Preventing thromboembolism after myocardial infarction: effect of low-dose heparin or smoking

Heparin and related drugs for venous thromboembolism prophylaxis: subcutaneous or intravenous continuous infusion?

In this article, the most evidenced approaches of unfractionated heparin administration for prevention of venous thromboembolism in medical and surgical hospitalized patients will be reviewed. Present data were collected by searching Scopus, PubMed, MEDLINE, Science direct, Clinical trials and Cochrane database systematic reviews. Subcutaneous low doses of unfractionated heparin (10000–15000 IU) in two or three divided doses per day are commonly administrated for venous thromboembolism prevention in different medical and surgical populations. In some populations such as obese surgical and critically ill patients, due to altered pharmacokinetics behavior of unfractionated heparin, continuous intravenous infusion of the low doses of unfractionated heparin has been proposed.

Prevention of venous thromboembolism in hospitalized acutely ill medical patients: focus on the clinical utility of (low-dose) fondaparinux

Venous thromboembolism (VTE) is a frequent complication among acutely ill medical patients hospitalized for congestive heart failure, acute respiratory insufficiency, rheumatologic disorders, and acute infectious and/or inflammatory diseases. Based on robust data from randomized controlled studies and meta-analyses showing a reduced incidence of VTE by 40% to about 60% with pharmacologic thromboprophylaxis, prevention of VTE with low molecular weight heparin (LMWH), unfractionated heparin (UFH), or fondaparinux is currently recommended in all at-risk hospitalized acutely ill medical patients. In patients who are bleeding or are at high risk for major bleeding, mechanical prophylaxis with graduated compression stockings or intermittent pneumatic compression may be suggested. Thromboprophylaxis is generally continued for 6 to 14 days or for the duration of hospitalization. Selected cases could benefit from extended thromboprophylaxis beyond this period, although the risk of major bleeding remains a concern, and additional studies are needed to identify patients who may benefit from prolonged prophylaxis. For hospitalized acutely ill medical patients with renal insufficiency, a low dose (1.5 mg once daily) of fondaparinux or prophylactic LMWH subcutaneously appears to have a safe profile, although proper evaluation in randomized studies is lacking. The evidence on the use of prophylaxis for VTE in this latter group of patients, as well as in those at higher risk of bleeding complications, such as patients with thrombocytopenia, remains scarce. For critically ill patients hospitalized in intensive care units with no contraindications, LMWH or UFH are recommended, with frequent and careful assessment of the risk of bleeding. In this review, we discuss the evidence for use of thromboprophylaxis for VTE in acutely ill hospitalized medical patients, with a focus on (low-dose) fondaparinux.

Thromboprophylaxis in non-surgical cancer patients

Acutely ill medical patients with cancer and cancer patients requiring non-surgical therapy are considered as non-surgical cancer patients and are at moderate to high risk of venous thromboembolism (VTE): approximately 10-30% of these patients may develop asymptomatic or symptomatic deep-vein thrombosis (DVT) or pulmonary embolism (PE), and the latter is a leading contributor to deaths in hospital. Other medical conditions associated with a high risk of VTE include cardiac disease, respiratory disease, inflammatory bowel disease, rheumatological and infectious diseases. Pre-disposing risk factors in non-surgical cancer patients include a history of VTE, immobilisation, history of metastatic malignancy, complicating infections, increasing age, obesity hormonal or antiangiogenic therapies, thalidomide and lenalidomide therapy. Heparins, both unfractionated (UFH) and low molecular weight heparin (LMWH) and fondaparinux have been shown to be effective agents in prevention of VTE in the medical setting with patients having a history of cancer. UFH and LMWH along with semuloparin also have a role in outpatients with cancer receiving chemotherapy. However, it has not yet been possible to demonstrate a significant effect on mortality rates in this population. UFH has a higher rate of bleeding complications than LMWH. Thromboprophylaxis has been shown to be effective in medical patients with cancer and may have an effect on cancer outcomes. Thromboprophylaxis in patients receiving chemotherapy remains controversial and requires further investigation. There is no evidence for the use of aspirin, warfarin or mechanical methods. We recommend either LMWH, or fondaparinux for the prevention of VTE in cancer patients with acute medical illnesses and UFH for those with significant severe renal impairment. For ambulatory cancer patients undergoing chemotherapy we recommend LMWH or semuloparin. These are safe and effective agents in the thromboprophylaxis of non-surgical cancer patients.

How I manage venous thromboembolism risk in hospitalized medical patients

Venous thromboembolism is a significant cause of illness and death worldwide. Large bodies of evidence support the heightened risk status of hospitalized medical patients, and that prophylactic measures significantly reduce the risk of thrombosis, yet these patients often fail to receive adequate prophylactic therapy. This failure may be accounted for by a lack of awareness of the relevant indications, poorly designed implementation systems, and clinical concerns over the side effects of anticoagulant medications. This article briefly summarizes our understanding of the clinical factors relevant to the evaluation of venous thromboembolism risk in hospitalized medical patients. We describe our approach to the use of thromboprophylaxis, through which we aim to minimize the disease burden of this under-recognized and preventable pathology.

