Hemorrhagic complications of long-term anticoagulant therapy

The historical origins of modern international normalized ratio targets

Prothrombin time (PT) and its derivative international normalized ratio (INR) are frequently ordered to assess the coagulation system. Plasma transfusion to treat incidentally abnormal PT/INR is a common practice with low biological plausibility and without credible evidence, yet INR targets appear in major clinical guidelines and account for the majority of plasma use at many institutions. In this article, we review the historical origins of INR targets. We recount historical milestones in the development of the PT, discovery of vitamin K antagonists (VKAs), motivation for INR standardization, and justification for INR targets in patients receiving VKA therapy. Next, we summarize evidence for INR testing to assess bleeding risk in patients not on VKA therapy and plasma transfusion for treating mildly abnormal INR to prevent bleeding in these patients. We conclude with a discussion of the parallels in misunderstanding of historic PT and present-day INR testing with lessons from the past that might help rationalize plasma transfusion in the future.

A Pharmacotherapy Clinic in a Neurologic Practice

Background:

Limited information exists on therapeutic drug monitoring of neurology patients. Although multiple reviews on anticoagulation clinics have shown good outcomes, the therapeutic endpoints achieved in patients enrolled in a pharmacotherapy clinic serving only those with a history of stroke/transient ischemic attack (TIA) have not been noted previously.

Objective:

To illustrate the drug therapy management role of a pharmacotherapist in a neurology clinic and provide evidence on the quality of the service by presenting data on therapeutic endpoints in the subset of patients who are on anticoagulant therapy for stroke prevention.

Methods:

Reported therapeutic endpoints included recurrent stroke/TIA, bleeding, time in therapeutic range (international normalized ratio [INR] range 2–3), adherence, and patient satisfaction with pharmaceutical care. Patients completed the Morisky self-report compliance questionnaire and the Pharmaceutical Care Satisfaction Questionnaire. Other information included medical history, medications, anticoagulation rationale, referring service, and therapeutic endpoints.

Results:

There were few adverse outcomes of bleeding or stroke. Time in therapeutic range for an INR of 2–3 was 59.67%. Of 251 INRs, 2 (0.8%) were greater than 5. Patient satisfaction with pharmaceutical care was high, as was adherence.

Conclusions:

The incidence of recurrent stroke/TIA and bleeding was rare, despite the inherently higher bleeding risk for stroke patients. Times in range of INRs were equivalent to those of other anticoagulation clinics. Patient satisfaction and adherence were good despite polypharmacy. Pharmacotherapists can be valuable additions to neurology clinics by helping neurologists in the management of the pharmacotherapy of their patients, including those on anticoagulation therapy for stroke/TIA.

The decision to anticoagulate: assessing whether benefits outweigh the risks for patients with atrial fibrillation

In a review of relevant articles from the Medline database on stroke risk in atrial fibrillation (AF) and adverse events related to anticoagulation treatment, we found that research to date shows a major potential benefit of warfarin therapy (International Normalized Ratio [INR] 2.0-3.0) for patients with AF (68% risk reduction in primary stroke prevention with warfarin vs. placebo). Despite this highly significant reduction in stroke risk, fewer than 50% of eligible patients are treated, in many cases because of fears of intracranial hemorrhage (ICH). The decision to implement anticoagulant therapy to improve outcome requires balancing the decreased risk for stroke against the increased risk for ICH. Various methods have been developed to define patient-specific stroke risk. In contrast, risk for ICH strongly correlates with the intensity of anticoagulation, which is an unpredictable but controllable variable requiring frequent dose adjustments. Recent studies have also identified subgroups of patients with neurologic pathologies who are at increased risk for ICH. However, when the INR is properly controlled, the benefit from anticoagulation therapy for patients with AF and other risk factors for stroke exceeds the risk for ICH. Careful monitoring of anticoagulation and warfarin dose titration to maintain the INR between 2.0 and 3.0 is critical for reducing the risk for ICH, as is excluding patients with neurologic conditions that increase the likelihood of ICH. Future developments, such as the introduction of oral direct thrombin inhibitors with more predictable pharmacokinetics than warfarin, may further improve the benefit-to-risk ratio of anticoagulation therapy for patients with AF.

Hemorrhagic Complications of Anticoagulant Treatment

This chapter about hemorrhagic complications of anticoagulant treatment is part of the seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Bleeding is the major complication of anticoagulant therapy. The criteria for defining the severity of bleeding varies considerably between studies, accounting in part for the variation in the rates of bleeding reported. The major determinants of vitamin K antagonist-induced bleeding are the intensity of the anticoagulant effect, underlying patient characteristics, and the length of therapy. There is good evidence that vitamin K antagonist therapy, targeted international normalized ratio (INR) of 2.5 (range, 2.0 to 3.0), is associated with a lower risk of bleeding than therapy targeted at an INR > 3.0. The risk of bleeding associated with IV unfractionated heparin (UFH) in patients with acute venous thromboembolism (VTE) is < 3% in recent trials. This bleeding risk may increase with increasing heparin dosages and age (> 70 years). Low molecular weight heparin (LMWH) is associated with less major bleeding compared with UFH in acute VTE. UFH and LMWH are not associated with an increase in major bleeding in ischemic coronary syndromes, but are associated with an increase in major bleeding in ischemic stroke. Information on bleeding associated with the newer generation of antithrombotic agents has begun to emerge. In terms of treatment decision making for anticoagulant therapy, bleeding risk cannot be considered alone, ie, the potential decrease in thromboembolism must be balanced against the potential increased bleeding risk.

