Circadian activity of the endogenous fibrinolytic system in stable coronary artery disease: effects of beta-adrenoreceptor blockers and angiotensin-converting enzyme inhibitors

Circadian and seasonal variation in onset of acute myocardial infarction

The aim was to investigate the circadian and seasonal variation of acute myocardial infarction (AMI). Clinical data of 3867 AMI patients hospitalized from November 2010 to October 2019 in the Border Yanbian Minority Autonomous Prefecture, China were collected, and 3158 patients with definite AMI onset times were analyzed. The clinical data analyzed included the time of onset, nationality, age, laboratory data. We divided the patients into 4 groups based on the timepoint of their AMI onsets: 00:00-05:59, 06:00-11:59, 12:00-17:59, and 18:00-23:59. We also divided the patients based on nationality: Chinese Korean and Han groups. We observed that there is a circadian rhythm in the incidence of AMI, and the peak of AMI is in the morning (7:00-9:00). Unexpectedly, the incidence of AMI was significantly lower in the cold winter than that of other 3 warm seasons (P < 0.01) and the peak of AMI presented at the months of the large contrast between day and night temperature difference (over 20°C) like May of Spring and October of Fall. Finally, there was no difference in circadian rhythm between Chinese Korean and Han, although these groups differed in age, body mass index, and the inflammatory cell level. These findings have shown a different seasonal and circadian variation in onset of AMI. Further studies are required to determine the pathophysiological mechanism(s) underlying these differences and to guide prevention of AMI for reducing its mortality and disability.

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

Circadian Distribution of Acute Myocardial Infarction in Different Age Groups

Many epidemiologic studies reported a morning peak in the incidence of acute myocardial infarction (AMI). However, clinical outcomes and the relation between age distribution and circadian pattern have not been fully investigated in a large number of patients. Our study aimed to clarify the impacts of onset time in circadian variation on incidence and clinical outcomes of AMI according to age. From the Korea Acute Myocardial Infarction Registry, we gathered data of 20,685 patients from 53 centers in Republic of Korea. Data from a total of 19,915 patients (11,339 ST elevation myocardial infarction, 8,576 non-ST elevation myocardial infarction) were analyzed from the registry, after exclusion of diagnoses other than AMI. A morning-dominant incidence was shown by sinusoidal function, in all patients and in all separate age groups (age < 55, 55 ≤ age < 75, 75 ≤ age). In-hospital mortality and major adverse cardiovascular events (MACEs), including cardiac deaths, noncardiac deaths, recurrent myocardial infarction, repeated percutaneous coronary intervention, and coronary artery bypass graft at 1, 12, and 24 months' follow-up, were compared in 4 periods (00:00~05:59, 06:00~11:59, 12:00~17:59, and 18:00~23:59), and no significant difference was noted. Kaplan-Meier curve was drawn for death and MACE-free survival, and no significant different event-free survival was depicted (p value = 0.31). In conclusion, the incidences of myocardial infarction by onset time were uneven in 24 hours, in all patients and age groups, by sinusoidal function. However, there were no significant differences in in-hospital mortality or MACEs in the 4 time periods during 24 months of follow-up.

Circadian patterns of ST elevation myocardial infarction in the new millennium

OBJECTIVE

Nearly four decades ago, a circadian pattern of acute myocardial infarction (AMI) with a peak in the early morning waking hours was described. The goal of the present study was to determine whether major changes in lifestyle and significant advances in medical therapy have altered this pattern in the intervening years.

DESIGN

Retrospective chart review.

SETTING

Tertiary care hospital in central Wisconsin.

METHODS

We examined circadian patterns of ST elevation myocardial infarction (STEMI) in 519 patients diagnosed with STEMI over a 5-year period. Time of symptom onset was obtained from patient self-reports in the medical record and was recorded over 24 hours.

RESULTS

We observed a circadian pattern of STEMI occurrence with a morning peak at approximately 11:30 AM. This pattern was highly significant in patients who were not using beta-blockers (P <0.0001) and had no history of diabetes (P <0.0001), but was otherwise absent. The circadian pattern appeared to be attenuated in patients of a younger age, female gender, or who used statins or aspirin. Peak STEMI occurrence was earlier in smokers than non-smokers.

