Using Thrombin Time to Evaluate the Efficacy of Anticoagulant Therapy for Acute Cerebral Infarction

Background

Acute ischemic stroke (AIS) is the second most common cause of death and the leading cause of disability in China. Intravenous (IV) recombinant tissue plasminogen activator and urokinase thrombolysis have shown to be effective for patients with AIS within six hours of onset [1-3]. However, there are currently no effective and safe treatments for patients with AIS after 6 hours of the onset of ischemic symptoms. Argatroban is a synthetic direct thrombin inhibitor derived from L-arginine. Argatroban exerts its anticoagulant effects by selectively binding to the ac- tivation site of thrombin, which leads to the inhibition of throm- bin-induced fibrin formation and platelet aggregation [4,5]. Pre- vious studies have demonstrated that argatroban could improve regional blood flow and ameliorate neurological deficits without increasing intracranial hemorrhage [6-10].

Compared with heparin, argatroban has a short elimination half- life of approximately 39-51 minutes. Moreover, argatroban has a predictable anticoagulant effect that does not potentiate hepa- rin-induced thrombocytopenia; thus, it causes less bleeding with the same anticoagulant effect [3,10,11]. LaMonte et al reported that argatroban exerted a safe anticoagulant effect in 171 patients with AIS within 12 hours of symptom onset without increasing intracranial hematoma [8]. However, there have been few stud- ies on the application of coagulation markers, including TT for assessing the anticoagulant pharmacological effects in patients with acute cerebral infarction. This study aimed to assess the efficacy and safety of IV argatroban in patients with AIS at >6 h after the onset of ischemic symptoms. Moreover, it aimed to evaluate the relationship between TT levels and the clinical ef- fectiveness and safety of IV argatroban therapy.

Materials and Method

Patients

we retrospectively analyzed 180 patients (102 males, 78 females; age <80 years) with AIS who received IV argatroban treatment between February 2019 and December 2019. These patients ad- mitted within 48 hours of the onset of symptoms with an NIHSS score of 4-22. All the patients met the diagnostic criteria of ce- rebral infarction formulated by the Fourth National Cerebrovas- cular Disease conference in 1995. All the patients suffered from mild to severe neurological symptoms, including hemiparesis,hemi-sensory disturbance, dysarthria, hemianopia, diplopia, and vertigo. The major risk factors for AIS, including hypertension, diabetes mellitus, cigarette smoking, severe alcohol drinking, hyperlipidemia, previous history of stroke, as well as underlying cardiac diseases e.g. atrial fibrillation, evaluated. All the patients underwent CT or MRI brain scanning before any treatments.

IV Argatroban

For the first two days, argatroban (Nova Stan, Mitsubishi Phar- ma Corporation, Osaka, Japan) was administered at a loading dose of 60 mg/day by continuous IV infusion. This was followed by IV infusion of 20 mg/day in two divided doses over three hours for the subsequent five days. All the patients received oral antiplatelet and IV edaravone along with argatroban treatment. The patients underwent routine CT examinations after the termi- nation of IV argatroban therapy. In the case of neurological dete- rioration, emergent CT was performed to detect any hemorrhage or progression of infarcted area.

Clinical Assessment

Clinical assessment included vital signs, blood glucose titration, complete blood counts, coagulation profile, NIHSS score, and CT/MRI scanning. A stroke team member obtained the NIHSS scores at admission, at 7 days after initial argatroban treatment, and on the discharge day.

The initial stroke severity was analyzed and divided into three categories based on the baseline NIHSS score as follows

1. Mild (0-6)

2. Moderate (7-15), and

3. Severe (>16).

Among the included patients, 46 (25.6%), 112 (62.2%), and 22 (12.2%) patients were diagnosed with mild, moderate, and severe stroke, respectively. The NIHSS score at admission compared to the score at 7 days after treatment. The levels of PT, aPTT and TT measured by enzyme-linked immunosorbent assay.

The Criterion of Therapeutic Effect

According to the evaluation criteria for the patients with acute cerebral infarction. The therapeutic effect was classified as com- plete recovery (function defect score decreased by 91%–100%), remarkable progress (function defect score decreased by 46%- 90%), progress (function defect score decreased by 18%-45%), no change (function defect score decreased to < 17%), and dete- rioration (function defect score increased by > 17%).

