 300 mg/dL were enrolled in a double-blind, placebo-controlled trial. More than one half had a history of hypertension, approximately one quarter were diabetics, and one third were current smokers. All women received dietary counseling. Lovastatin or placebo was begun at 20 mg/d and was titrated if necessary to 40 and then to 80 mg during the first 16 weeks to attain a fasting LDL cholesterol < or = 130 mg/dL. The mean lovastatin dose was 34 mg/d. Total and LDL cholesterol decreased by 24% and 32%, respectively, in lovastatin-treated women but by < 3% in women receiving placebo. Coronary arteriography was repeated after 2 years in 54 women (87%), and their 394 lesions were measured "blindly" on pairs of film with an automated computerized quantitative system. Progression, defined as a worsening in minimum diameter of one or more stenoses by > or = 0.4 mm, occurred in 7 of 25 lovastatin-treated women and 17 of 29 placebo-treated women (28% versus 59%, P = .031). New coronary lesions developed in 1 lovastatin-treated woman and 13 placebo-treated women (4% versus 45%, P < .001). The outcome for each of the angiographic end points was not significantly different between the women and the 245 men who completed the trial.

CONCLUSIONS

Lovastatin slows the progression of coronary atherosclerosis and prevents the development of new coronary lesions in women.

Prediction of acute coronary syndromes by percutaneous coronary angioscopy in patients with stable angina

To pinpoint the link between plaque characteristics and acute coronary syndromes, we performed a 12-month prospective follow-up study in 157 patients with stable angina pectoris in whom regular coronary plaques were observed by percutaneous coronary angioscopy. Acute coronary syndromes occurred more frequently in patients with yellow plaque than in those with white plaques (11 of 39 vs 4 of 118; p = 0.00021). Moreover, the syndromes occurred more frequently in patients with glistening yellow plaques than in those with nonglistening yellow plaques (9 of 13 vs 2 of 26; p = 0.00026). Thrombus arising from the ruptured identical plaques was confirmed by angioscopy as the culprit lesion of the syndromes. The results indicate that acute coronary syndromes occur frequently and in a short time in patients with glistening yellow plaques and that angioscopy but not angiography is feasible for prediction of the syndromes.

Histopathologic correlates of unstable ischemic syndromes in patients undergoing directional coronary atherectomy: in vivo evidence of thrombosis, ulceration, and inflammation

Complex coronary morphologic abnormalities with thrombus and ulceration have been recognized in acute ischemic syndromes by angiography, angioscopy, and autopsy. However, in vivo histopathologic correlates of unstable ischemic syndromes have not been described. The purpose of this study was to characterize intracoronary lesion morphologic abnormalities by analyzing specimens excised by directional atherectomy in patients with different ischemic syndromes. Tissue specimens removed by directional coronary atherectomy of primary lesions in native vessels were matched blindly to the clinical status of 130 patients representing 43% of a consecutive directional coronary atherectomy population of 300 patients; 824 specimens (range per patient 1 to 30, mean 6.3) were obtained. Clinical subgroups were prospectively classified as recent myocardial infarction (< or = 15 days, mean 6, range 1 to 15 days), 48 patients; prolonged rest angina, 34 patients; crescendo angina, 29 patients; and stable angina, 19 patients. Shavings were prospectively analyzed for presence of thrombus, ulceration, or chronic inflammatory cells. Thrombus was observed in 33 (69%) patients with recent myocardial infarction, 17 (50%) with rest angina, 12 (41%) with crescendo angina, 7 (37%) with stable angina (p = 0.048). Plaque ulceration was identified in 12 (25%) patients with recent myocardial infarction, 4 (12%) with rest angina, 2 (7%) with crescendo angina, and 1 (5%) with stable angina (p = 0.09). Inflammatory cells were noted in the specimens of 32 (67%) patients with recent myocardial infarction, 16 (45%) with rest angina, 12 (41%) with crescendo angina, and 9 (45%) with stable angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Human heart-type cytoplasmic fatty acid-binding protein in serum and urine during hyperacute myocardial infarction

