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Pharmacy Residency Research Project Manuscript
Effectiveness and Safety of Stroke Prevention Therapy in Hemodialysis and Peritoneal Dialysis
Patients with Atrial Fibrillation at Trillium Health Partners
Meiko Peng
Pharmacy Resident
Trillium Health Partners
2018‐2019
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Principle Investigator
Meiko Peng, BSc, RPh, PharmD
Pharmacy Resident
Co‐investigators
Rose Liao, BScPhm, RPh, PharmD, ACPR
Clinical Pharmacist
Project Site
Trillium Health Partners
2200 Eglinton Ave West
Mississauga, ON
L5M 2N1
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Effectiveness and Safety of Stroke Prevention Therapy in Hemodialysis and Peritoneal Dialysis
Patients with Atrial Fibrillation at Trillium Health Partners
Meiko Peng1,2, BSc, PharmD; Rose Liao1, BScPhm, PharmD, ACPR
Trillium Health Partners, Mississauga, Ontario1 Leslie Dan Faculty of Pharmacy, University of
Toronto, Toronto, Ontario2
ABSTRACT:
Background: Treatment with anticoagulation is the standard of care for stroke prevention in
patients with atrial fibrillation (AF). Patients with normal kidney function have direct oral
anticoagulants (DOACs) and warfarin as treatment alternatives; however, dialysis patients are
traditionally constrained to the latter. Due to limited trial data, oral anticoagulants’ efficacy for
stroke prevention in this patient population remains controversial.
Objectives: This study aims to investigate the association between stroke prevention therapy
(warfarin, DOACS, antiplatelets) and the risk for stroke and bleeding in dialysis patients with AF
at Trillium Health Partners – a regional stroke and dialysis centre.
Methods: Electronic records of adult stage 3‐5 chronic kidney disease (CKD) patients were
accessed to determine those with a stroke or bleed event between January 1st, 2008 and
December 31st, 2018. These patients were manually screened to identify those on dialysis with
AF. Patient, stroke, bleed characteristics, and stroke prevention therapy, if any, were
documented.
Results: Of 414 stage 3‐5 CKD patients who bled or stroked, there were 97 events (n=36
ischemic strokes; n=61 bleeds) in patients who had AF and dialysis. The stroke incidence rates
were 3.90 (95% CI ‐0.05,7.85), 6.50 (1.5,11.5), and 5.20 (0.64,9.76) per 100‐person‐years for
warfarin, non‐warfarin, and no‐therapy patients, respectively. The bleed incidence rates were
6.25 (95% CI 1.26,11.26), 7.70 (2.15,13.25), and 0.72 (‐0.97,2.41) per 100‐person‐years for
warfarin, non‐warfarin, and no‐therapy patients, respectively. If on warfarin therapy, younger
age, longer duration of dialysis and AF, and high HASBLED scores put patients at higher risk of
stroke, while longer AF duration and high CHA2DS2‐VASc and HASBLED scores put patients at
increased risk of bleed.
Conclusion: Though this study was unable to account for prescribing and confounding factors,
results suggest warfarin may be associated with lower stroke and comparable bleed rates
compared to non‐warfarin alternatives. Given the retrospective nature of the study, further
investigation is required.
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INTRODUCTION
Chronic kidney disease (CKD) is estimated to affect up to 2.3 million Canadians, and low
awareness often results in suboptimal management of the disease 1,2 . The Kidney Disease:
Improving Global Outcomes (KDIGO) defines CKD as the presence of kidney damage for more
than three months and subcategorizes the condition into stages depending on the glomerular
filtration rate (GFR) (Table 1) 3. Though symptoms rarely show until the later stages, CKD is a
gradually progressive disease. Pre‐dialysis include patients in CKD stage three or four as dialysis
is not yet required; however, it can readily progress into kidney failure, also known as end stage
kidney disease (ESKD), where patients are at stage five CKD and the kidneys stop functioning
well enough to survive without dialysis or kidney transplant.
Table 1. Criteria and Stages of CKD 3 A. Criteria of CKD
Markers of kidney damage (one or more)
Albuminuria (ACR* greater than 3 mg/mmol)
Urine sediment abnormalities
Electrolyte and other abnormalities due to tubular disorders
Abnormalities detected by histology
Structural abnormalities detected by imaging
History of kidney transplantation
Decreased GFR Less than 60 mL/min/1.73 m2 *ACR:albumin‐to‐creatinine ratio B. Stages of CKD
Stage GFR (ml/min/m2) Terms
1 >90 Normal or high
2 60‐89 Mildly decreased
3a 45‐59 Mildly to moderately decreased
3b 30‐44 Moderately to severely decreased
4 15‐29 Severely decreased
5 <15 Kidney failure
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Cardiovascular disease often coexists with CKD and one of the most common
comorbidities in this patient population is atrial fibrillation (AF). The overall prevalence of AF is
approximately 15% among hemodialysis (HD) patients, more than triple that of age‐matched
patients without ESKD 4. The two conditions have a close bidirectional relationship as CKD
increases risk of incident AF, while AF increases the risk of development and progression of
CKD. The presence of various conventional cardiovascular risk factors such as older age,
hypertension, diabetes, and obesity in patients with CKD predispose this patient population to
high burden of AF 5. Similarly, AF‐related decline in left ventricular function promotes CKD
progression via venous congestion, activation of the renin‐angiotensin‐aldosterone system
(RAAS), and renal microinfarcts 6.