Choosing the right heparin prophylaxis strategy in medical patients at risk for developing VTE: an evidence-based approach

Many acutely ill medical patients are at significant risk for developing venous thromboembolism (VTE) during hospitalization. Venous thromboembolism risk arises from both the presenting clinical condition as well as predisposing risk factors, such as advanced age. Thromboprophylaxis is underprescribed in these patients. Thrombotic risk assessment could encourage the prescribing of thromboprophylaxis and, therefore, improve patient protection against VTE. Current guidelines from the American College of Chest Physicians and the International Union of Angiology (IUA) recommend thromboprophylaxis with low-dose unfractionated heparin (UFH), a low-molecular-weight heparin (LMWH), or fondaparinux for acutely ill medical patients with VTE risk factors. However, the optimal dose regimen for UFH is unclear. The 2006 evidence-based guidelines from the IUA recommend a 3-times-daily dose regimen for UFH. However, UFH is usually administered twice daily despite a lack of evidence for the superiority of this regimen. Both heparin-induced thrombocytopenia and bleeding are associated with UFH, and to a lesser degree with alternative anticoagulants, such as the LMWHs. If utilized, an appropriate prophylaxis regimen in medical patients can reduce the risk of VTE and its burden.

VTE prophylaxis for the medical patient: where do we stand? - a focus on cancer patients

Acutely ill medical patients are at moderate to high risk of venous thromboembolism (VTE): approximately 10-30% of general medical patients may develop deep-vein thrombosis or pulmonary embolism, and the latter is a leading contributor to deaths in hospital. Medical conditions associated with a high risk of VTE include cardiac disease, cancer, respiratory disease, inflammatory bowel disease, rheumatological and infectious diseases. Pre-disposing risk factors in medical patients include a history of VTE, history of malignancy, complicating infections, increasing age, thrombophilia, prolonged immobility and obesity. Hence active cancer and a history of cancer are both strongly related to VTE in medical (non-surgical) patients. Heparins, both unfractionated (UFH) and low molecular weight (LMWH) and fondaparinux have been shown to be effective agents in prevention of VTE in this setting. However, it has not yet been possible to demonstrate a significant effect on mortality rates in this population. In medical patients, unfractionated heparin has a higher rate of bleeding complications than low molecular weight heparin. Thromboprophylaxis has been shown to be effective in medical patients with cancer and may have an effect on cancer outcomes. Thromboprophylaxis in patients receiving chemotherapy remains controversial and requires further investigation. There is no evidence for the use of aspirin, warfarin or mechanical methods. We recommend either low molecular weight heparin or fondaparinux as safe and effective agents in the thromboprophylaxis of medical patients.

Changes in glycaemic control and risk of coronary artery disease in type 1 diabetes mellitus: findings from the Pittsburgh Epidemiology of Diabetes Complications Study (EDC)

AIMS/HYPOTHESIS

To complete a comparative analysis of studies that have examined the relationship between glycaemia and cardiovascular disease (CVD)/coronary artery disease (CAD) and perform a prospective analysis of the effect of change in glycosylated Hb level on CAD risk in the Pittsburgh Epidemiology of Diabetes Complications Study (EDC) of childhood-onset type 1 diabetes mellitus (n = 469) over 16 years of two yearly follow-up.

METHODS

Measured values for HbA(1) and HbA(1c) from the EDC were converted to the DCCT-standard HbA(1c) for change analyses and the change in HbA(1c) was calculated (final HbA(1c) minus baseline HbA(1c)). CAD was defined as EDC-diagnosed angina, myocardial infarction, ischaemia, revascularisation or fatal CAD after medical record review.

RESULTS

The comparative analysis suggested that glycaemia may have a stronger effect on CAD in patients without, than in those with, albuminuria. In EDC, the change in HbA(1c) differed significantly between CAD cases (+0.62 +/- 1.8%) and non-cases (-0.09 +/- 1.9%) and was an independent predictor of CAD.

CONCLUSIONS/INTERPRETATION

Discrepant study results regarding the relationship of glycaemia with CVD/CAD may, in part, be related to the prevalence of renal disease. Measures of HbA(1c) change over time show a stronger association with CAD than baseline values.

Risk-assessment algorithm and recommendations for venous thromboembolism prophylaxis in medical patients

The risk for venous thromboembolism (VTE) in medical patients is high, but risk assessment is rarely performed because there is not yet a good method to identify candidates for prophylaxis.

PURPOSE

To perform a systematic review about VTE risk factors (RFs) in hospitalized medical patients and generate recommendations (RECs) for prophylaxis that can be implemented into practice.

DATA SOURCES

A multidisciplinary group of experts from 12 Brazilian Medical Societies searched MEDLINE, Cochrane, and LILACS.

STUDY SELECTION

Two experts independently classified the evidence for each RF by its scientific quality in a standardized manner. A risk-assessment algorithm was created based on the results of the review.

DATA SYNTHESIS

Several VTE RFs have enough evidence to support RECs for prophylaxis in hospitalized medical patients (eg, increasing age, heart failure, and stroke). Other factors are considered adjuncts of risk (eg, varices, obesity, and infections). According to the algorithm, hospitalized medical patients > or =40 years-old with decreased mobility, and > or =1 RFs should receive chemoprophylaxis with heparin, provided they don't have contraindications. High prophylactic doses of unfractionated heparin or low-molecular-weight-heparin must be administered and maintained for 6-14 days.

