DOI: https://doi.org/10.21203/rs.2.10861/v2
Ischemic stroke is the leading cause of death and disability among Chinese adults. 75% ischemic strokes are caused by atherothrombosis, and 20-25% are caused by atrial fibrillation (AF) [1,2]. It is believed that prethrombotic forces, along with endothelial dysfunction and blood stasis of AF are the basis of thrombus formation and growth, when large thrombi embolize to the cerebral circulation, leading to severe cerebral infarction. Strokes related to AF are associated with higher mortality and more severe neurologic disability [3-6].
Oxidized low density lipoprotein (Ox-LDL) has an important role in the pathogenesis of vascular atherosclerosis. It plays a pro-inflammatory and pro-atherogenic role by inducing endothelial dysfunction [7]. Atherosclerotic thrombosis and oxidative stress play key roles in acute ischemic stroke (AIS) [8,9]. Previous studies had shown that elevated plasma Ox-LDL levels were associated with coronary heart disease [10,11]. High concentrations of plasma Ox-LDL were associated with an increased incidence of metabolic syndrome [12]. However, data from studies on the predictive value of Ox-LDL levels for outcomes of ischemic stroke were scarce.
Increasing evidence suggested that statins had pleiotropic effects in addition to a lipid-lowering effect [13,14]. In clinical trials, statins had been shown to reduce cardiovascular events, including stroke, myocardial infarction and death [15-17]. Early statins administration enhances thrombolysis, augments antithrombotic responses, modulates endothelial nitric oxide synthase (eNOS), reduces nitric oxide production, decreases matrix metalloproteinase-9 (MMP-9) and ROS levels, increases cerebral blood flow [18-20]. On the other hand, statins could attenuate thrombus formation and thrombus growth, reduce infarct volume [16,17].
In a previous study, poststroke statins use was associated with improved 5-year survival in patients with AF-related stroke [21]. However, poststroke assessment of statins use was susceptible to some interference, such as survivor bias. A largest meta-analysis showed that statins use at the time of stroke onset was associated with improved clinical outcomes [22], but there was no AF subgroup analysis. There were limited studies about the potential use and effectiveness of reduce the plasma Ox-LDL and improve the outcome of AF-related stroke.
In this study, we assembled a cohort of patients with AF-related AIS from four centers. The purpose was to investigate whether prestroke statins use can reduce plasma Ox-LDL levels and improve 3-month clinical outcomes in patients with AF-related AIS.
Study Population
This study was a multicenter prospective study conducted in four medical centers: The Second People’s Hospital of Chengdu, Nuclear Industry 416 Hospital, Yongchuan Hospital and the First Affiliated Hospital, Chongqing Medical University. Patients with AIS were consecutively admitted to the stroke unit within 72 h of symptom onset from October 2015 to April 2018. Stroke was diagnosed according to clinical presentation, neurologic examination (sudden neurological deficit >24h that has a presumable vascular etiology), and the results of brain computed tomography (CT) scan or diffusion-weighted imaging magnetic resonance imaging (MRI). Electrocardiogram evidence of AF was confirmed in all patients within the prior 6 months. Ischemic stroke was not explained by other etiologies, such as large artery atherosclerosis, tumor, infection, vasculitis, small vessel disease, or procedural or surgical complication. Etiology of stroke was classified according the modified Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria in four medical centers. AF-relate stroke was confirmed by an experienced neurologist who blinded to the study. The severity of stroke was assessed using the National Institutes of Health Stroke Scale (NIHSS).
Inclusion criteria
Patients were included in the study only if they fulfilled all the following criteria: 1. Admission for first-ever AIS within 72h, and modified Rankin Scale (mRS) score was 0 before AIS; 2. Evidence of acute ischemic lesion consistent with clinical manifestations, and sudden neurological deficit >24h; 3. No patients received thrombolytic and mechanical thrombectomy therapy (because those patients undergo a different therapeutic strategy and a high percentage of hemorrhagic transformation); 4. Patients had to have electrocardiogram-confirmed AF within the prior 6 months. The CHA2DS2-VASc scoring system assesses the risk of stroke, with a score of 2 or greater indicating a need for anticoagulation. All patients received standard treatment after admission, which consisted of antiplatelet or anticoagulant therapy, lipid-lowering medications and so on.
