Intravenous Acetylsalicylic Acid – Dose-Related Effects on Platelet Function and Fibrinolysis in Healthy Males

Low-dose acetylsalicylic acid (ASA) has been shown to be beneficial in patients with acute myocardial infarction and unstable angina pectoris. Oral administration of ASA is difficult in the acute phase of these syndromes. In this study we evaluated the effect of 25 mg, 50 mg or 100 mg of ASA given as an intravenous bolus injection on platelet function and fibrinolysis in healthy males and related this to plasma concentrations of ASA. No adverse effects were found. A complete inhibition of serum thromboxane B2 synthesis was demonstrated 5 min after injection of 100 mg ASA intravenously. ASA disappeared from the circulation within 60 min after bolus injection and at this time thromboxane B2 synthesis was inhibited dose-dependently by 71%, 90% and 100% for doses of 25 mg, 50 mg and 100 mg, respectively. Inhibition of thromboxane B2 synthesis after 100 mg of intravenous ASA was still 96.5% at 24 h and 93.4% at 48 h after the injection. The bleeding time measured at 30 min after ASA administration was significantly prolonged on the average by 70 s, 144 s and 211 s after 25 mg, 50 mg and 100 mg of ASA, respectively. Minor, but significant changes were found in tissue plasminogen activator antigen and in plasminogen activator inhibitor within the first hour after injection of low dose ASA, but similar changes were found after injection of saline. No change in tissue plasminogen activator activity was found. We conclude, that intravenous administration of low dose ASA is safe and easy, and that almost immediate, complete blockage of serum thromboxane B2 synthesis can be obtained after a single intravenous bolus injection of 100 mg.

Renal effects of chronic exposure to organic solvents. A clinical controlled trial

Chronic effects of organic solvents on renal function were measured by creatinine clearances and urinary excretion rates of beta 2-microglobulin and albumin. Forty-three male printing trade workers occupationally exposed to different organic solvents for 9-25 years were compared with 43 age-matched male controls. No differences were found either in creatinine clearances or average basal levels of beta 2-microglobulin and albumin excretion rates, whereas a positive relation could be demonstrated between alcohol consumption on the day before the trial and urinary excretion rate of albumin. This investigation did not reveal any adverse renal effects of moderate chronic exposure to organic solvents in a group of active trade workers.

Renal effects of acute exposure to toluene. A controlled clinical trial

Urinary excretion rates of beta 2-microglobulin and albumin were measured in 43 male printing trade workers and 43 age-matched male controls before and during exposure to toluene, 382 mg/m3, for 6 1/2 hours in a climate chamber. There were no significant changes in renal excretion rates of albumin and beta 2-microglobulin during toluene exposure indicating that no causal relationship exists between moderate exposure to organic solvents and renal injury.

178 fatal cases of pulmonary embolism in a medical department

The diagnosis of pulmonary embolism was established during a 6-year period in 284 patients hospitalized in medical departments of a general hospital. Of the 183 patients who died, 178 were autopsied. A retrospective study was performed on the autopsy-verified fatal cases to correlate their clinical state to relevant postmortem findings. Two groups made thorough, independent evaluations of data from the medical and pathological records. In 95% of the patients a confirmed fatal pulmonary embolism constituted only a slight modification of life expectancy, because of concomitant complicating, severe, terminal disease. Reflecting this poor clinical state, only 26 patients (15%) had a diagnosis of pulmonary embolism premortally and of these patient, 13 died within 5 hours after onset of symptoms and 10 were treated with antithrombotic drugs. Our results seem to indicate an increase in the incidence of terminal diseases in the population of elderly, hospitalized patients and change the concept of fatal pulmonary embolism into an agonal incident in a terminal-care medical patient.

Improved nutritional status in elderly patients 6 months after stroke

INTRODUCTION

Nutritional status among stroke patients has received limited attention despite the fact, that it may have an influence on clinical outcome. Previous studies have estimated that 15-20 % of patients suffer from malnutrition in the acute phase of stroke, but so far no studies have focused on the late rehabilitation phase after stroke in the patients own home, where the attention on nutrition may be reduced.

AIMS

To determine the prevalence of malnutrition during 6 months of stroke rehabilitation, and to investigate the association between nutritional status, functional recovery, length of stay in hospital and infectious complications.

SUBJECTS AND METHODS

89 patients with ischemic stroke consecutively admitted to a geriatric stroke rehabilitation unit had their nutritional status evaluated in the hospital at 1 week and 5 weeks after stroke, and in their own home at 3 months and 6 months. Nutritional status was evaluated by body weight, body mass index (BMI), mid upper arm circumference (MAC), triceps skinfold thickness (TSF) and serum concentrations of albumin and transferrin. Malnutrition was defined if the patients had 2 or more abnormal nutritional variables.

RESULTS

We found a significant increase in albumin from 1 week to 6 months (P < 0.0001), and a significant increase in transferrin form 5 weeks to 6 months (P < 0.05). There was no significant change in weight or BMI from 1 week to 6 months. The number of patients with 2 or more abnormal nutritional variables was 31 (35 %) at 1 week and was reduced to 20 (22 %) at 6 months.

CONCLUSION

35 % of elderly patients with ischemic stroke admitted to a geriatric rehabilitation unit were malnourished 1 week after stroke. Particularly serum proteins and body fat were affected. Follow-up of nutritional variables showed improvement for serum proteins, and 22 % of the patients were malnourished 6 months after stroke.

Long-term anticoagulant therapy in patients with coronary artery disease

Secondary prevention of coronary events in coronary artery disease (CAD) patients with aspirin is generally accepted because of ease of administration, predictable safety, and proven efficacy. The use of long-term anticoagulant therapy with heparins, vitamin-K antagonists (VKAs), or thrombin inhibitors is, however, more controversial. During the last 40 years, several trials have been conducted in order to evaluate the role of anticoagulant therapy in patients with CAD as a protection against subsequent death and thrombo-embolic complications. The conducted trials are heterogeneous in many ways, concerning comparative medications, patient populations, endpoints and follow-up, which makes a standardized recommendation on the basis of these studies difficult. This review is an overview of the largest and best studies on this topic and discusses the scientific background for a possible use of VKA or an alternative anticoagulant treatment in CAD patients, looking at both the beneficial effects and the risk of bleeding.