CONCLUSIONS

Despite significant lifestyle changes and medical advances in the nearly four decades since a circadian pattern of AMI occurrence was first described, patients with STEMI had a circadian pattern of symptom onset with a morning peak. Use of beta-blockers and a history of diabetes mellitus abolished this pattern. Other modifying factors, including medications, age, and gender attenuated, but did not abolish, the circadian pattern.

Stimulated in vivo synthesis of plasminogen activator inhibitor-1 in human adipose tissue

Plasminogen activator inhibitor type-1 (PAI-1) is one of the most important inhibitors of endogenous fibrinolysis. Adipose tissue is a suggested source of the elevated plasma levels of PAI-1 in obesity. The relation between PAI-1 and inflammation is of particular interest, but current knowledge regarding regulation of PAI-1 in adipose tissue is mainly based on animal studies or ex vivo experiments on human cultured adipocytes. So far, no study has described stimulated gene expression and protein synthesis of PAI-1 in vivo in human adipose tissue. We used open heart surgery as a model of acute systemic inflammation. Twenty-two male patients underwent blood sampling and omental and subcutaneous adipose tissue biopsies for gene expression studies before and after surgery. Expression and localisation of PAI-1 antigen was evaluated by immunohistochemistry. After surgery gene expression of PAI-1 increased 27-fold in omental adipose tissue and three-fold in subcutaneous adipose tissue, but no differences were found in tissue-type plasminogen activator (t-PA) mRNA. PAI-1 antigen was localised within endothelial cells and in the adipose tissue interstitium close to vessels. The upregulated gene expression and protein synthesis in adipose tissue was followed by increased concentrations of PAI-1 antigen in plasma. In conclusion, we present for the first time that an acute systemic inflammation in humans increased gene expression and protein synthesis of PAI-1 in adipose tissue and that this increase was most prominent in omental adipose tissue. PAI-1 synthesis in adipose tissue due to acute systemic inflammation may be a link between inflammation and impaired endogenous fibrinolysis.

Role of patient chronotype on circadian pattern of myocardial infarction: a pilot study

Population-based studies indicate the risk of acute myocardial infarction (AMI) is greatest in the morning, during the initial hours of diurnal activity. The aim of this pilot study was to determine whether chronotype, i.e., morningness and eveningness, impacts AMI onset time. The sample comprised 63 morning- and 40 evening-type patients who were classified by the Horne-Östberg Morningness-Eveningness Questionnaire (MEQ) in the hospital after experiencing the AMI. The average wake-up and bed times of morning types were ~2 h earlier than evening types. Although the lag in time between waking up from nighttime sleep and AMI onset during the day did not differ between the two chronotypes, the actual clock-hour time of the peak in the 24-h AMI pattern did. The peak in AMI of morning types occurred between 06:01 and 12:00 h and that of the evening types between 12:01 and 18:00 h. Although the results of this small sample pilot study suggest one's chronotype influences the clock time of AMI onset, larger scale studies, which also include assessment of 24-h patterning of events in neither types, must be conducted before concluding the potential influence of chronotype on the timing of AMI onset.

The influence of bisoprolol dose on ADP-induced platelet aggregability in patients on dual antiplatelet therapy

PURPOSE

Dual antiplatelet therapy is recommended after acute coronary syndrome or after percutaneous coronary intervention with coronary stent implantation. Many of the patients on dual antiplatelet therapy receive β-blockers; some of them could have antiaggregatory effect. Bisoprolol is a highly selective adrenoceptor-blocker, which is often used in the settings of percutaneous coronary intervention or acute coronary syndrome in patients on dual antiplatelet therapy. Its antiaggregative effect has not been extensively studied. Therefore, the aim of this study is to investigate the effect of bisoprolol on ADP-induced platelet aggregation in patients on dual antiplatelet therapy.