Mechanical Prosthetic Valve Thrombosis: Case Report and Review of the Literature

Mechanical prosthetic valve thrombosis is a life-threatening complication necessitating immediate intervention. The presenting signs and symptoms of this illness are somewhat variable, but physical examination and transesophageal echocardiography enable rapid diagnosis. To avoid catastrophic complications, valve replacement or debridement, or thrombolysis in the correct setting, must be performed without delay. It is not entirely clear which therapy is superior. For any given patient, the risks of thrombolytic therapy, including bleeding, systemic embolism, and failure to restore valvular function, must be weighed against the risks of surgical intervention. Once the decision is made to operate, the choice of valve replacement versus debridement is one best made intraoperatively, upon visual inspection of the valve apparatus. Despite aggressive therapy, morbidity and mortality from prosthetic valve thrombosis and its treatment are not trivial. Fortunately, with current prosthetic devices and aggressive prophylactic anticoagulation, the incidence of prosthetic valve thrombosis remains low. Antiplatelet therapy may offer additional benefit to patients being prophylaxed with warfarin. This report details the case of a woman with aortic and mitral prosthetic valves who presented with heart failure and evidence of severe aortic prosthetic dysfunction after a period of suboptimal anticoagulation. She successfully underwent debridement of the mitral prosthesis and replacement of the aortic valve. The relevant literature is reviewed.

Ischemic stroke after acute myocardial infarction. A population-based study

BACKGROUND AND PURPOSE

Modern treatment may have influenced the risk of stroke after myocardial infarction (MI). The purpose of this study was to examine the incidence of ischemic stroke during the first month after an acute MI in an unselected population, to identify predictors of MI-related stroke, and to investigate the secular trend in MI-related stroke incidence.

METHODS

In this case-control study, from a population of approximately 310000 25- to 74-year-old inhabitants, case subjects with a stroke within 1 month after an MI were prospectively recorded in the population-based Northern Sweden MONICA (Monitoring of Trends and Determinants in Cardiovascular Disease) study from 1985 to 1994. The same number of control subjects with an MI but without a stroke were matched for age, sex, and year when MI occurred.

RESULTS

One hundred twenty-four case subjects were recorded. Fifty-one percent (63/124) of the strokes occurred within 5 days after onset of MI. The odds ratios (ORs) of an MI-related stroke were for a history of hypertension 1.7 (95% confidence interval [CI], 1.0 to 3.2), previous stroke 2.4 (CI, 1.0 to 6.1), chronic atrial fibrillation 3.0 (CI, 1.1 to 9.2), onset of atrial fibrillation during the hospital stay 3.5 (CI, 1.4 to 10.1), ST-segment elevation 2.4 (CI, 1.4 to 4.6), and anterior infarction 1.5 (CI, 0.9 to 2.6). In a conditional multiple logistic regression model, previous stroke (OR, 2.8; CI, 1.1 to 7.6), chronic atrial fibrillation (OR, 3.8; CI, 1.3 to 11.0), new-onset atrial fibrillation (OR, 4.6; CI, 1.6 to 12.8), and ST-segment elevation (OR, 3.4; CI, 1.6 to 7.4) were independent predictors of stroke. MIs preceding stroke were larger and in 51% were located anteriorly. There was a decrease in the incidence and event rate of MI-related stroke during the study period (P < .01 and P < .05, respectively).

CONCLUSIONS

The risk of stroke is highest the first 5 days after MI. Only approximately half of the strokes occurring the first month after an MI are preceded by an anterior MI. The most important predictors of MI-related stroke are atrial fibrillation (chronic or new onset), ST elevation, and a history of a previous stroke. There is a long-term trend toward a lower incidence of MI-related stroke. These findings have important implications concerning both the pathophysiology and prevention of MI-related stroke.

Long term follow up of patients with anterior myocardial infarction complicated by left ventricular thrombus in the thrombolytic era

OBJECTIVES

To examine the appearance and resolution of left ventricular thrombi and to study the relation between thrombus and mortality during long term follow up after anterior myocardial infarction.

DESIGN

Ninety nine consecutive patients were prospectively studied until the last included patient had been followed for one year. Streptokinase and aspirin were used routinely, anticoagulants only after a decision by the attending physician. Echocardiography was performed within 3 d of admission, before discharge, and after one, three, and 12 months.

SETTING

Umeå University Hospital, a teaching hospital in Northern Sweden.

MAIN OUTCOME MEASURES

Left ventricular thrombus, segmental myocardial function, and mortality during follow up.

RESULTS

Thirty patients (30%) had a thrombus on discharge. One month, three months, and 12 months after hospital discharge, the thrombus had resolved in 81%, 84%, and 90% of the patients, respectively. The proportion of resolved thrombi at one month was high irrespective of whether anticoagulants were given (10/11, 91%) or not (12/16, 75%), P = 0.4. New thrombi appeared in 12 patients after discharge and resolution and reapperance of thrombi continued during the follow up period. Patients who developed a thrombus during the hospital stay (n = 44, 44%) had more extensive myocardial dysfunction on discharge (P < 0.001) and significantly higher mortality during the follow up period than those without a thrombus (23% v 7%, P < 0.01).

CONCLUSIONS

With routine thrombolytic and aspirin treatment of anterior myocardial infarction, left ventricular thrombi usually resolve during the first month after hospital discharge. Appearance and resolution of thrombi continue, however, in a significant proportion of the patients during long term follow up. A left ventricular thrombus during the initial hospital stay is associated with high long term mortality.

