Laboratory-Based Markers as Predictors of Brain ...

Original Article

Advance Publication Journal of Vol. Atherosclerosis and Thrombosis 1 Journal of Atherosclerosis and Thrombosis 23, No. ● Accepted for publication: November 17, 2015 Published online: , January 19, 2016

Laboratory-Based Markers as Predictors of Brain Infarction During Carotid Stenting: a Prospective Study Martin Kuliha 1, 2, Martin Roubec 1, Andrea Goldírová 1, Eva Hurtíková 1, Tomáš Jonszta 3, Václav Procházka 3, Jaromír Gumulec 4, Roman Herzig 5 and David Školoudík 1, 2, 6 1

Department of Neurology, Comprehensive Stroke Center, University Hospital Ostrava, Czech Republic Department of Neurology and Center of Clinical Neuroscience, Charles University in Prague, 1st Faculty of Medicine and General University Hospital in Prague, Prague, Czech Republic 3 Department of Radiology, Comprehensive Stroke Center, University Hospital Ostrava, Czech Republic 4 Department of Hematology, Comprehensive Stroke Center, University Hospital Ostrava, Czech Republic 5 Department of Neurology, Comprehensive Stroke Center, Charles University Faculty of Medicine and University Hospital, Hradec Králové, Czech Republic 6 Department of Nursing, Faculty of Health Science, Palacký University Olomouc, Czech Republic 2

Aim: New ischemic lesions in the brain can be detected in approximately 50% of patients undergoing carotid artery stenting (CAS). We wished to discover the laboratory-based predictors of new infarctions in the brain after CAS. Methods: All consecutive patients with internal carotid artery stenosis of ≥ 70% with indication for CAS were enrolled in a prospective study for 16 months. All patients used dual antiplatelet therapy for ≥ 7 days before CAS. Neurologic examination and magnetic resonance imaging (MRI) of the brain were undertaken before and at 24 h after CAS. Samples of venous blood were collected at ＜ 24 h before CAS for the evaluation of hematology, reticulocytes, coagulation markers (PT, APTT, Fbg, Clauss), vWF antigen, PAI-1 activity, PAI-1 polymorphism 4G/5G, and the multiplate (aspirin and clopidogrel) resistance test. Blood samples for the assessment of anti-Xa activity were collected during CAS. Differences in the values of laboratory markers between patients with and without new ischemic lesions of the brain on control MRI were evaluated. Results: The cohort comprised 81 patients (53 males; mean age, 67.3±7.2 years). New ischemic infarctions in the brain on control MRI were found in 46 (56.8%) patients. Three of seven patients with resistance to aspirin or clopidogrel had a new ischemic infarction in the brain. No significant differences for particular markers were found between patients with and without an ischemic lesion in the brain. Conclusion: A high risk of a new ischemic infarction in the brain was detected in patients undergoing CAS, but a laboratory-based predictor of such an infarction could not be identified. J Atheroscler Thromb, 2016; 23: 000-000. Key words: Brain infarction, Carotid stenting, Coagulation marker, Magnetic resonance imaging

Introduction Stroke is the third most common cause of death Address for correspondence: David Školoudík, Department of Nursing, Faculty of Health Science, Palacký University Olomouc Tř. Svobody 8, CZ-771 11 Olomouc, Czech Republic E-mail: [email protected] Received: June 22, 2015 Accepted for publication: November 17, 2015

in most “developed” countries 1). Stenosis of the internal carotid artery (ICA) is one of the most common etiological factors of ischemic stroke, resulting in 10% – 35% of cases 2). The risk of stroke increases with an increased severity of ICA stenosis, and this risk is higher in symptomatic stenoses than in asymptomatic ones. Large clinical trials have demonstrated that carotid endarterectomy is beneficial for selected patients with a symptomatic ICA stenosis of ＞ 50% or

Advance Publication of Atherosclerosis and Thrombosis KulihaJournal et al . Accepted for publication: November 17, 2015 Published online: , January 19, 2016