METHODS

Platelet aggregability has been measured in 100 patients on dual antiplatelet therapy with multiplate analyzer using ADP test in blood samples anticoagulated with heparin. ADP test values have been expressed by arbitrary units/minute. In univariate and multivariate regression analyses, we have investigated the influence of bisoprolol and its dose and also different factors, such as risk factors, concomitant drugs and their dosage, laboratory findings, on ADP test values.

RESULTS

Univariate regression analysis showed significant correlation between the bisoprolol dose and the ADP test value (P=0.046, B=52.55, 95% confidence interval 0.87-104.23), which was also shown in the multivariate regression analysis (P=0.018; B=57.011; 95% confidence interval 10.455-103.567).

CONCLUSION

We have identified a positive correlation between bisoprolol dose and ADP-induced platelet aggregability in patients on dual antiplatelet therapy.

Additional impact of morning haemostatic risk factors and morning blood pressure surge on stroke risk in older Japanese hypertensive patients

AIMS

Stroke events occur most frequently in the morning hours. Impaired haemostatic activity and morning blood pressure (BP) surge, defined as the morning BP increase from sleep, have individually been associated with stroke risk in general or hypertensive populations. However, their combined impact on the risk of a stroke remains unknown.

METHODS AND RESULTS

A total of 514 hypertensive patients aged > 50 years (mean 72.3 years; 37% men) underwent 24 h BP monitoring, measurement of haemostatic risk factors [plasma fibrinogen, plasminogen activator inhibitor-1 (PAI-1), and prothrombin fragment 1+2(F1+2)], and brain MRI at baseline. The incidence of stroke was prospectively ascertained. During an average of 41 months (1751 person-years), there were 43 stroke events (ischaemic, 30; haemorrhagic, 5; undefined, 8). On multivariable analysis adjusted for confounding factors, the hazard ratio [HR (95% confidence interval (CI)] for stroke in the highest vs. lower quartiles of PAI-1 was 2.5 (1.3-4.6), that for F1+2 was 2.6 (1.4-5.0), and that for the morning BP surge was 1.2 (1.1-1.4; all P< 0.01). In particular, the ratio was substantially higher in cases with the highest quartile of both PAI-1 and F1+2 levels compared with those with the lower quartiles of both parameters (HR: 8.2; 95% CI: 3.7-18.2; P< 0.001). Among the patients with the highest quartile of the morning BP surge (n= 128), the multivariable HR (95% CI) for the highest vs. lower quartiles of PAI-1 was 3.4 (1.3-9.1) and that for F1+2 was 3.3 (1.3-8.7) (both P< 0.05).

CONCLUSION

High levels of plasma PAI-1 and F1+2, as well as an excessive morning BP surge, are independently and additively associated with an increased risk of stroke in older hypertensive patients.

A critical role of sympathetic nerve regulation for the treatment of impaired daily rhythm in hypertensive Dahl rats

There is a deep relationship between impaired circadian rhythm and hypertension. However, the detailed mechanisms between the daily sleep-wake rhythm and cardiovascular disorders have not yet been elucidated. To clarify the mechanism, we examined salt-sensitive Dahl rats that were fed normal chow (n=10), high-salt chow (n=10) and high-salt chow with bisoprolol (n=10). Simultaneous electroencephalogram, electromyogram and locomotor activity were examined to analyze the sleep-wake state. We also examined heart rate, blood pressure and echocardiographic findings to verify the presence of hypertension. Hypertension with impaired ventricular contraction was observed in the rats with high-salt-chow consumption whereas normal-chow rats did not show these disorders. Although rats with the normal diet showed a standard daily rhythm with normal rapid eye movement (REM) sleep duration and locomotor activity, the high-salt-diet group exhibited an impaired daily rhythm with suppressed REM sleep and significant abnormal locomotor activity. Bisoprolol significantly improved the daily sleep-wake rhythm and locomotor activity. We showed that an impaired daily rhythm was closely related to the development of hypertension. Regulation of sympathetic nerve alterations may have a key role in the treatment of hypertension and circadian rhythm disorder.