Exclusion criteria
Exclusion criteria included 1.A history of acute myocardial infarction, rheumatic heart disease, valvular atrial fibrillation, other severe arrhythmias(other severe atrioventricular block and supraventricular arrhythmia); 2. Vasculitis, renal failure (estimated glomerular filtration rate <30 ml/min.1.73 m2), active malignancies, severe pulmonary disease, hypohepatia, or procedural or surgical complications; and 3. A history of deep venous thrombosis or pulmonary embolism;4.Acute or chronic systemic inflammatory disease or autoimmune diseases. 5. Cerebral hemorrhage, fever (≥38℃), or hypoxia (arterial oxyhemoglobin saturation<90%) on admission.
Data collection
The previous medical history of all patients was collected to confirm whether statins were used before stroke. To rule out other severe arrhythmias and determine AF type, all patients underwent a 72 h-Holter electrocardiogram monitoring on the next day after admission, which was evaluated by two investigators who were blinded for patients. The interobserver data differences were resolved by consensus. Cardiac ultrasonography examination was performed on admission to exclude rheumatic heart disease.
Blood samples were collected from all stroke patients on admission and at 3 months. Plasma Ox-LDL levels were measured using the enzyme-linked immunosorbent assay (ELISA) (E-EL-H0124c, Wuhan, China) according to manufacturer’s protocol. Each sample was assayed in duplicate. The intraassay variation among the duplicates for all samples was <10%. The Ox-LDL levels were expressed in U/L. Level of plasma Ox-LDL was considered abnormal if it was ≥3.4u/l.
All patients were followed up once a month for a total of 3 months. All patients were followed up by face-to-face interview, and patient’s information was obtained from hospital medical records. Patients were evaluated by trained staffs, who were blinded to patients’ baseline clinical status. The outcome was defined as death, major disability (scores 3–5 on the modified Rankin Scale [mRS]), and composite outcome (death/major disability) at 3 months after stroke onset.
Statistical Analysis
First, patients were classified into prestroke statins use and no prestroke statins use groups according to statins use before stroke on admission. The data are presented as median values (interquartile range [IQR]), numbers (%), or mean values (±standard deviation). Demographic characteristics, vascular risk factors, current smoking, and so on were compared between the 2 subgroups by univariate analysis using Pearson χ2 test, Fisher exact 2-sided test, or Student’s t test, distributions of continuous variables were determined by the Kolmogorov–Smirnov test, Mann–Whitney two sample test was applied in case of non-normal distributions. Second, we performed logistic regression analyses to determine the association between baseline plasma Ox-LDL levels,3-month plasma Ox-LDL levels, prestroke statins use and outcomes (death, major disability and death/major disability), adjusting for all confounders (age, baseline NIHSS score, mean AF duration, CHA2DS2-VASc score, sex, BMI, hypertension, current smoking, current alcohol consumption, diabetes, hyperlipidemia, AF type, family history of stroke, prestroke statins use, Ox-LDL levels and use of antihypertensive, warfarin, direct oral anticoagulants, antiplatelets). The results were expressed as adjusted odds ratios (OR) with their corresponding 95% confidence intervals (CI). The data were analyzed using SPSS 22 software. P<0.05 was considered statistically significant.
Characteristics of the patients
A total of 242 AIS patients with AF (118 men; 124 females) were included in this study, their mean AF duration was 67.7 months. Of all patients, 85 had paroxysmal AF and 157 had persistent AF. 57 (23.6%) patients received anticoagulants, and 40(16.5%) patients received antiplatelets. 106 (43.8%) were assigned to the prestroke statins use group. The baseline characteristics of patients in the no prestroke statins use group (136) and prestroke statins use group (106) were compared (Table 1). At baseline, patients with prestroke statins use showed a significantly higher prevalence of hyperlipidemia than that in patients with no prestroke statins use (P<0.001). Patients with statins use showed significantly lower NIHSS score and Ox-LDL levels than patients with no statins use (P<0.005).
At discharge, all the patients were prescribed statins; 110 patients were prescribed direct oral anticoagulants, 61 in no prestroke statins group and 49 in prestroke statins group; 85 patients were prescribed warfarin, 46 in no prestroke statins group and 39 in prestroke statins group; 35 patients were prescribed antiplatelets, 25 in no prestroke statins group and 15 in prestroke statins group. 7 patients had intracranial hemorrhage conversion and 5 patients had gastrointestinal bleeding, who did not receive the anticoagulants and antiplatalets at discharge. After 4-8 weeks, 5 patients were prescribed direct oral anticoagulant, and 7 patients were prescribed antiplatelet therapy. No bleeding complications occurred during the follow-up period, and no patients stopped taking anticoagulants or antiplatelet drugs. There was no difference in direct oral anticoagulants, warfarin and antiplatelets between two groups(P>0.05). During the 3-month follow-up period, no patients were denied follow-up, and no patients had adverse reactions of statins.