Severe intoxication after an intentional overdose of amlodipine

Intoxication with 280 mg of amlodipine caused severe hypotension, third-degree heart block and hyperkalaemia in a 36-year-old female patient. The patient was initially treated with fluids, dopamine, calcium chloride, and epinephrine without effect. The patient was then given a bolus injection of insulin and glucose as a temporary mean to treat the hyperkalaemia. We observed a rise in blood pressure (BP) after insulin was given and the BP was subsequently responsive to epinephrine. A possible positive inotropic effect of insulin therapy in patients with calcium channel blocker intoxication is in accordance with previous findings. In conclusion, it is suggested that hyperinsulinaemia-euglycaemia therapy may be considered as a first-line therapy in calcium channel blocker intoxication.

A randomized controlled trial of shared care versus routine care for patients receiving oral anticoagulant therapy

OBJECTIVES

To evaluate the effect of a shared care programme (SCP), defined as a scheme based on shared responsibility, enhanced information exchange, continues medical education and explicit clinical guidelines, between general practitioners (GPs) and a hospital outpatient clinic (HOC), on oral anticoagulant therapy (OAT).

DESIGN

The study was a 2-year prospective, randomized, controlled trial, preceded by a 1-year period of observation.

SETTING

The HOC, GPs, and OAT patients in the admission area of Aarhus University Hospital, Aarhus County, Denmark, covering 310 300 inhabitants.

SUBJECTS

A total of 207 GPs, including their enlisted patients on OAT, were invited, and 61.4% accepted participation. They were randomized into an intervention group [group-INT: 64 GPs and 453 patients (170 patients on OAT throughout the study period, i.e. full follow-up)], and a control group [group-CON: 63 GPs and 422 patients (173 with full follow-up)]. The remaining 80 GPs served as a nonresponder group (group-NON) of 485 patients (184 with full follow-up).

MAIN OUTCOME MEASURE

Therapeutic control of OAT in terms of time spent by the patients within the therapeutic interval (TI) of an international normalized ratio (INR) between 2.0 and 3.5.

RESULTS

The groups did not differ significantly with regard to age, sex, OAT indication, anticoagulant drug used, or the therapeutic control at baseline. In a comparison based on intention-to-treat principles, the therapeutic control increased statistical significance amongst patients with full follow-up in group-INT compared with group-CON (median time within TI: group INT = 86.6% vs. 80.5%, P = 0.007).

CONCLUSION

An SCP of anticoagulant management is effective in reducing patient time outside the therapeutic INR interval in OAT patients randomly assigned to an SCP, as compared with a control group.

Benefits of extended treatment with dalteparin in patients with unstable coronary artery disease eligible for revascularization

AIMS

The FRISC II trial demonstrated that, for patients with unstable coronary artery disease, an early invasive strategy following acute treatment with dalteparin and aspirin, was superior to a more conservative approach. We evaluated whether it is beneficial to extend treatment with dalteparin to patients eligible for revascularization but for whom these procedures are performed after the initial hospital stay.

METHODS AND RESULTS

As a subanalysis of FRISC II, the efficacy and clinical safety of extended dalteparin treatment (5000 or 7500 IU.12h(-1) to day 90) compared with placebo was assessed in 1601 patients randomized to a non-invasive group who underwent revascularization only when necessary because of recurring symptoms, (re)infarction, or severe ischaemia. By day 90, 440 patients had undergone revascularization: 267 of these procedures occurred during the double-blind period. All patients initially received acute treatment (5-7 days from day 1) with dalteparin (120 IU/kg(-1) 12h(-1)). The incidence of death and/or myocardial infarction was monitored until revascularization or day 45 and until revascularization or day 90. There was a significant difference in the estimated probability of death and/or myocardial infarction until revascularization or day 90 in favour of dalteparin (log-rank test, P=0.0415) and there was a significant reduction in death and/or myocardial infarction in favour of extended dalteparin treatment at day 45, with a 57% relative risk reduction (P=0.0004). At day 90 the relative risk reduction was 29%. The safety profile of extended dalteparin treatment was similar to that of acute usage.

CONCLUSION

Extended dalteparin treatment for up to 45 days is effective and safe as a bridging therapy for patients with unstable coronary artery disease awaiting revascularization.

Incomplete thromboxane inhibition with 100 mg of intravenous acetylsalicylic acid in patients with acute ST elevation myocardial infarction: a placebo-controlled pilot trial

BACKGROUND

Acetylsalicylic acid (ASA) is now a standard treatment of acute myocardial infarction (AMI). ASA inhibits thromboxane A(2) (TXA(2)) production by blocking the constitutive cyclooxygenase (COX)-1 enzyme, but only to a small degree the inducible COX-2. COX-2 is induced by increased concentrations of cytokines, which is related to an enhanced inflammatory response. Previously, we have found a complete inhibition of TXA(2) synthesis in healthy volunteers after intravenous administration of 50 mg of ASA. We measured in a randomized, placebo-controlled pilot trial the effect of 100 mg of ASA injected intravenously on TXA(2) synthesis in AMI patients treated with streptokinase.

METHODS AND RESULTS

Nineteen patients with AMI treated with streptokinase were randomized to 100 mg of ASA or placebo injected intravenously. Se-TXB(2) and bleeding time were measured before and after drug administration. One hundred and eighty minutes after intravenous ASA administration, treatment with oral ASA was initiated. We found a significant decrease in serum concentrations of TXB(2) after 30, 60 and 180 min following ASA injection compared to placebo, but in none of the patients was complete inhibition of TXA(2) production achieved. No significant change in bleeding time could be demonstrated.

CONCLUSION

Intravenous ASA in a dosage of 100 mg did not completely prevent TXA(2) production in AMI patients treated with streptokinase. This may be due to synthesis of TXA(2) by the inducible COX-2 enzyme and/or to a transcellular metabolism in platelets of prostanoids generated by endothelial cells.

Bedside coagulometry during intravenous heparin therapy after coronary angioplasty

In order to assess the applicability of a bedside coagulometer for measurement of b-APTT, serial blood samples were obtained from 20 patients receiving intravenous heparin treatment following PTCA, and from 5 healthy volunteers. B-APTT was analysed bedside on the Hemochron coagulometer; p-APTT and p-heparin, measured as factor anti-Xa activity, were analysed ex-vivo in the laboratory. B-APTT values, determined by the Hemochron coagulometer, were closely correlated to p-heparin (r=0.83, p<0.001, SD=52 seconds (sec), n=89), and duplicate determinations of b-APTT on the Hemochron coagulometer showed an acceptable repeatability. However, an APTT ratio of 1.5-2.5 was not related to a therapeutic p-heparin level, neither as measured by the Hemochron device nor in the laboratory.

