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Keywords:Brain natriuretic peptideAcute ischemic stroke

atriethenrolled patients with AF within 7 days of an ischemic stroke and transient

factor for ischemic stroke. Thus, patients with ischemic stroke or when accompanied by AF [6,7]. A recent report concluded that plasma

Journal of the Neurological Sciences 301 (2011) 8689

Contents lists available at ScienceDirect

Journal of the Neur

.etransient ischemic attacks (TIA) and AF are at high risk of recurrentstroke [1]. Patients with left atrial thrombus are at particularly highrisk for thromboembolic events, and anticoagulant agents reduce thelikelihood of such events [2,3]. Therefore, to identify left atrialthrombus in acute ischemic stroke is important, and anticoagulanttherapy can prevent further brain ischemia.

Although transesophageal echocardiography (TEE) is a usefulclinical tool for identifying actual thrombi and for visualizingspontaneous echo contrast (SEC) in patients with AF, its semi-invasive nature precludes its application to patients with acute stroke.

BNPmight be a useful marker of vulnerability to thromboembolism inpatients with nonvalvular AF [8].

The present study investigates whether BNP levels could serve as auseful marker of left atrial thrombus during acute ischemic stroke andTIA in patients with AF.

2. Patients and methods

Between November 2006 and June 2008, we prospectivelyenrolled patients with AF within 7 days of onset of acute ischemicBrain natriuretic peptide (BNP) is a 32-with a 17-amino acid ring structure that was ibrain in 1988. It is a diuretic and vasodilato

Corresponding author. Department of Geriatric MeUniversity, Shitsukawa, Toon City, Ehime 791-0295, Japa+81 89 960 5852.

E-mail address: yokokada@mac.com (Y. Okada).

0022-510X/$ see front matter 2010 Elsevier B.V. Adoi:10.1016/j.jns.2010.10.017thmia and a major riskthat BNP is a marker of congestive heart failure [4]. Plasma BNP levelsare elevated in patients with acute ischemic stroke [5,6], particularlyAtrial brillation (AF) is a common arrhy1. IntroductionAtrial brillationTransesopageal echocardiographyEmboli detectionStroke biomarkersAnticoagulationCardioembolic stroke

thrombus. The incidence of hypertension was signicantly higher in the positive, than in the negative group(88.2% vs. 58.0%, p=0.020). The BNP level was also signicantly higher in the positive, than in the negativegroup (median (interquartile range) 189.8 (141.4-473.2) vs. 117.9 (70.3-187.1) pg/ml, p=0.012). Theoptimal cut-off value, sensitivity, and specicity of BNP levels to distinguish the positive, from the negativegroup were 140.0 pg/ml, 76.5%, and 62.0%, respectively. Multivariate logistic regression analysis demon-strated that a BNP concentration ofN140.0 pg/ml (odds ratio, 5.62; 95% CI, 1.3922.66, p=0.015) was anindependent factor associated with thrombus.Conclusion: Levels of BNP can serve as a marker of left atrial thrombus in acute ischemic stroke and TIA inpatients with AF.

2010 Elsevier B.V. All rights reserved.

mainly from the ventricular myocardium. A recent study has shownechocardiography (TEE) and then assigned them to groups based on the presence (positive group) or absence(negative group) of left atrial thrombus. Factors associated with atrial thrombus were investigated usingmultivariate logistic regression analysis.Results: Of the 67 (male, n=40; mean age, 76.511.1 years) enrolled patients, 17 (25.4%) had left atrialAccepted 19 October 2010Available online 20 November 2010ischemic attack (TIA). We measured BNP levels in all patients while they underwent transesophagealReceived in revised form 14 September 2010 Methods: We prospectivelyBrain natriuretic peptide is a marker assowith atrial brillation

Yoko Okada , Kensaku Shibazaki, Kazumi Kimura, NKazuto Kobayashi, Kennichiro SakaiDepartment of Stroke Medicine, Kawasaki Medical School, Okayama, Japan

a b s t r a c ta r t i c l e i n f o

Article history:Received 3 February 2010

Background: Patients withevents. We investigated wh

j ourna l homepage: wwwamino acid polypeptidesolated from the porcinery factor that is released

dicine and Neurology, Ehimen. Tel.: +81 89 960 5851; fax:

ll rights reserved.ated with thrombus in stroke patients

iko Matsumoto, Yasuyuki Iguchi, Junya Aoki,

al brillation (AF) and atrial thrombus are at high risk of thromboembolicer BNP levels can serve as a biological marker of thrombus.

ological Sciences

l sev ie r.com/ locate / jnsstroke and TIAwho underwent TEE. Patients were excluded if they didnot agree with the TEE examination, or if TEE could not be performedbecause of severe conditions such as large brain infarction withherniation, respiratory or cardiac failure. Patients with old myocardialinfarction (OMI), hypertrophic cardiomyopathy (HCM), and dialysis-dependent chronic renal failure were also excluded from the presentstudy because plasma BNP levels are increased under these circum-stances [9]. This study followed the principles outlined in the

of plasma BNP were entered into a multivariate analysis to determineadjusted odds ratios. Data were statistically analyzed using Stat View(version 5) and SPSS (version 11) software. Differences wereconsidered statistically signicant at the level of pb0.05.