Stroke is a common and often deadly complication of AF. Patients with AF on dialysis
have a five‐fold higher risk for a new stroke compared to the general AF population 7. The
interactions of platelet hyperactivity, changes in left atrial blood flow, and myocardial fibrosis,
contributed by both AF and CKD, result in a prothrombotic state that ultimately increases the
risk of thromboembolic events 8. Not only is there increased thromboembolic risk, presence of
severe CKD in patients with AF also increases the risk of bleeding where an inverse relationship
exists between declining GFR and increasing bleed events. Patients with HD have a 3‐10 times
higher risk of bleeding compared to the general population 9. Both intrinsic (reduced platelet
activity and impaired vessel‐wall‐platelet interactions) and extrinsic (use of non‐steroidal anti‐
inflammatory agents or heparin during HD) factors play important roles 10.
Treatment with anticoagulation has become the standard of care for stroke prevention
in patients with AF, where options are often dictated by the renal function. Patients with
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sufficient renal function have both warfarin, a vitamin‐K antagonist, and direct oral
anticoagulants (DOACs) in their arsenal of treatment alternatives; however, patients on dialysis
are generally limited to the former 11. Severe renal impairment historically excluded use of all
DOACs; however, the recent FDA approval of apixaban use for stroke prevention in patients on
HD suggest that DOACs may be a safe and effective alternative compared to warfarin 12. Other
alternatives include antiplatelets such as aspirin and clopidogrel, but they are known to be less
effective than anticoagulants in stroke prevention and specifically in renal impairment. Despite
their relative lack of efficacy, antiplatelets may be a viable option in patients who require stroke
protection but cannot tolerate the bleed risk of anticoagulants.
Risk stratification scores such as CHA2DS2VASc 13 and HASBLED 14 (Appendix A),
developed in the general population to assess thromboembolic and bleed risk, respectively,
unfortunately are not validated in patients with ESKD, as thromboembolic risk is often
overestimated, and bleed risk is underestimated 15. Efficacy of warfarin and DOACs for stroke
prevention in patients with stage three CKD has been shown to be similar to that of patients
without CKD 9. However, when patients transition into ESKD, their use is controversial as there
is currently no randomized trial of any oral anticoagulant in patients with ESKD and AF. Direct
oral anticoagulants are limited by lack of studies in ESKD while warfarin shows conflicting
results in various observational trials (Appendix B). Warfarin use is further burdened by side
effects such as vascular calcification and warfarin‐related nephropathy.
Currently, the 2014 AHA/ACC/HRS Guideline for the Management of Patients with Atrial
Fibrillation recommends patients with nonvalvular AF with CHA2DS2VASc score of ≥2 and who
have ESKD and on dialysis to receive warfarin for oral anticoagulation 14. This is contrasted by
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the focused 2014 Update of the Canadian Cardiovascular Society (CCS) for the Management of
Atrial Fibrillation where the authors took a more conservative approach by recommending
warfarin only for non‐dialysis patients and no anticoagulation for patients with ESKD on dialysis
due the inconsistent literature on warfarin’s efficacy in this population 16. KDIGO’s 2011
guideline further stratified the recommendation in patients with ESKD and AF to suggest that
routine anticoagulation is not indicated for primary prevention but is valid for secondary
prevention 17. No guidelines currently support use of DOACs based on lack of evidence, and do
not mention antiplatelets due to their known decreased efficacy.
RATIONALE FOR STUDY
Patients with AF who have CKD (GFR <60 mL/min/1.73m2), especially on dialysis, have a
higher risk of stroke and bleeding. Treatment with anticoagulation is the standard of care for
stroke prevention in patients with AF, but options are limited in the dialysis population due to
lack of robust randomized, controlled trials and the exclusion of this patient population in
development of major landmark trials and risk prediction scores 15. Compounded by its risk of
accelerating vascular calcification and difficulty maintaining a target INR range in this patient
population, use of warfarin specifically has been met with considerable uncertainty 18. Trillium
Health Partners (THP) serves a community of 1.5 million patients in the greater Toronto area.
The Credit Valley Hospital site houses the regional renal care centre, and the Mississauga
hospital site houses the regional stroke centre, providing an ideal environment where HD and
PD patients can be regularly followed and assessed by a multidisciplinary team of physicians,
pharmacists, and nurses. Investigation of the effectiveness and safety of stroke prevention
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therapy in patients with AF can help guide clinician prescribing and pharmacist monitoring
when assessing treatment decisions in this complex patient population.