Statistical Analysis

The NIHSS, aPTT, PT, and TT values expressed as mean ± SD. Pre- and post- treatment values compared using the unpaired t-test. Between-group comparisons performed using the chi- square test. Statistical significance was set at p < 0.05. All statis- tical analyses performed using the Stat View software (Macin- tosh version 5.0, SAS Institute).

Results

We enrolled 180 patients who were treated for deteriorating acute subcortical ischemic stroke. Table 1 presents the baseline characteristics of the patients. The average age of the patients was 63.13 ± 8.44 years. Moreover, 43.89% of the patients were ≥65 years old while 56.67% of the patients were male. The me- dian baseline National Institutes of Health Stroke Scale (NIHSS) score was 10 ± 4. The median time from onset to IV argatroban was 16 ± 8 hours with 44% of the patients receiving IV arga- troban within 12 hours. Further, 20% and 12% had moderate to severe middle cerebral artery stenosis and basal artery stenosis, respectively, based on computed tomography (CT) or magnet- ic resonance imaging (MRI). Furthermore, 25%, 12.5%, 62.5% had 0, 1 or 2, and 3 risk factors, respectively.

                                                                   Table 1: Baseline Characteristics of the Patients

Table 2 shows the values of different coagulate makers before and after argatroban therapy. There was a slightly increased aPTT prolongation after 24 h of argatroban treatment, which was 44% greater than the pretreatment value. Moreover, there was PT prolongation at 24 hours after initial treatment; howev- er, there was no significant difference with the baseline value. Plasma TT prolonged after therapy. The mean values before and after 24 hours of treatment with argatroban were 17.25 ± 2.64 and 56.73 ± 24.18, respectively.

                               Table 2: Values of Different Coagulation makers before and after Agatroban Therapy

The mean NIHSS scores after or before 7 days of treatment with argatroban were 10 ± 4 (range: 4-22) and 6.98 ± 3.88 (range: 0-16), respectively. Among the included patients, 44 (24.44%) patients showed complete recovery, 61 (33.89%) patients showed remarkable progress, 32 (17.78%) patients made prog- ress, 28 (15.56%) patients showed no change, and 15 (8.33%) patients worsened after treatment with argatroban. Taken to- gether, the total effective rate was 76.11%. Further, 72, 96, 12, patients with plasma TT were tested within 40 s (Table 3, group a), 40-80 s (Table 3, group b), and > 80 s (Table 3, group c). In group a, the mean NIHSS score decreased from 10.01 ± 3.86 to 7.92 ± 4.45 at 7 days after argatroban treatment. Moreover, 16 (22.22%), 22 (30.56%), 10 (13.89%), 17 (23.61%), and 7 (9.72%) patients showed complete recovery, remarkable prog-ress, progress, no change, and worsening after treatment with argatroban, respectively. Taken together, the total effective rate was 66.67%. In-group b, the mean NIHSS score decreased from 9.79 ± 3.49 to 6.14 ± 3.88. Further, 24 (25%), 35 (36.46%), 20 (20.83%), 10 (10.42%), and 7 (7.29%) patients showed com- plete recovery, remarkable progress, progress, no change, and worsening after treatment with argatroban, respectively. Taken together, the total effective rate was 82.29%. In-group c, the mean NIHSS score decreased from 11.62 ± 2.28 to 8.11 ± 2.03. Moreover, 4 (33.33%), 4 (33.33%), 2 (16.67%), 1 (8.33%), and 1 (8.33%) patient showed complete recovery, remarkable prog- ress, progress, no change, and worsening treatment with argatro- ban. Taken together, the total effective rate was 83.33%.

                                        Table 3: Therapeutic Effect in the Different Groups

None of the patients showed severe systemic or symptomatic intracerebral bleeding. Hemorrhagic infarction developed in one patient in-group c; however, the patient’s symptoms did not worsen.

Discussion

Most patients with AIS cannot reach the hospital within six hours of symptom onset, and therefore there is a specific need for an effective and safe treatment for these patients, which is yet to be established. Argatroban, which is a synthetic peptido- mimetic antithrombin agent, is the first clinical anticoagulant to exclusively target thrombin. The present study showed that IV argatroban therapy could prevent recurrence and progression of thrombosis in the infarcted area. A previous study showed that argatroban allowed safe anticoagulation in patients with AIS at 12 hours after the onset of symptoms without increasing intra- cranial hematoma. In this study, we observed that IV argatroban treatment achieved good results and had a very low hemorrhagic risk (1/180 patient, 0.56%). The median NIHSS score at admis- sion (10 ± 4) decreased to 6.98 ± 3.88 after 7 days of therapy. Appropriate supportive care, including blood pressure, glucose, and lipid control, was paramount to achieving these results. Clinical symptom deterioration occurred in patients with severe stenosis of the middle or basal cerebral artery (10/15 patients, 66.67%).