BACKGROUND

When administering intravenous heparin during angioplasty procedures, a quick and reliable method for safe and effective monitoring of anticoagulation is necessary.

OBJECTIVE

To assess the applicability of a bedside coagulometer, measuring the activated partial thromboplastin time (APTT) in patients receiving intravenous heparin treatment after percutaneous transluminal coronary angioplasty (PTCA).

METHODS

In patients with stable angina pectoris, receiving intravenous heparin treatment following PTCA, serial blood samples were obtained by venipuncture and from the arterial sheath for analysis of whole blood APTT (b-APTT), and plasma heparin concentration (p-heparin). Additionally, in healthy volunteers blood samples were obtained after a single bolus injection of heparin. B-APTT was analysed bedside on the Hemochron coagulometer; p-APTT and p-heparin, measured as factor anti-Xa activity, were analysed ex-vivo in the laboratory using conventional analytical methods.

RESULTS

In 20 patients a total of 94 venous and 69 arterial blood samples were analysed, and in five healthy volunteers analyses were performed in 20 venous blood samples. B-APTT values, determined by the Hemochron coagulometer, were closely correlated to p-heparin (r=0.83, p<0.001, SD=52 seconds (sec), n=89). An APTT ratio of 1.5-2.5 was not related to a therapeutic p-heparin level, however, neither when using APTT assessed by the Hemochron device nor APTT measured in the laboratory. Duplicate determinations of b-APTT on the Hemochron coagulometer showed an acceptable repeatability; the mean difference between duplicate measurements was 4 sec (coefficient of variation (c.v.)=6%, p<0.05, n=163).

CONCLUSIONS

In patients receiving intravenous heparin after PTCA treatment, b-APTT values measured by the Hemochron method showed an acceptable repeatability and were significantly correlated to p-heparin.

[Abciximab (ReoPro) in the treatment of acute coronary syndromes]

Platelet activation plays a major role in the pathophysiology of acute coronary syndromes (ACS). Inhibition of platelet function is the basic pharmacological treatment of ACS. Platelet membrane glycoprotein IIb/IIIa inhibitors, a new class of potent antiplatelet agents, have been used in the treatment of ACS and in the prevention of complications after percutaneous coronary interventions (PCI). Several large clinical trials have demonstrated the effectiveness of this class of agents. The first of these agents to show beneficial effects after coronary interventions was the mouse/human chimeric Fab fragment antibody c7E3 abciximab (ReoPro). The purpose of this article is to describe the pharmacology of abciximab and to review the results of the clinical trials carried out with the drug in patients with ACS, treated either with or without acute/elective PCI.

[Tirofiban (Aggrastat). A non-peptide glycoprotein IIb/IIIa receptor inhibitor]

Platelet aggregation and thrombus formation on a ruptured atherosclerotic plaque plays an important role in the pathogenesis of acute coronary syndromes. Activation of glycoprotein IIb/IIIa receptors (GP-receptors) on the surface of platelets is the final common pathway which leads to the binding of fibrinogen and crosslinking of platelets to form the white thrombus. Antiplatelet therapy reduces the risk of ischaemic complications in patients with acute coronary syndromes. Recently, the GP-receptor antagonists have been introduced. They inhibit the binding of fibrinogen to the GP-receptors and thus prevent platelet aggregation. Tirofiban is a low molecular, intravenously administered GP-receptor antagonist, which in combination with unfractionated heparin in several controlled studies has been shown to decrease morbidity and mortality in patients with unstable angina pectoris and non-Q-wave infarction and, in patients subsequently undergoing percutaneous coronary intervention.

[Clinical studies on glycoprotein IIb/IIIa receptor antagonist]

Platelet activation plays a major role in the pathophysiology of acute coronary syndromes (ACS), and inhibition of platelet function is the basic pharmacological treatment of ACS. Platelet membrane glycoprotein IIb/IIIa inhibitors, a new class of potent antiplatelet agents, have been used in the treatment of ACS, as well as in the prevention of complications after percutaneous coronary interventions. The aim of this article is to describe the potential possibilities of platelet inhibition and to review the pharmacology of glycoprotein IIb/IIIa inhibitors, the results of the clinical trials with these agents, and their current use in the pharmacological treatment of ACS and in relation to percutaneous coronary intervention.

Percutaneous transluminal coronary angioplasty versus thrombolysis in acute myocardial infarction

The aim of this study was to evaluate the outcome of primary percutaneous transluminal coronary angiography (PTCA) in the treatment of acute myocardial infarction (AMI) The study included patients with electrocardiographic signs of transmural AMI, symptom duration of less than 12 h, and with no contraindications to thrombolytic therapy. Patients who had undergone primary PTCA were matched consecutively, for age, gender, infarct localization and duration of symptoms, to patients who had received thrombolytic therapy (82 patients to each group). Patients who were admitted to hospital during daytime had a primary PTCA, whereas those admitted outside daytime were given thrombolytic therapy. In the primary PTCA group, 9 patients had a combined endpoint compared with 22 patients in the thrombolysis group (p < 0.02 ). In-hospital mortality was 3.7% in the PTCA group and 4.9% in the thrombolysis group (ns). At six months, a combined endpoint occurred in 23 patients in the primary PTCA group and in 50 patients in the thrombolysis group (p < 0.00005). Six months' mortality was 4.9% in the PTCA group and 7.3% in the thrombolysis group (ns). Among patients in the PTCA group, left ventricular ejection fraction was significantly higher, stay in hospital was shorter and there were significantly fewer incidences of heart failure and severe arrhythmias than among patients in the thrombolysis group. The results of primary PTCA implemented in our departments are comparable with those reported in randomized trials from experienced centres. Our study indicates that patients treated with primary PTCA have fewer complications, a better left ventricular systolic function and a shorter hospital stay compared with patients treated with thrombolysis.