Study Objectives
1. The number of HD/PD patients with AF who had a stroke or bleed at THP and were on
stroke prevention therapy, if any:
a. Warfarin
b. DOACs: apixaban, rivaroxaban, dabigatran, edoxaban
c. Antiplatelets: ASA, clopidogrel, ticagrelor, prasugrel, ticlopidine
2. For patients who had a stroke or bleed, identify associated factors (demographic,
clinical) for each type of stroke prevention
METHODS
Study Design
A retrospective chart review of electronic charts was performed to identify adult dialysis
patients with AF who had a stroke or bleed event at THP between January 1st, 2008 and
December 31st, 2018.
Study Population
Inclusion Criteria
≥18 years of age
Experienced a stroke or bleed event within the study time frame
Diagnosed with AF (atrial flutter, paroxysmal, chronic)
Receiving HD or PD at THP at time of stroke or bleed event
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Exclusion Criteria
Patients on warfarin, DOAC, or antiplatelet therapy appropriately for indications other
than prevention of stroke in AF
Undergoing and/or underwent catheter ablations
A list of stage 3‐5 CKD patients who had a nephrology clinic visit at THP within the
study’s 10‐year time‐frame was generated from the Renal Information System (RIS). These
renal accounts were cross‐referenced with ICD‐10 admission codes from the Discharge Abstract
Database (DAD) for stroke, defined as ischemic, hemorrhagic, TIA, or unknown source
confirmed via CT/MRI, or bleed, defined as gastrointestinal, intracerebral, intraocular, or
unspecified location. Specific ICD‐10 codes included in the study are listed in Appendix C. The
ICD‐10 codes utilized were assessed to ensure there were no significant changes over the 10‐
year time frame. These patients’ consultation notes and discharge summaries were manually
consulted from Meditech to identify patients who had AF and were on dialysis at the time of
the event. Stroke and bleed events were only included in the analysis if they occurred after the
diagnosis of AF. For any stroke or bleed events that occurred prior to the diagnosis of AF,
Meditech notes and laboratory results (48‐hour Holter monitoring, ECG, echocardiogram) were
assessed for 2 weeks after the event to determine whether the stroke was cardioembolic.
Data collection included baseline patient characteristics, stroke and bleed
characteristics, and type of stroke prevention therapy, if any. Concomitant medications were
recorded as 1) the baseline medications present when the patient entered the study (defined as
the time of the stroke or bleed event), and 2) as new medications started within 7 days prior to
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the day of the stroke and bleed event. To assess effect of INR on warfarin therapy, INR values
were recorded and defined as the average of INR values available 7 days prior to the stroke or
bleed event. The full list of documented parameters is in Appendix D.
Statistics were performed using mean calculations with standard deviations. Statistically
significant differences in baseline characteristics were tested using one‐way ANOVA and
unpaired T‐test for continuous variables, and Fisher’s exact and chi‐square test for dichotomous
variables. The results were analyzed into three groups, those on 1) warfarin therapy, 2) non‐
warfarin therapy (DOACs, antiplatelets), and 3) no‐therapy. A 95% confidence interval and
statistically significance cut‐off of p=0.05 was used. Incidence rate per 100‐person years was
defined as the number of events divided by amount of person‐time observed.
RESULTS
Over the 10‐year study period, 414 stage 3‐5 CKD patients who bled or stroked were
screened and 78 patients met the inclusion criteria. There were 97 total events (n=36 ischemic
strokes; n=61 major bleeds) in patients who had AF and dialysis.
Stroke
The most common stroke type was MCA (31%) followed by occipital strokes (19%)
(Figure 1). Of 36 stroke patients, 9 stroked on warfarin, 15 stroked on non‐warfarin alternatives
(DOACS n=2; antiplatelets n=13), and 12 stroked on no therapy. Warfarin had the lowest stroke
incidence rate of 3.90 (95% CI ‐0.05,7.85) compared to non‐warfarin therapy of 6.50 (95% CI
1.5,11.5) and no‐therapy of 5.20 (95% CI 0.64,9.76) per 100‐person‐years (Figure 2). The mean
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INR of warfarin users was 1.64 ± 0.38. Baseline characteristics of stroke patients are outlined in
Table 2. Warfarin users had a mean age of 75.76 and were mostly males (67%) while no‐
therapy patients had a mean age of 77.73 and were mostly females (67%). The majority (83%)
of patients were on HD, where the cause of kidney dysfunction was largely due to
hypertension, diabetes or both. Warfarin users have longer dialysis (9.44 ± 7.13 years) and AF
(7.59 ± 6.07 years) vintage compared to non‐warfarin (2.25 ± 1.99; 2.30 ± 3.74) and no‐therapy
patients (2.41 ± 1.89; 2.58 ± 3.94). If on warfarin therapy, younger age, longer AF and dialysis
duration, and high HASBLED scores increased the risk of stroke. Majority of warfarin (78%) was
used for secondary prevention while non‐warfarin (60%) and no‐therapy (67%) were used
mostly for primary prevention (Figure 3).