CONCLUSIONS

A multidisciplinary group generated evidence-based RECs and an easy-to-use algorithm to facilitate VTE prophylaxis in medical patients.

Pharmacological prevention of venous thromboembolism in medical patients at risk

Acutely ill general medical patients are at moderate-to-high risk of venous thromboembolism (VTE); approximately 10-30% may develop deep vein thrombosis or pulmonary embolism, the latter being a leading contributor to deaths in hospital. Medical conditions associated with a high risk of VTE include cardiac disease, cancer, respiratory disease, inflammatory bowel disease, and infectious disease. Predisposing risk factors for VTE in medical patients include history of VTE, history of malignancy, complicating infections, increasing age, thrombophilia, prolonged immobility, and obesity. Unfractionated heparin (UFH), low-molecular weight heparin (LMWH), and fondaparinux sodium have been shown to be effective agents in the prevention of VTE in medical patients. In this setting, UFH has a higher rate of bleeding complications than LMWH. There is no evidence supporting the use of aspirin, warfarin, or mechanical methods to prevent VTE in medical patients. We recommend either LMWH or fondaparinux sodium as well tolerated and effective thromboprophylactic agents in medical patients.

Emerging Strategies in the Prevention of Venous Thromboembolism in Hospitalized Medical Patients

Venous thromboembolism (VTE) remains a significant cause of morbidity and mortality in hospitalized patients with acute medical illness. The high prevalence of VTE in this patient population, its clinically silent nature, and associated morbidity and mortality indicate that prophylactic therapy is appropriate in those determined to be at increased risk. Unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) have been shown to reduce the incidence of VTE and are the primary therapies used for prophylaxis in these patients. Although both UFH and LMWH have received grade 1A recommendations for the prevention of VTE in at-risk medical patients in the 2004 American College of Chest Physicians consensus conference statements, LMWH has advantages over UFH in its once-daily dosing scheme, reduced incidence of major and minor bleeding events, and reduced incidence of heparin-induced thrombocytopenia. Fondaparinux is a novel antithrombotic agent characterized by specificity for factor Xa and a lack of platelet interaction. A recent clinical trial in hospitalized patients with acute medical illness found that fondaparinux significantly reduced the incidence of both VTE and fatal pulmonary embolism compared with placebo, without increased major bleeding. Despite the availability of effective thromboprophylactic therapies, VTE prophylaxis continues to be underutilized in hospitalized medical patients.

Deep vein thrombosis during prolonged mechanical ventilation despite prophylaxis

OBJECTIVE

To determine the prevalence of deep vein thrombosis (DVT) among patients requiring prolonged mechanical ventilation in the intensive care unit.

DESIGN

Prospective cohort study.

SETTING

Medical intensive care unit of a university-affiliated urban teaching hospital.

PATIENTS

Patients requiring mechanical ventilation for >7 days.

INTERVENTIONS

All patients admitted to the medical intensive care unit requiring prolonged mechanical ventilation underwent duplex ultrasonography of their lower extremities and upper extremities every 7 days. The main outcome identified was the presence of DVT. Secondary outcomes included hospital mortality, hospital and intensive care unit lengths of stay, and the occurrence of pulmonary embolism.

MEASUREMENTS AND MAIN RESULTS

A total of 110 patients requiring mechanical ventilation for >7 days were enrolled. Prophylaxis against DVT was employed in 110 of the patients (100%). A total of 26 patients (23.6%) developed DVT. Patients with DVT were statistically more likely to have underlying malignancy (30.8% vs. 8.3%; p =.004) and longer durations of central venous catheterization (26.9 +/- 22.2 days vs. 14.5 +/- 12.1 days; p =.024) compared with patients without DVT. There were no statistically significant differences in hospital mortality or lengths of stay in the hospital and intensive care unit for patients with and without DVT. Patients documented to have DVT by using duplex ultrasonography had a statistically greater frequency of subsequent pulmonary embolism during their hospitalization (11.5% vs. 0.0%; p =.012).

CONCLUSION

The occurrence of DVT is common among patients requiring prolonged mechanical ventilation in the intensive care unit setting despite the use of prophylaxis measures. These data suggest that alternative strategies for the prevention of DVT should be evaluated. Additionally, early detection methods should be considered to reduce the potential morbidity associated with untreated DVT in this high-risk population.

Clinical effects of anticoagulant therapy in suspected acute myocardial infarction: systematic overview of randomised trials

OBJECTIVES

Most randomised trials of anticoagulant therapy for suspected acute myocardial infarction have been small and, in some, aspirin and fibrinolytic therapy were not used routinely. A systematic overview (meta-analysis) of their results is needed, in particular to assess the clinical effects of adding heparin to aspirin.

DESIGN

Computer aided searches, scrutiny of reference lists, and inquiry of investigators and companies were used to identify potentially eligible studies. On central review, 26 studies were found to involve unconfounded randomised comparisons of anticoagulant therapy versus control in suspected acute myocardial infarction. Additional information on study design and outcome was sought by correspondence with study investigators.

SUBJECTS

Patients with suspected acute myocardial infarction.

INTERVENTIONS

No routine aspirin was used among about 5000 patients in 21 trials (including half of one small trial) that assessed heparin alone or heparin plus oral anticoagulants, and aspirin was used routinely among 68,000 patients in six trials (including the other half of one small trial) that assessed the addition of intravenous or high dose subcutaneous heparin.