Table 1. Comparison of baseline characteristics between patients with no prestroke statins use prestroke statins use groups.
|
No prestroke statins use group (136) |
Prestroke Statins use group (106) |
OR(95% CI) |
P* |
Age, y (Mean SD) |
66.1±10.5 |
67.2±9.9 |
|
0.303 |
NIHSS score, median (IQR) |
11 (7-14) |
8(6-12) |
|
0.041 |
Mean AF duration, m(Mean SD) |
67.7±10.0 |
67.8±11.3 |
|
0.915 |
CHA2DS2-VASc, median (IQR) |
4(3-5) |
4(3-5) |
|
0.090 |
Females, n (%) |
66 (48.5%) |
58 (54.7%) |
1.29 (0.77-2.13) |
0.339 |
Men, n (%) |
70 (51.5% |
48 (45.3%) |
1.29 (0.77-2.13) |
0.339 |
BMI≥24 kg/m, n (%) |
36 (26.5%) |
37 (34.9%) |
1.50 (0.86-2.59) |
0.156 |
Hypertension, patients, n (%) |
90 (66.8%) |
79 (74.5%) |
1.50 (0.85-2.63) |
0.160 |
Current Smoking, n (%) |
46 (33.8%) |
30 (28.3%) |
0.77 (0.45-1.34) |
0.359 |
Current alcohol consumption, n (%) |
41 (30.2%) |
24 (22.6%) |
0.67 (0.38-1.22) |
0.191 |
Diabetes, n (%) |
37 (27.2%) |
31 (29.2%) |
1.11 (0.63-1.94) |
0.736 |
Hyperlipidemia, n (%) |
40 (29.4%) |
79 (74.5%) |
7.02 (3.96-12.4) |
<0.001 |
AF Type |
|
|
|
|
Paroxysmal, n (%) |
47(34.6) |
38(35.8) |
0.95(0.56-1.61) |
0.835 |
Permanent, n (%) |
89(65.4) |
68(64.2) |
0.95(0.56-1.61) |
0.835 |
Family history of stroke, n (%) |
28 (20.6%) |
23 (21.7%) |
1.07 (0.57-1.99) |
0.834 |
Ox-LDL,U/L (Mean SD) |
37.6±5.1 |
33.5±5.5 |
|
<0.001 |
Medication use |
|
|
|
|
Warfarin, n (%) |
20 (14.7%) |
19 (17.9%) |
1.27 (0.64-2.52) |
0.499 |
direct oral anticoagulants, n (%) |
10(7.4%) |
8(7.5%) |
1.03(0.39-2.70) |
0.954 |
antiplatelets, n (%) |
25(18.4) |
15(14.2) |
0.73(0.36-1.45) |
0.379 |
Antihypertensive, n (%) |
76 (55.9%) |
58 ((54.7%) |
0.95 (0.57-1.59) |
0.856 |
Bold indicates P-values less than 0.05.
*Comparison between no prestroke statins use and prestroke statins use groups. The data are presented as median values (interquartile range [IQR]), numbers (%), or mean values (±standard deviation). Categorical variables are expressed as frequency (percent) for P values. Pearson χ2 test, Fisher exact 2-sided test, Student’s t test, distributions of continuous variables were determined by the Kolmogorov–Smirnov test, Mann–Whitney two sample test was applied in case of non-normal distributions.
Plasma Ox-LDL levels in the prestroke statins use and no prestroke statins use groups
Plasma Ox-LDL levels were significantly lower in the prestroke statins use group on admission (33.5±5.5 vs 37.6±5.1, P<0.001). Compared with the baseline, Ox-LDL levels of the 3-month treatment period decreased both in two groups, the prestroke statins use group had lower Ox-LDL level (24.4±7.6 vs 29.3±6.0, P<0.001). Ox-LDL levels decreased about 27.1% in the prestroke statins use group, 22.1% in the no prestroke statin use group. The data showed significantly different Ox-LDL levels in the two groups at different time points.