We have previously reported that serum and/or urinary human heart-type cytoplasmic fatty acid-binding protein (HH-FABPc) can be used as an early indicator of myocardial injury (Clin Biochem 1991; 24: 195-201). To confirm the usefulness of HH-FABPc as an early diagnostic indicator of acute myocardial infarction (AMI), its serum and urinary levels were measured in samples obtained within 6 h after the onset of acute coronary syndrome related symptoms. Samples were collected from 97 patients, who were composed of 63 with AMI, 24 with unstable angina and 10 with chest pain syndrome. The positivity of serum and urinary HH-FABPc and cardiac creatine kinase isozyme MB (CK-MB) was analyzed in these samples. Serum HH-FABPc levels in AMI were above normal in 91.4% (64/70) of the samples tested within 3 h of the onset of symptoms and in 100% (111/111) of those tested at 3-6 h. Elevated urinary HH-FABPc levels in AMI were obtained in 88.9% (8/9) of samples at 0-3 h and in 75% (6/8) at 3-6 h. CK-MB activity in AMI was positive in 20% (8/40) and 66.3% (53/80) of serum samples at 0-3 h and 3-6 h, respectively. HH-FABPc was always positive when a serum sample was positive for CK-MB. Serum HH-FABPc at 0-6 h in chest pain syndrome and in unstable angina were positive in 17.8% (5/28) and 56.7% (34/60), respectively. The elevated HH-FABPc in serum and urine was noted much earlier than that of CK-MB during the hyperacute phase of AMI. HH-FABPc showed high positive value in unstable angina, but it was low in normal coronary patients having chest pain. However, HH-FABPc level in unstable angina and chest pain syndrome was lower than that of AMI. Thus, HH-FABPc may be a valuable indicator for the diagnosis of hyperacute myocardial infarction.

Relation of plasma lipoprotein(a) to infarct artery patency in survivors of myocardial infarction

BACKGROUND

In the minutes to days after myocardial infarction, endogenous lysis of an occlusive coronary arterial thrombus occurs in most subjects. Compared with those in whom thrombolysis does not occur, those with antegrade flow in the infarct artery have improved left ventricular performance, less left ventricular dilatation, and improved survival. This study was performed to assess intrinsic hemostasis and fibrinolysis in survivors of myocardial infarction with or without antegrade perfusion of the infarct artery.

METHODS AND RESULTS

In 105 survivors of infarction (75 men, 30 women; age, 30 to 80 years) not given thrombolytic therapy, coronary angiography revealed a patent (group 1, n = 52) or occluded (group 2, n = 53) infarct artery. Plasma concentrations of plasminogen, fibrinogen, tissue plasminogen activator activity, infarct artery. Plasma concentrations of plasminogen, fibrinogen, tissue plasminogen activator activity, plasminogen activator inhibitor activity, cholesterol, triglycerides, and lipoproteins, including lipoprotein(a) (Lp[a]), were measured in blood procured 23 +/- 13 (mean +/- SD) months after infarction. Groups 1 and 2 were similar in age, sex, race, cardioactive medications, infarct artery, extent of coronary artery disease, and left ventricular performance. Of the plasma constituents assayed, the groups were similar except that Lp(a) averaged 18.5 +/- 21.7 mg/dL in group 1 and 49.1 +/- 44.8 mg/dL in group 2 (P < .001). This difference was evident in both Caucasian (n = 65) (P = .009) and African American (n = 40) (P = .01) subjects.

CONCLUSIONS

Survivors of myocardial infarction who failed to recanalize the infarct artery have higher plasma Lp(a) concentrations than those with a patent infarct artery. Lp(a) may inhibit intrinsic fibrinolysis.

The independent roles of diet and serum lipids in the 20th-century rise and decline of coronary heart disease mortality

Risk factors are causally related to coronary heart disease (CHD), but in widely varying historic, geographic, socioeconomic, and individual relationships. Serum cholesterol is only one of many risk factors that, even when considered together in prospective studies, account for well under half of the CHD incidence. It is neither primarily regulated by the diet nor significantly related to it. Many findings discordant with widespread beliefs about a causal role of the diet in CHD are reviewed. It may be concluded that dietary fats are largely not responsible for relationships of serum cholesterol to CHD, or for its 20th-century rise and decline.