Dietary fish oil reduces microvascular thrombosis in a porcine experimental model

Microvascular thrombosis plays a significant role in the pathophysiology of ischaemic reperfusion injury. A fish oil-supplemented diet containing n-3 polyunsaturated fatty acids (PUFA) reduces thromboxane A(2) (TxA(2)) synthesis and, thus, vasoconstriction and platelet aggregation. The aim of this study was to elucidate whether n-3 PUFA in a porcine model of ischaemia and reperfusion injury 1) inhibit accumulation of platelets and fibrinogen in ischaemia-reperfusion injured tissue, 2) prolong the bleeding time, and 3) inhibit TxA(2) synthesis. Nine pigs were fed a standard diet supplemented with 7 g n-3 PUFA/day for 3 weeks. Nine pigs on the standard diet served as controls. Unilateral myocutaneous flaps were exposed to ischaemia for a period of 6 hours. Contralateral flaps were nonischaemic. Tissue contents of radioactive-labelled platelets and fibrinogen were measured after 4 hours of reperfusion. Platelet count, serum TxB(2), and the cutaneous bleeding time were measured before and after 3 weeks of diet. In the fish oil group, the accumulation of platelets was significantly reduced in all the myocutaneous flaps, except in the ischaemic skin part, when compared to control animals. Fibrinogen was significantly reduced in nonischaemic flaps, but not in ischaemic flaps. After the feeding period, the level of TxB(2) was significantly lowered in the fish oil group (p<0.01). No difference in the bleeding time was observed. Thus, dietary supplementation with n-3 PUFA inhibits the formation of microvasculatory thrombosis in this model.

[Anticoagulant treatment]

In 1998, the sale of vitamin K antagonists (VKA) in Denmark corresponded to the amount used for treatment of more than 20,000 patients for one year. This is more than three times more than ten years earlier. The reasons for the increasing use of VKA are new indications for permanent anticoagulant treatment, especially chronic atrial fibrillation and venous thromboembolism associated with permanent thromboembolic risk factors. The risk of bleeding is higher in the introductory phase of anticoagulant treatment than later on. It is now recommended to commence anticoagulant therapy without a loading dose. This seems to hasten a good estimate of the maintenance dose. The metabolism of VKA depends on a number of genetic and acquired factors. Knowledge of these factors is crucial for optimal regulation of the treatment, and it is important that patients at start of treatment are thoroughly informed about these factors in order to minimize the risk of complications.

Targeting treatment for optimal outcome

Rapid assessment of patients presenting with acute chest pain is essential, in order to distinguish between those who have a life-threatening condition, such as myocardial infarction or unstable angina, and the substantial proportion who do not have an acute coronary syndrome. It is thus of vital importance that reliable techniques are available to facilitate rapid risk stratification, as an aid to both clinical diagnosis and management strategy decisions. Assessments based on clinical findings, electrocardiographic monitoring, symptom-limited exercise testing, and biochemical marker measurements, used either singly or in various combinations, can fulfill this role. The present paper reviews some of the recent data that demonstrate the value of these techniques. Very few studies allow conclusions to be drawn about optimal treatment strategies in relation to groups stratified according to prognostic markers, and the question of whether intense medical treatment or early invasive intervention is most beneficial is one that clinical trials have yet to address adequately. In the recently completed Fragmin and Fast Revascularization during InStability in Coronary artery disease (FRISC II) study, comparisons were made of clinical outcomes achieved with early invasive versus noninvasive (i.e., medical) management strategies, and with short-term versus prolonged anticoagulation with dalteparin sodium (Fragmin), in patients with unstable coronary artery disease. All study participants underwent symptom-limited exercise testing and provided blood sample for measurements of biochemical markers; continuous electrocardiography monitoring and echocardiography were also performed in a high proportion of patients. Data from the FRISC II trial thus shed further light on the issue of risk stratification and its use to determine optimal treatment strategies.

Intravenous acetylsalicylic acid, magnesium and their combination in experimental arterial thrombosis in rats

Intravenous acetylsalicylic acid (ASA) and magnesium (Mg) both possess antiplatelet properties and are thus potential inhibitors of the formation of arterial thrombi. Their effect on the dynamic aspects of arterial thrombus formation was investigated following intravenous administration of both substances alone and in combination. A blinded, placebo-controlled, in-vivo study was performed in 71 rats. Thrombus formation was induced by a standardized arteriotomy in the right femoral artery with inversion of the vessel wall during subsequent closure. Thrombus formation was recorded on video tapes and analysed off-line for 30 min. Animals were randomly assigned to one of four groups: 20 mg bolus of ASA followed by 0.3 mmol/h Mg (ASA/Mg group); NaCl followed by 0.3 mmol/h Mg (Mg group); 20 mg bolus of ASA followed by NaCl (ASA group); or NaCl throughout the experiment (control group). In the ASA-treated groups, serum levels of thromboxane B2 were reduced significantly, and the Mg-treated groups reached a serum level of Mg just above 2.0 mmol/l. No significant differences were observed in initial or maximum thrombus area or in mean thrombus area during the study period. In the ASA/Mg group, a trend towards reduced thrombus formation was observed (P = 0.06). In the same group, seven of 22 animals developed an occlusive thrombus (P < 0.01), an unexpected adverse event possibly related to the combined administration of ASA and Mg.

[Magnesium supplementation to patients with type II diabetes]

The purpose of this study was to evaluate Mg status by nuclear magnetic resonance spectroscopy in a group of well-regulated non-insulin-dependent diabetic (NIDDM) patients without angiopathy. Furthermore, to investigate the effect of Mg supplementation on markers of diabetic control, hemostatic function, platelet reactivity and endothelial function in the same patient population. A double-blinded, placebo-controlled and randomized crossover study was carried out, with two 8-weeks treatment periods (360 mg Mg/day) separated by a 4-weeks wash-out period. 11 well-regulated NIDDM patients participated in the study. Eight weeks of Mg supplementation significantly raised the level of free intracellular Mg in the diabetic patients (157.35 +/- 16.53 vs. 197.49 +/- 27.60 microM; p < 0.01). No changes were observed neither in plasma level of von Willebrand factor antigen, fibrinogen and fibronectin nor in platelet release of thromboxane B2 (TxB2). Similarly, markers of diabetic regulation, HbA1c and fructosamine, showed no significant changes. These results suggest that even well regulated NIDDM patients have marked Mg deficiency. Restoring this deficiency had no effect on diabetic control, markers of platelet reactivity, hemostatic function and endothelial function.