Risk of stroke during long-term anticoagulant therapy in patients after myocardial infarction

Myocardial infarction survivors have an increased risk of stroke, which is reduced with long-term anticoagulant therapy. However, an estimated 10-times increase in risk of bleeding during such treatment has been reported. We evaluated the risk of stroke in patients after a myocardial infarction and examined the relationship of the risk of intracranial hemorrhage or cerebral infarction and the intensity of anticoagulant therapy. The study population consisted of 3,404 post-myocardial infarction patients who took part in a randomized, double-blind, placebo-controlled trial. Patients were randomized to treatment with anticoagulants (international normalized ratio range, 2.8-4.8) or matching placebo. Mean follow-up was more than 3 years. The incidence of stroke analyzed on "intention-to-treat" was 0.7 per 100 patient-years in the anticoagulant patients against 1.2 in placebo, a hazard ratio of 0.60, with 95% confidence interval of 0.40 to 0.90. In the anticoagulation group, 15 patients had cerebral infarction and 17 an intracranial bleeding, 3 of which occurred after withdrawal of treatment. In the placebo group, the numbers were 43 and 2. Of the 14 intracranial bleeds during anticoagulation, 6 occurred at an international normalized ratio between 3.0 and 4.0 and 8 at greater than 4.0. These results confirm that long-term anticoagulant therapy substantially reduces the risk of stroke in post-myocardial infarction patients. The increased risk of bleeding complications associated with anticoagulant therapy is offset by a marked reduction in ischemic events. The risk of intracranial bleeding is directly related to the intensity of anticoagulant treatment.

Carpentier-Edwards pericardial bioprosthesis in aortic position: long-term follow-up 1980 to 1994

Aortic valve replacement with Carpentier-Edwards pericardial bioprosthesis was associated with excellent midterm clinical results. Long-term evaluation, however, remained to be determined. We reviewed the first 124 patients who underwent aortic valve replacement with a Carpentier-Edwards bioprosthesis at the Hôpital Broussais between 1980 and 1985. There were 67 males (54%) and 57 females (46%). The mean age at operation was 65 years (range, 18-83 years). The operative mortality (30 days) was 4%. All but 2 patients were followed up for an average of 7.7 years and a total of 973 patient years. There were 45 late deaths (4.7%/patient-year) of which 16 were valve-related (1.7%/patient-year). The actuarial survival rate was 49.9% at 12 years. The actuarial rate for freedom from valve-related mortality was 78.3% at 12 years. There were 7 thromboembolic events in 5 patients and 3 anticoagulation-related hemorrhages. Freedom from structural valve deterioration was 100% at 12 years and 83.3% at 13 years. We conclude that implantation of Carpentier-Edwards pericardial bioprosthesis in aortic position is associated with an excellent long-term clinical outcome. It is believed that the improved results of this valve result from the following original features: fully flexible stent, distensible struts, infrastent tissue mounting, optimal tissue orientation, and improved preservation.

Hydroxyurea for patients with essential thrombocythemia and a high risk of thrombosis

BACKGROUND

Abnormalities in the number and function of platelets may contribute to thromboembolic complications in patients with essential thrombocythemia. We assessed whether maintaining the platelet count below 600,000 per cubic millimeter with hydroxyurea reduces the incidence of thrombosis in patients with essential thrombocythemia and a high risk of thrombosis.

METHODS

A total of 114 patients with essential thrombocythemia (77 women and 37 men; median age, 68 years; range, 40 to 85) and a median platelet count of 788,000 per cubic millimeter (range, 533,000 to 1,240,000 per cubic millimeter) were randomly assigned to receive hydroxyurea (56 patients) or no myelosuppressive therapy (58 patients). Ninety-seven (85 percent) were over 60 years old, and 52 (46 percent) had had thrombosis. The two groups were matched for age, sex, and platelet count at randomization. Antiplatelet prophylaxis with aspirin or ticlopidine was not stopped. Follow-up lasted a median of 27 months in both groups.

RESULTS

Two patients (3.6 percent) treated with hydroxyurea had thrombotic episodes (one stroke and one myocardial infarction), whereas 14 patients (24 percent) in the control group had thrombotic episodes (one stroke, five transient ischemic attacks, five peripheral arterial occlusions, one deep-vein thrombosis, and two cases of superficial thrombophlebitis). The difference (20.4 percentage points; 95 percent confidence interval, 8.5 to 32 percent) was statistically significant (chi-square with Yates' correction, 8.3; 1 df; P = 0.003).

CONCLUSIONS

Hydroxyurea is effective in preventing thrombosis in high-risk patients with essential thrombocythemia.

Healthcare as a commons

In September 1994, the New York Times carried a front page article declaring healthcare reform dead in Congress. The obituary on healthcare followed a Congressional decision not to pursue the issue further in 1994. Although Congress and the President will likely revisit healthcare reform during 1995, the choices may be between various incremental steps, rather than substantive changes to bring about universal coverage.

Deep vein thrombosis. Diagnosis and management

In at least 50% of patients with suspected deep vein thrombosis, the diagnosis is not confirmed by objective testing. The addition of impedance plethysmography and real-time B-mode ultrasound with color-enhanced Doppler imaging to the available diagnostic modalities has altered the approach to clinical evaluation. Pharmacologic treatment has evolved to place emphasis on the use of subcutaneous heparins of greater efficacy and the reduction of hemorrhagic risk with the use of the INR system when warfarin is recommended for long-term therapy. Use of new approaches for diagnosis and management offers the potential of more prompt and accurate diagnosis, more effective therapy, and a reduction in the incidence of pulmonary thromboembolism.