Inhibition of platelet accumulation by beta 1-adrenoceptor blockade in the thoracic aorta of rabbits subjected to experimental sympathetic activation

Arterial platelet adhesion is an initiating event in the thrombo-embolic complications of atherosclerosis and may also accelerate the development rate of atherosclerotic lesions. Psychosocial stress has been shown to accelerate atherogenesis in animals, an effect probably mediated via beta-adrenoceptor activation. In view of the postulated roles of platelets and beta-adrenoceptor activation in atherosclerosis development, we decided to test whether beta blockade affects arterial platelet accumulation. We studied the accumulation of radioactivity from 111In-labelled platelets on the wall of the thoracic aorta of rabbits as a measure of platelet accumulation. During the exposure to the labelled platelets, the animals were also exposed to 3 hours of chloralose anesthesia. This is a reproducible model of experimental sympathetic activation, including beta-adrenoceptor activation, which we used to amplify possible effects of beta-blockade on platelet-vessel wall interaction. The effectiveness of the anesthesia in increasing sympathetic activity was verified by significant rises in mean arterial blood pressure (from 77 to 88 mmHg), heart rate (190 to 290 bpm), and plasma levels of norepinephrine (1.0 to 3.3 nM) and epinephrine (0.13 to 0.83 nM). In chloralose anesthetized rabbits, approximately 30 x 10(-9)% of the injected 111In accumulated in each square millimeter of intima at unbranched thoracic aorta. Platelet accumulation was significantly higher at arterial branching points, 70% higher at intercostal artery bifurcations, and 150% higher at coronary artery bifurcations than in unbranched aortic intima. Pretreatment with metoprolol in a dose resulting in "therapeutic" plasma levels significantly reduced platelet accumulation by 48% in unbranched aorta, 65% at intercostal, and 53% at coronary artery bifurcations.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation of reciprocal ST-segment depression after acute myocardial infarction with coronary angiographic findings

We studied 266 consecutive patients with acute myocardial infarction to assess the significance of electrocardiographic "mirror images". Ninety-four (group A) had anterior wall and 132 (group B) had inferior wall infarction. Thirty-one group A patients had stenosis of the right coronary artery greater than 85% in diameter (subgroup A1), and 63 either had a normal right coronary artery or less than 85% stenosis (subgroup A2). Of group B patients 62 had greater than 85% stenosis of the left anterior descending (subgroup B1) and 70 had a left anterior descending or less than 85% stenosis (subgroup B2). ST-segment depression was significantly greater in depth and duration in subgroup A1 than A2 (p = 0.02) and in subgroup B1 than B2 (p = 0.02, p = 0.01, respectively). Left ventricular ejection fraction was lower in subgroup A1 than A2 (p less than 0.001) and in B1 than B2 (p less than 0.001). There was a strongly positive correlation between depth and duration of ST-segment depression and the Gensini index (r = 0.78, 0.84) for anterior and inferior infarction, respectively. In conclusion, increased depth and duration of ST-segment depression opposite the infarct are indicative of ischemia, and are related to the extent of coronary artery disease, the degree of stenosis of the vessels supplying the opposite wall and of left ventricular dysfunction.

Effect of acetylcholine on the highly stenotic coronary artery: difference between the constrictor response of the infarct-related coronary artery and that of the noninfarct-related artery

