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Health news headlines can be deceiving. Why is topical vitamin C important for skin health? Preventing preeclampsia may be as simple as taking an aspirin. Caring for an aging parent? Tips for enjoying holiday meals. The number of major bleeding events was also higher for the combination warfarin and aspirin therapy group, with a cumulative incidence of 5. At 1 year, ED visits related to bleeding were higher for the combination warfarin and aspirin group Similarly, hospital admissions related to bleeding were higher for the combination warfarin and aspirin group compared with the warfarin monotherapy group 8.
These findings also persisted during most of the follow-up period. While receiving combination warfarin and aspirin therapy, 2. At 1 year, 1. The cumulative incidence of thrombosis-related admissions for patients receiving combination warfarin and aspirin therapy was 2.
Mortality rates for the 2 groups were similar at 1 year as well 4. The type of thrombotic event ischemic stroke, transient ischemic attack, deep vein thrombosis, pulmonary embolism, and other including left atrial thrombus, valvular thrombus, or thromboembolism of unknown origin or the rate of central nervous system bleeding did not significantly differ between the 2 groups. In sensitivity analyses, the above findings were largely unchanged.
In the first sensitivity analysis eliminating patients who initiated or discontinued aspirin therapy during follow-up , all of the above findings were unchanged, except the category of major bleeding no longer maintained statistical significance eTable 1 in the Supplement. In further sensitivity analyses, we excluded patients with a history of stroke, transient ischemic attack, heart valve replacement, or recent MI.
The results were largely unchanged from the primary analysis. Although the incidence of major bleeding events was higher for patients receiving combination warfarin and aspirin therapy compared with those receiving warfarin monotherapy at 1 year 5.
The sample size was smaller for this analysis, with patients in each group. Treatment with combination warfarin and aspirin therapy compared with warfarin monotherapy was associated with a significant increase in bleeding, major bleeding, ED visits, and hospitalizations. These results persisted for at least 3 years of follow-up, without any observed added benefit regarding thrombotic events.
The rates of combination warfarin and aspirin use did not significantly change over time, reflecting the limited data available to guide clinical decisions for this patient population. The publication of the American College of Chest Physicians guidelines 10 about the management of atrial fibrillation did not seem to have any influence regarding aspirin use in this population.
The observed rate of aspirin use among patients without clear therapeutic indication is consistent with what has been reported previously. Patients with substantial vascular or thrombotic risk factors may be intentionally maintained on combination warfarin and aspirin therapy.
Prospective studies are needed, especially for high-risk patients, to determine the optimal patient selection for and duration of combination therapy. Potential need of patients to require multiple antithrombotic medications is a common clinical scenario. Our nonrandomized data suggested that the number needed to harm 26 , 27 may only have been 36 persons for major bleeding and 29 persons for hospital admission among patients receiving combination warfarin and aspirin therapy compared with those receiving warfarin monotherapy.
An intervention targeted at reducing aspirin use in this population could have profound public health impact if these estimates are confirmed in prospective studies. Antiplatelet therapy use is dynamic for many patients. The clinicians at the anticoagulation clinics in this study routinely assessed the use of antiplatelet medications, which was a notable strength of this study. Removing matched patients who initiated or discontinued aspirin therapy during the study period in our first sensitivity analysis gave very similar results eTable 1 in the Supplement.
Major bleeding was significantly different only for the first year but not for the duration of follow-up.
Differences in bleeding after the first year may have been affected by bleeding events during the first year or by the lower power of the study to detect a difference.
Our second sensitivity analysis focused on patients without atherosclerotic comorbidity found higher bleeding complications with combination warfarin and aspirin therapy compared with warfarin monotherapy.
The observed rate of any bleeding reported in our study was high compared with other studies, resulting from the thoroughness of our manual data collection. Any bleeding in this study was by patient report only. The rate of major bleeding events for unmatched patients eTable 4 in the Supplement is consistent with the published literature.