Monitoring the status of anticoagulation is an important clini- cal parameter in patients with acute cerebral infarction during IV anticoagulant therapy. Although argatroban commonly used in patients with AIS, there have only been a few studies on the relationship between the anticoagulation degree and clinical out- comes. A previous study recommended the analysis of the aPTT for argatroban. A steady-state aPTT was achieved after several hours of treatment, which should be approximately 1.5-3.0 fold increase of the aPTT baseline; however, it should not exceed 100 seconds (Kawai et al., 1996). In North America, a randomized, double-blinded, placebo-controlled study on direct thrombin in- hibition in AIS showed that argatroban at each dose prolonged the aPTT without increasing symptomatic intracranial hemor- rhage or major bleeding [12]. We measured the values of aPTT, PT, and TT in the peripheral blood of patients who received ini- tial therapy for 24 hours. Further, we analyzed the relationship between blood coagulation biomarkers (aPTT, PT, TT) and the therapeutic effect. Consistent with previous findings, we found a slightly increased aPTT prolongation after 24 hours of argatro- ban treatment; however, the value was only about 44% greater than the pretreatment level. Notably, plasma TT was significant- ly prolonged after 24 hours of argatroban treatment.

In our study, the patients were allocated to three groups accord- ing to the TT value, which indicated the anticoagulation degree. There was no significant inter-group difference in the total effec- tive rate after IV argatroban. We observed high rates of positive outcomes in all three groups. However, the proportion of patients who completely recovered in Group b and Group c was signifi- cantly higher than that in Group a. Given the hemorrhagic risk, we observed that when the TT value was 40–80 seconds, IV arg- atroban effectively improved the complete recovery rate without increasing the hemorrhage risk. In addition, we found that TT prolongation did not increase the total effective rate; however, it increased the chance of complete recovery and reduced the risk of worsening. Moreover, our results indicated that therapy with argatroban should be monitored using TT. Thrombin Time (TT) assessment at 24 hours after initial therapy for confirm- ing whether the desired therapeutic range and dose adjustment was achieved may be required to achieve the target Thrombin Time (TT). However, given the effect of individual variations on anticoagulant activity, it is difficult to determine the optimal argatroban dose to avoid hemorrhagic complications. Therefore, there is a need for large-scale randomized controlled trials to confirm our findings.

Conclusion

We found that IV argatroban could be an effective and safe treat- ment for patients with AIS at >6 h after the onset of ischemic symptoms. Moreover, our findings suggest that Thrombin Time (TT) could be used as an indicator for the evaluation of argatro- ban efficacy.

Abbreviations

IV: Intravenous

AIS: Acute Ischemic Stroke

aPTT: Activated Partial Thromboplastin Time

PT: Prothrombin Time

TT: Thrombin Time

NIHSS: National Institutes of Health Stroke Scale

CT: Computed Tomography

MRI: Magnetic Resonance Imaging

Declarations

Ethics Approval and Consent to Participate

The study was approved by Ethic Committee of the First Affil- iated Hospital of Harbin Medical University, and the need forinformed consent was waived owing to its retrospective design by the Ethics Committee of the First Affiliated Hospital of Har- bin Medical University.

Availability of Data and Materials

The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Funding

This work was supported in part by Postdoctoral Scientific Re- search Development Fund of Heilongjiang (LBH-Q18081 and LBH-Q19159). Scientific Research and Innovation Fund of the First Hospital of Harbin Medical University (2020M16).

Authors Contribution

Qianqian Li, Tingjiao Liu and Qian Shi was responsible for the study design, investigation, writing-original draft, conceptual- ization, and methodology. Yan Gao, Xinxin Guo and Ying Jia mainly contributed to formal analysis, data curation, review writing, and editing. Shanshan Yang revised and edited the man- uscript for important intellectual content, as well as project ad- ministration and funding acquisition. All the authors approved the final version of the manuscript and agreed to be accountable for all study aspects.

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