[Percutaneous transluminal coronary angioplasty in acute myocardial infarction. A prospective controlled study]

In the present study we compared the outcome of primary percutaneous coronary angioplasty (PTCA) (PTCA without prior or concomitant administration of thrombolytic drugs) in 82 consecutive patients with acute myocardial infarction (AMI) with the outcome of 82 AMI patients, who were treated with intravenous thrombolysis. The thrombolysis patients were prospectively matched to the angioplasty patients regarding age, sex, duration of symptoms and infarct localisation. The in-hospital mortality was 3.7% in the PTCA group versus 4.9% in the thrombolysis group. Thrombolysis-treated patients had increased use of diuretics and ACE-inhibitors as compared to PTCA-treated patients. The mean ejection fraction was 52 +/- 11% in the PTCA group versus 47 +/- 10% (p = 0.01) in the thrombolysis group. We conclude that initial Danish experience with primary PTCA is promising, and that this treatment may favourably affect the outcome of acute myocardial infarction.

Thrombotic complications in coronary angioplasty--ionic versus non-ionic low-osmolar contrast media

It has been suggested that the potential for thrombo-embolic complications is greater with the use of non-ionic contrast agents than with ionic contrast agents. The increasing use of interventional therapy in patients with acute coronary disease makes the discussion of a possible relationship between thrombo-embolic complications and use of non-ionic contrast media pertinent. It has been shown that ionic contrast media have a marked effect on the coagulation system and platelet function. The non-ionic contrast media have a less pronounced effect on the coagulation system and platelet function although there is no evidence of a thrombogenic effect. The anticoagulant effect observed with ionic contrast media in connection with coronary angiography or angioplasty (PTCA) is short and disappears as soon as the medium is excreted. Therefore an effective antithrombotic treatment in relation to the procedure is necessary. Larger randomized clinical studies need to be performed with effective antithrombotic regimens in order to clarify any difference in thrombo-embolic complications from the different contrast media. Until then, the non-ionic contrast media should be preferred to the ionic contrast media in high-risk PTCA, owing to their overall lower toxicity and fewer adverse reactions.

[From paroxysmal to chronic atrial fibrillation]

Chronic atrial fibrillation is by definition always preceded by paroxysmal atrial fibrillation. The electropathophysiological mechanisms underlying paroxysmal atrial fibrillation are reviewed: atrial electrophysiological inhomogeneity, atrial ectopic activity, and cardiac autonomic dysfunction. Safe and effective interventions that prevent the progression from paroxysmal into chronic atrial fibrillation have not yet been developed. Such developments should be given high priority, as the consequences of chronic atrial fibrillation--stroke and heart failure--are unacceptable.

Early administration of intravenous magnesium inhibits arterial thrombus formation

An antiplatelet effect of magnesium has been demonstrated in vitro and ex vivo, and this effect may be advantageous in patients with acute myocardial infarction to inhibit reocclusion after coronary angioplasty or thrombolysis. We investigated the antithrombotic in vivo effect of intravenous magnesium in a placebo-controlled, blinded study in 46 male Wistar rats. Thrombus formation was induced by standardized arteriotomy of the femoral artery and partial inversion of the vessel wall to produce a thrombogenic area. The vessel was transilluminated and visualized dynamically by in vivo microscopy. Thrombus area was measured every minute for 30 minutes after removal of the vessel clamp by image analysis techniques, and the number of visible emboli was registered. Animals were randomized into three groups: groups 1 and 2 received saline (control group, n = 15) or MgSO4 (Mg-early group, n = 15), respectively, during the entire infusion period. In group 3 intravenous saline was given during preparation of the arteriotomy followed by infusion of MgSO4 (Mg-late group, n = 16) from 10 minutes after removal of the vessel clamp. Thrombus area was significantly reduced by 75% in the Mg-early group (P < .005) but not in the Mg-late group compared with the control group. Mean number of emboli was reduced during magnesium infusion. The serum magnesium level increased to 2.2 (2.1 to 2.5) and 3.5 (3.0 to 4.2) mmol/L after infusion in the Mg-late and the Mg-early group, respectively. In the present study, intravenous infusion of MgSO4 significantly reduced thrombus formation in vivo but only when it was given before reperfusion. The antithrombotic effect of magnesium may be utilized in patients with acute myocardial infarction to reduce the rate of reocclusion. Magnesium infusion may also be of value in elective arterial angioplasty, but this option has not been investigated in clinical trials. However, correct timing of magnesium administration is critical to obtain an efficient antithrombotic effect.

Magnesium inhibits platelet activity--an in vitro study

The in vitro effect of magnesium (Mg) on platelet aggregation and platelet release function was evaluated in healthy volunteers. Platelet aggregation was induced with collagen, ADP, or thrombin after incubation of the sample with saline or increasing concentrations of magnesium sulphate (MgSO4) (0.5-8.0 mM). Mg showed a dose-dependent inhibition of platelet aggregation in whole blood, platelet rich plasma and washed platelets. An antiaggregatory effect was also present with low Mg concentrations. Statistically significant inhibition of the mean aggregation response was obtained in 83% of the different media and agonists tested following the addition of 1.0 mM Mg. The remaining 17% were significantly inhibited with the addition of 2.0 mM Mg. The platelet synthesis of thromboxane A2 and release of beta-thromboglobulin were also inhibited by Mg, in a dose-dependent manner. In order to evaluate if any of these effects were modified by conventional antithrombotic treatment with low-dose acetylsalicylic acid (ASA), volunteers were asked to meet on two consecutive days. On day 2 the participants were given 300 mg ASA orally, one hour prior to blood sampling. The Mg mediated effects were present independent of this pretreatment with ASA. Following stimulation with collagen a synergistic effect of Mg and ASA was demonstrated on platelet aggregation. The platelet inhibiting effect demonstrated in this study may in part explain the beneficial effect of Mg infusion in some patients with acute myocardial infarction. The effect of Mg infusion, given alone or administered simultaneously with ASA, should also be evaluated in other arterial thrombotic disease states.