3. Results

We enrolled 72 patients with AF who underwent TEE for ischemicstroke and TIA. Those with OMI (n=1), HCM (n=2) and dialysis-dependent chronic renal failure (n=2) were excluded. Therefore, thestudy included 67 patients (17 with TIA; 27 females, age, (meanSD)76.511.1 years). The meanSD of the NIHSS score on admissionand of the mRS at discharge were 7.78.0 and 2.31.8, respectively.Seventeen (25.4%) patients had left atrial thrombus. Table 1 shows thebaseline characteristics of the two groups. The proportion ofhypertension (negative vs. positive: 58.0% vs. 88.2%; p=0.020) wassignicantly higher in the positive, than in the negative group. On theother hand, platelet count (21.28.4 vs. 16.35.6104/l,p=0.022) was signicantly lower in the positive than in the negativegroup. None of the other variables signicantly differed.

3.1. TEE ndings

The interval from stroke onset to TEE did not differ between thetwo groups (7.95.7 vs. 10.88.2 days, p=0.239). Flow velocity inthe LAA (28.115.7 vs. 14.53.2 cm/s, pb0.001) was signicantlylower in the positive, than in the negative group. On the other hand,the SEC grade (1.91.1 vs. 3.30.6, pb0.001) was signicantlyhigher in the positive, than in the negative group whereas the LAA

Table 1Clinical characteristics.

Prior congestive heart failure 5 (10.0) 3 (17.6) 0.326Prior ischemic stroke 15 (30.0) 4 (23.5) 0.430

BNP (pg/ml)

87Y. Okada et al. / Journal of the Neurological Sciences 301 (2011) 8689Declaration of Helsinki and was approved by the Ethics Committee ofKawasaki Medical School Hospital. Atrial brillation was diagnosedfrom a history of AF, 12-lead electrocardiography (ECG) ndings uponadmission, as well as ECG and 24-h Holter ECG ndings duringhospitalization.

We assigned the patients according to the presence (positivegroup) or absence (negative group) of left atrial thrombus andmeasured BNP levels at the time of TEE. All patients also underwentcomputed tomography or magnetic resonance imaging. We assessedage, gender, prior congestive heart failure, prior cerebral infarction,anticoagulants use before TEE, National Institutes of Health strokescale (NIHSS) score upon admission [10], functional outcome athospital discharge using the modied Rankin scale (mRS) [11], andcardiothoracic ratios (CTR) on chest X-rays. We also evaluated thefollowing vascular risk factors: hypertension (dened as use ofantihypertensive agents, systolic blood pressure140 mm Hg or adiastolic blood pressure90 mm Hg before, or 2 weeks after strokeonset); diabetes mellitus (dened as use of oral hypoglycemic agentsor insulin, or fasting blood glucose126 mg/dl, or glycosylatedhemoglobin6.4%); hyperlipidemia (dened as use of antihyperlipi-demic agents or serum cholesterol220 mg/dl) and smoking habit(dened as a history of cigarette smoking during the preceding3 months).

Blood samples were withdrawn upon admission from all patientsto determine baseline values for the main hemostatic variables(leukocyte count, platelet count, high sensitive C-reactive protein(CRP), Prothrombin Time-International Normalized Ratio (PT-INR),D-dimer, thrombin-antithrombin III complex (TAT) and brinogen).

2.1. Echocardiography

We performed TEE using an HDI 5000 (Philips Medical Systems,Bothell, WA, USA) with a 4- to 7-MHz wideband multiplanetransducer. After local pharyngeal anesthesia with lidocaine jellyand spray, patients were placed in the left lateral position fortransducer insertion. The left atrium and the left atrium appendage(LAA) were observed in longitudinal views to detect left atrialthrombus and SEC, the severity of which was semi-quantitativelygraded (scored from 0 to 4) [12]. Velocity proles of the LAA wereobtained by placing the pulsed Doppler sample volume at 12 cm intothe orice of the LAA. The emptying ow velocity signals within eachR-R interval were averaged over a minimum of ve cardiac cycles. Thearea of the LAA was measured in B-mode, short axis views with theaortic valve. The results were recorded on super VHS videotapes andreviewed.