Atrial fibrillation: epidemiology and the risk and prevention of stroke

Atrial fibrillation is a common disorder and the incidence increases with each decade of life. Previously, rheumatic mitral valve disease has been the condition most highly associated with atrial fibrillation. However, with the decreasing incidence of rheumatic heart disease, other conditions have assumed greater importance and now congestive cardiac failure, coronary artery disease, and hypertension are the most commonly associated conditions. Nonrheumatic atrial fibrillation is associated with an approximately five-fold increase in the risk of ischemic stroke and a 5% to 7% yearly risk that increases with age. In addition, atrial fibrillation is associated with an increased incidence of silent cerebral infarction and increased mortality. However, whether atrial fibrillation is independently associated with the risk of stroke or is a marker of underlying cardiac disease is contentious. Until recently, the use of preventive therapy has been controversial. However, data from four recently published, prospective randomized studies clearly support the use of warfarin prophylaxis in nonrheumatic atrial fibrillation. Within the diverse group of patients with nonrheumatic atrial fibrillation there are high and low risk subgroups and identification of these may influence decisions regarding antithrombotic prophylaxis. With a few exceptions, however, this remains an area in which there are contradictory findings in the literature. The role of aspirin for prophylaxis in nonrheumatic atrial fibrillation remains unclear and further evaluation awaits the publication of ongoing studies.

Role of prophylactic anticoagulation for direct current cardioversion in patients with atrial fibrillation or atrial flutter

The need for prophylactic anticoagulation to prevent embolism before direct current cardioversion is performed for atrial fibrillation or atrial flutter is controversial. To examine this issue further, a retrospective review was undertaken to assess the incidence of embolic complications after cardioversion. The review involved 454 elective direct current cardioversions performed for atrial fibrillation or atrial flutter over a 7 year period. The incidence rate of embolic complications was 1.32% (six patients); the complications ranged from minor visual disturbances to a fatal cerebrovascular event. All six patients had atrial fibrillation, and none had been on anticoagulant therapy (p = 0.026). The duration of atrial fibrillation was less than 1 week in five of the six patients who had embolic complications. Baseline characteristics of patients with a postcardioversion embolic event are compared with those of patients who did not have an embolic event. There was no difference in the prevalence of hypertension, diabetes mellitus or prior stroke between the two groups, and there was no difference in the number of patients who were postoperative or had poor left ventricular function. Left atrial size was similar between the two groups. No patient in the embolic group had valvular disease. No patient with atrial flutter had an embolic event regardless of anticoagulant status; therefore, anticoagulation is not recommended for patients with atrial flutter undergoing cardioversion. Prophylactic anticoagulation is pivotal in patients undergoing elective direct current cardioversion for atrial fibrillation, even those with atrial fibrillation of less than 1 week's duration.

Oral anticoagulant therapy. Newer indications and an improved method of monitoring

Oral anticoagulants remain time-tested therapeutic agents. A number of new indications for use of these drugs have recently emerged, especially nonvalvular atrial fibrillation. New information on the factors associated with adverse reactions to oral anticoagulants is available, along with improved knowledge on how to evaluate and treat such complications. A major advance in the safer use of these drugs in North America will accompany increased application of the International Normalized Ratio in reporting prothrombin time.

Dilated cardiomyopathy with mitral regurgitation: decreased survival despite a low frequency of left ventricular thrombus

Ninety-one patients with dilated cardiomyopathy were studied by two-dimensional, pulsed, and color Doppler echocardiography (1) to detect and quantify mitral regurgitation (MR), (2) to record apical flow velocities in systole and diastole, and (3) to detect the presence of left ventricular thrombi. MR was detected in 57% of the patients and thrombi were present in 40%, but the occurrence of both MR and thrombus was rare (8%). Apical flow velocity was significantly higher throughout the cardiac cycle in the group with MR (diastole 15 +/- 7 vs 9 +/- 7 cm/sec; systole 29 +/- 12 vs 16 +/- 13 cm/sec; p less than 0.001 for both), accounting for the rarity of thrombi in this group. Follow-up data on 89% of the patients showed markedly decreased survival in the group with MR (22% vs 60% at 32 +/- 6 months, p less than 0.005), and this was evident even in patients with mild MR. Thus although MR is a noninvasively obtainable marker of a large subgroup of patients with dilated cardiomyopathy "protected" from left ventricular thrombus formation, it is a sensitive marker of decreased survival.

Predictors of left atrial thrombus in mitral valve disease

OBJECTIVE

To determine the risk factors for left atrial thrombus (LAT) and the prevalence of thrombi in cases of mitral valve disease whose severity was judged to necessitate surgical intervention.

DESIGN

Hospital record review of all operative cases from 1982 to 1985.

SETTING

A community serving a referral population encompassing 1.5 million people. Only two hospitals in the geographic area performed cardiac surgery, and both hospitals' records were reviewed.

PATIENTS

All 372 patients who underwent either mitral valve replacement or open mitral commissurotomy.

