Background and aim.
Direct oral anticoagulants (DOACs) are first line therapy in primary and secondary stroke prevention in patients with nonvalvular atrial fibrillation (NVAF). Number of patients with DOAC initiation in clinical practice is rising rapidly. Meta-analysis and large randomized controlled trials (RCT) have undoubtedly shown that DOACs were comparably effective to vitamin K antagonists (VKA) in preventing stroke causing less amount of major bleeding. RCTs mainly included patients receiving DOACs for the primary prevention. There are no data on the efficacy and safety of reduced DOAC doses in RCTs, with the exception of dabigatran. Patients who suffered ischemic stroke (IS) 14 days prior to their inclusion in RCTs were not studied.
Despite the high efficacy and safety of DOACs, 1-2% of patients suffer acute IS. The gold standard treatment for patients with acute IS is recanalization therapy, which includes intravenous thrombolysis (IVT) and mechanical recanalization (MeR). Treatment with IVT is currently possible only in dabigatran-treated patients after reversal of anticoagulation with antidote, or in other DOAC-treated patients when specific coagulation tests prove the absence of anticoagulation effect. In the absence of other options, most patients who suffer acute IS on DOAC therapy are treated with MeR, which is only possible in rare centers, and only when large vessel is occluded. Data on recanalization outcomes in DOAC-treated patients with acute IS are limited.
Similarly, data on prognosis and conditions for possible DOAC reinitiation in patients who suffered intracranial hemorrhage (ICH) on DOAC therapy, are also lacking. These patients are at high risk from developing IS without DOAC therapy, but on the other hand they are more prone to recurrent ICH on DOAC therapy.
The purpose of this doctoral thesis is to analyze factors which influence the outcome of stroke in patients treated with DOACs by our own clinical research and results.
Research design, methods.
In the first study all consecutive patients with DOAC prescription in secondary prevention from September 2012 till end of April 2018 at Clinical department of vascular neurology and neurological intensive care (KOVNINT) were included. In May 2018, a validated questionnaire on change of therapy, complications and adherence, was sent to the patient. We analyzed patient’s characteristics, efficacy and safety of DOACs in secondary stroke prevention. Our results were descriptively compared to results of RCTs and Danish registry.
In the second study all consecutive patients receiving dabigatran, who were treated with IVT from 2016 until end of March 2020 at KOVNINT, were included. By analysing treatment outcome, effectiveness and safety of IVT was evaluated. Results were descriptively compared to results of our similar patients treated with IVT without anticoagulation therapy (ACT) and with results of similar analysis from German registry. The study of this issue was concluded with a systematic review and analysis of the efficacy and safety of IVT treatment of all cases of dabigatran-treated patients, published in the literature by the end of October 2020. In addition, the outcome of dabigatran-treated patients with intracranial haemorrhage (ICH) who received idarucizumab from 2016 till end of March 2020 at KOVNINT, was studied. Results were desciptively compared to results of similar analysis from German registry.
In the third study all consecutive patients with acute IS on DOAC therapy, who were treated with MeR at KOVNINT from January 2013 till August 2019, were included. The collected data on efficacy and safety of MeR treatment were evaluated by a descriptive comparison with the results of studies in patients without ACT.
In the last study all consecutive DOAC-treated patients with ICH at KOVNINT from September 2012 till end of December 2018, were included (patients with an underlying structural cause and hemorrhagic transformation (HT) of IS were excluded). By analysing the data, predefined diagnostic protocol with criteria for safe DOAC reinitiation, was proposed. Safety and effectiveness of DOAC re-initiation after ICH in DOAC-treated patients was explored and prognostic factors for recurrent ICH were identified.
Results.