2

an asymptomatic ICA stenosis of ＞ 60% 3-6). In the last decade, carotid artery stenting (CAS) has become an alternative treatment for carotid stenosis because general anesthesia and surgical incisions can be avoided. These features have reduced the incidence of postoperative wound problems and injury to the cranial nerve compared with surgery 7, 8). Recent studies have shown carotid endarterectomy and CAS to be associated with a similar prevalence of postoperative death and disabling stroke, but silent infarctions in the brain can be detected more often after CAS 9-11). Atheromatic mass embolization is considered to be the main cause of new infarctions in the brain during CAS as well as local thrombosis with distal embolization caused by the mechanical damage of the endothelium and exposure of procoagulative plaque components 12). Formation of small thrombi on catheters and guidewires used for CAS procedures could be the additional causes of local thrombosis 13). Endogenous hypofibrinolytic conditions caused by high levels of plasminogen activator inhibitor-1 antigen have also been suggested to be the cause for silent infarction after CAS 14). Dual antiplatelet therapy with clopidogrel and acetylsalicylic acid significantly reduces the prevalence of CAS-related peri- and postprocedural thromboembolic complications 15). Low efficacy of resistance to antiplatelet therapy could increase the risk of new ischemic lesions in the brain during and after CAS 16). Scholars have reported a prevalence of resistance of 6% – 27% in different populations for acetylsalicylic acid 17, 18) and of 15% – 30% for clopidogrel 19-21). Selection of patients carrying a high risk of periprocedural ischemic infarction could decrease the risk of stroke, transient ischemic attack (TIA), and subsequent cognitive decline in patients undergoing CAS. Aim The aim of the present study was to ascertain the laboratory markers associated with a higher risk of new infarctions in the brain after CAS. Methods The present study was conducted in accordance with the Helsinki Declaration of 1975 (as revised in 2004 and 2008). It was approved by the ethics committee of University Hospital Ostrava, Ostrava, Czech Republic (MZ10-FNO). All patients provided written informed consent before enrolment. The study has been registered at www.clinicaltrials.gov (NCT02310191).

Patients Inclusion criteria were as follows: symptomatic or asymptomatic ICA stenosis of ≥ 70% detected by duplex ultrasonography and confirmed using computed tomography angiography (CTA); indication for CAS according to criteria set by the American Heart Association 22); age of 40 – 80 years; functional independency (modified Rankin scale, 0 – 2 points); and no contraindication to magnetic resonance imaging (MRI), CTA, or digital subtraction angiography. Consecutive patients were enrolled between July 2012 and June 2014. CAS All procedures were performed via the femoral approach using the Seldinger method. More than 500 CAS procedures were undertaken at our center during the previous 5 years. All patients were on long-term aspirin (100 mg/day) therapy and were administered with a 525-mg loading dose of clopidogrel. A dose of 10,000 units of unfractionated heparin was administered at the beginning of the intervention. A cerebral protection device (FilterWire EZ TM; Boston Scientific, Natick, MA, USA) was used in all but two patients, in whom it was not possible to navigate the device into the appropriate position because of difficult anatomy. Choice of the type of covered stent and other specific intervention strategies were left to the discretion of interventional radiologists. All patients underwent diagnostic angiography for the verification of the characteristics of ICA stenosis. Four-vessel angiography was used only in patients with multiple stenoses detected on CTA. After the predilatation of stenosis (if needed), an appropriate stent for each stenosis was implanted and then dilated using a balloon catheter. Angiography was used to evaluate intracranial circulation as well as the position of the implanted stent. MRI MRI was conducted before and at 24 h after intervention using a 1.5-T Avanto system (Siemens, Erlangen, Germany). The protocol comprised four sequences as follows: (i) transverse T2-weighted spin echo [echo time, 100 ms; repetition time, 4,310 ms; section thickness, 5.0 mm; matrix size, 192×256; gap, 0.5 mm; field of view (FOV), 250 mm; FOV ph, 75%; echo train length (ETL), 9; number of excitations, 1]; (ii) diffusion-weighted imaging (DWI; echo time, 130 ms; repetition time, 4,500 ms; b, representing a factor of diffusion-weighted sequences: b = 0 and b = 1,000 s/mm2; section thickness, 5.0 mm; gap, 1 mm; matrix size, 192×192; FOV, 255 mm; FOV ph, 100%; number of excitations, 4; echo spacing, 0.93

Advance Publication of Atherosclerosis and Thrombosis 3 Predictors of Journal Brain Infarction Accepted for publication: November 17, 2015 Published online: , January 19, 2016 Table 1. Studied laboratory markers Marker

Normal range 3.8 – 5.2×10

Erythrocytes (n/mL) Reticulocyte index

2.0 – 3.0

Reticulocytes (%)

0.5 – 2.5 150 – 400×10 3

Platelet count (n/mL) Immature platelet fraction (%)

1.4 – 4.3

Mean platelet volume (fL)

7.8 – 11.0

Prothrombin time (s)

11 – 14

Activated partial thromboplastine time (s)

24.7 – 37.1 1.8 – 4.2

Fibrinogen (g/L) Antifactor Xa activity (kIU/L)

NA

von Willebrand factor antigen (%)

50 – 150

PAI-1 activity (ng/mL)

1.0 – 25.0

PAI-1 polymorphism 4G/5G

Multiplate aggregometry

Collecting tube

Analyzator

S-Monovette® 7.5 mL tube with potassium EDTA (Sarstedt, Nümbrecht, Germany)

Sysmex XE-5000 analyzator (Sysmex Corporation, Kobe, Japan)

S-Monovette® 2.9 mL tube with 3.2% citrate (Sarstedt, Nümbrecht, Germany)

Sysmex CA-7000 analyzator (Sysmex Corporation, Kobe, Japan)

6

Sysmex CA-1500 analyzator (Sysmex Corporation, Kobe, Japan) S-Monovette® 2.9 mL tube with 3.2% citrate (Sarstedt, Nümbrecht, Germany)

Rotor-gene 3000A (Corbett, Sydney, Australia)

NA AA (U)

71.0 – 115.0

ADP (U)

57.0 – 113.0

Microtitration plate reader PR3100 TSC (BIO-RAD, Hercules, CA, USA).