Association Between Plasma Ox-LDL levels and Prognosis
We also analyzed whether the plasma Ox-LDL levels had effect on outcomes. 70 (70/242, 28.9%) patients had died during follow-up, and 86 patients had major disability at 3 months. Compared with the surviving patients, the patients who died had higher Ox-LDL levels (37.9±5.6 vs 35.0±5.5, P<0.001) on admission, and at 3 months (28.8±4.7 vs 26.5±7.3, P=0.039). Patients with major disability had higher Ox-LDL levels than patients with good prognosis on admission (36.4±6.0vs 33.6±4.6, P=0.004), there was no significant difference between two groups at 3 months (27.6±6.4 vs 25.4±8.0, P = 0.099). In the multivariable logistic regression model, adjusting for age, baseline NIHSS score, mean AF duration, CHA2DS2-VASc score, sex, BMI, hypertension, current smoking, current alcohol consumption, diabetes, hyperlipidemia, AF type, family history of stroke, prestroke statins use, and use of antihypertensive, warfarin, direct oral anticoagulants, antiplatelets, baseline plasma Ox-LDL levels were associated with increased risk of 3-month mortality(adjusted OR, 1.05; 95% CI, 0.99-1.12; P=0.047), there was no association between baseline plasma Ox-LDL levels and major disability (adjusted OR, 1.04; 95% CI, 0.96-1.12; P=0.335), and composite outcome (adjusted OR, 1.07; 95% CI, 0.99-1.14; P=0.072); similarly, 3-month plasma Ox-LDL levels were not associated with mortality (adjusted OR, 1.05; 95% CI, 0.99-1.10; P=0.096), major disability (adjusted OR, 1.04; 95% CI, 0.99-1.10; P=0.182), and composite outcome (adjusted OR, 1.04; 95% CI, 0.98-1.09 ; P=0.146).
Multivariable Models on the Association Between prestroke statins use and Death/Major disability
70 patients had died, and they had a significantly higher NIHSS score (13.4±6.4 vs 9.1±4.1, P<0.001), older age (68.6±11.3 vs 65.7±9.7, P=0.022), and lower percentage of prestroke statins use [32.9% (23/70) vs 48.3% (83/172); OR, 0.53 (95% CI, 0.30-0.94); P=0.029] on admission. In the multivariable logistic regression model, after adjustment for all confounders, prestroke statins use was associated with decreased risk of 3-month mortality(adjusted OR, 0.38; 95% CI, 0.16-0.91; P=0.031),and higher NIHSS score was associated with increased risk of mortality at 3 months(adjusted OR, 1.18; 95% CI, 1.11-1.27; P<0.001); 3-month plasma Ox-LDL levels were entered into multivariate logistic regression, prestroke statins use was associated with decreased risk of 3-month mortality(adjusted OR, 0.36; 95% CI, 0.15-0.84; P=0.019),and higher NIHSS score was associated with increased risk of mortality at 3 months(adjusted OR, 1.18; 95% CI, 1.10-1.26; P<0.001).
In addition to the 70 deaths, of the remaining 172 patients, 83 patients were in the prestroke statins use group, 32 (32/83, 38.6%) patients had a major disability, which was lower percentage than that in patients with no prestroke statins use (54/89, 60.7%); patients with 3-month major disability had a significantly higher NIHSS at admission (10.3±4.2 vs 8.0±3.7, P<0.001) than that in patients with a good prognosis.
In the multivariable logistic regression model, after adjusting for all confounders, prestroke statins use was associated with decreased risk of 3-month major disability (adjusted OR, 0.38; 95% CI, 0.15–0.99; P=0.047) and composite outcome (adjusted OR, 0.31; 95% CI, 0.17-0.74; P=0.009), and higher NIHSS score was associated with increased risk of 3-month major disability (adjusted OR, 1.17; 95% CI, 1.06–1.30; P=0.003) and composite outcome (adjusted OR, 1.20; 95% CI, 1.10-1.29; P<0.001); 3-month plasma Ox-LDL levels were entered into multivariate logistic regression, prestroke statins use was associated with decreased risk of 3-month major disability (adjusted OR, 0.38; 95% CI, 0.15–0.95; P=0.038) and composite outcome (adjusted OR, 0.27; 95% CI, 0.11-0.64; P=0.003), and higher NIHSS score was associated with increased risk of 3-month major disability (adjusted OR, 1.17; 95% CI, 1.06–1.30; P=0.003) and composite outcome (adjusted OR, 1.19; 95% CI, 0.10-1.29; P<0.001).
