Elsevier

Mayo Clinic Proceedings

Volume 70, Issue 8, August 1995, Pages 725-733
Mayo Clinic Proceedings

Bleeding and Thromboembolism During Anticoagulant Therapy:A Population-Based Study in Rochester, Minnesota

https://doi.org/10.4065/70.8.725Get rights and content

Objective

To estimate the incidence of and identify risk factors for hemorrhage and thromboembolism during long-term anticoagulant therapy.

Design

We conducted a population-based retrospective cohort study of all residents of Rochester, Minnesota, in whom a course of warfarin therapy intended to last for more than 4 weeks was initiated between Sept. 1, 1987, and Dec. 31, 1989.

Methods

Medical records were reviewed, and pertinent data were compiled. All bleeding complications were classified as minor or major on the basis of the bleeding severity index, and thromboembolic events were classified as major if they were fatal or life-threatening. Cumulative incidences of adverse events were analyzed statistically.

Results

During the study period, 261 patients had incident courses of anticoagulation (52% were male, 61% were 65 years of age or older, and 31 % were 75 years of age or older), with 221 patient-years of warfarin exposure. The primary indications for anticoagulation were venous thromboembolism (39%); stroke or transient ischemic attack (21%); atrial fibrillation (11 %); and coronary artery disease, procedures for coronary artery disease, or cardiomyopathy (7%). The cumulative incidence of major hemorrhage at 1, 3, 12, and 24 months was 1.6%, 3.3%, 5.3%, and 10.6%, respectively, and of major or minor thromboembolic events was 2.3%, 5.0%, 7.4%, and 13.1%, respectively. In multivariate analysis, (1) a malignant condition was significantly associated with major hemorrhage; (2) malignant disease and history of peptic ulcer were significantly associated with the combined outcome of major or minor hemorrhage; and (3) malignant disease was significantly associated with any thromboembolism. Age, sex, atrial fibrillation, history of gastrointestinal hemorrhage, history of peptic ulcer, alcohol abuse, hypertension, stroke, and the Charlson comorbidity index were not significantly associated with major hemorrhage.

Conclusion

In this population-based study, including a high proportion of elderly patients, malignant disease at initiation of warfarin anticoagulation was significantly associated with both major hemorrhage and any thromboembolism. Advanced age is not a contraindication to anticoagulant therapy.

Section snippets

METHODS

Background.—Medical care for the residents of Rochester, Minnesota, is provided by the Mayo Clinic, Olmsted Medical Group, and a small number of independent providers. The Mayo Clinic uses a dossier (or unit record) system wherein all data on a specific patient are contained in a single file. In the community, anticoagulant therapy is monitored in only three laboratories, each of which maintains records of all such tests performed. We used a comprehensive medical diagnostic index to identify

RESULTS

Patient Characteristics and Indications for Anticoagulant Therapy.-During the 28-month study period, 261 patients had incident courses of long-term oral anticoagulant therapy with warfarin, a total of 221 patient-years of warfarin exposure. Of the patients, 52% were male. The median age of the study group was 69 years (range, 6 to 96); 39% of patients were younger than 65 years of age, 30% were 65 to 74 years old, and 31% were 75 years old or older (Table 1). The decision to initiate long-term

DISCUSSION

Warfarin therapy can be initiated only after the risks of thromboembolism related to a patient's underlying condition are weighed against the risks of hemorrhagic complications of such anticoagulant therapy. Our current study is the first to provide data on hemorrhagic and thromboembolic complications of anticoagulant therapy in a population-based cohort. Therefore, our results should apply to most practice settings, because we studied all patients who received warfarin in the community and not

CONCLUSION

The current population-based study of hemorrhagic and thromboembolic episodes in patients receiving warfarin anticoagulation allowed easy and well-monitored medical care and frequent follow-up. Even in this setting, the cumulative risks of major and minor hemorrhage and thromboembolism were substantial and were higher than those reported in clinical trials. The decision to recommend long-term treatment with warfarin must be weighed in light of these findings.

Cited by (0)

This study was supported in part by Research Grants AR 30582 and HL 46974 from the National Institutes of Health, Public Health Service, by FD-T-000886 from the Food and Drug Administration, and by Mayo Foundation.

*

Current address: Prairie Cardiovascular Clinic, Springfield, Illinois.

*

Current address: Georgetown University Medical Center, Washington, DC.

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