New insights into the circadian rhythm of acute myocardial infarction in subgroups

The aim of this study was to determine the existence of the circadian rhythm (CR) in the onset of acute myocardial infarction (AMI) in different patient subgroups. Information was collected about 41,244 infarctions from the database of the ARIAM (Analysis of Delay in AMI) Spanish multicenter study. CR in AMI were explored in subgroups of cases categorized by age, gender, previous ischemic heart disease (PIHD), outcome in coronary care unit, infarction electrocardiograph (ECG) characteristics (Q wave or non-Q wave), and location of AMI. Cases were classified according to these variables in the different subgroups. To verify the presence of CR, a simple test of equality of time series based on the multiple-sinusoid (24, 12, and 8 h periods) cosinor analysis was developed. For the groups as a whole, the time of pain onset as an indicator of the AMI occurrence showed a CR (p<0.0001), with a morning peak at 10:10 h. All the analyzed subgroups also showed CR. Comparison between subgroups showed significant differences in the PIHD (p<0.01) and infarction ECG characteristics (p<0.01) groups. The CR of the subgroup with Q-wave infarction differed from that of non-Q wave subgroup (p<0.01) when the patients had PIHD (23% in Q wave infarction vs. 39.2% in non-Q wave). AMI onset followed a CR pattern, which is also observed in all analyzed subgroups. Differences in the CR according to the Q/non-Q wave infarction characteristics could be determined by PIHD. The cosinor model fit with three components (24, 12, and 8 h periods) showed a higher sensitivity than the single 24 h period analysis.

The impact of time and day on the presentation of acute coronary syndromes

BACKGROUND

The frequency of acute myocardial infarction (AMI) peaks on Mondays and in the mornings. However, the distribution of the types of acute coronary syndromes (ACS), including unstable angina (UA), has not been systematically evaluated.

HYPOTHESIS

The distribution of the types of ACS and clinical presentations varies by time and day of admission.

METHODS

A retrospective cohort study was conducted in 1,946 consecutive nontransfer ACS admissions (1999-2004) to a tertiary-care academic center to assess presenting clinical variables in patients admitted on days versus nights (6 P.M.-6 A.M.) and weekdays versus weekends (Friday 6 P.M.-Monday 6 A.M.).

RESULTS

There were fewer ACS admissions than expected on nights and weekends (p < 0.001), but the proportion of patients with ACS presenting with ST-elevation myocardial infarction (STEMI) is 64% higher on weekends (p < 0.001) and 31% higher on nights (p = 0.022). This increased proportion with STEMI results in a greater proportion of ACS with AMI on weekends (up arrow 10%, p = 0.006) and nights (up arrow 7%, p = 0.033). Using multivariate modeling, the increase in patients with AMI on weekends was not explained by conventional risk predictors.

CONCLUSIONS

Although fewer patients with ACS presented on nights and weekends, patients at those times were more likely to have an AMI, driven largely by an increased proportion with STEMI at those times. Consideration should be given to these findings when developing clinical care paradigms, health care staffing needs, and when comparing new treatment outcomes in patients with ACS.

Is the effect of antihypertensive drugs on platelet aggregability and fibrinolysis clinically relevant?

Hypertension is associated with decreased fibrinolytic potential, mainly expressed as elevated plasma plasminogen activator inhibitor type 1 (PAI-1) levels, and increased platelet aggregability, which may account in part for the increased risk of atherosclerosis and its clinical complications in hypertensive patients. The effects of antihypertensive drugs on this prothrombotic state have been investigated and controversial findings have been reported, possibly because of differences in study designs, patients selected, and methodology used. Scarce and conflicting data exist about the effects of diuretics and beta-adrenoceptor antagonists on the fibrinolytic system, whereas ACE inhibitors have generally been reported to improve the fibrinolytic balance by decreasing plasma PAI-1 levels, calcium channel antagonists have been shown to increase tissue plasminogen activator (tPA) activity, and angiotensin II type 1 (AT(1)) receptor antagonists seem to exert neutral effects. beta-Adrenoceptor antagonists, calcium channel antagonists, and AT(1)-receptor antagonists have been reported to exert anti-aggregatory effects on platelets, while contrasting data exist about the influence of ACE inhibitors. Clinical implications of the changes induced by antihypertensive drugs on the fibrinolytic balance and platelet function are still debated. In particular, the question of whether these changes may translate into different degrees of cardiovascular protection in hypertensive patients remains unanswered. While awaiting more information from clinical trials, the choice of antihypertensive drugs, particularly in high-risk patients, should take into account effects beyond their BP-lowering efficacy. Selected agents should have a favorable, or at least neutral, impact on fibrinolytic function and platelet activity.