MAIN OUTCOME MEASUREMENTS

Death, reinfarction, stroke, pulmonary embolism, and major bleeds (average follow up of about 10 days).

RESULTS

In the absence of aspirin, anticoagulant therapy reduced mortality by 25% (SD 8%; 95% confidence interval 10% to 38%; 2P = 0.002), representing 35 (11) fewer deaths per 1000. There were also 10 (4) fewer strokes per 1000 (2P = 0.01), 19 (5) fewer pulmonary emboli per 1000 (2P < 0.001), and non-significantly fewer reinfarctions, with about 13 (5) extra major bleeds per 1000 (2P = 0.01). Similar sized effects were seen with the different anticoagulant regimens studied. In the presence of aspirin, however, heparin reduced mortality by only 6% (SD 3%; 0% to 10%; 2P = 0.03), representing just 5 (2) fewer deaths per 1000. There were 3 (1.3) fewer reinfarctions per 1000 (2P = 0.04) and 1 (0.5) fewer pulmonary emboli per 1000 (2P = 0.01), but there was a small non-significant excess of stroke and a definite excess of 3 (1) major bleeds per 1000 (2P < 0.0001).

CONCLUSIONS

The clinical evidence from randomised trials dose not justify the routine addition of either intravenous or subcutaneous heparin to aspirin in the treatment of acute myocardial infarction (irrespective of whether any type of fibrinolytic therapy is used).

Randomised, controlled trial of low-dose heparin for prevention of fatal pulmonary embolism in patients with infectious diseases. The Heparin Prophylaxis Study Group

BACKGROUND

Fatal pulmonary embolism and other thromboembolic complications are common in hospital inpatients. However, there is little evidence on the routine use of pharmacological thromboprophylaxis in non-surgical patients. We assessed the efficacy and safety of low-dose heparin in the prevention of hospital-acquired, clinically relevant, fatal pulmonary embolism in patients with infectious diseases.

METHODS

Our study used the postrandomisation consent design. 19,751 consecutive patients, aged 55 years or older, admitted to departments of infectious diseases in six Swedish hospitals, were screened for inclusion in the randomised, controlled, unblinded, multicentre trial. Of the eligible patients, 5776 were assigned subcutaneous standard heparin (5000 IU every 12 h) until hospital discharge or for a maximum of 3 weeks; 5917 were assigned no prophylactic treatment (control group). We sought consent only from the heparin group. Follow-up was for 3 weeks after discharge from hospital or for a maximum of 60 days from randomisation. The primary endpoint was necropsy-verified pulmonary embolism of predefined clinical relevance.

FINDINGS

By intention-to-treat analysis mortality was similar in the heparin and control groups (5.3 vs 5.6%, p = 0.39) and the median time from admission to death was 16 days in both groups (IQR 8-31 vs 6-28 days). Necropsy-verified pulmonary embolism occurred in 15 heparin-treated and 16 control-group patients. There was a significant difference between heparin and control groups in median time from randomisation to fatal pulmonary embolism (28 [24-36] vs 12.5 [10-20] days, p = 0.007). This difference corresponds to the duration of heparin prophylaxis. Non-fatal thromboembolic complications occurred in more of the control than of the heparin group (116 vs 70, p = 0.0012).

INTERPRETATION

Our findings do not support the routine use of heparin prophylaxis for 3 weeks or less in large groups of non-surgical patients. Further studies are needed to investigate whether heparin prophylaxis of longer duration may prevent fatal pulmonary embolism.

The venous thrombotic risk in nonsurgical patients

The risk of venous thromboembolism is not restricted to surgical situations: previous surgery is encountered in less than one-third of fatal pulmonary embolism cases, and less than 30% of patients hospitalised because of venous thromboembolic events are surgical patients. Some nonsurgical situations, e.g. ischaemic strokes and myocardial infarction (AMI), have been identified as having a risk for thromboembolism. More recently, critically ill patients in intensive care wards have been shown to be exposed to a significant risk of deep venous thrombosis. More often, at-risk situations in nonsurgical patients are less well defined. Clinical trials assessing the efficacy and safety of prophylactic methods in nonsurgical patients are rare, with the exception of those involving stroke and AMI. Several clinical trials have demonstrated that low molecular weight heparins are a suitable alternative to low dose unfractionated heparin in medical patients, offering a decrease in the number of injections and a lower potential for heparin-induced thrombocytopenia. Further research is needed to characterise the extent and duration of the risk of thromboembolism in nonsurgical patients, and the global benefit/risk ratio of various methods of prevention.

