Youngchai Ko

Eulji University, Daiden, Daejeon, South Korea

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Publications (15)45.8 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Background Recent methodological advances in recanalization therapy may alter recanalization strategies and clinical outcomes in patients with symptomatic occlusion of intracranial cerebral arteries. However, few studies have analyzed these changes at a national level, with none conducted in Korea. Methods On the basis of a prospective multicenter stroke registry database in Korea, 642 consecutive patients hospitalized within 12 hours of the onset with symptomatic occlusion of intracranial major cerebral arteries between March 2010 and November 2011 were identified. Recanalization therapy was used in 48% (n = 307) of patients; intravenous thrombolysis only (IVT) in 46%, intra-arterial thrombolysis only (IAT) in 16%, and combined thrombolysis (CMT) in 38%. Of the 166 patients treated by IAT or CMT, the Penumbra system or the Solitaire was used in 58% of patients. Results Early neurologic improvement (ENI), 3-month modified Rankin scale (mRS) score of 2 or less, and symptomatic hemorrhagic transformation (SHT) were observed in 43%, 39%, and 9% of the patients in the IVT group; 52%, 27%, and 12% of the patients in the IAT group; and 54%, 39%, and 12% of the patients in the CMT group, respectively. Compared with no treatment, adjusted odd ratios (95% confidence intervals) of recanalization therapy were 1.59 (1.04-2.42) for ENI, 1.37 (.81-2.30) for 3-month mRS score of 2 or less, and 2.58 (1.12-5.91) for SHT. Conclusions The variety and active use of endovascular approaches were quite noticeable. As a whole, recanalization therapy tended to contribute to favorable outcomes despite a significant increase of symptomatic hemorrhage.
    Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 01/2014;
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    ABSTRACT: Background We aimed to assess the impact of symptomatic steno-occlusion (SYSO) of cerebral arteries and its characteristics on subsequent ischemic event (SIE) in patients with acute ischemic stroke. Methods Using a prospective stroke registry database, we identified consecutive patients with ischemic stroke who were hospitalized within 48 hours of symptom onset. SYSO denoted significant stenosis or occlusion of major cerebral arteries with ischemic lesions at the corresponding arterial territories and was characterized by its location and severity. Primary outcome was SIE that was defined as ischemic progression or recurrence within 1 year. Results In total, 1546 patients (age, 67.4 ± 13.0 years; median National Institutes of Health Stroke Scale score, 4) were enrolled in this study. The cumulative risk of SIE was 14.5% at 7 days, 14.9% at 14 days, 15.5% at 90 days, and 16.9% at 1 year. Patients with SYSO had significantly higher SIE rates compared with those without SYSO (23.0% versus 11.6%). Of the characteristics of SYSO, the location, not the severity, was significantly associated with SIE (P < .001 and P = .186, respectively). Multiple (adjusted hazard ratio, 5.85; 95% confidence interval, 1.81-18.85), intracranial internal carotid artery (ICA) (3.54; 1.21-8.21), and extracranial ICA SYSO (2.88; 1.01-8.21) raised the risk of SIE. Conclusions Subsequent cerebral ischemic events (progression or recurrence) after an acute ischemic stroke occur mostly within several days of stroke onset and is associated with the location, but not the severity, of symptomatic steno-occlusion of cerebral arteries.
    Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 01/2014;
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    ABSTRACT: Although ethnic or cultural differences affect prevalence of cardiovascular risk factors, limited information is available about the age- and gender-stratified prevalence of the risk factors in Asian stroke population. We assessed gender- and age-stratified prevalences of major risk factors in Korean stroke patients, and assumed that the gender differences are attenuated by adjustment with lifestyle factors. Using the nationwide hospital-based stroke registry, we identified 9417 ischemic stroke patients admitted between April 2008 and January 2011. Prevalence of hypertension, diabetes, hyperlipidemia, atrial fibrillation, prior stroke, and coronary heart disease was assessed in both genders by age groups. We analyzed gender differences of the prevalence among the age groups by calculating prevalence ratio, and further explored the influence of lifestyle factors on the gender difference in multivariable analyses. Hypertension and hyperlipidemia were more common in men until middle age, but after that more common in women, whereas diabetes was more common in women after 65 years of age. Atrial fibrillation increased steadily with age in both genders but was more common in women through all age groups. Prior stroke and coronary heart disease showed inconsistent gender differences. Gender differences in hypertension and diabetes among the age groups were attenuated by adjustment with accompanying risk factors including lifestyle factors. Korean women with stroke had more hypertension and hyperlipidemia after middle age, more diabetes after 65 years, and more atrial fibrillation throughout all ages. Strategies to control risk factors in women at risk for stroke are eagerly needed.