Hirudin blood tube 3.0 mL (Double wall) (Dynabyte GmbH, München, Germany)

Multiplate 5.0 analyzator (Dynabyte GmbH, München, Germany)

AA – arachidonic acid; ADP – adenosine diphosphate; EDTA – ethylenediaminetetraacetic acid; NA – not applicable; PAI-1 – plasminogen activator inhibitor-1

ms; bandwidth, 1240 Hz/Px), and apparent diffusion coefficient maps were obtained in all cases; (iii) T2 star-weighted gradient-recalled echo (GRE) sequence for the detection of bleeding (including microbleeds); and (iv) fluid-attenuated inversion recovery (FLAIR; echo time, 109 ms; repetition time, 8,000 ms; inversion time, 2,500 ms; section thickness, 5.0 mm; matrix size, 256×151; gap, 0.5 mm; FOV, 250 mm; FOV ph, 77.0%; number of excitations, 1; ETL, 5). Apparent diffusion coefficient maps were obtained in all cases. Sequences were applied at an identical level, with the same slice thickness and identical cut number. Slice thickness comprised the cut thickness (5 mm) plus gap (10%). The standard number of slices was 25. In accordance with previous studies 9-11), new ischemic lesions in the brain were defined as hyperintense lesions on postintervention DWI that were not present on pretreatment MRI. Ischemic lesions in the

brain (number and total volume of hyperintense lesions on DWI) were evaluated by a radiologist and neurologist blinded to the study protocol, and disagreements were resolved by consensus. Images acquired before and after intervention were evaluated to assess the presence, number, manually measured volume, and location of new ipsilateral ischemic lesions in the brain after CAS. Laboratory Tests Venous blood samples (Table 1) were collected at ＜ 24 h before CAS from all patients. Blood samples for the assessment of anti-Xa activity were collected during CAS at the time of catheter insertion into the carotid stenosis of ≥ 30 min after heparin administration. The platelet function test was performed by the method of whole blood impedance aggregometry using a multiple platelet function analyzer, Multiplate.

4


Aggregation results were obtained after the following 6 min as the mean of two measurements in the form of a curve on the basis of which the area under the curve (AUC) was determined. The AUC reference ranges for the ASPI test (cyclooxygenase dependent aggregation using arachidonic acid sensitive to ASA and other inhibitors of platelet cyclooxygenase) and ADP test (ADP-induced platelet activation sensitive to clopidogrel and other ADP receptor antagonists) were 71-115 U and 57-113 U, respectively, in accordance with the manufacturer’s recommendations. Based on the literature data, it was accepted that in patients who take ASA, an AUC of ＜ 30 U indicates aspirin sensitivity (ASA responders) 23) and an AUC of ＞ 40 U indicates aspirin resistance (ASA non-responders) 24). In patients who take clopidogrel, an AUC of ＜ 31 U indicates clopidogrel sensitivity (clopidogrel responders) 25) and an AUC of ＞ 46 U indicates clopidogrel resistance (clopidogrel non-responders) 26). Evaluation of Carotid Stenosis The grade of ICA stenosis was evaluated by duplex ultrasound 27) and was confirmed by CTA [according to criteria of the North American Symptomatic Carotid Endarterectomy Trial (NASCET)] 28). Plaque type (fibrous or calcified) and plaque ulcerations were evaluated using duplex ultrasound. Clinical Examinations Comorbidities (arterial hypertension, diabetes mellitus, hyperlipidemia, ischemic heart disease, and atrial fibrillation), current medications (antiplatelet drugs such as acetylsalicylic acid, clopidogrel, anticoagulants, and hypolipidemic agents including statin dose), smoking status, and alcohol abuse were documented. Physical and neurological examinations were conducted for evaluating neurological deficits and dependency (assessed using a modified version of the Rankin scale). Statistical Analyses The primary endpoint was to ascertain if there was a correlation between selected laboratory markers and new ischemic lesions in the brain using DWIMRI performed at 24 h after the intervention in patients undergoing CAS. Sample size was based on a 20% difference in the value of particular laboratory markers between patients with and without new ischemic lesions on follow-up MRI. Calculations suggested that ≥ 80 patients were required to reach a significant difference with an alpha value of 0.05. Normality of data distribution was checked using the Shapiro – Wilk test. Data with a