2.2. BNP measurements

Whole blood samples were collected from a peripheral vein at thetime of TEE into tubes containing ethylenediamine tetraacetic acidand then BNP levels were measured using a uorescent immuno-chromatographic assay (SHIONOSPOT BNP, Shionogi & Co. Ltd.,Osaka, Japan) within 15 min. The normal BNP value at our institutionis 18.4 pg/ml and the assay detection limit is 5.9 pg/ml.

2.3. Statistical analysis

We compared clinical characteristics including BNP levels betweenthe two groups using the 2 and MannWhitney U tests. Factorsassociated with BNP levels were examined using the MannWhitneyU test and linear regression analysis. We subanalyzed the associationbetween BNP and TEE ndings including LAA ow velocity, SEC gradeand LAA area. The optimal cut-off points of each continuous variableto discriminate the positive from the negative group were determinedfrom receiver operating characteristics (ROC) curves. Finally, factors

with a probability of b0.1 on univariate analysis and the optimal levelMedian (IQR) 117.9 (70.3187.1) 189.8 (141.4473.2) 0.012MeanSD 146.5119.0 307.3270.6

Data are shown as meanSD or number (%). TIA, transient ischemic attack; WBC,white blood cell; PLT, platelets; CRP, C-reactive protein; TAT, thrombin-antithrombin IIIcomplex; BNP, brain natriuretic peptide; NIHSS, National Institutes of Health strokescale; mRS, modied Rankin scale; IQR, interquartile range.Anticoagulants use before TEE 36 (72.0) 15 (83.3) 0.124TIA 8 (16.0) 0 (0.0) 0.082Cardiothoracic ratio 60.27.0 62.35.2 0.293NIHSS on admission 7.07.8 9.88.3 0.235mRS at discharge 2.6 (05) 2.2 (06) 0.30101 22 (44.0) 7 (41.2) 0.83923 12 (24.0) 4 (23.5) 0.96945 15 (30.0) 6 (35.3) 0.684Death 0 (0.0) 1 (5.9) 0.560WBC (/l) 69362772 66692108 0.960PLT (10,000/l) 21.28.4 16.35.6 0.022CRP (mg/dl) 1.363.18 1.585.43 0.828PT-INR 1.210.29 1.360.38 0.1162.0 2 (4.0) 2 (11.8) 0.243

PT-INR before TEE 1.480.53 1.690.61 0.2582.0 5 (27.8) 7 (14.0) 0.369

D-dimer (g/ml) 2.43.0 3.23.9 0.747TAT (ng/ml) 9.311.3 11.511.8 0.197Fibrinogen (mg/dl) 318117 32970 0.221Negative group Positive group p

n=50 n=17

Age (years) 76.411.7 76.59.5 0.729Female gender 17 (34.0) 10 (58.8) 0.065Hypertension 29 (58.0) 15 (88.2) 0.020Diabetes mellitus 10 (20.0) 6 (35.3) 0.171Hyperlipidemia 7 (14.0) 3 (17.6) 0.492Smoking status 26 (52.0) 7 (41.2) 0.313

area did not differ between the two groups (6.171.92 vs. 6.812.63 cm2, p=0.384; Table 2).

3.2. Levels of BNP

The median (interquartile range, IQR) BNP level was 129.4 (76.0221.4) pg/ml. The value was signicantly higher in the positive, thanin the negative group (median (IQR) 189.8 (141.4473.2) vs. 117.9(70.3187.1) pg/ml, p=0.012; Fig. 1). The BNP level was positively

Table 2TEE ndings.

Negative group Positive group p

LA SEC 42 (84.0) 17 (100.0) 0.082SEC grade 1.91.1 3.30.6 b0.001LAA out ow (cm/s) 28.115.7 14.53.2 b0.001LAA area (cm2) 6.171.92 6.812.63 0.384

Data are shown as meansSD or number (%). LA SEC, left atrial spontaneous echocontrast; LAA, left atrium appendage.

Table 3Association between BNP and clinical characteristics.

p r

Age 0.023 0.277NIHSS on admission 0.031 0.263mRS at discharge 0.005 0.340LAA ow velocity (cm/s) 0.037 0.258

NIHSS, National Institutes of Health stroke scale; mRS, modied Rankin scale; LAA, leftatrium appendage.