In the first study we confirmed that DOACs are effective and safe in secondary stroke prevention in standard and reduced doses. Five-hundred sixty-six patients were prescribed DOAC for secondary stroke prevention from 2012 to 2018. Data was gathered for 510 patients with an average observational time 2,6 years. The mean age of patients was 78 years. Dabigatran was prescribed in 66%, apixaban in 21% and rivaroxaban in 13% of patients. Fifty-eight % of patients were prescribed reduced DOAC dose. Yearly incidences of recurrent IS, major bleeding and ICH were 1,7%, 1,6% and 0,2%. We found that yearly incidences of recurrent IS, major bleeding and ICH were low and comparable to results of RCTs and Danish registry for standard and reduced doses. DOAC initiation in the early phase of stroke is effective and safe, considering all the usual factors suggesting the possibility of bleeding or HT. Dabigatran was the most prescribed DOAC, therefore the results are reliable for dabigatran and less so far for other DOACs. Additionally, very high adherence rate of DOAC therapy in secondary stroke prevention was observed, with only 7,3% of patients reporting discontinuation of DOAC therapy. Our data show that adherence in secondary stroke prevention is higher compared to primary prevention.
In the second study we confirmed that IVT in dabigatran-treated patients with acute IS after anticoagulation reversal with idarucizumab is effective and safe. Twenty-two dabigatran-treated patients with mean age 75 years received IVT after reversal. Median improvement of National Institues of Health Stroke Scale (NIHSS) at discharge was 7. Favourable functional outcome (mRS ⡤ 2) after 3 months was achieved in 86% of patients. Symptomatic intracranial haemorrhage (SICH) occurred in 5% and 14% of patients died. Outcome of treatment was comparable to outcome reported in the German study. Good functional outcome was achieved statistically significantly more often in patients with acute IS treated with IVT after reversal compared to patients without ACT (n=182) (86 % vs. 57 %; p < 0,05). Effectiveness and safety of IVT in patients on dabigatran was additionally supported with results of systematic review of all published cases in literature. By analyzing the outcome of dabigatran treated patients with ICH receiving idarucizumab (n=13), we found that idarucizumab could improve treatment outcome of those patients, as mortality rate was lower (15 %) as described mortality rate in DOAC-treated patients with ICH without specific antidote treatment (18-27 %) in the literature. Our results were comparable to results from German cohort.
In the third study we confirmed that MeR in DOAC-treated patients with acute IS is effective and safe. Thirty-two patients with large artery occlusion, aged 75 years were treated with MeR. Significanant clinical improvement, 24 hours after revacularization (NIHSS improvement of ⡥ 8 points), occurred in 25 % of patients. A favourable treatment outcome (mRS ⡤ 2) after 3 months was achieved in 44% of patients. SICH occurred in 6% of patients and 9% died. Outcome of MeR treatment in our study was comparable to results of meta-analysis in clinical trials in patients without ACT. Effectiveness and safety of MeR in our DOAC-treated patients was additionally confirmed with the results of our center published in year 2015, which included patients treated with MeR from 2009 to 2012. The study from 2015 showed high recanalization rate (84% of patients achieved Thrombolysis in Cerebral Infarction Scale (TICI) 2b/3), 16 % mortality and improved clinical status (mRS ⡤ 2) in 40 % of patients.
In the last research we confirmed that in carefully selected DOAC-treated patients with ICH re-initiation of DOAC could be safe and effective. Fifty-four patients aged 80 suffered cebtral nervous system (CNS) hemorrhage, 18 patients died within a month. The average observational time was 590 days. By analising the data, a predefined protocol with criteria for safe DOAC reinitiation after ICH was formulated. DOACs were reinitiated in 36% of patients and none of them suffered a reccurrent ICH. We found that in patients in whom the cause of bleeding was excluded (6 patients), the same type and dose of DOAC was reinitiated. In patients with intracerebral hemorrhage (7 patients) in case of well controlled risk factors and with head magnetic resonance tomography (MRT) excluded cerebral amyloid angiopathy (CAA), a reduced DOAC dose was reiniatied, most commonly dabigatran.
Conclusions.
DOACs are effective and safe therapy in secondary stroke prevention in standard and reduced doses. Efficacy and safety is comparable to primary prevention studies. Prescription of DOACs in the early phase after acute IS is effective and safe. In dabigatran-treated patients with acute IS IVT after idarucizumab reversal is effective and safe. In dabigatran-treated patients with ICH idarucizumab improves patient’s functional outcome. In carefully selected patients after ICH DOAC reinitiation might be safe and effective.
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