Magnesium inhibits platelet activity--an infusion study in healthy volunteers

Magnesium (Mg) has shown the ability to inhibit arterial thrombus formation in some experimental animal studies. This effect may be due to an inhibition of platelet reactivity as in vitro studies have demonstrated that Mg inhibits platelet aggregation. In order to evaluate the in vivo effect of Mg in humans measurements of platelet activity, fibrinolytic activity, as well as measurements of prostacyclin (PGI2), and nitric oxide (NO) release were performed after infusion of magnesium sulphate (MgSO4) in healthy volunteers. In a placebo controlled, cross-over study in 14 healthy male subjects, 8 mmol MgSO4 was given as an intravenous bolus over 15 min followed by 3 mmol MgSO4/h. The mean S-Mg concentration increased from 0.85 to 1.50 mM during the Mg infusion period. A transient decrease in blood pressure was observed during the initial bolus infusion of Mg. Haemodynamic parameters were otherwise unstable. The bleeding time increased by 48% during the Mg infusion (p < 0.005), and in accordance with this, ex vivo platelet aggregation in platelet rich plasma was significantly inhibited, both following collagen (p = 0.02) and ADP (p = 0.04) stimulation. There were no significant changes in plasma beta-thromboglobulin concentration or the excretion of 2,3-dinor-thromboxane B2 in the urine. Neither tissue plasminogen activator (t-PA)activity, tissue plasminogen activator (t-PA)antigen nor plasminogen activator inhibitor (PAI)antigen changed during the Mg infusion period. There was no sign of increased release of PGI2 from the vessel wall as judged by urinary concentration of 2,3-dinor-6-keto-prostaglandin F1 alpha. Nor was there any sustained increase in the release of NO, measured as nitrate concentration in urine. However, a transient increase in NO release was observed during one sample period. In conclusion a reduced platelet activity and increased bleeding time, was found during Mg infusion in healthy volunteers. Fibrinolytic activity showed no changes. An anti-platelet effect may in part be responsible for the beneficial effect of Mg, described in patients with acute myocardial infarction (MI) and preeclampsia.

Magnesium inhibits human platelets

Magnesium (Mg) may inhibit experimental arterial thrombus formation by inhibition of platelet activity. However, inhibition of platelet aggregation has mainly been shown with high concentrations of magnesium ( > 2 mM). To test the effects of Mg in more clinically relevant concentrations, an in vitro study was performed where platelets were incubated with MgSO4 in the concentration range of 0.5-8.0 mM. Healthy volunteers participated on 2 consecutive days. On Day 2 the volunteers ingested 300 mg of acetylsalicylic acid (ASA) 1 h before blood sampling. Blood was anticoagulated with hirudin and platelet aggregation was performed in platelet-rich plasma (PRP) after incubation with saline or MgSO4 for 5 min. Platelets were stimulated with threshold concentrations of collagen or ADP or a fixed high concentration of collagen (5 micrograms/ml) on both days. A concentration dependent inhibition of platelet aggregation was found after addition of MgSO4. A statistically significant inhibition (P < 0.05) was present at 0.5-1.0 mM MgSO4. The effect of Mg was independent of pretreatment with ASA. Following maximal stimulation with collagen in PRP, a synergistic inhibition of ASA and Mg on platelet aggregation was demonstrated. Administration of MgSO4 in clinically relevant concentrations showed a dose-dependent inhibition of platelet aggregation. Platelet inhibition also occurred after ASA administration and concomitant medication induced a synergistic effect.

[Anticoagulant and thrombolytic therapy in deep venous thrombosis and pulmonary embolism]

During the last 10 years anticoagulant (AC) therapy and thrombolytic treatment of venous thromboembolism (VT) have been evaluated in randomized studies. Adjusted subcutaneous (s.c.) heparin and low molecular weight heparin (LMWH) are found at least as effective as intravenous (i.v.) infusion of heparin in deep venous thrombosis (DVT) without an increased bleeding risk. In pulmonary embolism (PE) randomized trials assessing the efficacy of s.c. heparin and LMWH are missing. Oral AC-treatment can be initiated from the first or second day in VT. The recommended duration is three months for medical patients, and 4 weeks seem appropriate for surgical patients that are completely mobilized and without persisting predisposing factors. Long-term efficacy of thrombolytic treatment of DVT has only been assessed in small trials showing a trend towards reduced risk of developing chronic venous insufficiency. Short-term thrombolytic treatment of DVT is evaluated in ongoing trials. In the treatment of PE short-term thrombolysis with either t-PA or urokinase is found to be as effective as long-term thrombolytic treatment with a reduced bleeding risk. Thrombolytic therapy rapidly reduces embolic mass and stabilizes haemodynamics, but mortality and long-term efficacy of thrombolysis and AC-treatment versus AC-treatment alone in PE are being assessed in ongoing studies.

[Interaction between thrombocytes and blood vessel wall--significance for acute ischemic coronary syndromes]

Intracoronary thrombus formation is the essential pathogenic substrate for the development of the acute ischaemic coronary syndromes (unstable angina pectoris (UAP), acute myocardial infarction (MI) and sudden cardiac death). Rupture of an atherosclerotic plaque has been shown to be of major importance for initiation of the thrombogenic process, but the reactivity of the circulating platelets and their interaction with the coronary vessel wall are also important for the formation and propagation of the intracoronary thrombus. The evidence favouring the role of platelets is: 1) the aggregability of platelets is increased in the morning where the incidence of MI and sudden cardiac death has been shown to be high, 2) shortened bleeding time and increased mean platelet volume in the acute phase of MI, 3) the synthesis of proaggregatory thromboxane A2 is increased in the acute phase of MI and in UAP, 4) a high platelet count and an increased ADP-induced platelet aggregation predispose to MI and death in healthy males, 5) high mean platelet volume and increased spontaneous platelet aggregation are risk factors for MI and death in patients with a recent MI, 6) the platelet inhibitor, acetylsalicylic acid, has been shown to reduce the incidence of MI and mortality in patients with silent myocardial ischaemia, stable and unstable angina pectoris and in patients with MI.

Silent pulmonary embolism in patients with deep venous thrombosis. Incidence and fate in a randomized, controlled trial of anticoagulation versus no anticoagulation

OBJECTIVES

A high frequency of asymptomatic pulmonary embolism (PE) in patients with deep venous thrombosis (DVT) has been reported, but information about the outcome of the patients with PE remains sparse. The aims of the present study were to assess the prevalence of silent PE in patients with symptomatic, venographically proven DVT, and to evaluate the natural history of silent PE.

DESIGN

Consecutive patients from one centre of primary care were included in a randomized, open study with blinded control. All patients gave written, informed consent.

SUBJECTS

Eighty-seven consecutive patients with venographically proven DVT and with a perfusion-ventilation lung scintigraphy performed within 48 h of the DVT diagnosis were included. On the 10th and 60th days the lung scintigraphy was repeated in 80 and 60 patients, respectively. All the patients were followed for 3 months in the out-patient clinic.