Figure 1. Stroke Types
Figure 2. Stroke incidence rates with 90% confidence interval
MCA stroke 31%
Lacunar 5%
Occipital 19%
Parietal 8%
ACA 3%
Pontine 3%
Thalamic 3%
Cerebellar 11%
TIA 11%
Frontal 3%
Mixed 3%
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Table 2. Statistically significant baseline characteristics in stroke patients
Figure 3. Number of strokes by stroke prevention therapy (n=36)
Bleed
Upper gastrointestinal (GI) bleed represented approximately 50% of bleed types,
followed by lower GI bleeds (20%) (Figure 4). All identified intracranial hemorrhages (11%, n=3)
were caused by warfarin. Of 61 patients who had a major bleed, 26 (43%) bled on warfarin, 32
(52%) on non‐warfarin alternatives (DOACs n=3, antiplatelets n=24, heparin n=5), and 3 (5%) on
no‐therapy. Warfarin had comparable bleed incidence rate of 6.26 (95% CI 1.26,11.26)
compared to non‐warfarin therapy of 7.70 (95% CI 2.15, 13.25) per 100 person‐years, with no‐
therapy of 0.72 (95% CI ‐0.97,2.41) per 100‐person‐years having the lowest rates of bleeding
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(Figure 5). The mean INR of warfarin users was 4.14 ± 2.98. In bleed patients, the age and sex of
warfarin and non‐warfarin users were comparable. There was no difference in dialysis vintage
but warfarin users who had longer AF duration had increased risk of bleeding (Table 3). For
those on warfarin therapy, both higher CHA2DS2VASc and HASBLED scores increased the risk of
bleeding compared to non‐warfarin users. Though both warfarin and antiplatelets users had
similar total number of bleeds, 23% of warfarin users at baseline had a documented previous
bleed compared to 62.5% of antiplatelets users who had a documented bleed (Figure 6).
Figure 4. Bleed Types
Figure 5. Bleed incidence rates with 95% confidence interval
Upper GI 51%
Lower GI 20%
Hematuria 6%
Brain 11%
Oral 3%
Nose 2%
Pulmonary 2%
Other 5%
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Table 3. Statistically significant baseline characteristics in bleed patients.
Figure 6. Number of bleeds by stroke prevention therapy (n=61)
DISCUSSION
Treatment with anticoagulation is the standard of care for stroke prevention in patients
with AF, but options are limited in the dialysis population. Warfarin has historically been the
treatment of choice, but this evidence is extrapolated from the non‐dialysis population, and
there is increasing observational data that questions the effectiveness and safety of warfarin in
this patient population. In a retrospective cohort study, Chan et al. found that warfarin may be
associated with an increased risk for new strokes (HR 1.93, CI 1.29,2.90) in dialysis patients
after an average follow‐up of 1.6 years 19. In these patients, even those with high CHADS2
scores and with history of previous strokes did not benefit from warfarin. However, a Danish
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study in 2012 described the protective effects of warfarin on stroke (HR 0.44, CI 0.26,0.74) in
dialysis patients. A Canadian study performed in elderly patients hospitalized for AF showed
that HD patients did not benefit from warfarin therapy (HR 1.14, CI 0.78,1.67) and was
associated with a 44% higher risk for bleeding (HR 1.44, CI 1.13,1.85) 20. The average stroke
incidence rate on warfarin cited in the literature range from 3.20 to 5.61 per 100‐person‐years.
Currently, there are no randomized trials that assess the risk‐benefit ratio of warfarin in
dialysis patients with AF. Though many meta‐analyses were conducted in attempt to clarify the
current conflicting literature landscape, results regarding stroke outcomes remain
contradictory. Interestingly, in Dahal et al.’s meta‐analysis of 13 studies, they found that
warfarin had a lower risk of stroke in non‐ESKD patients while it had no effects on risks of
stroke in ESKD patients 21. This support the current rationale that while warfarin is still effective
as described by the drug’s landmark trials in the general population, it may not have the same
efficacy in dialysis patients. Despite the contradicting literature on stroke outcomes, a common
theme from the current literature was that warfarin was associated with significantly increased
risk of bleeding in the dialysis population. The average bleed incidence rate on warfarin cited in
the literature range from 5.90 to 17.6 per 100‐person‐years.