normal distribution (age, severity of ICA stenosis, and time of procedure) are reported as the mean±standard deviation. Remaining variables are presented as the mean, median, and interquartile range. The following variables to determine the possible predictors of new brain ischemia were statistically analyzed: age, gender, laboratory markers, arterial hypertension, diabetes mellitus, coronary heart disease, atrial fibrillation, hyperlipidemia, statin use, smoking, alcohol abuse, occlusion side, severity (%), symptoms of treated ICA stenosis, plaque type and ulceration, time from symptom onset to intervention, duration of intervention, protection use, and severity of contralateral ICA stenosis. Continuous variables were compared using the Student’s t -test if the distribution was normal; alternatively, the Mann – Whitney U -test was used. Categorical variables were compared by Fisher’s exact test. The PAI-1 polymorphism 4G/5G was compared using the chi-square test. P value of ＜ 0.05 was considered to be statistically significant. Data were analyzed using SPSS v17.0 (IBM, Armonk, NY, USA). Results The study cohort comprised 81 patients (53 males; mean age, 67.3±7.2 years), as shown in Fig. 1. New ischemic infarctions in the brain on follow-up MRI were found in 46 (56.8%) patients. New ischemic infarctions in the brain in both hemispheres were detected in 21 (25.9%) patients and infarctions of ≥ 0.5 mL were detected in 11 (13.6%) patients. TIA or stroke within 30 days did not occur in any patient. No significant differences in particular laboratory markers, atherosclerosis risk factors, plaque type, and severity of ICA stenosis were found between patients with and without a new infarction in the brain (Table 2). Resistance to acetylsalicylic acid was detected in one (1.2%) patient and resistance to clopidogrel was detected in six (7.4%) patients. The patient with resistance to acetylsalicylic acid had no new ischemic lesion in the brain. Three of six patients with resistance to clopidogrel had new ischemic lesions in the brain. Discussion In the present study, we found new ischemic lesions in the brain in 56.8% of patients after CAS. New lesions were localized in ＞ 1 cervical artery territory in 25% of patients. Nevertheless, TIA or stroke within 30 days did not occur in any patient. Several studies have reported a high prevalence (≤ 70%) of new ischemic lesions in the brain for patients after under-

Advance Publication of Atherosclerosis and Thrombosis 5 Predictors of Journal Brain Infarction Accepted for publication: November 17, 2015 Published online: , January 19, 2016 SDWLHQWV LQGLFDWHGWR&$6

&RQWUDLQGLFDWLRQWRPDJQHWLFUHVRQDQFH SDWLHQWV

6WHQRVLVSDWLHQWV 2XWRIDJHUDQJHSDWLHQWV :LWKP56!SDWLHQWV 1RWSHUIRUPHG&7DQJLRJUDSK\EHIRUH &$6SDWLHQWV

5HIXVHGLQIRUPHGFRQVHQWSDWLHQWV

SDWLHQWV HQUROOHG Fig. 1. Study flow chart CAS – carotid angioplasty with stenting; CT – computed tomography; mRS – modified Rankin score

going CAS 9-11, 29). These new lesions have been found not only in the ipsilateral hemisphere but also in the contralateral hemisphere or in the posterior circulation 30-32). In accordance with our results, other studies have demonstrated that most of the new ischemic lesions in the brain detected by DWI after CAS were asymptomatic and that few patients developed TIA or stroke 11, 29). However, the long-term impact of these lesions remains unclear, with some studies suggesting possible deterioration of cognitive functions 11, 33). In the present study, we focused on any blood disorder that could be associated with a new ischemic brain lesion after CAS, but a laboratory-based predictor of new infarctions in the brain was not found. Moreover, there was a paradoxical tendency of a

higher risk of a new infarction in the brain in patients with a shorter prothrombin time, lower international normalized ratio (INR), and lower activity of anti-factor Xa at the time of catheter insertion into the carotid stenosis as well as at 30 min after heparin administration. Antiplatelet therapy can decrease the risk of stroke by 15% – 20% 34). Resistance to dual antiplatelet therapy was found in 9% of patients, a finding that is in accordance with studies in which aspirin resistance was found in 6% – 27% and clopidogrel resistance was found in 15% – 30% of patients 17-21). However, the results of multiplate aggregometry did not differ significantly between patients with and without new ischemic lesions in the brain in the present study.

