Abstract Number: PB2041
Meeting: ISTH 2020 Congress
Theme: Venous Thromboembolism and Cardioembolism » Atrial Fibrillation
Background: For some warfarin-treated patients, the addition of aspirin (ASA) significantly increases bleeding without reducing thrombosis. We implemented a nurse/pharmacist-lead quality improvement intervention aimed at reducing inappropriate ASA use.
Aims: To assess changes in inappropriate ASA use, bleeding, and thrombosis event rates.
Methods: Within the six-center Michigan Anticoagulation Quality Improvement Initiative, we implemented an anticoagulation-clinic based quality improvement intervention that identified warfarin-treated patients with atrial fibrillation (Afib) or venous thromboembolism (VTE) without a clear indication for concomitant ASA (eg. coronary artery disease, mechanical heart valve). If the indication for adding ASA was unclear, the patient’s care provider was contacted to advise if ongoing ASA+warfarin was recommended. ASA was discontinued if suggested by their managing doctor. Data was abstracted by trained abstractors, using predefined forms, and verified through chart audits. The intervention was implemented between Q4 2017 and Q2 2018. In December 2019, the rates of inappropriate ASA use, bleeding, and thrombotic outcomes were compared pre- and post-intervention using Poisson Regression with robust standard error. Site specific definitions of inappropriate ASA use and implementation dates were used.
Results: A total of 5,980 and 1,634 patients with AFib and/or VTE without an indication for ASA use were identified during the pre- and post-implementation periods, respectively. Inappropriate ASA use was reduced by over 50% from pre- to post-implementation (Figure). Patients were followed an average of 17.6 months pre-intervention and 11.3 months post-intervention. The rate of bleeding, major bleeding, emergency room visits, and hospitalizations related to bleeding were all significantly lower in the post- vs. pre-intervention period (Table). We did not observe a difference in thrombotic outcomes but data on myocardial infarction may not have been well captured.
Conclusions: Our multi-center quality improvement intervention was associated with a significant reduction in inappropriate ASA use and lower rates of bleeding among patients anticoagulated with warfarin for AFib and/or VTE.
| Pre-intervention* N=5,980 | Post-intervention* N=1,634 | P value | |
| Aspirin n (%) | 1,541 (25.8) | 323 (19.8) | <0.01 |
| Patients in both groups n (%) | 1,036 (17.3) | 1,036 (63.4) | — |
| Event rate (95% CI) # of events/100 patient-years | |||
| Any bleeding | 26.2 (25.1 – 27.3) | 17.1 (15.1 – 19.3) | <0.01 |
| Major bleeding | 3.9 (3.5 – 4.3) | 3.2 (2.4 – 4.3) | 0.023 |
| CRNMB | 8.5 (7.9 – 9.1) | 5.2 (4.1 – 6.5) | <0.01 |
| Admission for bleeding | 6.3 (5.7 – 6.8) | 4.5 (3.5 – 5.7) | <0.01 |
| Thrombosis¶ | 2.4 (2.0 – 2.7) | 2.0 (1.4 – 2.9) | 0.76 |
| *The pre-intervention group includes patients that were no longer followed by the Michigan Anticoagulation Quality Improvement Initiative prior to the intervention. The pre and post intervention groups were not mutually exclusive. Indications for ASA use were assessed at enrollment for the pre-intervention group and at the first follow-up visit post-intervention for the post-intervention group. Comparisons of event rates are adjusted for ASA indication and HAS-BLED score/CHA2DS2-VASc score, as assessed for the pre-intervention group at enrollment and the post-intervention group at the time of the intervention or, if enrolled post-intervention, at the time of enrollment. Aspirin use was assessed at enrollment for the pre-intervention group. Aspirin use for the post-intervention group was assessed at the first follow-up visit post-intervention. ¶Thrombosis includes any new ischemic or embolic stroke, transient ischemic attack, pulmonary embolism, deep vein thrombosis, intracardiac thrombus, or other/unknown clot. Abbreviations: ASA, aspirin; CRNMB, clinically relevant non-major bleeding. | |||
[Table 1: Event rates of patients on warfarin for AFib and/or VTE without an indication for ASA use pre and post intervention]
[Figure 1. Inappropriate aspirin use by quarter pre- and post- intervention]
| Pre-intervention* N=5,980 | Post-intervention* N=1,634 | P value | |
| Aspirin n (%) | 1,541 (25.8) | 323 (19.8) | <0.01 |
| Patients in both groups n (%) | 1,036 (17.3) | 1,036 (63.4) | — |
| Event rate (95% CI) # of events/100 patient-years | |||
| Any bleeding | 26.2 (25.1 – 27.3) | 17.1 (15.1 – 19.3) | <0.01 |
| Major bleeding | 3.9 (3.5 – 4.3) | 3.2 (2.4 – 4.3) | 0.023 |
| CRNMB | 8.5 (7.9 – 9.1) | 5.2 (4.1 – 6.5) | <0.01 |
| Admission for bleeding | 6.3 (5.7 – 6.8) | 4.5 (3.5 – 5.7) | <0.01 |
| Thrombosis¶ | 2.4 (2.0 – 2.7) | 2.0 (1.4 – 2.9) | 0.76 |
| *The pre-intervention group includes patients that were no longer followed by the Michigan Anticoagulation Quality Improvement Initiative prior to the intervention. The pre and post intervention groups were not mutually exclusive. Indications for ASA use were assessed at enrollment for the pre-intervention group and at the first follow-up visit post-intervention for the post-intervention group. Comparisons of event rates are adjusted for ASA indication and HAS-BLED score/CHA2DS2-VASc score, as assessed for the pre-intervention group at enrollment and the post-intervention group at the time of the intervention or, if enrolled post-intervention, at the time of enrollment. Aspirin use was assessed at enrollment for the pre-intervention group. Aspirin use for the post-intervention group was assessed at the first follow-up visit post-intervention. ¶Thrombosis includes any new ischemic or embolic stroke, transient ischemic attack, pulmonary embolism, deep vein thrombosis, intracardiac thrombus, or other/unknown clot. Abbreviations: ASA, aspirin; CRNMB, clinically relevant non-major bleeding. | |||
[Table 1: Event rates of patients on warfarin for AFib and/or VTE without an indication for ASA use pre and post intervention]
To cite this abstract in AMA style:
Schaefer JK, Errickson J, Gu X, Alexandris-Souphis T, Ali MA, Haymart B, Kaatz S, Kline-Rogers E, Kozlowski JH, Krol GD, Shah V, Sood SL, Froehlich JB, Barnes GD. Reduced Bleeding After an Intervention to Limit Excess Aspirin Use Among Patients on Chronic Warfarin [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/reduced-bleeding-after-an-intervention-to-limit-excess-aspirin-use-among-patients-on-chronic-warfarin/. Accessed September 24, 2023.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/reduced-bleeding-after-an-intervention-to-limit-excess-aspirin-use-among-patients-on-chronic-warfarin/