MAIN RESULTS

Twenty-six patients (7%) were noted to have LAT at surgery. Five preselected factors were significantly (p less than 0.05) associated with LAT in univariate analysis: female gender, prior history of embolism, prior anticoagulant therapy, mitral stenosis (MS), and atrial fibrillation (AF). In logistic regression analysis, only MS and AF remained as significant independent predictors of LAT. Mitral stenosis patients in sinus rhythm had a relatively low [2.4 +/- 3.3% (observed +/- 95% confidence interval)] likelihood of having an LAT. Likewise, mitral regurgitation patients in sinus rhythm (n = 139) had an extremely low (0.7 +/- 1.4%) prevalence of LAT. In contrast, MS patients in AF (n = 122) had a prevalence of LAT of 18.0 +/- 6.8%.

CONCLUSIONS

These findings indicate that, overall, LAT in mitral valve disease may be less common than previous studies have suggested. In addition, mitral valve disease patients who remain in sinus rhythm appear to have a low risk of harboring an LAT. Conversely, MS patients, especially those in AF, appear to be at high risk of harboring an LAT. These results may be helpful in formulating strategies for the use of prophylactic anticoagulation in categories of patients with clinically severe mitral valve disease, or perhaps in estimating the likelihood of a cardiac source of embolism in mitral valve disease patients with suspected cerebral or peripheral emboli.

Factors relevant to preventing embolic stroke in patients with non-rheumatic atrial fibrillation

Whether or not to treat patients with non-rheumatic atrial fibrillation with anticoagulants to prevent embolic stroke is a dilemma for physicians. If randomized trials, currently underway, demonstrate a beneficial effect, the dilemma will not be solved because not all of the relevant factors can be addressed by trials. We used current knowledge about non-rheumatic atrial fibrillation and a method of obtaining patient-derived weights for avoiding stroke from eight medically trained subjects, to determine the overall benefit of anticoagulants and to see what factors were relevant and what effect each might have in deciding whether to use anticoagulant therapy. Using standard assumptions, anticoagulants gave an expected benefit for all subjects. The expected benefit (expressed in terms of lives per 1000 saved due to anticoagulants) varied between 5.4 and 46.7. This benefit remained for all subjects when we did a sensitivity analysis for different rates of stroke prevented by anticoagulants and different rates of intracranial hemorrhage caused by anticoagulants. When we used different baseline rates of stroke and different impacts of major hemorrhagic complications the benefit disappeared for 3 and 4 subjects respectively. We found the factors that were most crucial to the decision will not be included in randomized trials; the weight that an individual would place on avoiding embolic stroke vs the risk of intracranial bleeding from anticoagulant therapy; and the rate of embolic stroke that could be expected for the subject at risk. Factors which will be measured in randomized trials, will change results less substantially: the increased risk of major hemorrhages; the proportion of strokes that could be prevented by treatment; the increase in risk of intracranial hemorrhage. This method of analysis suggests that for most patients anticoagulants are beneficial and that the most important factor in determining this result is the value that subjects put on different outcomes.

A bleeding risk index for estimating the probability of major bleeding in hospitalized patients starting anticoagulant therapy

PURPOSE

To construct and test prospectively a bleeding risk index for estimating the probability of major bleeding in hospitalized patients starting long-term anticoagulant therapy.

PATIENTS AND METHODS

In an inception cohort of 617 patients starting long-term anticoagulant therapy in one hospital, data were gathered retrospectively and bleeding was classified using reliable explicit criteria. We constructed a bleeding risk index by identifying and weighting independent predictors of major bleeding using a multivariate proportional-hazards model. The bleeding risk index was tested in 394 other patients prospectively identified in a second hospital. The index was compared to physicians' predictions.

RESULTS

Major bleeding developed before discharge in 61 of all 1,011 patients (6%). The bleeding risk index included four independent risk factors for major in-hospital bleeding: the number of specific comorbid conditions; heparin use in patients aged 60 years or older; maximal prothrombin or partial thromboplastin time 2.0 or more times control; liver dysfunction worsening during therapy. In the testing group, the index predicted major bleeding, which occurred in 3% of 235 low-risk patients, 16% of 96 middle-risk patients, and 19% of 63 high-risk patients (p less than 0.001). The bleeding risk index performed as well as physicians' predictions, and integration of the bleeding risk index with physicians' predictions led to a classification system that was more sensitive (p = 0.03) than physicians' predictions alone. In 86% of patients with a high risk of major bleeding, we identified specific ways of improving therapy, e.g., avoiding overanticoagulation and nonsteroidal anti-inflammatory agents.

CONCLUSION

The bleeding risk index provides valid estimates of the probability of major bleeding in hospitalized patients starting long-term anticoagulant therapy and complements physicians' predictions. The possibility that bleeding can be prevented in high-risk patients warrants prospective evaluation.

Is atrial fibrillation an independent risk factor for stroke?

That non-rheumatic atrial fibrillation is an independent risk factor for cerebral infarction has not been established with certainty. The rationale underlying contemporary clinical trials of warfarin therapy for the prevention of stroke in patients who have non-rheumatic atrial fibrillation is that the majority of strokes in such patients are due to cardiogenic cerebral embolism. However, there is evidence to suggest that the increased probability of stroke attributed to this arrhythmia is due to its association with other risk factors such as hypertension, diabetes mellitus, and atherosclerosis. The question of who should be anticoagulated is a major public health issue since atrial fibrillation is present in approximately ten per cent of the general population aged 65 or more years.