Circadian variation in myocardial ischemia: the possible mechanisms involving in this phenomenon

Circadian rhythms have long been recognized to occur in many biologic phenomena, including secretion of hormones as well as autonomic nervous system. There is increasing evidence that circadian rhythms have been also found in cardiovascular events, for example, myocardial infarction, sudden cardiac death as well as stroke have shown a circadian pattern of the distribution. Transient myocardial ischemia, detected by ambulatory ST segment monitoring, is also unevenly distributed during the day. The pathophysiology and the mechanism underlying these variations are the focus of much investigation, while it is not full understood up to date. Heart rate, blood pressure, neural and humoral vasoactive factors such as plasma norepinephrine levels and renin activity, and probably also contractility are increased in the morning hours, indicating that increase in myocardial oxygen demand contribute importantly to the increased prevalence of ischemia in the morning. Our recent study found that circadian rhythm of ischemic threshold detected by repetitive exercise treadmill tests in patients with chronic coronary artery disease is also apparently associated with levels of plasma ET-1. This information should enable better understanding as well as treatment on patients on circadian variation of cardiovascular events.

Disasters and the heart: a review of the effects of earthquake-induced stress on cardiovascular disease

There is growing evidence that stress contributes to cardiovascular disease. Chronic stress contributes to the atherosclerotic process through increased allostatic load, which is mediated by the neuroendocrine and immune systems (sympathetic nervous system and hypothalamus-pituitary adrenal axis) and related chronic risk factors (insulin resistance syndrome, hypertension, diabetes, and hyperlipidemia). In addition, acute stress can trigger cardiovascular events predominantly through sympathetic nervous activation and potentiation of acute risk factors (blood pressure increase, endothelial cell dysfunction, increased blood viscosity, and platelet and hemostatic activation). Earthquakes provide a good example of naturally occurring acute and chronic stress, and in this review we focus mainly on the effects of the Hanshin-Awaji earthquake on the cardiovascular system. The Hanshin-Awaji earthquake resulted in a 3-fold increase of myocardial infarctions in people living close to the epicenter, particularly in women, with most of the increase occurring in nighttime-onset events. There was also a near doubling in the frequency of strokes. These effects may be mediated by changes in hemostatic factors, as demonstrated by an increase of D-dimer, von Willebrand factor, and tissue-type plasminogen activator (tPA) antigen. Blood pressure also increased after the earthquake, and was prolonged for several weeks in patients with microalbuminuria.

Circadian variation in ischemic threshold in patients with stable angina: relation to plasma endothelin-1

To investigate circadian variation in ischemic threshold in chronic coronary heart disease (CHD) and its relation to plasma endothelin-1 (ET-1), 21 patients with stable angina underwent treadmill exercise tests twice within a day, performed at 8-9 AM for the first test and at 3-4 PM for the second one. Ischemic threshold was defined as the heart rate at the onset of 1 mm ST segment depression during exercise tests. Blood samples were taken at 5 minutes before each exercise test, and plasma ET-1 was measured for determining the possible relation to ischemic threshold in patients with CHD. The results showed that the heart rate-ischemic threshold in individual patients varied by 10 +/- 1% (range, 2-15%) in the morning and 9 +/- 1% (range, 2-14%) in the afternoon, while there was a mean (11.2%) reduction in the ischemic threshold between 2 time points, with the ischemic threshold being significantly lower in the morning compared with that in the afternoon (115 +/- 22 bpm vs 128 +/- 31 bpm p<0.04). ET-1 values were 6.20 +/- 2.44 ng/L in the morning hours and 4.02 +/- 1.61 ng/L in the afternoon hours, with a statistical significant difference (p<0.01). In conclusion, the present study indicated that circadian variation of plasma levels of ET-1 was likely to be one of the most likely mechanisms involved in reduction in the ischemic threshold in the morning hours.