6


Table 2. Study results Patients without a new ischemic lesion

Patients with a new ischemic lesion

P value

Number of patients; n

35

46

NA

Age; mean±SD; years

66.5±7.2

67.9±7.2

0.201

Male gender; n (%)

26 (74.3)

27 (58.7)

0.164

Symptomatic ICA stenosis; n (%)

13 (37.1)

19 (41.2)

0.819

Stenosis severity detected by duplex ultrasound; mean±SD; %

78.4±11.3

81.7±9.9

0.169

Stenosis severity detected by CTA; mean±SD; %

78.0±15.9

78.8±13.2

0.806

Plaque calcifications; n (%)

18 (51.4)

24 (52.2)

1.000

Plaque ulcerations; n (%)

25 (71.4)

31 (67.4)

0.810

Right-side stenosis; n (%)

14 (40.0)

18 (39.1)

1.000

53.9±32.1

53.6±28.7

0.968

18 (51.4)

33 (71.7)

0.069

28 (80.0); 2 (5.7); 2 (5.7); 2 (5.7); 0 (0); 1 (2.9)

33 (71.7); 7 (15.2); 0 (0); 4 (8.7); 1 (2.2); 1 (2.2)

0.310

31 (88.6)

38 (82.6)

0.539

4 (11.4); 0 (0); 0 (0); 0 (0)

4 (8.7); 1 (2.2); 2 (4.3); 1 (2.2)

0.391

32 (91.4); 3 (8.6); 0 (0)

43 (93.5); 2 (4.3); 1 (2.2)

0.511

34 (97.1)

42 (91.3)

0.383

1 (2.9)

1 (2.2)

1.000

33.6±8.0

37.3±7.6

0.703

Erythrocytes; mean, median (IQR); n/mL

4.62, 4.70 (4.35-4.90)

4.58, 4.65 (4.20-4.90)

0.255

Reticulocyte index; mean, median (IQR)

1.038, 0.970 (0.700-1.240)

0.906, 0.845 (0.593-1.128)

0.076

1.6, 1.6 (1.1-1.9)

1.6, 1.4 (1.1-1.7)

0.226

199.8, 201.0 (152.0-233.0)

222.7, 200.0 (182.0-255.0)

0.082

Immature platelet fraction; mean, median (IQR); %

4.83, 4.00 (3.20-5.50)

5.22, 4.60 (3.60-6.20)

0.166

Mean platelet volume; mean, median (IQR); fL

10.9, 11.0 (10.3-11.3)

11.0, 11.0 (10.6-11.6)

0.245

Prothrombin time; mean, median (IQR); s

10.99, 10.90 (10.65-11.20)

11.24, 11.10 (10.80-11.50)

0.062

Activated partial thromboplastine time; mean, median (IQR); s

30.96, 30.50 (28.95-32.60)

31.01, 30.70 (20.80-30.70)

0.452

3.24, 3.41 (2.56-3.70)

3.35, 3.36 (2.85-3.73)

0.444

Contralateral ICA stenosis severity; mean±SD; % 4-vessel angiography; n (%) Stent type (Wallstent; Acculink; Omnilink; Zilver; Crystalo; Sinus); n (%) Stent primoimplantation; n (%) Size of PTA balloon – predilatation (3/20; 3.5/20; 4/20; 5/20); n (%) Size of PTA balloon – stent dilatation (5/20; 5.5/20; 3/40); n (%) Filter protection use; n (%) Incidence of no flow of filter; n (%) Procedure time; mean±SD; min

Reticulocytes; mean, median (IQR); % Platelet count; mean, median (IQR); n/mL

Fibrinogen; mean, median (IQR); g/L

Advance Publication of Atherosclerosis and Thrombosis 7 Predictors of Journal Brain Infarction Accepted for publication: November 17, 2015 Published online: , January 19, 2016 (Cont Table 2) Patients without a new ischemic lesion

Patients with a new ischemic lesion

P value

von Willebrand factor antigen; mean, median (IQR); %

178.2, 184.0 (134.5-211.5)

173.1, 149.1 (126.8-191.5)

0.113

PAI-1 activity; mean, median (IQR); ng/mL

17.88, 14.60 (11.7-24.7)

18.33, 15.05 (10.43-11.45)

0.429

PAI-1 polymorphism 4G/4G; n (%) 4G/5G; n (%) 5G/5G; n (%) Multiplate aggregometry AA; mean, median (IQR); U

12 (34.3) 17 (48.6) 6 (17.1)

25 (54.3) 12 (26.1) 9 (19.6)

0.099

8.4, 6.0 (2.5-12.0)

11.6, 9.0 (4.0-16.0)

0.082

Multiplate aggregometry ADP; mean, median (IQR); U

26.1, 23.0 (11.0-34.0)

24.0, 22.0 (10.5-31.5)

0.476

Antifactor Xa activity 0 min; mean, median (IQR); kIU/ L

1.90, 1.96 (1.17-2.57)

2.32, 2.47 (1.42-3.06)

0.061

Antifactor Xa activity 30 min; mean, median (IQR); kIU/L

2.11, 2.20 (1.60-2.56)

2.46, 2.48 (1.97-2.88)

0.053

Arterial hypertension; n (%)

34 (97.1)

46 (100)

0.432

Diabetes mellitus; n (%)