To examine the constrictor response of the infarct-related stenotic coronary artery in comparison with that of noninfarct-related stenotic arteries, acetylcholine in maximal doses of 100 micrograms for the left and 50 micrograms for the right coronary artery was injected into the 16 infarct-related coronary arteries of 16 patients with previous myocardial infarction (group 1) and into 19 stenotic coronary arteries of 16 patients with stable angina without myocardial infarction (group 2). Acetylcholine's effects on lumen diameter and area were quantitatively analyzed at the stenotic segment and its proximal segment without significant stenosis. Acetylcholine decreased lumen diameter and area at the stenotic segments from 0.72 +/- 0.18 to 0.18 +/- 0.33 mm and from 0.45 +/- 0.22 to 0.10 +/- 0.22 mm2, respectively, in group 1 (both p less than 0.01) and from 0.75 +/- 0.22 to 0.49 +/- 0.30 mm and 0.48 +/- 0.29 to 0.26 +/- 0.23 mm2, respectively, in group 2 (both p less than 0.01). Acetylcholine decreased the diameter and area at the proximal segment from 2.71 +/- 0.75 to 2.38 +/- 0.6 mm and from 6.18 +/- 3.4 to 4.71 +/- 2.23 mm2, respectively, in group 1 (both p less than 0.01) and from 2.31 +/- 0.67 to 1.95 +/- 0.59 mm and from 4.5 +/- 2.97 to 3.22 +/- 1.96 mm2, respectively, in group 2 (both p less than 0.01). The changes in diameter and area at the stenotic segment in group 1 were significantly greater than those in group 2 (both p less than 0.01); there were no significant differences between groups in the changes at the proximal segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic coronary artery constriction leads to moderate myocyte loss and left ventricular dysfunction and failure in rats

Coronary artery narrowing, ranging from 19% to 61%, was induced in rats and ventricular performance, myocardial damage, and myocyte hypertrophy were examined 1 mo later. Animals were separated into two groups, exhibiting ventricular dysfunction and failure, respectively. Dysfunction consisted of a 2.4-fold increase in left ventricular end diastolic pressure (LVEDP), 15% decrease in left ventricular peak systolic pressure (LVPSP), 24% reduction in developed pressure (DP), and a 16% depression in-dP/dt. Failure was defined on the basis of a 4.7-fold elevation in LVEDP, and a 26%, 47%, 45%, and 41% decrease in LVPSP, DP, +dP/dt, and -dP/dt. Moreover, in this group, right ventricular end diastolic and systolic pressures increased 5.5- and 1.2-fold. Left and right ventricular weights expanded 23% and 51% with dysfunction and 30% and 56% with failure. Left ventricular hypertrophy was characterized by ventricular dilation and wall thinning which were more severe in the failing animals. Foci of damage were found in both groups but tissue injury was more prominent in the endomyocardium and in failing rats. Finally, myocyte loss in the ventricle was 10% and 20% with dysfunction and failure whereas the corresponding enlargements of the unaffected myocytes were 34% and 53%. Thus, coronary narrowing led to abnormalities in cardiac dynamics with an increase in diastolic wall stress and extensive ventricular remodeling in spite of a moderate loss of myocytes and compensatory reactive hypertrophy of the viable cells.

Protein C activation following coronary artery occlusion in the in situ porcine heart

BACKGROUND

Activated protein C, the body's natural anticoagulant, may play a role in protecting the heart during and following an occlusion of the left anterior descending coronary artery (LAD) in the porcine heart.

METHODS AND RESULTS

Infusion of 1 unit thrombin over 30 seconds into the LAD of juvenile pigs produced a prolongation of the Xa clotting time (153 +/- 14%) in blood drawn from the anterior interventricular vein (AIV). The action of the anticoagulant was blocked by a polyclonal immunoglobulin G antibody directed against porcine activated protein C. A brief (30 seconds) occlusion of the LAD induced a similar prolongation of the Xa clotting time (138 +/- 11%), which was also blocked by the polyclonal antibody. To determine whether activated protein C helps sustain the heart during and following a 2-minute occlusion, three groups of pigs were studied: 11 controls, six receiving activated porcine protein C, and nine receiving a monoclonal antibody (HPC4) that blocks protein C activation. Relative to the controls, HPC4-treated animals recovered function, as measured by the maximum time derivative of left ventricular pressure and segmental shortening, more slowly and were not able to sustain this recovery. Animals receiving activated protein C recovered more quickly and sustained this recovery.