Trial of different intensities of anticoagulation in patients with prosthetic heart valves

We compared the efficacy and complications of anticoagulation with warfarin in 258 patients with prosthetic heart valves treated with regimens of "moderate intensity" (prothrombin-time ratio, 1.5; international normalized ratio, 2.65) or "high intensity" (prothrombin-time ratio, 2.5; international normalized ratio, 9) in a prospective, randomized study. The two patient groups were followed up for 421 patient-years and 436 patient-years, respectively. Eleven patients were lost to follow-up. Thromboembolism occurred with similar frequency in the two groups (4.0 and 3.7 episodes per 100 patient-years, respectively), but there was a total of 6.2 bleeding episodes per 100 patient-years in the moderate-intensity group, as compared with 12.1 episodes in the high-intensity group (P less than 0.002). There were 5.2 episodes of minor bleeding per 100 patient-years in the moderate-intensity group, as compared with 10.1 episodes in the high-intensity group (P less than 0.01). Major bleeding was also more common in the high-intensity group (2.1 episodes per 100 patient-years--including the only two fatal hemorrhages--as compared with 0.95 episode in the moderate-intensity group), but the difference was not statistically significant. We conclude that a moderate anticoagulant effect (prothrombin-time ratio, about 1.5) in patients with a mechanical prosthetic heart valve offers protection equivalent to that of more intensive therapy, but at a significantly lower risk.

Ten-year results with the St. Jude Medical prosthesis

Although the hemodynamic characteristics and durability of the St. Jude valve prosthesis have been reported, the need for and the degree of anticoagulation in patients who receive these valves remain uncertain. Our 10-year experience with 165 patients (100 men and 65 women, mean age of 58 +/- 13 years), who underwent valve replacement with St. Jude prostheses, is reported. Of the 165 patients, 147 were treated with warfarin. A prothrombin time 1.3 to 1.8 times control (range 15 to 20 seconds) was maintained in 134 patients with single valve and 1.8 to 2 times control (range 20 to 25 seconds) in 13 patients with double valve prostheses. The 10-year actuarial event-free incidence from thromboembolic and hemorrhagic complications was 84 and 95%, respectively. Of the 8 patients receiving antiplatelet therapy alone, 4 had thromboembolic events. Of the 10 patients on neither warfarin nor antiplatelet therapy, 3 had thromboembolic events. The 10-year actuarial event-free incidence from valve failure was 95%. The 10-year actuarial patient survival was 55%. Thus, the St. Jude valve is a safe and reliable prosthesis with acceptable overall long-term performance in patients given a modest anticoagulation regimen. Patients who receive St. Jude prosthetic valves without anticoagulants have a high incidence of thromboembolic events despite therapy with antiplatelet agents.

The effects of long-term antithrombotic treatment on left ventricular thrombi in patients after an acute myocardial infarction

Sixty patients (48 men and 12 women; aged 36 to 72 years, mean 48 +/- 9), who survived an acute anterior myocardial infarction and in whom left ventricular thrombus was detected by cross-sectional echocardiography 1 to 2 days before they were discharged from the hospital, were prospectively studied. All had evidence of left apical wall motion abnormalities. They were randomly divided into three groups of 20 patients each. Group A was given a full dose of oral anticoagulants, group B was given aspirin, 650 mg/day, and group C received no antithrombotic therapy. Echocardiography was performed every 3 months in all patients, and they were followed for 9 to 24 months (mean 16 +/- 5 months). Twelve patients in group A had complete resolution of the thrombus and three had a significant decrease in the size of the thrombus (greater than or equal to 50% of initial thickness) during the first trimester after acute infarction. In group B the thrombus resolved in nine patients and was significantly diminished in four during the first trimester of follow-up. In group C the thrombus resolved in two patients during the first trimester and showed a significant decrease in size in two patients during the second trimester of follow-up. Two patients in group C initially had recurrent transient cerebral ischemic attacks, which did not recur after aneurysmectomy. One patient in group C had a peripheral embolic episode in the femoral artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Discrepant INR values: a comparison between Manchester and Thrombotest reagents using capillary and venous samples

The International Sensitivity Index (ISI) for different thromboplastin reagents is obtained by calibration against WHO reference preparations. It is hoped that calculation of the International Normalized Ratio (INR) from the ISI will permit accuracy and conformity in reporting laboratory assays of warfarin effect even across a range of different techniques. We have examined the INR values of 128 warfarin patients obtained by four different techniques in common use, namely venous and capillary Thrombotest and venous and capillary Manchester reagent. Discrepant INR values were obtained. The mean Manchester venous INR values were lower than those obtained by the other three methods (P less than 0.0001). This suggests that patients dosed by reference to Manchester venous INR are liable to receive more warfarin than those dosed by the other methods.

Major bleeding in outpatients treated with warfarin: incidence and prediction by factors known at the start of outpatient therapy

PURPOSE

To determine the incidence of major bleeding in outpatients treated with warfarin and to identify predictive factors known at the start of therapy.

PATIENTS AND METHODS

The records of 565 patients starting outpatient therapy with warfarin upon discharge from a university hospital were reviewed. Follow-up information was obtained for 562 patients (99.5%). Bleeding was classified as major or minor using explicit criteria. The cumulative incidence of bleeding was estimated by means of survival analysis. Independent risk factors for major bleeding were identified using Cox regression analysis in 375 randomly chosen patients; they were tested in the remaining 187 patients.