Critical role of pulmonary angiography in the diagnosis of pulmonary emboli following cardiac surgery

This study was conducted to identify patients at high risk of the development of Pulmonary Embolism (PE) after open heart surgery, to evaluate pertinent diagnostic methods, and to assess the mortality associated with this complication. We evaluated the records of 2,551 consecutive patients who underwent open heart surgery over a 10-year period to identify those patients in whom PE developed. All surgical reports, ventilation/perfusion scans, pulmonary angiograms, and autopsies from the same period were also reviewed. Preoperative and postoperative risk factors for pulmonary embolism were also analyzed, as well as the outcome of this complication in each type of surgical procedure. Pulmonary embolism was identified in 69 (2.7%) patients after open heart surgery, in 43 (62.3%) of whom the diagnosis was established within the first week of surgery. Factors associated with high incidence for PE were hyperlipidemia, congestive heart failure and heparin-induced thrombocytopenia (P < 0.001); obesity and prolonged mechanical ventilation (P < 0.005); and prior right heart catheterization by the femoral approach and prior PE and/or deep vein thrombosis (P < 0.05). The diagnosis of PE was established by a high-probability ventilation/perfusion scan in 25 patients, by pulmonary angiography in 42 (29 of whom had prior V/Q scan read as intermediate or low probability for PE) and by autopsy in two patients. The mortality rate in patients who had PE was 7.2%, while in those without this complication it was 3.2%. These findings suggest that aggressive approach for the diagnosis of PE by pulmonary angiography whenever the V/Q scan is not read as high probability is crucial in patients with recent open heart surgery; such approach may identify patients with PE at an early stage and may have an impact in reducing mortality incurred by this complication. This diagnostic assessment should be emphasized in the perioperative period, especially in patients with multiple significant and identifiable risk factors for PE.

Acute myocardial infarction. Then and now

Dramatic changes in the management of acute myocardial infarction (AMI) have occurred in the past decade. While previous management strategies were primarily supportive, current strategies focus on achieving and maintaining patency of the infarct-related artery restoring blood flow to jeopardized myocytes, preserving left ventricular function, and preventing recurrences and complications in addition to promoting healing. Restoration of blood flow can be achieved pharmacologically with thrombolytic agents or mechanically with percutaneous transluminal coronary angioplasty (PTCA). Early use of antiplatelet agents and anticoagulants helps maintain patency of the infarct-related arteries and prevents thromboembolic complications. Administration of beta-blockers and angiotensin enzyme inhibitors are more specific means of conserving myocardium and preserving ventricular function. Additionally, several strategies for preventing arrhythmias such as prophylactic lidocaine use and routine long-term suppression of premature ventricular contractions with antiarrhythmic drugs are no longer routinely advocated. Basically, in the era prior to the eighth decade of this century, the primary direction of the therapeutic strategy for AMI was to reduce the oxygen demands in the infarcted myocardium; whereas in the subsequent years, the emphasis shifts to improvement in oxygen delivery, via thrombolysis, PTCA, and coronary artery bypass graft surgery. These interventional changes, when added to greater sophistication in the use of drugs to reduce oxygen demands, resulted in significant lowering of myocardial mortality.

Heparin Study in Internal Medicine (HESIM): design and preliminary results

The Heparin Study in Internal Medicine (HESIM) compares the efficacy and safety of an unfractionated (UF) heparin with a low molecular weight (LMW) heparin (CY 216 D) for prevention of proximal deep vein thrombosis (DVT) and pulmonary embolism (PE) in medical inpatients with a high risk for development of thromboembolism. Patients are randomized and receive three times daily 5000 IU UF heparin or once daily 3100 IU LMW heparin and two placebo injections subcutaneously for 10 days. All patients are screened for the presence of proximal DVT at day 1 and 10 by real-time B-mode compression sonography and for PE by repeated clinical examinations. Perfusion scintigraphy is used for confirmation of the clinical diagnosis of PE. The study protocol includes a stratified randomization of patients on admission to the hospital according to one of the following main diagnoses: malignant disease, cardiovascular disease, bronchopulmonary disease, neurologic disease, and other diseases. The present study may serve as a model for further clinical trials in medical inpatients using the biometric approach of statistical analysis for proving equivalence of drug efficacy, and to adopt less sensitive but noninvasive methods for the detection of primary endpoints.

Pulmonary embolism in the cardiac surgical patient

Pulmonary embolism (PE) is thought to occur infrequently after cardiac operations, possibly because systemic heparinization during cardiopulmonary bypass prevents deep vein thrombosis. This retrospective study was undertaken to determine the actual incidence of PE after cardiac operations and to identify risk factors. Between January 1, 1985, and December 31, 1989, 5,694 adult patients (greater than 18 years old) had open heart operations at the Johns Hopkins Hospital. Thirty-two patients (20 men and 12 women) had PE within 60 days of operation, an overall PE incidence of 0.56%. The diagnosis of PE was established by ventilation/perfusion scan, pulmonary angiogram, or autopsy. Mortality among patients with PE was 34%. Using a case-control method, preoperative and postoperative risk factors for PE were identified by multivariate and multiple logistic regression analyses. Preoperative risk factors included bed rest (p less than 0.003), prolonged hospitalization before operation (p less than 0.004), and cardiac catheterization performed through the groin within 15 days before operation (p less than 0.01). Post-operative risk factors were congestive heart failure (p less than 0.008), prolonged bed rest (p less than 0.05), and deep vein thrombosis (p less than 0.03). This study demonstrates that PE is an unusual complication after cardiac operations, has a high mortality rate, and is often related to perioperative immobility and recent groin catheterization. These results also suggest that minimizing preoperative hospital stay may be important in PE prophylaxis.