Table 2 Multivariable Models Showing Association Between prestroke Statins use and Prognosis
|
OR (95% CI) |
P* |
Death |
0.38(0.16-0.91) |
0.031 |
Major disability (mRs3-5) |
0.38 (0.15-0.99) |
0.047 |
Major disability (mRs3-5)+ death |
0.31(0.17-0.74) |
0.009 |
Bold indicates P-values less than 0.05.
*Multivariable adjusted for age, baseline NIHSS score, mean AF duration, CHA2DS2-VASc score, sex, BMI, hypertension, current smoking, current alcohol consumption, diabetes, hyperlipidemia, AF type, family history of stroke, prestroke statins use, baseline Ox-LDL levels and use of antihypertensive, warfarin, direct oral anticoagulants, antiplatelets.
AF can increase platelet reactivity, lead to thrombin generation, and platelet aggregation, which underlie the formation of a thrombus, and the size of a thrombus can affect the infarct volume and severity of stroke [23]. According to previous study, AF increases the incidence of stroke fivefold, patients with cardioembolic strokes were at greater risk of death, severe disability and risk of hemorrhagic transformation [24]. Oral anticoagulants were the most effective treatment for preventing cardioembolic stroke, but in our country, the rate of AF treatment was very low. In our study, 57(23.56%) patients were received the oral anticoagulants, the result was consistent with previous study [25].
Statins had pleiotropic effects in addition to LDL-C lowering. Data had shown that statins had benefits on the endothelium, platelets, myocardium. Severe studies showed that prestroke statins use was associated with milder stroke severity at stroke onset [26,27]. In this study, we found that prestroke statins use among AF-related stroke was associated with lower NIHSS score on admission, this study suggested that the prestroke statins use might reduce the severity of stroke. Several studies had demonstrated a beneficial effect of baseline statins on the outcome of patients with stroke [28,29]; patients with prestroke statins were more likely to achieve good functional outcome, but few studies had focused on stroke associated with AF. Examining AF patients was important, because the source of these strokes was the left atrium or left atrial appendage, and AF-related stroke was associated with high morbidity and mortality. A previous analysis of lipid lowering treatment in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial demonstrated decreased ischemic stroke (HR 0.56;95% CI,0.36 to 0.89; P=0.01) among individuals with AF used lipid lowering therapy at baseline, but this analysis did not evaluate differences in ischemic stroke functional outcomes. A meta-analysis showed that the association of prestroke statins use and good functional outcome was significant in patients with large artery atherosclerosis and small vessel occlusion, but not in cardioembolic stroke [30]. In a recent study by Ko et al, that enrolled 1030 AF-related ischemic stroke patients followed up for 30 days, the authors aimed to observe the influence of prestroke statins use on functional outcome, the results showed that prestroke statins use among patients with AF-related ischemic stroke was associated with a 32% reduction in the risk of the stroke being severe at the time of discharge or decreased mortality at 30 days[31], but the limitation of this study was that the patients were followed up for a short time, only investigated clinical outcome at discharge and the 30-day mortality rate. In our study, all the patients were followed for 3 months, we found that prestroke statins use had lower mortality and major disability in AF-related AIS.
There are biological mechanisms underlying the association between statins use and improved clinical outcomes after ischemic stroke. Prestroke statins use was associated with increased collateral blood flow, which might be beneficial in cardioembolic stroke and reduce infarct size [32, 33], and in the animal model, atorvastatin use could increase angiogenic responsiveness[34,35], and rosuvastatin could increase neovascularization via mechanisms independent of lipid lowering[29]. Statins could reduce platelet activation, inhibit subclinical inflammation, oxidative stress, improve endothelial dysfunction [36-40], and significantly reduce venous thromboembolism [40]. Statins had also been reported to decrease levels of C-reactive protein, interleukin-6, TNF-α, improve left ventricular function among individuals with heart failure [41].
The mechanism of increased plasma Ox-LDL levels after AIS was unclear, although it was speculated that AIS was associated with enhanced oxidative stress, which can further oxidize native LDL-cholesterol to Ox-LDL [42,43]. Another possible explanation might be the increase in lipolysis and lipid peroxidation after AIS [44,45]. In this study, we found that plasma Ox-LDL levels were high on admission and decreased at 3 months after stroke. We also found that Ox-LDL levels were significantly lower in the prestroke statins use group on admission, and elevated plasma Ox-LDL levels were associated with increased risk of 3-month mortality. These findings suggest that plasma Ox-LDL levels may be a useful marker for monitoring the oxidative status of the brain after cerebral infarction, and prestroke statins use might inhibit Ox-LDL production, protect endothelial function.