Our institution revealed a stroke incidence of 3.90 per 100‐person‐years on warfarin
therapy (CI ‐0.05,7.85), which is comparable to the literature. Stroke incidence on warfarin was
lower than those on no therapy, and those on non‐warfarin therapy. THP’s bleed incidence is
also comparable to the literature where our centre demonstrated similar bleed rates between
warfarin and non‐warfarin patients, with those on no therapy having the lowest rates of
bleeding. Non‐warfarin therapy consisted of mainly antiplatelet users as DOAC use in dialysis
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patients with AF was still largely contraindicated during the study timeframe. Clinical trial data
on DOACs in this indication are lacking and pharmacokinetic studies that act as surrogates for
safety and efficacy cannot be linearly translated into clinical practice. Overall, efficacy of
warfarin compared to DOACs in stroke and bleed cannot be determined due to DOACs’ low
usage in the study. However, we did find that the stroke incidence was higher in the non‐
warfarin group, likely as it is well known that antiplatelets are inferior to anticoagulants for
stroke prevention in AF 22.
Furthermore, warfarin’s effectiveness could not be appropriately assessed as all patients
who stroked on warfarin had subtherapeutic INRs (1.64 ± 0.38). Confounding variables such as
differing INRs were not addressed due to the retrospective design and small sample size of this
study. A Swedish study demonstrated that most dialysis patients would benefit from warfarin if
it was feasible to achieve optimal management of stroke and bleeding risk factors and tight
control of anticoagulation 23. While maintaining a time in therapeutic range (TTR) of ≥65‐70%
has been shown to be required for ideal protection from warfarin, this is known to be very
difficult in clinical practice for the general population, let alone in dialysis patients where
decreasing GFR further reduces the likelihood of achieving desired TTR 24. Interestingly, INR and
TTR was not readily assessed in many observational studies, likely not only is it difficult to
maintain INR records with retrospective designs, dialysis patients are known to be challenging
to maintain in therapeutic range. Similarly, all patients who bled on warfarin in our study had
supra‐therapeutic INR (4.14 ±2.98), making it difficult to appropriately determine warfarin’s
true bleed risk.
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At THP, warfarin is primarily used for secondary prevention of strokes – which is
consistent with the latest Kidney Disease: Improving Global Outcomes (KDIGO) 2011 guideline
recommendation 17. Though warfarin has historically been the first line choice for stroke
prevention in dialysis patients, it is now generally reserved for those who have already suffered
a stroke, with the thought that they will gain the most benefit despite the growing documented
risks. Antiplatelets or no anticoagulation were common choices in patients for primary
thromboprophylaxis with careful assessment of the stroke and bleeding profile of the individual
patient. Accordingly, we found that warfarin is primarily used for patients without a history of
bleeds at our institution. Interestingly, we found that 63% of antiplatelet users had a
documented previous bleed compared to only 23% of warfarin users who had a previous bleed.
This suggests that practitioners are reserving antiplatelets for those at high bleed risks and only
using warfarin when the bleed risk profile is favorable. Consequently, using antiplatelets or no
therapy at all are usually the first line options when a patient first present with AF if they have
no previous documented stroke. In a survey of nephrologists and cardiologists across Canada,
both cardiologists and nephrologist recommend anticoagulant therapy more when stroke risk is
high and less when bleed risk is high. Moreover, cardiologists are three times more likely to
recommend anticoagulant therapy than nephrologists, regardless of the bleeding or stroke risk
profile. Our study was not able to assess the physician’s specialty when deciding treatment.
It is important to note that the retrospective design of this study is a limitation, as many
confounding factors could not be controlled, and the data relied on accurate documentation.
Confounding variables such as sub‐therapeutic warfarin dosing, low DOAC usage, and
prescribing preferences were not addressed. Further, the small sample size of the study limited
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our ability to perform regression analysis. Finally, the study was unable to acquire a true
denominator of dialysis and AF patients who did not have a stroke or bleed event as a
comparator due to Information/Technology limitations and inability to access data in a timely
manner during the study timeframe. This study had limited external validity as it was focused at
a single institution, and only patients’ in‐hospital data were analyzed and use of anticoagulation
for stroke prevention beyond hospitalization was unknown.
FUTURE DIRECTIONS
This study provided a preliminary overview of the practice patterns of stroke prevention
at THP. Further steps involve continuing data collection for a larger sample size such that the
study will be better powered to distinguish statistically significant differences and resolving
confounding variables. With increasing evidence of warfarin’s potential risks in dialysis patients,
alternative agents are required. Use of DOACs can potentially overcome many of the difficulties
that are associated with warfarin. They can be safely used in the general population, but their
data in the dialysis population have been limited. Recently, the US Food and Drug
Administration cautiously extended apixaban use to patients with ESKD on HD based on a
pharmacokinetic study of eight patients 25. Additional studies in Canada are currently underway
to further explore the role of DOACs for stroke prevention in dialysis patients as they are still
used with caution in practice today 26. Randomized controlled trials that compare warfarin to
DOACs are required to help clarify and guide practitioners in making more informed treatment
decisions in this complex patient population.