Medical management of acute myocardial infarction in Ireland: information from the Second International Study of Infarct Survival (ISIS-2)

We report the management of the 831 patients from 18 hospitals which constituted the Irish component of the 17,183 subjects enrolled in the ISIS-2 trial which studied the effects of streptokinase infusion and aspirin therapy given to patients presenting within 24 hours of the onset of suspected acute myocardial infarction. 34% of Irish patients (IP) presented for treatment within 4 hours of the development of symptoms. This compared to 44% of the overall group (OG) (p less than 0.001). This represented the lowest percentage of patients presenting within 4 hours in any of the participating countries. The mean delay time from onset of symptoms was 7.9 hours in IP compared to 6.9 in OG (p less than 0.001). The mean delay time in Ireland was longer than the mean delay time in any of the participating countries. The mean age and systolic blood pressure at presentation was similar in both groups. It was planned to treat 12% IP with aspirin compared to 10% OG (p-NS), and 71% IP with subcutaneous heparin compared with 47% OG (p less than 0.001). Intravenous heparin was planned treatment in 20% IP and 24% OG (p less than 0.01). Planned oral anticoagulant therapy was similar in both groups (p-NS). Planned use of intravenous betablockers occurred in only 2% IP and 6% OG (p less than 0.001). 9% IP and 22% OG received steroids before streptokinase infusion (p less than 0.001). 65% IP and 47% OG received subcutaneous heparin (p less than 0.001). The use of intravenous heparin and oral anticoagulants was similar in IP and OG (p-NS).(ABSTRACT TRUNCATED AT 250 WORDS)

"Idiopathic" deep venous thrombosis: the value of routine abdominal and pelvic computed tomographic scanning

Recent studies have demonstrated an increased incidence in the diagnosis of malignancy subsequent to the diagnosis of deep venous thrombosis or pulmonary embolus. We reviewed 237 patients with venographically proven deep venous thrombosis over eight years. Of these, 216 had at least one predisposing cause for deep venous thrombosis; of the remaining 21 patients, three had hemoglobin determinations revealing anemia and were subsequently shown to have a malignant disease. One patient had two chief complaints and was shown to have deep venous thrombosis and malignant disease. The 17 remaining patients underwent computed tomographic scan of the abdomen and seven (41%) had abnormalities which proved to be malignant in origin. One further patient was diagnosed with carcinoma of the cervix two months following the onset of deep venous thrombosis. The remaining 10 patients continued free of malignant disease. Five have died of circulatory causes in the follow-up period. Seven of the nine patients diagnosed with malignancy succumbed within six months of the diagnosis. We conclude that only a small group of patients with deep venous thrombosis will have no identifiable cause for deep venous thrombosis and be asymptomatic for malignancy. Complete blood count, physical examination and computed tomographic scan of the abdomen at the time of venographic diagnosis of deep venous thrombosis is useful in diagnosis of "occult" malignancy. The number of gynecologic tumors would suggest the need for pelvic examination as well as radiographic examination. The presence of deep venous thrombosis and malignant disease is an ominous prognostic sign.

Management of the patient following coronary thrombolysis

Myocardial salvage can be maximized by the early institution of thrombolytic therapy and aspirin. Certain patients may benefit from the administration of intravenous heparin, beta blockers, or nitroglycerin. The routine use of percutaneous transluminal coronary angioplasty (PTCA) or calcium-channel blockers does not appear to be warranted. Recurrent myocardial ischemia should be vigorously treated with medical therapy and there may be value in cardiac catheterization, followed by PTCA or bypass surgery, depending upon the extent of myocardium at risk and the underlying coronary anatomy. Long-term morbidity and mortality may be reduced by instituting aspirin and beta blockers as well as by modifying risk factors. There is no evidence for the long-term benefit from any calcium-channel blocker. Oral anticoagulation may be warranted in those patients with a mural thrombus, congestive heart failure, or atrial fibrillation. ACE inhibitors may be of value in the presence of left ventricular dysfunction and certainly in the presence of symptomatic congestive heart failure. Antiarrhythmic therapy is generally indicated only for symptomatic or life-threatening arrhythmias. Residual myocardial ischemia should be sought by exercise testing, and those patients with poor exercise tolerance generally warrant cardiac catheterization in consideration for revascularization.

Prevention of venous thrombosis and pulmonary embolism

Deep vein thrombosis (DVT) leads to hospitalization for up to 600,000 persons each year in the United States. Venous thrombosis in itself may be benign, but the condition can lead to dangerous complications and has a high recurrence rate. Strategies to prevent DVT involve prevention of stasis and reversal of changes in blood coagulability that allow thrombi to form. Pharmacologic agents have been effective in reducing the incidence of DVT and pulmonary embolism. Low-dose subcutaneous heparin is considered a nearly ideal DVT preventative for surgically treated patients. The risk of hemorrhage is the main limitation to routine use of subcutaneous anticoagulants for DVT, but careful patient selection can minimize that risk. After anticoagulant therapy with heparin, generally for 7 to 10 days, oral warfarin is the drug of choice for maintenance anticoagulation to prevent DVT recurrence. Therapy for pulmonary embolism is the same as for DVT--immediate anticoagulation with heparin followed by maintenance with warfarin.