    International Journal of Stroke 10/2013; · 2.75 Impact Factor
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    ABSTRACT: Despite substantial differences in clinical features between Asian and Western stroke patients, there are no published prognostic tools validated in an Asiatic population for thrombolytic therapy. We assessed the ability of the iScore to predict the clinical response after intravenous thrombolysis with tissue plasminogen activator (tPA) in a Korean stroke population. We applied the iScore to eligible participants in the nationwide multicenter stroke registry in Korea. Main outcome measures were poor functional outcome defined as having a modified Rankin Scale score 3-6 and death at 3 months. Symptomatic intracranial hemorrhage (sICH) was evaluated as a safety outcome. C statistic was calculated to assess performance of iScore. Among 4760 patients with an acute ischemic stroke, 622 (13.1%) received tPA, 548 patients had complete information for the analysis. C statistics for poor functional outcome and death at 3 months were .813 (95% confidence interval [CI]: .778-.848) and .820 (95% CI: .769-.872), respectively. Overall, there was a high correlation between observed and expected outcome for poor functional outcome (Pearson correlation coefficient, r = .982) and for death at 3 months (r = .950) at the risk score level. An iScore of 180 or more was associated with a more than 2 times risk of poor functional outcome and about 6 times risk of death at 3 months. There was an interaction between the iScore and tPA for a poor functional outcome (P value for the interaction < .001). We found a gradient effect in the incident risk of sICH with the iScore. The iScore reliably predicts stroke outcomes after tPA in Asiatic population.
    Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 06/2013;
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    ABSTRACT: OBJECTIVE: We aimed to study various measures of blood pressure (BP) in the subacute phase of ischemic stroke to determine whether any of them predicted clinical outcome. METHODS: In this retrospective observational study, a consecutive series of patients hospitalized for ischemic stroke within 48 hours of onset were enrolled. The subacute stage of stroke was defined as the time period from 72 hours of symptom onset to discharge or transfer. During this period, mean, maximum, maximum - minimum, SD, and coefficient of variation of systolic BP (SBP) and diastolic BP (DBP) were determined. A baseline severity-adjusted analysis was performed using each patient's 3-month modified Rankin Scale score as the primary outcome. RESULTS: Among a total of 2,271 patients, the median number of BP measurements was 34 per person and the median interval from onset to discharge was 8.7 days. Measures of variability of BP were associated with poor outcome. One SD increase of maximum - minimum (odds ratio [OR], 1.26; 95% confidence interval [CI], 1.12-1.42), SD (OR, 1.20; 95% CI, 1.07-1.34), or coefficient of variation (OR, 1.21; 95% CI, 1.09-1.35) for SBP, but not mean level of SBP (OR, 0.92; 95% CI, 0.79-1.07), was independently associated with poor outcome. Results were similar for DBP. CONCLUSION: This study shows that variability of BP, but not average BP in the subacute stage of ischemic stroke, is associated with functional outcome at 3 months after stroke onset.
    Neurology 10/2012; · 8.25 Impact Factor
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    ABSTRACT: Multidetector-row CT (MDCT) is emerging as a new tool for diagnosing aortic atherothrombotic disease (AAD). We elucidated whether MDCT-detected AAD is associated with an increased risk of early ischemic lesion recurrence on diffusion-weighted MRI after ischemic stroke. A consecutive series of patients with acute ischemic stroke confirmed using diffusion-weighted MRI who were hospitalized within 48 hours after symptom onset and underwent MDCT were identified in a prospective stroke registry database. AAD on MDCT was defined as the presence of plaque formation that was noncalcified and ≥4 mm thick, ulcerative, or soft and thrombosed (vulnerable) in the proximal aortic arch. Ischemic lesion recurrence on diffusion-weighted MRI was defined as the occurrence of any new lesion separate from the index lesion on follow-up diffusion-weighted MRI performed within 14 days after symptom onset. A total of 138 patients was selected. MDCT detected AAD in 24 of 138 (17.4%); ≥4 mm thickness in 17 of 138 (12.3%); ulcerated plaque in 20 of 138 (14.5%); and vulnerable plaque in 16 of 138 (11.6%). With respect to diffusion-weighted MRI lesion recurrence, the crude ORs (95% CIs) were as follows: AAD, 3.56 (1.43-8.89); vulnerable plaque, 3.21 (1.11-9.30); ulcerated plaque, 3.37 (1.27-8.95); and ≥4 mm thickness of the noncalcified plaque, 4.23 (1.11-16.19). These results remained significant after adjustments for potential confounders were made. This study shows that AAD detected by MDCT increases the risk of early ischemic lesion recurrence after acute ischemic stroke, thus supporting the role of MDCT in diagnosing AAD and assessing its contribution to recurrence.