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CONCLUSION
Warfarin use at THP has comparable stroke and bleed rates as the literature. Our
current practice of reserving warfarin for secondary stroke prevention aligns with the KIDGO
2011 guidelines, where anticoagulation in primary prevention is often not pursued due to
increased risk of bleeding, calciphylaxis, and lack of systemic evidence for stroke prevention
benefit with warfarin. Use of warfarin for secondary stroke prevention should be considered in
dialysis patients who have a low bleed risk profile. Though this study was unable to account for
prescribing and confounding factors, results suggest warfarin may be associated with lower
stroke and comparable bleed rates compared to non‐warfarin alternatives. Given the
retrospective nature of the study, further investigation is required.
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REFERENCES
1. Levin, A. et al. Guidelines for the management of chronic kidney disease. Can. Med.
Assoc. J. 179, 1154–1162 (2008).
2. Potpara, T. S., Ferro, C. J. & Lip, G. Y. H. Use of oral anticoagulants in patients with atrial
fibrillation and renal dysfunction. Nat. Rev. Nephrol. 14, 337–351 (2018).
3. Akbari, A. et al. Canadian Society of Nephrology Commentary on the KDIGO Clinical
Practice Guideline for CKD Evaluation and Management. Am. J. Kidney Dis. 65, 177–205
(2015).
4. Hart, R. G., Eikelboom, J. W., Brimble, K. S., McMurtry, M. S. & Ingram, A. J. Stroke
prevention in atrial fibrillation patients with chronic kidney disease. Can. J. Cardiol. 29,
S71‐8 (2013).
5. Benjamin, E. J. et al. Heart Disease and Stroke Statistics‐2017 Update: A Report From the
American Heart Association. Circulation 135, e146–e603 (2017).
6. Bansal, N., Hsu, C. Y. & Go, A. S. Intersection of cardiovascular disease and kidney
disease: atrial fibrillation. Curr. Opin. Nephrol. Hypertens. 23, 275–282 (2014).
7. Seliger, S. L. et al. Risk factors for incident stroke among patients with end‐stage renal
disease. J. Am. Soc. Nephrol. 14, 2623–31 (2003).
8. Watson, T., Shantsila, E. & Lip, G. Y. Mechanisms of thrombogenesis in atrial fibrillation:
Virchow’s triad revisited. Lancet 373, 155–166 (2009).
9. Hart, R. G., Pearce, L. A., Asinger, R. W. & Herzog, C. A. Warfarin in atrial fibrillation
![Page 21: University of Toronto T-Space - Effectiveness and Safety of Stroke … · 2020. 1. 22. · KDIGO’s 2011 guideline further stratified the recommendation in patients with ESKD and](https://reader035.vdocument.in/reader035/viewer/2022071502/6121b2e4f2dde20796001216/html5/thumbnails/21.jpg)
patients with moderate chronic kidney disease. Clin. J. Am. Soc. Nephrol. CJASN 6, 2599–
2604 (2011).
10. Lau, Y. C., Proietti, M., Guiducci, E., Blann, A. D. & Lip, G. Y. H. Atrial Fibrillation and
Thromboembolism in Patients With Chronic Kidney Disease. J. Am. Coll. Cardiol. 68,
1452–1464 (2016).
11. Fanikos, J., Burnett, A. E., Mahan, C. E. & Dobesh, P. P. Renal Function Considerations for
Stroke Prevention in Atrial Fibrillation. Am. J. Med. 130, 1015–1023 (2017).
12. Siontis, K. C. et al. Outcomes Associated with Apixaban Use in End‐Stage Kidney Disease
Patients with Atrial Fibrillation in the United States. Circulation 28, 28 (2018).
13. Kirchhof, P. et al. 2016 ESC Guidelines for the management of atrial fibrillation developed
in collaboration with EACTS. Eur. Heart J. 37, 2893–2962 (2016).
14. January, C. T. et al. 2014 AHA/ACC/HRS guideline for the management of patients with
atrial fibrillation: Executive summary: A report of the American College of
cardiology/American heart association task force on practice guidelines and the heart
rhythm society. Circulation 130, (2014).
15. Keskar, V. & Sood, M. M. Use of Oral Anticoagulation in the Management of Atrial
Fibrillation in Patients with ESRD: Con. Clin. J. Am. Soc. Nephrol. CJASN 11, 2085–2092
(2016).
16. Verma, A. et al. 2014 Focused Update of the Canadian Cardiovascular Society Guidelines
for the Management of Atrial Fibrillation. Can. J. Cardiol. 30, 1114–1130 (2014).
![Page 22: University of Toronto T-Space - Effectiveness and Safety of Stroke … · 2020. 1. 22. · KDIGO’s 2011 guideline further stratified the recommendation in patients with ESKD and](https://reader035.vdocument.in/reader035/viewer/2022071502/6121b2e4f2dde20796001216/html5/thumbnails/22.jpg)
17. Herzog, C. A. et al. Cardiovascular disease in chronic kidney disease. A clinical update
from Kidney Disease: Improving Global Outcomes (KDIGO). Kidney Int 80, 572–586
(2011).