INTERVENTIONS

All patients were ambulated from the first day and were allocated randomly to no anticoagulant (non-AC) therapy or to AC therapy with intravenous heparin infusion for at least 6 days and oral AC therapy for 3 months.

RESULTS

Forty-three of these patients had a high probability lung scintigraphy for PE. Distal vein and femoral vein thrombosis embolized in 33 and 53% of patients, respectively. The progression rate after 60 days was 3% in both the AC and the non-AC group and after 10 days the rates were 13 and 8%, respectively.

CONCLUSIONS

A high frequency of silent PE in patients with DVT both above and below the knee is demonstrated. AC treatment did not influence the resolution rate of PE or the rate of clinical PE in a 3-month follow-up period.

Low dose acetylsalicylic acid in the antithrombotic treatment of patients with stable angina pectoris and acute coronary syndromes (unstable angina pectoris and acute myocardial infarction)

Acetylsalicylic acid has an antithrombotic effect by inhibition of thromboxane A2 synthesis in platelets. Thromboxane A2 is a potent stimulator of platelet aggregation and vasoconstriction and synthesis may be completely inhibited by a single oral dose of 150 mg acetylsalicylic acid or an intravenous dose of 100 mg. A daily maintenance dose of 75 mg acetylsalicylic acid is sufficient to effectively inhibit thromboxane A2 synthesis in long-term treatment. Acetylsalicylic acid therapy reduces acute myocardial infarction and sudden death in patients with stable angina pectoris and the drug is equally effective in patients with symptomatic and 'silent' angina pectoris. Early intervention with acetylsalicylic acid in patients with unstable angina pectoris reduces the risk of acute myocardial infarction and death. In patients with acute myocardial infarction, acute therapy with acetylsalicylic acid significantly reduces mortality both in monotherapy and in combination with thrombolytics. In the secondary prophylaxis following acute myocardial infarction, acetylsalicylic acid reduces the incidence of reinfarction and coronary death. Treatment of 100 patients with acute coronary syndrome (unstable angina pectoris or acute myocardial infarction) for 2 years may hinder the development of 3-4 fatal and 4 non-fatal vascular events. The risk of gastrointestinal side-effects and bleeding during acetylsalicylic acid therapy is dose-dependent and the incidence is low with a daily dose of 75-150 mg.

Anticoagulant therapy in deep venous thrombosis. A randomized controlled study

Ninety patients with venographically proven deep venous thrombosis(DVT) but without clinical signs of pulmonary embolism(PE) were randomized into two different treatment regimens to compare the safety and efficacy of continuous intravenous heparin and oral anticoagulant(AC) treatment versus non-AC treatment. All patients in the two treatment groups were actively mobilized from the day of admission and wore graduated compressing stockings. In the non-AC-group the patients were treated with phenylbutazone for ten days. Treatment with heparin was maintained for 6 days and oral AC treatment was given from the third day and continued for 3 months. Venography was repeated after 30 days. A perfusion-ventilation lung scan was performed on day 1-2, 10 and 60. In fifty-nine patients a revenography was performed, twenty nine in the AC-group and thirty in the non-AC group. For distal veins regression was found in nine and eight respectively (4.4% in favour of AC, 95% confidence limit 27.5% to -18.7%) and in proximal veins regression was found in five and eight, respectively (10.9% in favour of AC, 95% confidence limit 32.0% to -10.1%). No difference in lung scans was found after 10 days (0.8% in favour of AC, 95% confidence limit 21.5% to -19.9%) or after 60 days (3.3% in favour of non-AC treatment, 95% confidence limit 21.8% to -28.5%). In the AC group the incidence of bleeding complications was 8.3%. No side-effects of phenylbutazone was found. The present controlled clinical study demonstrated no effect of AC-treatment on DVT progression in actively mobilized patients wearing graduated compressing stockings when compared to a non-AC treated group receiving analgetic therapy with phenylbutazone. However, the patient population of the study is relatively small with wide confidence intervals for differences between groups. Before more general recommendations can be made, a large scale placebo-controlled study is needed to evaluate the possible effect of AC-treatment in DVT patients, who can be mobilized from the first day.

Observer variation in the interpretation of ventilation-perfusion lung scintigraphy

The diagnosis of pulmonary embolism (PE) remains one of the most difficult in clinical medicine, and the diagnostic value of lung scintigraphy has been questioned. To evaluate the observer variation in the interpretation of ventilation-perfusion lung scanning in the diagnosis of PE, 87 lung scintigrams from consecutive patients with phlebography-proven deep venous thrombosis and without clinical signs of PE were randomly mixed with 50 reference lung scintigrams from patients with PE symptoms. The scintigrams were reevaluated blind by two experienced clinical physiologists. Each observer evaluated each lung scintigram twice and recorded whether the lung scan was normal or abnormal. If it was abnormal, the location and number of segment defects were registered. The intraobserver agreement, including number and location of segments, ranged from 0.77 to 0.85 and for the diagnosis of PE from 0.88 to 0.92 with a kappa of 0.80-0.84. The values for the interobserver agreement for the diagnosis of PE were 0.73-0.80 with a kappa of 0.56-0.67. It is concluded that in the interpretation of ventilation-perfusion lung scintigraphy the use of a simple scheme-deciding whether there is segmental ventilation-perfusion mismatch or not-has a good reproducibility with a high kappa for inter- and intraobserver variation and can serve as a simple routine method for diagnosing PE.

Dipyridamole and Platelet Release of Platelet-derived Growth Factor

Platelet-derived growth factor (PDGF) and β-thromboglobulin (β-TG) are released from platelet alpha-granules during platelet activation. PDGF is a potent chemoattractant and mitogen for human vascular smooth muscle cells, and may be important in the development of late restenosis following angioplasty and in atherogenesis. In recent studies, where PDGF release into serum was evaluated indirectly by measuring (3)H-thymidine incorporation into fibroblasts, it was reported that the antiplatelet drug dipyridamole (DPM) decreased serum levels of PDGF. Such selective inhibition of the PDGF-release would have potential important implications for patients with atherosclerosis and for patients undergoing angioplasty. We therefore measured platelet content of PDGF and β-TG as well as platelet release of PDGF using a newly developed radioimmunoassay in healthy volunteers before and immediately after ingestion of DPM 100 mg t.i.d. for 3 days. We found no significant differences in platelet content of PDGF or β-TG before and after DPM. PDGF release from platelets isolated from plasma by gel filtration and stimulated with thrombin as well as platelet release of PDGF into serum was also unaffected by DPM. In conclusion, treatment with DPM does not affect platelet content of PDGF or β-TG. The treatment did not inhibit the platelet-release of PDGF as previously reported, neither via direct effects on platelets nor on inhibitory plasma components. DPM may, however, inhibit (3)H-thymidine incorporation into fibroblasts.