88 Y. Okada et al. / Journal of the Neurological Sciences 301 (2011) 8689related to clinical variables such as age (r=0.277, p=0.023), NIHSSon admission (r=0.263, p=0.031), and mRS at discharge (r=0.340,p=0.005). LAA ow velocity (r=0.258, p=0.037) was negativelyassociated with BNP levels. None of the other variables signicantlydiffered (Table 3).

Female, hypertension, platelet count and BNP level were chosen aspossible factors associated with left atrial thrombus. The optimal cut-off value to distinguish the positive from the negative group wasassessed by analyzing ROC curves. The area under the curve using BNPto predict left atrial thrombus was 0.685 (p=0.024). At a BNP level of140.0 pg/ml, sensitivity and specicity were 76.5% and 64.0%,respectively. The cut-off platelet count that identied the positivegroup with the highest sensitivity and specicity was 15.510,000/l(58.8% and 71.9%, respectively). The ndings of the multivariatelogistic regression analysis revealed that a BNP value of N140.0 pg/ml(odds ratio, 5.62; 95%CI, 1.3922.66, p=0.015) was an independentfactor associated with left atrial thrombus. (Table 4).

4. Discussion

We demonstrated that the mean BNP level in the AF patients withleft atrial thrombus was signicantly higher than in those withoutthrombus. A BNP value of N140 pg/ml was an independent factor of

BNP level(pg/ml) p = 0.012

600

800

1000Negative Positive0

200

400

Fig. 1. BNP levels of both groups. The BNP level was signicantly higher in the positivethan in the negative group (median (IQR) 189.8 (141.4473.2) vs. 117.9 (70.3187.1)pg/ml, p=0.012).left atrial thrombus in our patients with AF accompanied by acuteischemic stroke and TIA.

Possible explanations for these ndings are as follows. Firstly, leftatrial dysfunction such as low LAA ow velocity and high SEC gradeare powerful predictors of left atrial thrombus formation [13,14]. Inthe present study, BNP levels signicantly and negatively correlatedwith LAA peak velocity, which is compatible with previous ndings[15,16]. Therefore, BNP might be increased in patients with AF andLAA dysfunction. Secondly, congestive heart failure is also anindependent predictor of left atrial thrombus [17] and it frequentlycomplicates ischemic stroke with AF. Therefore, the BNP level (as amarker of congestive heart failure) could also be elevated in patientswith ischemic stroke and AF.

Shimizu et al. reported that plasma BNP levels are higher in non-valvular AF patients with, than without left atrial thrombus [6].Therefore, we believe that high BNP levels in patients with AFaccompanied by acute ischemic stroke and TIA are at high risk for leftatrial thrombus.

Although cardiac thrombus can be identied and spontaneousecho contrast can be visualized by TEE, this procedure is contra-indicated for some patients with acute stroke because it is semi-invasive. A simple BNP assay has recently been developed that candetermine BNP levels at bedside within about 15 minutes. Our studyshowed that the BNP level was associated with left atrial thrombusand left atrial dysfunction. Therefore, if a BNP value is N140 pg/ml, leftatrial thrombus should be considered, and such patients should betreated with anticoagulants such as heparin or warfarin as soon aspossible to prevent further ischemic events.

We demonstrated that BNP was associated with left atrialthrombus in the present study. However, BNP is not likely to bepredictive marker of left atrial thrombus because of cut-off levels ofBNP to distinguish the positive group from the negative group had lowsensitivity and specicity. Not only heart dysfunction but alsohypercoagulopathy and hyperviscosity may be associated with leftthrombus formation.

This study has several limitations. Firstly, not all patients withacute ischemic stroke and transient ischemic attack who are admittedto our hospital undergo TEE, which might have introduced a selectionbias. Secondly, we did not assess cardiac function such as ejectionfraction and left ventricular end diastolic pressure. Thirdly, themeasurement time points differed between BNP and other hemostatic

markers.

Table 4Multivariate logistic regression analysis.

Thrombus

p Odds ratio 95%CI

Female gender 0.091 3.09 0.8311.44Hypertension 0.140 3.65 0.6520.39PLTb15.510,000 l 0.495 1.60 0.426.13BNPN140 pg/ml 0.015 5.62 1.3922.66

PLT, platelet count; BNP, brain natriuretic peptide.

5. Conclusion

Levels of BNP could serve as a useful marker of left atrial thrombusin patients with AF accompanied by acute ischemic stroke and TIA.

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89Y. Okada et al. / Journal of the Neurological Sciences 301 (2011) 8689

Brain natriuretic peptide is a marker associated with thrombus in stroke patients with atrial fibrillationIntroductionPatients and methodsEchocardiographyBNP measurementsStatistical analysis

ResultsTEE findingsLevels of BNP

DiscussionConclusionReferences