Losartan and perindopril effects on plasma plasminogen activator inhibitor-1 and fibrinogen in hypertensive type 2 diabetic patients

BACKGROUND

This study compared the effects of losartan and perindopril on plasma plasminogen activator inhibitor-1 (PAI-1) and fibrinogen in hypertensive type 2 diabetic patients.

METHODS

We studied 85 nonsmoking outpatients, aged 46 to 64 years, with mild to moderate essential hypertension (diastolic blood pressure [BP] > 90 and < 110 mm Hg) and well controlled type 2 diabetes mellitus. After a 4-week washout placebo period, patients were randomized to received perindopril 4 mg once daily (n = 42) or losartan 50 mg once daily (n = 43) for 12 weeks according to a double-blind, parallel-group design. At the end of the placebo and active treatment periods, BP was measured and plasma PAI-1 and fibrinogen were evaluated.

RESULTS

Both perindopril and losartan reduced systolic and diastolic BP values (-16/15 mm Hg and -15/14, respectively; P < .001 v placebo), with no difference between the two treatments. Plasma PAI-1 was reduced by perindopril (-10 ng/dL, P = .028 v placebo) but not by losartan (+4 ng/dL, NS), the difference between the two treatments being statistically significant (P < .01). Plasma fibrinogen showed no significant change with both drugs, although a decreasing trend was noted with perindopril.

CONCLUSIONS

These findings indicate that perindopril but not losartan decreases PAI-1 in hypertensive type 2 diabetic patients, which suggests that the PAI-1 lowering effect is unrelated with AT, receptor blockade and could rather be due to the fact that the endothelial receptors that mediate PAI-1 expression in response to angiotensin II are not type 1 receptor subtypes. Different effects of the two drugs on the bradykinin system might also be implicated.

Identification of a tightly regulated hypoxia-response element in the promoter of human plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) plays a key role in control of coagulation and tissue remodeling and has been shown to be regulated by a number of cell stimuli, among those hypoxia. In this study we characterize the hypoxia-mediated induction of PAI-1 in human hepatoma cell line HepG2. We found that PAI-1 is tightly regulated in a narrow oxygen gradient. After incubation at oxygen concentrations of 1% to 2%, a 60-fold increase in PAI-1 messenger RNA levels was observed, whereas mild hypoxic conditions of more than 3.5% did not appear to induce transcription. Moreover, increased levels of PAI-1 protein were observed after incubation at low oxygen tensions. Through sequence analysis, several putative hypoxia-response elements (HREs 1-5) were identified in the human PAI-I promoter. Reporter gene assays showed that the HRE-2 (-194 to -187) was necessary and sufficient for the hypoxia-mediated response. By electrophoretic mobility assay we observed hypoxia-dependent binding of a protein complex to the HRE-2 motif. Further analysis demonstrated that HRE-2 was specifically recognized by the hypoxia-inducible transcription factor 1alpha-arylhydrocarbon nuclear translocator complex. Taken together, our data demonstrate that hypoxia-induced transcription is mediated through HIF-1 interaction with the HRE-2 site of the human PAI-1 promoter.

Plasminogen activator inhibitor type-1 in cardiovascular disease. Status report 2001

Plasminogen activator inhibitor type-1 (PAI-1) is known to contribute to thrombus formation and to the development and the clinical course of acute and chronic cardiovascular disease, as well as of other arterial and venous thromboembolic diseases. Recently, an important role of elevated pretreatment levels of PAI-1 for failure of thrombolytic therapy of acute myocardial infarction has been discussed. PAI-1 plasma levels depend on the one hand on gene regulation but are related on the other hand to known risk factors of atherosclerosis like insulin resistance, diabetes or hypertriglyceridemia, respectively. Furthermore, an activated renin-angiotensin-aldosterone system (RAAS) significantly contributes to the upregulation of PAI-1 concentration via a receptor-mediated mechanism. In accordance to the known mechanisms of regulation of PAI-1 plasma levels, the use of specific agents like antidiabetic drugs, fibrates, statins, ACE inhibitors and angiotensin II type-1 receptor-blockers may contribute to the downregulation of circulating PAI-1 and, therefore, increase the fibrinolytic capacity and consecutively counteract the thrombotic tendency. To further improve the efficacy of thrombolytic therapy, a PAI-1 resistant variant of t-PA, TNK-t-PA, has been developed and is now available for acute myocardial infarction.