CONCLUSIONS

These data indicate that an ischemic insult induces rapid activation of protein C in the coronary microcirulation and that blocking this activation impairs recovery.

Myocardial infarction with minimal coronary atherosclerosis in the era of thrombolytic reperfusion. The Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) Study Group

The incidence of minimal residual atherosclerotic coronary obstruction after successful intravenous thrombolytic therapy was evaluated in 799 patients with acute myocardial infarction. Minimal residual coronary obstruction (less than or equal to 50%) was observed on selective coronary angiography performed 90 min after initiation of thrombolytic therapy in 43 patients (5.5%). In 42 other patients (5.4%), a greater than 50% but less than 100% residual stenosis noted at 90 min demonstrated further resolution of obstruction to less than 50% at an angiographic follow-up study 7 to 10 days later. Patients with minimal residual coronary obstruction were significantly younger (52 +/- 10.7 versus 56.7 +/- 10 years; p = 0.002) and had less multivessel coronary disease (p less than 0.001), better initial left ventricular ejection fraction (54 +/- 12% versus 50.2 +/- 11.4%; p = 0.006) and a lower in-hospital mortality rate (1% versus 7%; p = 0.04) than did patients who had a significant (greater than 50%) residual coronary obstruction after intravenous thrombolysis. Long-term follow-up study of patients with a minimal coronary lesion (average 1.5 +/- 0.6 years) and those with significant residual stenosis (average 1.6 +/- 0.7 years) demonstrated that the incidence of death (2.4% in patients with minimal stenosis versus 3.5% in those with significant stenosis) and recurrent myocardial infarction (5% each) were similar in both groups. New strategies are needed to prevent coronary rethrombosis in patients with minimal atherosclerosis after thrombolytic therapy for acute myocardial infarction.

Potential usefulness of combined thromboxane A2 and serotonin receptor blockade for preventing the conversion from chronic to acute coronary artery disease syndromes

Evidence suggests that unstable angina, non-Q-wave myocardial infarction and Q-wave myocardial infarcts represent a continuum, such that transient reduction in coronary blood flow associated with platelet aggregation and dynamic vasoconstriction at sites of coronary artery stenosis and endothelial injury lead to abrupt development of unstable angina. Factors potentially responsible for the conversion from chronic to acute coronary artery disease include endothelial injury at sites of stenosis. The endothelial injury may be the result of plaque fissuring or ulceration, hemodynamic factors (including systemic arterial hypertension or flow shear stress), infection, smoking, coronary arteriography or balloon angioplasty. Clinical and experimental animal studies suggest that interference with thromboxane and serotonin contributions to platelet aggregation and dynamic coronary artery constriction may prevent chronic coronary artery disease syndromes from converting to acute disease. To protect against this process may require both thromboxane and serotonin receptor antagonists or a combination of thromboxane synthesis inhibitor and receptor antagonist with a serotonin receptor antagonist. Further studies are needed to test this hypothesis.

Mechanisms of ischemia in coronary artery disease: spontaneous decrease in coronary blood supply

Myocardial ischemia has traditionally been related to increased demand, but recent data suggest that intermittent episodes of decreased supply are also important. This article discusses the phenomena underlying the factors that produce spontaneous (non-effort-related) ischemia. These include local arterial phenomena, arterial plaques, endothelial phenomena, neural phenomena, and circadian patterns. The clinical spectrum of myocardial ischemia can be viewed as an interplay among supply, demand, local arterial reactivity, and acute plaque disruption. In addition, neural phenomena and circadian patterns of multiple cardiovascular phenomena combine to make the coronary circulation susceptible to an increased concentration of events in the morning hours, around the time of awakening. With this extension of our understanding of myocardial ischemia, we have reasonable assurance that methods of treatment will advance significantly in the near future.