RESULTS

Major bleeding occurred in 65 patients (12%) and was fatal in 10 patients (2%). The cumulative incidences of major bleeding at one, 12, and 48 months were 3%, 11%, and 22%, respectively. The monthly risk of major bleeding decreased over time, from 3% during the first month of outpatient therapy to 0.3% per month after the first year of therapy. Five independent risk factors for major bleeding--age 65 years or greater, history of stroke, history of gastrointestinal bleeding, a serious comorbid condition (recent myocardial infarction, renal insufficiency, or severe anemia), atrial fibrillation--predicted major bleeding in the testing group; the cumulative incidence of major bleeding at 48 months was 2% in 57 low-risk patients, 17% in 110 middle-risk patients, and 63% in 20 high-risk patients.

CONCLUSION

These findings provide a quantitative basis for evaluating the risk of major bleeding in individual patients at the start of outpatient therapy with warfarin. Whether the risk of bleeding can be reduced in high-risk patients without reducing the benefit of therapy remains to be determined.

Bleeding in outpatients treated with warfarin: relation to the prothrombin time and important remediable lesions

PURPOSE

To determine the relation of bleeding to prothrombin times and important remediable lesions in outpatients treated with warfarin.

PATIENTS AND METHODS

An inception cohort of 565 patients starting outpatient therapy with warfarin on discharge from a university hospital was assembled. Detailed records of outpatient prothrombin times were obtained for 103 of 130 case subjects with major or minor bleeding and for 117 control patients without bleeding. A nested case-control design was used to evaluate the association of bleeding with temporally related prothrombin times; odds ratios were estimated using multivariate logistic regression analysis to control for known predictors of major bleeding. The relation of bleeding to important remediable lesions was determined in all 130 cases of bleeding.

RESULTS

For each 1.0 increase in the prothrombin time-to-control ratio, the odds ratio for major bleeding during the week after a prothrombin time measurement increased 80%; the odds ratio for minor bleeding increased 50%. These odds ratios were lower during the first month of therapy and higher thereafter. Bleeding was related to important remediable lesions in 49 of 130 cases (38%), but these lesions were unknown before bleeding in only 22 cases (17%). The mean prothrombin time rose sharply at the time of bleeding in patients without important remediable lesions, but not in patients with lesions. New, previously unknown lesions (including nine malignancies) were discovered in 20 of 59 case subjects (34%) with gastrointestinal bleeding or hematuria, but in only two of 71 case subjects (3%) with other bleeding (p less than 0.001).

CONCLUSION

Our results provide a valid quantitative basis for estimating the odds of bleeding in relation to the prothrombin time and the yield of diagnostic evaluation in patients with bleeding.

Warfarin for dilated cardiomyopathy: a bloody tough pill to swallow?

Although current recommendations for the treatment of dilated cardiomyopathy include long-term anticoagulation to diminish the likelihood of systemic embolization, there have been no clinical trials examining the effectiveness of anticoagulation in preventing systemic embolization in these patients. Furthermore, those recommendations do not address the issue of the quality of life associated with long-term warfarin therapy. Using decision analysis, the authors examined the benefits and risks of long-term anticoagulation for patients 35 to 75 years of age who have dilated cardiomyopathy. The results show that anticoagulant therapy increases quality-adjusted life expectancy by 76 to 128 days, depending on the patient's age. Sensitivity analysis, however, demonstrates that the outcome is dependent on the disutility associated with long-term warfarin therapy. Interestingly, anticoagulation exerts most of its benefit by preventing pulmonary embolization, not systemic embolization. The authors conclude that the current recommendation to anticoagulate these patients, although probably correct for many patients, should take into consideration the change in lifestyle imposed by long-term anticoagulant therapy. For some patients, the benefit may not outweigh the sacrifice.

Haemorrhagic and thromboembolic complications in patients with atrial fibrillation on anticoagulant prophylaxis

We studied clinically relevant haemorrhagic and thromboembolic events in 213 patients with atrial fibrillation (AF) during 818 patient-years of anticoagulant (AC) treatment. The incidence of complicating events per 100 patient-years of treatment in three groups of patients, those with mitral valve disease (MVD; n = 34), without MVD (n = 102) and those with previous thromboembolism (TE; n = 77) was: major peripheral haemorrhages 3.1, 3.3 and 8.2 (non-MVD vs. TE group, P less than 0.05), cerebrovascular events 3.9, 3.0 and 3.0 (NS), and peripheral arterial thromboembolism 0, 0 and 1.5 (non-MVD vs. TE group, P less than 0.05). The proportion of thrombotest values less than 5 and/or greater than 20% at regular check-ups was 9.8% in patients with and 6.9% in patients without major peripheral haemorrhages (P less than 0.01). Major peripheral haemorrhages are frequent in patients with AF receiving AC treatment. They are most likely to occur in those with previous thromboembolism and among those with unstable AC control.

Treatment of envenomation by Echis coloratus (mid-east saw scaled viper): a decision tree

Envenomation by Echis coloratus causes a transient hemostatic failure. Systemic symptoms, hypotension and evident bleeding are rare, with only one reported fatality. In this paper, we examine the decision to treat victims of Echis coloratus by a specific horse antiserum. The decision model considers the mortality of treated and untreated envenomation, and the side effects of antiserum treatment: fatal anaphylaxis, serum sickness and increased risk of death after a possible repeated exposure to horse antiserum in the future. The results of the analysis are not sensitive to variations in the probability of side effects of antiserum treatment. They are sensitive to variations in the risk of bleeding after envenomation, in the degree of reduction of this risk by antiserum treatment and in the risk of dying after an event of bleeding. Prompt administration of antiserum appears to be the treatment of choice if it reduces the risk of bleeding from 23.6% to 20.3% and if 1.6% or more of the bleeding events are fatal. We conclude that presently available data support antiserum treatment of victims of Echis coloratus who present with hemostatic failure, even though the advantage imparted by this treatment appears to be small.