18. Kruger, T. & Floege, J. Vitamin K antagonists: beyond bleeding. Semin. Dial. 27, 37–41
(2014).
19. Chan, K. E., Lazarus, J. M., Thadhani, R. & Hakim, R. M. Warfarin use associates with
increased risk for stroke in hemodialysis patients with atrial fibrillation. J Am Soc Nephrol
20, 2223–2233 (2009).
20. Shah, M. et al. Warfarin use and the risk for stroke and bleeding in patients with atrial
fibrillation undergoing dialysis. Circulation 129, 1196–1203 (2014).
21. Dahal, K., Kunwar, S., Rijal, J., Schulman, P. & Lee, J. Stroke, Major Bleeding, and
Mortality Outcomes in Warfarin Users With Atrial Fibrillation and Chronic Kidney
Disease. Chest 149, 951–959 (2016).
22. Spence, J. D. Cardioembolic stroke: Everything has changed. Stroke and Vascular
Neurology 3, 76–83 (2018).
23. Friberg, L., Benson, L. & Lip, G. Y. Balancing stroke and bleeding risks in patients with
atrial fibrillation and renal failure: the Swedish Atrial Fibrillation Cohort study. Eur. Heart
J. 36, 297–306 (2015).
24. Bonde, A. N. et al. Effect of Reduced Renal Function on Time in Therapeutic Range
Among Anticoagulated Atrial Fibrillation Patients. J. Am. Coll. Cardiol. 69, 752–753
![Page 23: University of Toronto T-Space - Effectiveness and Safety of Stroke … · 2020. 1. 22. · KDIGO’s 2011 guideline further stratified the recommendation in patients with ESKD and](https://reader035.vdocument.in/reader035/viewer/2022071502/6121b2e4f2dde20796001216/html5/thumbnails/23.jpg)
(2017).
25. Wang, T. K., Sathananthan, J., Marshall, M., Kerr, A. & Hood, C. Relationships between
Anticoagulation, Risk Scores and Adverse Outcomes in Dialysis Patients with Atrial
Fibrillation. Heart. Lung Circ. 25, 243–249 (2016).
26. Schneider, P. J., Murphy, J. E. & Pedersen, C. A. Impact of medication packaging on
adherence and treatment outcomes in older ambulatory patients. J. Am. Pharm. Assoc.
(2003). 48, 58–63 (2008).
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APPENDICES
Appendix A
CHA2DS2VASc score
Risk Factors Score
Congestive heart failure 1
Hypertension 1
Age ≥75 2
Age 65‐74 1
Diabetes mellitus 1
Stroke/TIA/thromboembolism 2
Vascular disease 1
Female 1
HASBLED score
Risk Factors Score
Uncontrolled hypertension (systolic blood
pressure > 160 mmHg)
1
Abnormal renal function* and/or liver function^ 1 point each
History of stroke 1
Bleeding 1
Labile INR (unstable or high INRs with time in
therapeutic range of <60%)
1
Elderly (>65 years of age) 1
Drugs (antiplatelet agents, non‐steroidal anti‐
inflammatory drugs, etc.) or alcohol
1 point each
*defined as chronic dialysis, renal transplantation or serum creatinine ≥200 µmol/L ^defined as bilirubin >2 times the upper limit of normal (ULN) in association with aspartate aminotransaminase (AST), alanine aminotransaminase (ALT) or alkaline phosphatase (ALP) >3 X ULN
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Appendix B
Efficacy and safety of warfarin in preventing strokes in ESRD patients with AF
Trial Study Origin, Design
Population Intervention/Comparator
Results Comments
Winkelmayer et al. 2011 (23)
United States/ Retrospective
2313 HD patients (249 on warfarin) Inclusion: Incident dialysis patients ≥66 years old on their first ESRD service date Exclusion: Not enrolled in a drug coverage program in the previous year, had Medicare claims with diagnosis for AF prior start of chronic dialysis
Intervention: Warfarin Comparator: No warfarin use
Primary endpoint: Occurrence of ischemic stroke (HR 0.92, 95% CI 0.61‐1.37) Safety endpoint: Risk of hemorrhagic stroke (HR 2.38, 95% CI 1.15‐4.96)
‐No INR data available
Olesen et al. 2012 (20)
Denmark/ Retrospective
1378 dialysis patients (77.9% HD, 15.4% PD, 6.7% transplant) (178 on warfarin) Inclusion: Discharged from hospital with diagnosis of non‐valvular AF Exclusion: Death, had thromboembolic event, had major bleeding during the 7 days before baseline assessment
Intervention: Warfarin Comparator: No warfarin use
Primary endpoint: Hospitalization or death from ischemic stroke or systemic thromboembolism (HR 0.44, 95% CI 0.26‐0.74) Safety endpoint: Bleeding events (GI, intracranial, urinary tract, airway) (HR 1.33, 95% CI 1.16‐1.53)