Protection of the myocardium during myocardial infarction: pharmacologic protection during thrombolytic therapy

The most effective way to protect injured myocardium during the early phases of evolving myocardial infarction is with reperfusion. However, reperfusion may induce further myocardial injury. Alterations in the major determinants of myocardial oxygen demand, including increases in heart rate, contractile state and myocardial wall tension may also increase infarct size. An understanding of the basic mechanisms involved in the evolution of myocardial injury during myocardial infarction is important to the development of protective strategies that may reduce infarct size or attenuate reperfusion-induced myocardial injury, or both. Selective calcium antagonists, beta blockers, and phospholipase antagonists or inhibitors may reduce infarct size in association with early reperfusion. Reperfusion injury may be attenuated by free radical scavengers and calcium antagonists. Reinfarction, after the initial event, may ultimately be reduced in frequency by pharmacologic strategies that interfere with platelet adhesion, aggregation, and mediator release from activated platelets and white cells that promote further platelet aggregation or induce coronary artery vasoconstriction. Included among protective strategies are thromboxane receptor antagonists and synthesis inhibitors, serotonin receptor antagonists, possibly leukotriene synthesis inhibitors or receptor antagonists, and aspirin. Future clinical trials should test the combined efficacy of reperfusion and selected pharmacologic strategies that alter calcium accumulation in the injured myocardium, diminish the injurious effects of beta- and alpha-adrenergic mechanisms and oxygen-derived free radicals on injured myocytes, and prevent reocclusion mediated by platelets and platelet mediators.

Angiographic morphology of coronary artery stenoses in prolonged rest angina: evidence of intracoronary thrombosis

Previous clinical and angiographic/histopathologic correlative studies have demonstrated that angiographic findings of occlusive thrombus, intraluminal filling defects and complex lesion morphology indicate the presence of intracoronary thrombosis. The purpose of this study was to determine whether the presence of these descriptors of intracoronary thrombosis is associated with the syndrome of prolonged rest angina. The coronary angiograms of 50 patients with prolonged rest angina without myocardial infarction (group I) and 42 concurrent patients with stable angina (group II) were reviewed without knowledge of the clinical syndrome. Patients with prior myocardial infarction, coronary angioplasty or coronary artery bypass graft surgery were excluded, as were patients with important aortic stenosis. Each coronary artery stenosis in a major epicardial vessel was evaluated for the presence or absence of intracoronary thrombus (defined using standard criteria), complex lesion morphology (defined as the presence of haziness, a smudged appearance or irregular lesion margins) and eccentricity, and the frequency of each of these findings in groups I and II was compared. Intracoronary thrombus was present significantly more often in group I patients (42%) than in group II patients (17%) (chi 2 5.77; p less than 0.02). Complex lesion morphology was also present significantly more often in group I (44%) than in group II (14%) patients (chi 2 8.17; p less than 0.01). Either standard criterion for intracoronary thrombus or complex morphology was present in 70% of group I but only 21% of group II patients (chi 2 19.7; p less than 0.001). These results support a strong association of the angiographic descriptors of intraluminal thrombosis with the clinical syndrome of prolonged rest angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiographic characteristics of the infarct-related coronary artery in patients with angina pectoris after myocardial infarction

To elucidate the pathophysiology of angina pectoris after myocardial infarction, we analyzed the coronary stenoses in 45 subjects (28 men, 17 women, aged 33 to 67 years) with recent (less than or equal to 60 days) infarction, significant narrowing of only the infarct-related artery, and residual anterograde flow in this artery. Postinfarction angina was absent in 19 (group I) and present in 26 (group II). The groups were similar in age, left ventricular function, incidence with which each coronary artery was involved, as well as stenosis diameter (1.0 +/- 0.3 vs 0.9 +/- 0.4 mm [mean +/- standard deviation], respectively, difference not significant), stenosis area (0.9 +/- 0.4 vs 0.8 +/- 0.8 mm2, respectively, difference not significant), percent diameter narrowing (65 +/- 5 vs 66 +/- 9, respectively, difference not significant), and stenosis eccentricity. However, those with postinfarction angina had longer stenoses (group I, 4.3 +/- 1.4 mm; group II, 10.3 +/- 4.0 mm; p less than 0.001). Thus, patients with postinfarction angina and residual anterograde flow in the infarct artery may have angina due to a marked reduction in anterograde flow, caused by a long stenosis. There is no apparent relation between stenosis eccentricity and postinfarction angina.