14 (40.0)

20 (43.5)

0.822

Hyperlipidemia; n (%)

29 (82.9)

36 (78.3)

0.779

Ischemic heart disease; n (%)

12 (34.3)

19 (41.3)

0.645

1 (2.9)

5 (10.9)

0.228

11 (31.4)

11 (23.9)

0.463

Atrial fibrillation; n (%) Smoking; n (%) Alcohol abuse; n (%) Statin use; n (%)

3 (8.6) 28 (80.0)

0 (0) 34 (73.9)

0.707 0.603

ADP – adenosin diphosphate; AA – arachidonic acid; CTA – computed tomography angiography; ICA – internal carotid artery; IQR – interquartile range; NA – not applicable; PAI-1 – plasminogen activator inhibitor-1, SD – standard deviation

Microembolism is frequently considered to be the cause of silent as well as clinically symptomatic new ischemic lesions in the brain, and there is an association with the risk of cognitive deficit after the intervention 20). However, only few studies on new ischemic lesions in the brain after CAS have focused on the mechanism of action and risk factors of these lesions. Among vascular risk factors, only coronary artery disease has been identified as a significant predictor of microembolism after CAS 23). Main documented risk factors associated with periprocedural risk of embolization are excessive manipulation with CAS devices 35), plaque instability 36), anatomic abnormalities (particularly tortuosity of the aortic arch and carotid artery) 30, 32), and atherosclerotic aortic plaques 30, 37). In

addition, after several days or even after ＞ 6 months of CAS, there have been reports of postintervention microembolism events 38, 39). These risk factors are based on debris production by the manipulation of intervention devices, particularly in atherosclerotic plaques. Thrombus formation on endovascular devices may represent another risk factor 38). Nevertheless, our results showed that a laboratory-based predictor of new infarctions in the brain was not found. Thus, the etiology of new infarctions in the brain after CAS is not known. Limitations of the Study This was a pilot study; hence, a small cohort represents the first limitation. Second, laboratory markers


8

were selected on the basis of the literature and widely used laboratory tests. Third, our study did not consider the possibility of delayed microembolic events. Conclusion CAS is associated with a higher risk of new ischemic lesions in the brain after the procedure than that for carotid endarterectomy. Risk factors and the mechanism of action of microembolization have not been completely elucidated. No correlation was found between the selected laboratory markers and new ischemic lesions in the brain for patients undergoing CAS. Further studies focusing on other laboratory markers that are less frequently employed are required. Acknowledgement The study was supported by the grants from the Internal Grant Agency of the Ministry of Health of the Czech Republic (NT/11386-5/2010, NT/134984/2012, NT/11046-6/2010), and by the internal grants from the University Hospital Ostrava (MH CZ DRO – FNOs/2012 and MH CZ - DRO – FNOs/ 2014). Conflicts of Interest Martin Kuliha: Nothing to declare. Martin Roubec: Nothing to declare. Andrea Goldírová: Nothing to declare. Eva Hurtíková: Nothing to declare. Tomáš Jonszta: Nothing to declare. Václav Procházka: Nothing to declare. Jaromír Gumulec: Nothing to declare. Roman Herzig: Nothing to declare. David Školoudík: Nothing to declare.

References 1) Tegos TJ, Kalodiki E, Daskalopoulou SS, and Nicolaides AN: Stroke: epidemiology,clinical picture, and risk factors-Part I of III. Angiology, 2000; 51: 793-808 2) Mohr JP, Choi DW, Grotta JC, Weir B, and Wolf PA: Stroke: Pathophysiology, Diagnosis, and Management. Philadelphia: Elsevier Inc, 4th Edition, 2004 3) Barnett HJ, Taylor DW, Eliasziw M, Fox AJ, Ferguson GG, Haynes RB, Rankin RN, Clagett GP, Hachinski VC, Sackett DL, Thorpe KE, Meldrum HE, and Spence JD: Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators. N Engl J Med, 1998; 339: 1415-1425