‐Outcomes did not differ according to type of renal‐replacement therapy‐No INR data available
Shah et al. 2014 (19)
Canada/ Retrospective
1626 dialysis (HD, PD) patients (756 on warfarin) Inclusion: Patients ≥65 years admitted to hospital with a primary or secondary diagnosis of AF
Intervention: Warfarin Comparator: No warfarin use
Primary endpoint: Hospitalization from ischemic stroke (HR 1.14, 95% CI, 0.78‐1.67) Safety endpoint: Bleeding events (intracranial, GI, intraocular, hematuria, unspecified)
‐% HD/PD not reported ‐No INR data available ‐Stratified by CHA2DS2VASc and HASBLED
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(HR1.44, 95% CI, 1.13‐1.85)
score
Genovesi et al. 2015 (21)
Italy/ Prospective
290 HD patients (134 on warfarin) Inclusion: At least one documented paroxysmal or persistent AF episode, or with permanent AF
Intervention: Warfarin Comparator: No warfarin use
Primary endpoint: Occurrence of stroke (ischemic or hemorrhagic) (HR 0.12, 95% CI, 0.00‐3.59) Safety endpoint: Occurrence of hemorrhagic events (HR 3.96, 95% CI, 1.15‐13.68)
‐Included INR and TTR data: overall mean TTR 54% (IQR 41‐67%) ‐Stratified by CHA2DS2VASc and HASBLED score
Shen et al. 2015 (22)
United States/ Retrospective
12,284 HD patients (1838 on warfarin) Inclusion: Had a new diagnosis of AF and Medicare coverage Exclusion: History of valvular disease
Intervention: Warfarin Comparator: No warfarin use
Primary endpoint: Occurrence of ischemic stroke (HR 0.73, 95% CI, 0.44‐1.20) Safety endpoint: Hemorrhagic stroke (HR 1.92, 95% CI, 0.82‐4.48); GI bleeding (HR 1.36, 95% CI, 0.89‐2.07)
‐No INR data available
HR, hazard ratio; 95% CI, 95% confidence interval; INR, international normalized ratio
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Appendix C
ICD‐10 codes
ICD‐10 admission codes for stroke I63, I64, G45 (excluding G45.5)
ICD‐10 admission codes for bleed Intracranial hemorrhage: I61 Gastrointestinal hemorrhage: K92.0, K92.1, K92.2 (first 3 are main codes), K25.0, K25.2, K25.4, K25.6, K26.0, K26.2, K26.4, K26.6, K27.0, K27.2, K27.4, K27.6, K28.0, K28.2, K28.4, K28.6, K29.0 Intraocular hemorrhage: H43.1, H35.6 Hematuria: N02, R31
*ICD‐10 codes were adapted from Shah et al. 2014 20
Appendix D
Parameters Collected
Patient Demographics Age (years) Gender: male, female Body mass index (kg/m2): <18.5, 18.5‐24.9, 25‐29.9, 30‐39.9, ≥40 Smoking status: current smoker, former smoker, non‐smoker, unknown status Alcohol consumption: non‐drinker, ex‐drinker, current‐drinker, heavy‐drinker (≥3 drinks/day), unknown drinker status
Stroke Characteristics Date of stroke Type of stroke
Bleed Characteristics Date of bleeding event Source of bleed
Stroke Prevention Therapy
Drug name, dose, route, frequency, and start date (at time of entering study, and at time of the stroke or bleed event) Primary or secondary prevention
Past Medical History Congestive heart failure
Hypertension
Diabetes mellitus
Stroke/TIA/thromboembolism
Vascular disease (includes coronary artery disease, peripheral artery disease)
Abnormal liver function
Abnormal renal function
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Bleeding
Labile INRs (if data available)
Alcohol abuse
Dyslipidemia
Active malignancies
Chronic lung disease (asthma, COPD)
Concomitant Medications Baseline medications (likely to affect risk of bleeding):
NSAIDs: ibuprofen, naproxen, celecoxib, diclofenac
Low‐molecular weight heparin (LMWHs): enoxaparin, dalteparin, tinzaparin, fondaparinux
Steroids: prednisone, prednisolone, methylprednisolone
Acid suppression medications: PPIs (pantoprazole, lansoprazole, omeprazole, rabeprazole) , H2RAs (ranitidine, famotidine, cimetidine)
New starts (likely to cause drug interactions and/or affect INR):
Antibiotics (especially fluoroquinolones, clarithromycin, metronidazole, septra)
Antifungals (especially fluconazole)
Phenytoin
Amiodarone
Rifampin
Carbamazepine
Vitamin K
Azathioprine
Trazodone
Sucralfate
Lab values INR (average of INR values available 7 days prior to the stroke or bleed event)