Antithrombotic therapy in acute myocardial infarction: prevention of venous, left ventricular and coronary artery thromboembolism

The antithrombotic approach to patients with acute myocardial infarction in the prevention of venous, left ventricular and coronary artery thromboembolic events should be based on an understanding of pathogenesis and risk. Coronary thrombotic events involve conditions of high shear rate present in areas of vessel stenosis or disrupted atherosclerotic plaque, which lead to activation of both platelets and the coagulation system, and are best prevented by platelet inhibitors alone or in combination with an anticoagulant. However, thromboembolism that originates in the venous system or cardiac chambers is related to situations of blood stasis and low shear rate, which predominantly result in clotting activation and fibrin-thrombus formation and are best approached with anticoagulant therapy. For prevention of venous thrombosis and pulmonary embolism, early mobilization is essential and should be supplemented by low-dose heparin in patients at high risk, including the elderly and those with large infarcts, heart failure or previous thromboembolic events. For prevention of left ventricular mural thrombosis and systemic embolism, high-dose heparinization is indicated in patients with large infarcts, particularly in the anterior location and in those with heart failure. Subsequently, warfarin therapy should be considered for patients at high embolic risk, including those with echocardiographic evidence of mobile and protruding thrombi, severe left ventricular dysfunction or prior emboli. In patients with acute infarction, aspirin is recommended for preventing coronary reocclusion and reinfarction. Although anticoagulants may also be of benefit for this purpose, their use is still controversial.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between smoking and fibrinolytic system with special reference to t-PA and PA inhibitor

Recently tissue plasminogen activator (t-PA) has been clinically applied to the thrombolytic therapy of myocardial infarction. We investigated relationship between cigarette smoking and fibrinolytic system, namely the plasma level of t-PA antigen, plasminogen activator inhibitor (PAI), and PA activity. Nineteen healthy volunteers were asked to smoke for 10 min. The plasma levels of t-PA antigen, PAI activity, PA activity and catecholamine were measured together with measurement of blood pressure and heart rate before, soon after or 30 min after cigarette smoking. Plasma t-PA antigen after cigarette smoking increased to 8.83 +/- 3.11 ng per ml, significantly higher (p less than 0.005) than 6.35 +/- 1.7 ng/ml before cigarette smoking. Plasma PAI activity after cigarette smoking was 5.52 +/- 2.03 u/ml, significantly higher (p less than 0.05) than 4.18 +/- 1.06 u/ml before smoking. Plasma PA activity after smoking was 6.28 +/- 3.85 u/ml significantly higher (p less than 0.05) than 4. 49 +/- 2.74 u/ml. Furthermore, plasma epinephrine level after smoking increased to 59.1 +/- 52.4 pg/ml (p less than 0.1), compared with 36.2 +/- 22.5 pg/ml before smoking. There was a positive correlation between the rate of increase in plasma t-PA antigen and the rate of increase in plasma epinephrine after smoking. It is suggested that plasma epinephrine was related to the mechanism of increased plasma levels of t-PA in cigarette smoking.

Postinfarction angina

In conclusion, the PIA patient is at high risk, with higher early as well as late mortality. The pathophysiology of PIA is complex and may vary from patient to patient. The concepts of ischemia at a distance and ischemia in the infarct zone have led to a better understanding of early PIA. Coronary spasm may play an important role in most PIA patients as in the general population of patients with angina pectoris. Medical therapy is efficacious in many, although it may on rare occasion aggravate myocardial ischemia. Urgent coronary arteriography is generally safe and should be performed as soon as possible for medically refractory PIA. CABG appears to be safe in experienced hands, but its timing must be individualized. The IABP should be reserved for more unstable patients for fear of vascular complications. Randomized controlled trials such as the BARI Trial will further compare PTCA with CABG.

Preventive and therapeutic approach to venous thromboembolic disease and pulmonary embolism--can death from pulmonary embolism be prevented?

Venous thromboembolism produces chronic sequelae in the legs and occasional immediate mortality due to pulmonary embolism. Because it occurs in certain high risk situations (for example, after surgery) its prevention is a practical proposition. This has been attempted using many different approaches. Administration of low dose heparin with or without dihydroergotamine to enhance venous return has been one of the most widely tested regimens. There is little doubt that this can prevent, in many patient groups, postoperative deep venous thrombosis and fatal pulmonary embolism, with a low incidence of adverse reactions. Some particularly high risk postoperative patient groups (for example, those undergoing hip surgery) warrant more aggressive measures to prevent thrombosis. Surveys have shown that increasing use is being made of this approach, and it is hoped that all surgeons will adopt a policy that will reduce postoperative venous thrombosis and pulmonary embolism. A reduction in the incidence of venous thromboembolism in large acute myocardial infarction is achieved by low dose heparin, although early mobilization is important. In addition, many of the patients at risk merit full dose anticoagulation to prevent intracardiac thromboembolism. Established venous thrombosis is treated effectively by intravenous heparin, followed by warfarin to keep the prothrombin time at 1.2 to 1.5 times control, as assessed using rabbit thromboplastin; most patients need three months of treatment. Anticoagulation is warranted for pulmonary embolism, with fibrinolytic therapy reserved for patients with massive embolism and hemodynamic compromise. Embolectomy is a heroic measure, which may occasionally be lifesaving.