Our study results may advance the field, with a long duration of follow-up in a real-world setting. The detailed propensity score match of numerous variables significantly limited potential confounders. Furthermore, sensitivity analyses showing similar results increased confidence in our results. Our results were supported by the findings of similar studies about this topic. That study differed because it included dabigatran 6.
In , Johnson et al 33 published a similar study through Kaiser Permanente Colorado Anticoagulation Service with 6 months of follow-up. In that study of more than patients, combination therapy was similarly associated with increased bleeding events but not with coronary events after adjustment for confounding factors. Our study results, a decade later, were striking because excess aspirin use among patients treated with warfarin continued at high rates. Whereas this study did not randomize aspirin use between the 2 groups, strong propensity score matching using numerous covariates enabled us to reduce selection biases and allowed for the comparison of 2 well-matched groups that would mimic a randomized clinical trial, as closely as a nonrandomized study design will allow.
While our propensity score matching was comprehensive for potential confounding variables, it is always possible that some unknown confounders were present that could have influenced the results eFigure 2 in the Supplement. In addition, our analysis did not adjust for the severity of the comorbid conditions, and it was conceivable that a patient with, for example, uncontrolled diabetes or hypertension, may have benefited more from the addition of aspirin therapy than a patient with well-managed comorbid conditions.
Strengths of the study were that patients were closely followed up while enrolled in the anticoagulation clinics, with data collected using predefined forms that included relevant clinical outcomes. Random medical record audits validated the accuracy of the data.
The population-based cohort may have been more likely to reflect real-world practice compared with patients in a clinical trial. Despite being part of a quality improvement collaborative, all patients received standard anticoagulation care, and their findings likely are generalizable to other settings including anticoagulation clinics and high-quality care outside of anticoagulation clinics.
By controlling for warfarin management through the use of the TTR variable, we tried to limit variation between groups to the receiving of aspirin alone. We caution against extrapolating these findings to patients receiving direct oral anticoagulants with aspirin because the outcomes may be significantly different. Potential limitations to the study included issues surrounding generalizability because of the geographically limited patient population followed up at the anticoagulation clinics.
In addition, any medication changes, especially nonprescription aspirin use, may not have been well captured. However, given that data in this registry were abstracted from the medical record and that nurses and pharmacists in the anticoagulation clinic routinely reviewed any new or changed medications especially antithrombotic medications, such as aspirin , we believe our findings are reliable and robust. This belief is supported by the results of the sensitivity analysis, in which patients with a known change in aspirin-use status were excluded eTable 1 in the Supplement.
Recent MI, an exclusion criterion for the study, was defined on the MAQI 2 data collection form as an event that occurred fewer than 6 months before warfarin therapy initiation. Therefore, a low number of included patients may have been within a year of having a MI and had a stronger indication for concomitant aspirin use.
A total of patients 3. The key is finding the right balance, picking the right patient and then discussing risk-tolerance with the patient. It turns out, rightly I think, that most medical doctors lean heavily towards stroke prevention. They know how awful strokes can be. And this thinking has led to combining these two classes of drugs.
Intuitively, the combination makes sense. Cover the bases. In a validation study of the BRI, the rate of major bleeding was found to be 0. In patients with acute coronary syndrome, a coronary stent, or a mechanical valve, combination therapy is usually recommended.
In patients who have undergone percutaneous coronary intervention with stent implantation, dual antiplatelet therapy with aspirin and a thienopyridine—ie, clopidogrel Plavix or ticlopidine Ticlid —is superior to aspirin or warfarin alone in reducing the risk of stent thrombosis and major adverse cardiovascular events such as myocardial infarction or urgent revascularization.
The duration of triple therapy is guided by the type of stent used. For bare metal stents, aspirin, clopidogrel or ticlopidine, and warfarin should be given for at least 1 month, after which clopidogrel or ticlopidine may be discontinued.
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