4) Rothwell PM, Gutnikov SA, and Warlow CP: European Carotid Surgery Trialist’s Collaboration. Reanalysis of the final results of the European Carotid Surgery Trial. Stroke, 2003; 34: 514-523 5) Endarterectomy for asymptomatic carotid artery stenosis. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. JAMA, 1995; 273: 1421-1428 6) Skoloudik D: Neurosonologie, Grada, Praha, Czech Republic, 2003 7) Yavin D, Roberts DJ, Tso M, Sutherland GR, Eliasziw M, and Wong JH: Carotid endarterectomy versus stenting: a meta-analysis of randomized trials. Can J Neurol Sci, 2011; 38: 230-235 8) Economopoulos KP, Sergentanis TN, Tsivgoulis G, Mariolis AD, and Stefanadis C: Carotid artery stenting versus carotid endarterectomy: a comprehensive meta-analysis of short-term and long-term outcomes. Stroke, 2011; 42: 687-692 9) Bonati LH, Jongen LM, Haller S, Flach HZ, Dobson J, Nederkoorn PJ, Macdonald S, Gaines PA, Waaijer A, Stierli P, Jäger HR, Lyrer PA, Kappelle LJ, Wetzel SG, van der Lugt A, Mali WP, Brown MM, van der Worp HB, Engelter ST and ICSS-MRI study group: New ischaemic brain lesions on MRI after stenting or endarterectomy for symptomatic carotid stenosis: a substudy of the International Carotid Stenting Study (ICSS). Lancet Neurol, 2010; 9: 353-362 10) Schnaudigel S, Gröschel K, Pilgram SM, and Kastrup A: New brain lesions after carotid stenting versus carotid endarterectomy: a systematic review of the literature. Stroke, 2008; 39: 1911-1919 11) Kuliha M, Roubec M, Procházka V, Jonszta T, Hrbáč T, Havelka J, Goldírová A, Langová K, Herzig R, and Školoudík D: Randomized clinical trial comparing neurological outcomes after carotid endarterectomy or stenting. Br J Surg, 2015; 102: 194-201 12) Pasternak RC, Baughman KL, Fallon JT, and Block PC: Scanning electron microscopy after coronary transluminal angioplasty of normal canine coronary arteries. Am J Cardiol, 1980; 45: 591-598 13) Grunwald IQ, Reith W, Kühn AL, Balami JS, Karp K, Fassbender K, Walter S, Papanagiotou P, and Krick C: Proximal protection with the Gore PAES can reduce DWI lesion size in high-grade stenosis during carotid stenting. EuroIntervention, 2014; 10: 271-276 14) Vucković BA, Djerić MJ, Ilić TA, Canak VB, KojićDamjanov SLj, Zarkov MG, and Cabarkapa VS: Fibrinolytic parameters, lipid status and lipoprotein(a) in ischemic stroke patients. Srp Arh Celok Lek, 2010; 138 (Suppl 1): 12-17 15) Enomoto Y, and Yoshimura S: Antiplatelet therapy for carotid artery stenting. Interv Neurol, 2013; 1: 151-163 16) Ryu DS, Hong CK, Sim YS, Kim CH, Jung JY, and Joo JY: Anti-platelet drug resistance in the prediction of thromboembolic complications after neurointervention. J Korean Neurosurg Soc, 2010; 48: 319-324 17) Hovens MM, Snoep JD, Eikenboom JC, van der Bom JG, Mertens BJ, and Huisman MV: Prevalence of persistent platelet reactivity despite use of aspirin: a systematic review. Am Heart J, 2007; 153: 175-181

Advance Publication of Atherosclerosis and Thrombosis 9 Predictors of Journal Brain Infarction Accepted for publication: November 17, 2015 Published online: , January 19, 2016 18) Mansour K, Taher AT, Musallam KM, and Alam S: Aspirin resistance. Adv Hematol, 2009; 2009: 937352 19) Feher G, Feher A, Pusch G, Koltai K, Tibold A, Gasztonyi B, Papp E, Szapary L, Kesmarky G, and Toth K: Clinical importance of aspirin and clopidogrel resistance. World J Cardiol, 2010; 2: 171-186 20) Heyer EJ, Sharma R, Rampersad A, Winfree CJ, Mack WJ, Solomon RA, Todd GJ, McCormick PC, McMurtry JG, Quest DO, Stern Y, Lazar RM, and Connolly ES: A controlled prospective study of neuropsychological dysfunction following carotid endarterectomy. Arch Neurol, 2002; 59: 217-222 21) Gurbel PA, Antonino MJ, and Tantry US: Recent developments in clopidogrel pharmacology and their relation to clinical outcomes. Expert Opin Drug Metab Toxicol, 2009; 5: 989-1004 22) Brott TG, Halperin JL, Abbara S, Bacharach JM, Barr JD, Bush RL, and American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines; American Stroke Association; American Association of Neuroscience Nurses; American Association of Neurological Surgeons; American College of Radiology; American Society of Neuroradiology; Congress of Neurological Surgeons; Society of Atherosclerosis Imaging and Prevention; Society for Cardiovascular Angiography and Interventions; Society of Interventional Radiology; Society of NeuroInterventional Surgery; Society for Vascular Medicine; Society for Vascular Surgery; American Academy of Neurology and Society of Cardiovascular Computed Tomography. 2011 ASA/ACCF/AHA/AANN/ AANS/ACR/ASNR/CNS/SAIP/ SCAI/SIR/SNIS/SVM/ SVS guideline on the management of patients with extracranial carotid and vertebral artery disease: executive summary. Stroke, 2011; 42: 420-463 23) Al-Azzam SI, Alzoubi KH, Khabour O, Alowidi A, and Tawalbeh D. The prevalence and factors associated with aspirin resistance in patients premedicated with aspirin. Acta Cardiol, 2012; 67: 445-448 24) von Pape KW, Dzijan-Horn M, Bohner J, Spannagl M, Weisser H, and Calatzis A. Control of aspirin effect in chronic cardiovascular patients using two whole blood platelet function assay: PFA-100 and Multiplate. Hamostaseologie, 2007; 27: 155-160 25) Ranucci M, Baryshnikova E, Soro G, Ballotta A, De Benedetti D, and Conti D; Surgical and Clinical Outcome Research (SCORE) Group. Multiple electrode whole-blood aggregometry and bleeding in cardiac surgery patients receiving thienopyridines. Ann Thorac Surg, 2011; 91: 123-129 26) Sibbing D, Braun S, Morath T, Mehilli J, Vogt W, Schömig A, Kastrati A, von Beckerath N. Platelet reactivity after clopidogrel treatment assessed with point-of-care analysis and early drug-eluting stent thrombosis. J Am Coll Cardiol, 2009; 53: 849-856 27) von Reutern GM, Goertler MW, Bornstein NM, Del Sette M, Evans DH, Hetzel A, Kaps M, Perren F, Razumovky A, von Reutern M, Shiogai T, Titianova E, Traub-