Effect of early anticoagulation on the frequency of left ventricular thrombi after anterior wall acute myocardial infarction

To determine the effect of early anticoagulation on the incidence of left ventricular thrombi complicating anterior acute myocardial infarction (AMI), 82 consecutive patients admitted within 12 hours of symptom onset and with electrocardiographic changes consistent with anterior AMI were randomly assigned to 1 of 2 treatment groups. Group 1 patients received high-dose intravenous heparin to maintain the whole blood clotting time between 15 and 20 minutes, and commenced warfarin therapy within 48 hours. Group 2 patients received low-dose subcutaneous heparin and warfarin therapy if the peak creatine kinase level was more than 1,000 U/liter. Eighteen group 2 patients received warfarin, but none had a therapeutic prothrombin ratio within 5 days. The presence and morphologic characteristics of thrombus were assessed by serial 2-dimensional echocardiography. Thirty patients were excluded because AMI was not confirmed or because of technically unsatisfactory echocardiograms, death, surgery or, in group 1 patients, inadequate anticoagulation. Thrombi were identified in 29 of 52 patients (56%): in 14 of 25 group 1 patients (56%) and 15 of 27 group 2 patients (56%). Twenty-three thrombi formed within 3 days. Thrombi were protruding rather than mural only in 3 group 2 patients. The groups did not differ in baseline characteristics or in incidence, time of appearance or morphologic characteristics of thrombus (p greater than 0.05, beta for more than 25% reduction in incidence with group 1 treatment less than 0.10). Systemic embolism occurred only in 1 group 2 patient with mural thrombus.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effect of smoking on fibrinolysis: increase in the activity level of circulating extrinsic (tissue-type) plasminogen activator

The acute effect of cigarette smoking on the fibrinolytic enzyme system in blood was studied. It was found imperative to have an initial 30 min rest period, after venipuncture, to obtain a stable baseline in the fibrinolytic studies. The average heart rate, in inhaling smokers, increased from 64 to a peak of 79 beats min-1, 5-10 min after commencement of smoking. A peak in fibrinolytic activity was found to occur later, at 22.5 min. Analysis of the increase in fibrinolytic activity revealed no demonstrable activation of intrinsic systems via factor XII, nor changes in plasminogen, prekallikrein and C1-inactivator. No plasmin-alpha 2-antiplasmin complexes were detectable. The increase (P less than 0.01) was found to be due to extrinsic (tissue-type) plasminogen activator, revealed as C1-inactivator-resistant plasminogen activator activity, and further identified by quenching with anti-tissue plasminogen activator IgG. Thus, smoking appears to elicit a significant increase in the level of activity of circulating extrinsic plasminogen activator.

Randomized versus historical controls for clinical trials

To compare the use of randomized controls (RCTs) and historical controls (HCTs) for clinical trials, we searched the literature for therapies studied by both methods. We found six therapies for which 50 RCTs and 56 HCTs were reported. Forty-four of 56 HCTs (79 percent) found the therapy better than the control regimen, but only 10 of 50 RCTs (20 percent) agreed. For each therapy, the treated patients in RCTs and HCTs of the same therapy was largely due to differences in outcome for the control groups, with HCT control patients generally doing worse than the RCT control groups. Adjustment of the outcomes of the HCTs for prognostic factors, when possible, did not appreciably change the results. The data suggest that biases in patient selection may irretrievably weight the outcome of HCts in favor of new therapies. RCTs may miss clinically important benefits because of inadequate attention to sample size. The predictive value of each might be improved by reconsidering the use of p less than 0.05 as the significance level for all types of clinical trials, and by the use of confidence intervals around estimates of treatment effects.

Prevention of pulmonary emboli in a respiratory intensive care unit: efficacy of low-dose heparin

Ninety-eight patients admitted to our respiratory intensive care unit during a one-year period were compared retrospectively with 99 well-matched patients admitted during a second one-year period. The use of prophylactic low-dose heparin in the second year was associated with a significant decrease in pulmonary emboli documented by ventilation-perfusion scan, pulmonary angiography, and autopsy. No specific bleeding complications could be directly attributed to the use of low-dose heparin. The frequency and severity of gastrointestinal hemorrhage as determined by hemoglobin fall and transfusion requirements were not significantly affected by the prophylactic use of low-dose heparin. Low-dose heparin appears to be effective and safe in respiratory intensive care unit patients in the prevention of pulmonary emboli.

Leucocyte ascorbate levels and postoperative deep venous thrombosis

Forty-four general surgical patients were included in a prospective, randomized double-blind controlled trial of ascorbic acid (500 mg b.d.) or placebo for 7 days before operation. This was to test the hypothesis that vitamin C may reduce the instance of deep venous thrombosis postoperatively. Venous blood samples were taken before entering the trial, just immediately before surgery, on the day of operation and on three further occasions at 3-day intervals postoperatively for leucocyte ascorbic acid concentration (LAC). Venous thrombosis was diagnosed using the 125I-fibrinogen test and the leg scans interpreted by Roberts' criteria. There was no significant difference in the incidence of DVT between the treatment and placebo groups. In those with DVT (n = 23) the mean LAC on the day of operation was not significantly different from that in those without DVT. However, on the sixth and ninth postoperative days LAC levels were significantly lower in the DVT group. These results suggest that the administration of ascorbic acid preoperatively does not reduce the incidence of DVT, but a striking decrease in the LAC levels in the DVT patients is in keeping with the hypothesis that the initial event in the pathogenesis of DVT is adherence of leucocytes to the venous endothelium.