Prothrombin time ratio and other factors associated with bleeding in patients treated with warfarin

We previously showed that the risk of major hemorrhage in patients with venous thromboembolism treated with warfarin was strongly related to duration of anticoagulant therapy. We here report the results of a more detailed analysis of factors other than duration of warfarin therapy associated with the risk of hemorrhage in these patients. Almost 7% of patients had a major hemorrhage on warfarin and an additional 23.7% had at least one minor bleeding episode. Age, female sex, and congestive heart failure were associated with small increases in the risk of major hemorrhage but not with the risk of minor bleeding. A prothrombin time ratio greater than 2.5 was associated with a fourteen-fold increase in the risk of a major hemorrhage (95% CI 5.1, 42.7), but major hemorrhages occurred in patients on warfarin at all measured values of the prothrombin time ratio. Taken together with the findings from our previous analysis, the study suggests that prevention of bleeding in patients on warfarin would best be accomplished by minimizing the duration of warfarin therapy, by scrupulous monitoring of the prothrombin time ratio, and by considering the "therapeutic range" for the prothrombin time ratio to be somewhat less than 2.0-2.5.

The bleeding severity index: validation and comparison to other methods for classifying bleeding complications of medical therapy

Reports of bleeding complications of medical therapy should be based on valid methods of classification, but the reproducibility of existing methods has not been tested. Therefore, we prospectively studied three methods to classify the severity of bleeding: a purely subjective implicit method, a previously published explicit method using brief criteria, and the bleeding severity index, which is a new explicit method using detailed criteria about the amount, rate, and consequences of bleeding. Three physicians independently reviewed abstracts of 168 patients treated with anticoagulants. The proportion of cases classified as major bleeding varied widely when the implicit method was used (2, 14 and 39%), less when the old explicit method was used (28, 40 and 47%), and not at all when the new bleeding severity index was used (20, 20 and 20%). Intraobserver agreement was excellent for both explicit methods (kappa greater than or equal to 0.95). However, interobserver agreement was better for the bleeding severity index (kappa = 0.87) than for the old explicit method (kappa = 0.69) or the implicit method (kappa = 0.39). We conclude that the classification of bleeding complications of medical therapy depends on the method used. In comparison to older methods, the bleeding severity index is highly reproducible and should be tested more widely to determine whether it can be applied to the burgeoning clinical research in anticoagulation and thrombolysis.

Fate of left ventricular thrombi in patients with remote myocardial infarction or idiopathic cardiomyopathy

Although left ventricular thrombi that form acutely after myocardial infarction frequently resolve spontaneously or with anticoagulant therapy, the fate of left ventricular thrombi in patients with remote myocardial infarction or with idiopathic cardiomyopathy remains unknown. To determine the natural history of such chronic left ventricular thrombi, we performed serial echocardiograms on 51 patients with remote myocardial infarction (greater than or equal to 3 months; mean, 31 +/- 41 months) and on nine patients with idiopathic dilated cardiomyopathy. Mean follow-up was 24 +/- 22 months during which 3.5 +/- 1.4 echocardiograms were obtained. Studies were interpreted by blinded observers, and an increase or decrease of more than 5 mm in maximal thrombus thickness was defined as significant. Among all 60 patients left ventricular thrombi were unchanged in 24 (40%), completely resolved in 24 (40%), decreased in size in four (7%), increased in size in five (8%), and decreased and then increased in size in three (5%). Results in patients with remote infarction and idiopathic cardiomyopathy were similar. Warfarin therapy, which was at the discretion of the primary physician, was associated with a higher prevalence of thrombus resolution compared with no therapy (59% vs. 29%, p = 0.02). Definite systemic emboli occurred in seven patients (12%), all at times while they were not anticoagulated. Among the 48 thrombi that were present on two or more echocardiograms, changes in thrombus shape (classified as protruding or flat) occurred in only 16%, and changes in thrombus movement (classified as mobile or immobile) occurred in only 10%.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimum use of anticoagulants in pregnancy

Pregnant women pose special problems when deciding upon optimal anticoagulant therapy. Heparin does not cross the placenta and is probably safe for the fetus. Long term heparin therapy is occasionally associated with maternal haemorrhage and rarely with symptomatic osteoporosis. Coumarin derivatives, however, cross the placenta and are potentially teratogenic, particularly in the first trimester. Neonatal infant haemorrhage is a possibility if warfarin is administered to the pregnant mother near term. For the prevention and treatment of venous thromboembolism, heparin is the anticoagulant of choice since its safety and efficacy are well established. For the prevention of systemic embolism associated with prosthetic heart valves or valvular heart disease, the efficacy of heparin has not been established. Nevertheless, 12-hourly subcutaneous heparin in doses to prolong a mid-interval activated partial thromboplastin time (aPTT) to 1.5 times control is likely to be effective and safe. An alternative is to use heparin for the first trimester, change to warfarin until the middle of the third trimester, then to restart heparin until term. However, before warfarin is used in pregnant patients, the risks should be carefully explained to the patient to help avoid medicolegal problems. Warfarin can be safely used postpartum by the breast-feeding mother.