ner P, Venketasubramanian N, Wong LK, and Yasaka M; Neurosonology Research Group of the World Federation of Neurology: Grading carotid stenosis using ultrasonic methods. Stroke, 2012; 43: 916-921 28) Ferguson GG, Eliasziw M, Barr HW, Clagett GP, Barnes RW, Wallace MC, Taylor DW, Haynes RB, Finan JW, Hachinski VC, and Barnett H: The North American Symptomatic Carotid Endarterectomy Trial: surgical results in 1415 patients. Stroke, 1999; 30: 1751-1758 29) Tedesco MM, Coogan SM, Dalman RL, Haukoos JS, Lane B, Loh C, Penkar TS, and Lee JT. Risk factors for developing postprocedural microemboli following carotid interventions. J Endovasc Ther, 2007; 14: 561-567 30) Hammer FD, Lacroix V, Duprez T, Grandin C, Verhelst R, Peeters A, and Cosnard G. Cerebral microembolization after protected carotid artery stenting in surgical high-risk patients: results of a 2-year prospective study. J Vasc Surg, 2005; 42: 847-853 31) du Mesnil de Rochemont R, Schneider S, Yan B, Lehr A, Sitzer M, and Berkefeld J: Diffusion-weighted MR imaging lesions after filter-protected stenting of high-grade symptomatic carotid artery stenoses. AJNR Am J Neuroradiol, 2006; 27: 1321-1325 32) Tedesco MM, Lee JT, Dalman RL, Lane B, Loh C, Haukoos JS, Rapp JH, and Coogan SM: Postprocedural microembolic events following carotid surgery and carotid angioplasty and stenting. J Vasc Surg, 2007; 46: 244-250 33) Paraskevas KI, Lazaridis C, Andrews CM, Veith FJ, and Giannoukas AD: Comparison of cognitive function after carotid artery stenting versus carotid endarterectomy. Eur J Vasc Endovasc Surg, 2014; 47: 221-231 34) Sandercock PA, Counsell C, Gubitz GJ, and Tseng MC: Antiplatelet therapy for acute ischaemic stroke. Cochrane Database Syst Rev, 2008; 3: CD000029 35) Aikawa H, Kodama T, Nii K, Tsutsumi M, Onizuka M, Iko M, Matsubara S, Etou H, Sakamoto K, and Kazekawa K: Intraprocedural plaque protrusion resulting in cerebral embolism during carotid angioplasty with stenting. Radiat Med, 2008; 26: 318-323 36) Rosenkranz M, Wittkugel O, Waiblinger C, Thomalla G, Krutzelmann A, Havemeister S, Zeumer H, Gerloff C, and Fiehler J: Cerebral embolism during carotid artery stenting: role of carotid plaque echolucency. Cerebrovasc Dis, 2009; 27: 443-449 37) Faggioli G, Ferri M, Rapezzi C, Tonon C, Manzoli L, and Stella A: Atherosclerotic aortic lesions increase the risk of cerebral embolism during carotid stenting in patients with complex aortic arch anatomy. J Vasc Surg, 2009; 49: 80-85 38) Jiang L, Ling F, Wang B, and Miao Z: Insight into the periprocedural embolic events of internal carotid artery angioplasty. A report of four cases and literature review. Interv Neuroradiol, 2011; 17: 452-458 39) Censori B, Camerlingo M, Casto L, Partziguian T, Caverni L, Bonaldi G, and Mamoli A: Carotid stents are not a source of microemboli late after deployment. Acta Neurol Scand, 2000; 102: 27-30