Plasminogen activator inhibitor type-1 (part one): basic mechanisms, regulation, and role for thromboembolic disease

Plasminogen activator inhibitor type-1 (PAI-1) is a rapid inhibitor of tissue plasminogen activator (tPA) in circulation. Evidence suggests that the PAI-1 concentration is responsible for the regulation of the endogenous fibrinolytic system through its tPA/PAI-1 interactions. Accordingly, increased levels of PAI-1 have emerged as a masker for an increased thrombolic risk. This article represents a status report of mechanism of action, regulation of plasma levels, as well as the role of PAI-1 in arterial and venous thromboembolic disease.

Modification of high blood pressure after myocardial infarction

The treatment of high blood pressure (BP) after myocardial infarction is extremely important to decrease reinfarction and mortality. BP should be controlled more strictly in this high-risk hypertensive population. Recently, many clinical trials have demonstrated the benefits of lifestyle modification and antihypertensive agents, particularly beta-blockers and angiotensin-converting-enzyme inhibitors for the treatment of acute myocardial infarction. Treatment with these agents that modify BP may benefit even normotensive patients after a myocardial infarction, although the benefit is greater in hypertensives.

Comparative effect of angiotensin-converting enzyme inhibition and angiotensin II type 1 receptor antagonism on plasma fibrinolytic balance in humans

Angiotensin-converting enzyme (ACE) inhibition significantly decreases plasminogen activator inhibitor-1 (PAI-1) without altering tissue plasminogen activator (tPA) during activation of the renin-angiotensin-aldosterone system in humans. Because ACE inhibitors and angiotensin II type 1 (AT(1)) receptor antagonists differ in their effects on angiotensin II formation and bradykinin degradation, the present study compared the effect of equivalent hypotensive doses of an ACE inhibitor and AT(1) antagonist on fibrinolytic balance. Plasma PAI-1 antigen, tPA antigen, plasma renin activity, and aldosterone were measured in 25 normotensive subjects (19 white, 6 black; 14 men, 11 women; mean age 38.5+/-1.8 years; mean body mass index 25.3+/-0.7 kg/m(2)) during low salt intake alone (10 mmol Na/d), low salt intake + quinapril (40 mg PO bid), and low salt intake + losartan (50 mg PO bid). Compared with low salt alone (systolic blood pressure [BP] 118.8+/-2.2 mm Hg), both quinapril (106.3+/-2.5 mm Hg, P<0.001) and losartan (105.4+/-2. 8 mm Hg, P<0.001) reduced BP. No statistical difference was found between quinapril and losartan in their BP lowering effect. Losartan (P=0.009), but not quinapril, lowered heart rate. Both drugs significantly lowered aldosterone (P<0.001 versus low salt alone for each); however, this effect was significantly greater for quinapril than for losartan (P<0.001 for quinapril versus losartan). Treatment with quinapril, but not with losartan, was associated with a decrease in both PAI-1 antigen (P=0.03) and activity (P=0.018). PAI-1 activity was lower during treatment with quinapril than with losartan (P=0.015). The average PAI-1 antigen concentration was 13. 0+/-2.0 ng/mL during low salt alone, 10.5+/-1.6 ng/mL during quinapril treatment, and 12.3+/-2.1 ng/mL during losartan treatment. In contrast, plasma tPA antigen concentrations were reduced during treatment with losartan (P=0.03) but not with quinapril. This study provides the first evidence that ACE inhibitors and AT(1) antagonists differ in their effects on fibrinolytic balance under conditions of activation of the renin-angiotensin-aldosterone system. Further studies are needed to address the mechanism for the contrasting effects of these 2 classes of drugs on fibrinolysis and to define the clinical significance of these differences.