Specific platelet mediators and unstable coronary artery lesions. Experimental evidence and potential clinical implications

We have speculated previously that the abrupt conversion from chronic stable to unstable angina and the continuum to acute myocardial infarction may result from myocardial ischemia caused by progressive platelet aggregation and dynamic vasoconstriction themselves caused by local increases in thromboxane and serotonin at sites of coronary artery stenosis and endothelial injury. Platelet aggregation and dynamic coronary artery vasoconstriction probably result from the local accumulation of thromboxane and serotonin and also relative decreases in the local concentrations of endothelially derived vasodilators and inhibitors of platelet aggregation, such as endothelium-derived relaxing factor (EDRF) and prostacyclin. With severe reductions in coronary blood flow caused by these mechanisms, platelet aggregates may increase, and an occlusive thrombus composed of platelets and white and red blood cells in a fibrin mesh may develop. When coronary arteries are occluded or narrowed for a sufficient period of time by these mechanisms, myocardial necrosis, electrical instability, or sudden death may occur. We believe that unstable angina and acute myocardial infarction are a continuum in relation to the process of coronary artery thrombosis and vasoconstriction. When the period of platelet aggregation or dynamic vasoconstriction at sites of endothelial injury and coronary artery stenosis is brief, unstable angina or non-Q wave infarction may occur. However, when the coronary artery obstruction by these mechanisms is prolonged for several hours, Q wave myocardial infarction results. Chronic endothelial injury and coronary artery stenosis are probably associated with the accumulation of platelets, white and red blood cells, and a fibrin mesh at the site of stenosis and endothelial injury.

The thrombolytic effects of native tissue-type plasminogen activator (AK-124) on experimental canine coronary thrombosis

To evaluate the thrombolytic effects of the native tissue-type plasminogen activator (t-PA), the authors used a thrombus model simulating clinical situations. The native t-PA (AK-124) was obtained from human-derived normal cells. Experimental canine coronary thrombosis was produced by partial constriction and endothelial denudation of the vessel. In 19 dogs, coronary occlusive thrombus was produced. Three hours after total occlusion of the coronary artery with thrombus, the authors attempted the thrombolytic therapy in 16 dogs. Histologically, three-hour thrombus was composed of a mixture of platelet aggregates, fibrin, and blood cells. They infused 0.375 mg/kg t-PA intravenously in 7 dogs and 20,000 IU/kg urokinase (UK) in 9. Coronary recanalization was achieved in 5 (71%) with t-PA infusion and 6 (67%) with UK infusion. Plasma fibrinogen levels decreased to 76% of preinfusion value in the dogs with t-PA infusion and to 34% in those with UK infusion. Coronary reocclusion occurred in 2 dogs with t-PA and 3 with UK. Thus, the native t-PA (AK-124) can provide coronary thrombolysis without severe depletion of plasma fibrinogen levels.

Localization of tissue factor in the normal vessel wall and in the atherosclerotic plaque

Tissue factor (TF)-producing cells were identified in normal human vessels and atherosclerotic plaques by in situ hybridization and immunohistochemistry using a specific riboprobe for TF mRNA and a polyclonal antibody directed against human TF protein. TF mRNA and protein were absent from endothelial cells lining normal internal mammary artery and saphenous vein samples. In normal vessels TF was found to be synthesized in scattered cells present in the tunica media as well as fibroblast-like adventitial cells surrounding vessels. Atherosclerotic plaques contained many cells synthesizing TF mRNA and protein. Macrophages present as foam cells and monocytes adjacent to the cholesterol clefts contained TF mRNA and protein, as did mesenchymal-appearing intimal cells. Significant TF protein staining was found deposited in the extracellular matrix surrounding mRNA-positive cells adjacent to the cholesterol clefts and within the necrotic cores. These results suggest that deposition of TF protein in the matrix of the necrotic core of the atherosclerotic plaque may contribute to the hyperthrombotic state of human atherosclerotic vessels.