In this study, we found that prestroke statins use in patients presenting with AF-related ischemic stroke was associated with a reduction in the risk of major disability and death, this association persisted after adjustment for all confounders including age, baseline NIHSS score, mean AF duration, CHA2DS2-VASc score, sex, BMI, hypertension, current smoking, current alcohol consumption, diabetes, hyperlipidemia, AF type, family history of stroke, prestroke statins use, baseline or 3-month Ox-LDL levels and use of antihypertensive, warfarin, direct oral anticoagulants, antiplatelets, these results suggested that prestroke statins use could improve clinical outcome in AF-related AIS.
Some limitations of this study merit consideration. First, in most cases we relied on baseline and 3-month blood sample, thus we could not account for variations in Ox-LDL levels that occur over time. Repeat assays could provide additional information on its prognostic implications in AF-related AIS. Second, the limitations of our study were related to the small number of patients and the short duration of the study. Third, although we adjusted for NIHSS score, which had been shown to correlate with infarction volume, we lacked data on infarction volume. Forth, there were many different types of statins, and it was possible that each drug had different effects on the prognosis of stroke, this study did not separately list the effects of a given statin on the prognosis of stroke, on the other had, we did not know the exact time and dose of statins, so the relationship between dose and time dependence on prognosis had not been assessed. Fifth, patients received thrombolytic and mechanical thrombectomy therapy were excluded, which limited the generalizability of the results. Sixth, Ox-LDL had an established role in the pathogenesis of atherosclerosis, the carotid stenosis or vessel occlusion were not analyzed in this study, which might have an impact on the results. The strength of our study included that it was a multicenter clinical study with the collection of a broad range of clinical data, its analysis, adjusting for a wide variety of confounding factors, the results were very reliable.
In conclusion, our findings indicated that AF-related stroke was associated with high mortality and major disability. Prestroke statins use could reduce plasma Ox-LDL level and improve clinical outcomes in patients with AF after acute ischemic stroke.
CI: Confidence Interval; M: Mean; OR: Odds Ratio; SD: Standard Deviation; Ox-LDL: oxidized low density lipoprotein; AIS: acute ischemic stroke; AF: atrial fibrillation; IQR: interquartile range
Ethics approval and consent to participate
We obtained ethical approval for this study from the Medical and Health Research Ethics Committee in Second people’s Hospital of Chengdu, the Second Affiliated Hospital of Chengdu College, Nuclear Industry 416 Hospital of Chengdu, and Chongqing Medical University.The current study was carried out according to the Declaration of Helsinki. If the patient has consciousness disorder or aphasia, the decision cannot be made by themselves, the consent form can be signed by the patient's legal proxies. Prior to enrollment, all patients or their legal proxies will be given detailed information about the aims, scope and possible consequences of the trial by a physician. No diagnostic or interventional procedures required for the clinical trial. Written informed consent was obtained from all study participants or their legal proxies.
Consent for publication
Not applicable.
Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Competing interests
The authors declare that they have no competing interests.
Funding
This work was funded by the Health and Family Planning Commission of Chengdu (2015009), which is not involved in the database management (collection, analysis, interpretation of data) and has no access to patient information. The funding body did not participate in designing the study or writing the manuscript. The study protocol has undergone peer-review process by the funding body.
Authors’ contributions
LYH was responsible for the concept and design of the study, data collection and analysis and the first draft of the paper and final manuscript. Ronghua Xu and JW was responsible for the concept and design of the study, the data analysis and interpretation. WWD was responsible for overseeing the concept and design of the study, the data analysis and interpretation, and writing the paper. LLZ YSD, LJZ and WZ were responsible for data collection. All authors read and approved the final manuscript for publication.
Acknowledgments
We thank all patients and their families for generously consenting to use of human tissues in this research.
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24 Gebreyohannes EA, Bhagavathula AS, Tegegn HG. Poor outcomes associated with antithrombotic undertreatment in patients with atrial fibrillation attending Gondar University Hospital: a retrospective cohort study.Thromb J. 2018;16:22. https:// doi: 10.1186/s12959-018-0177-1. eCollection 2018.