Increased blood loss after preoperative NSAID. Retrospective study of 186 hip arthroplasties

We have evaluated bleeding during and after hip replacement in 186 patients in relation to preoperative intake of nonsteroidal anti-inflammatory drugs (NSAID) combined with low molecular weight heparin. NSAID was associated with increased preoperative bleeding and blood transfusion requirements.

Platelet-derived growth factor release and antiplatelet treatment with low-dose acetylsalicylic acid

Platelet-derived growth factor (PDGF) and beta-thromboglobulin (beta-TG) are released from alpha granules during platelet activation. PDGF may play a role in the development of atherosclerosis and the late restenosis after percutaneous transluminal coronary angioplasty (PTCA). The effect of acetylsalicylic acid (ASA) on PDGF release was studied in healthy volunteers before and twelve hours after ingestion of 300 mg ASA. PDGF, beta-TG, and thromboxane B2(TxB2) were measured by radioimmunoassay (RIA) in serum and in platelet rich plasma (PRP) after submaximal stimulation with collagen. TxB2 decreased significantly from 0.9 +/- 0.3 ng/(mL x 10(6) platelets) to 0.006 +/- 0.005 ng/(mL x 10(6) platelets) (mean +/- SD) in serum after ASA ingestion while PDGF and beta-TG remained unchanged. Measurements in PRP after stimulation with collagen showed a significant decrease in PDGF (from 21.5 +/- 1.4 pg/(mL x 10(6) platelets) to 1.8 +/- 4.1 (pg/mL x 10(6) platelets), in beta-TG (from 21.0 +/- 13.3 ng/(mL x 10(6) platelets) to 2.2 +/- 1.4 ng/(mL x 10(6) platelets)) and in TxB2 (from 143.6 +/- 80.7 pg/(mL x 10(6) platelets) to 0.5 +/- 0.6 pg/(mL x 10(6) platelets)) after treatment with ASA. In conclusion low-dose ASA inhibits collagen-induced release of both beta-TG and PDGF in PRP and TxB2-synthesis in PRP and serum.

Doxazosin treatment in patients with prostatic obstruction. A double-blind placebo-controlled study

The safety and efficacy of the selective alpha 1-blocking agent doxazosin 4 mg once daily in the symptomatic treatment of benign prostatic hyperplasia were evaluated in a randomized, double-blind and placebo-controlled 9-week study of 100 patients. By patients' overall assessment of voiding difficulties, 79% in the doxazosin group (DG) and 44% in the placebo group (PG) reported improvement (p = 0.001). In the DG, improvement was noted in 63% of obstructive symptoms compared to 32% in the PG (p = 0.015), whereas improvement was noted in 76% and 45%, respectively, of irritative symptoms (p = 0.12). Daytime frequency was reduced by 1.5 in the DG and increased by 0.3 in the PG (p = 0.001), and nocturia was reduced by 1.1 and 1.0, respectively (p = 0.12). Maximum urinary flow rate was improved by 1.5 ml/s in the DG, while it deteriorated by 0.3 ml/s in the PG (p = 0.11). Considering postvoid residual urine volume, cystometry variables (first sensation and bladder capacity) and adverse events there was no difference between the two groups. In conclusion, doxazosin 4 mg once daily is safe and effective in relieving symptoms in patients with BPH.

Intravenous acetylsalicylic acid--dose-related effects on platelet function and fibrinolysis in healthy males

Low-dose acetylsalicylic acid (ASA) has been shown to be beneficial in patients with acute myocardial infarction and unstable angina pectoris. Oral administration of ASA is difficult in the acute phase of these syndromes. In this study we evaluated the effect of 25 mg, 50 mg or 100 mg of ASA given as an intravenous bolus injection on platelet function and fibrinolysis in healthy males and related this to plasma concentrations of ASA. No adverse effects were found. A complete inhibition of serum thromboxane B2 synthesis was demonstrated 5 min after injection of 100 mg ASA intravenously. ASA disappeared from the circulation within 60 min after bolus injection and at this time thromboxane B2 synthesis was inhibited dose-dependently by 71%, 90% and 100% for doses of 25 mg, 50 mg and 100 mg, respectively. Inhibition of thromboxane B2 synthesis after 100 mg of intravenous ASA was still 96.5% at 24 h and 93.4% at 48 h after the injection. The bleeding time measured at 30 min after ASA administration was significantly prolonged on the average by 70 s, 144 s and 211 s after 25 mg, 50 mg and 100 mg of ASA, respectively. Minor, but significant changes were found in tissue plasminogen activator antigen and in plasminogen activator inhibitor within the first hour after injection of low dose ASA, but similar changes were found after injection of saline. No change in tissue plasminogen activator activity was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma thromboxane B2 as an early marker of acute graft rejection after heart transplantation: preliminary report

Six patients undergoing heart transplantation were followed up by serial endomyocardial biopsies to detect signs of graft rejection and the plasma level of thromboxane B2 was measured at the same time. During the operative procedure and concomitant with histologic signs of acute graft rejection, the plasma level of thromboxane B2 significantly increased. After immunosuppressive treatment with steroids and either antithymocyte globulin or monoclonal antibody, regression of the histologic signs of rejection and a significant fall in the level of thromboxane B2 were documented. We conclude that the plasma level of thromboxane B2 may be useful as an early marker of acute graft rejection after heart transplantation.

[Apical hypertrophic cardiomyopathy]

Apical hypertrophic cardiomyopathy is a subtype of non-obstructive hypertrophic cardiomyopathy characterized by a unique spade-like configuration and apical obliteration in the left ventriculogram as well as in the long axis two-dimensional echocardiogram. The symptoms and electrocardiographic findings in apical hypertrophic cardiomyopathy are quite similar to ischemic heart disease and confusion of the two diseases is obvious. An illustrative case, in which ventriculographic and echocardiographic findings were diagnostic for apical hypertrophic cardiomyopathy, is presented.