    Stroke 03/2012; 43(3):764-9. · 6.16 Impact Factor
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    ABSTRACT: Asymptomatic hemorrhagic transformation (HT) is not associated with immediate deterioration of patients with acute ischemic stroke. However, it is unclear whether it is clinically innocuous with respect to long-term outcome. The aim of this study was to determine the impact of asymptomatic HT on 3-month outcome. A consecutive series of 1,618 patients, hospitalized between January 2004 and August 2007 for ischemic stroke within 7 days from symptom onset were identified in a prospective stroke registry database. Those who had no evidence of acute cerebral ischemia on diffusion-weighted MRI, who did not undergo T2-weighted gradient echo MRI, whose modified Rankin Scale (mRS) score at 3 months after stroke onset was not available, or who had symptomatic HT were excluded. The odds ratio (OR) of asymptomatic HT was calculated for the full distribution of mRS score and adjusted for variables with p < 0.25 with respect to their associations with asymptomatic HT or functional outcome. Of 1,412 patients eligible for the study, 100 (7.1%) had asymptomatic HT. Patients who experienced asymptomatic HT were more likely to have cardioembolic stroke, to receive thrombolytic therapy, to receive anticoagulation with heparin, and to have a higher initial NIH Stroke Scale score. The crude and adjusted ORs of asymptomatic HT for an increment of mRS score at 3 months were 2.94 (95% confidence interval 2.05-4.24) and 1.90 (1.27-2.82), respectively. Our study shows that the odds of a worse outcome are increased by a factor of 2 in patients with asymptomatic HT compared with those without HT after acute ischemic stroke.
    Neurology 02/2012; 78(6):421-6. · 8.25 Impact Factor
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    ABSTRACT: Elevated blood pressure (BP) is commonly observed in acute ischemic stroke and is known to be associated with hemorrhagic transformation (HT). However, the effect of BP variability on the development of HT is not known well. A consecutive series of patients with acute ischemic stroke, who were hospitalized within 24 hours of onset and showed no HT on initial gradient echo MRI, were enrolled in this study. BP measurements during the first 72 hours were obtained, and BP variability of each patient was described using various summary parameters: SD, maximum (max), minimum (min), difference between max and min (max-min), average squared difference between successive measurements (sv), and maximum sv (svmax). Of 792 patients meeting the eligibility criteria, 70 (8.8%) developed HT. Among BP variability parameters categorized into quartiles, SBP(max), SBP(min), SBP(max-min), SBP(svmax), DBP(SD), DBP(max), DBP(min), DBP(max-min), and DBP(svmax) were significantly associated with HT independent of mean SBP, age, interval from onset to arrival, initial stroke severity, diabetes mellitus, stroke subtype, thrombolysis, initial glucose, and total cholesterol (P<0.05 on likelihood ratio test of trend). The analyses about the interaction between thrombolysis and variability parameters showed that the effects of BP variability on the development of HT did not differ by whether patients received thrombolysis or not. Our study suggests that we may consider not only the absolute level of BP but also its variability to prevent hemorrhagic transformation.
    Stroke 11/2010; 41(11):2512-8. · 6.16 Impact Factor
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    ABSTRACT: The effect of previous antiplatelet use on stroke severity is controversial. We assume that this controversy is attributable to its difference according to the stroke mechanism. Using a prospective stroke registry, patients who were hospitalized because of ischemic stroke and had relevant lesions on MRI were selected. Patients who were using anticoagulants or whose stroke subtype was categorized as stroke of other determined etiology or undetermined etiology were excluded. Baseline stroke severity was measured using the National Institutes of Health Stroke Scale scores at presentation and was compared between no previous antiplatelet users and previous antiplatelet users with stratification by stroke subtypes. Among the 1622 patients, a total of 490 (30.2%) patients reported use of an antiplatelet within 1 week of stroke onset. The baseline National Institutes of Health Stroke Scale score showed no difference between the nonantiplatelet and antiplatelet groups by crude comparison. However, the interaction between previous antiplatelet use and stroke subtype was significant (P=0.023) in a multivariable analysis; when the study subjects were stratified by stroke subtype, the difference in baseline National Institutes of Health Stroke Scale between the nonantiplatelet and platelet groups was significant in the large artery atherothrombosis group but not in those with cardioembolism and small-vessel occlusion before and after adjustments. Our study suggests that the reduction of initial stroke severity in the previous antiplatelet users may differ by stroke mechanism.
    Stroke 06/2010; 41(6):1200-4. · 6.16 Impact Factor
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    ABSTRACT: Ischemic lesion recurrence on diffusion-weighted imaging (DWI-LR) is a frequently observed phenomenon after acute ischemic stroke. However, no study has elucidated the impact of DWI-LR on functional outcome. Among a consecutive series of patients who presented with focal symptoms or signs compatible with stroke within 48 hours from the onset over a 50-month period, those who had relevant ischemic lesions on initial DWI and underwent follow-up DWI within 14 days after the onset were enrolled in this study. As outcome variables, the scores on the modified Rankin Disability Scale (mRDS) at 3 months and 1 year were measured prospectively and dichotomized into good (0-2) vs. poor (3-6). When calculating odds ratios (ORs), adjustment was performed for age, previous stroke, initial score on the NIH Stroke Scale, stroke subtype, and IV thrombolysis. Among those 786 patients finally enrolled in this study, 221 (28.1%) had DWI-LR. For a poor outcome at 3 months, the crude ORs of any, symptomatic, and asymptomatic DWI-LR were 2.70 [95% confidence interval (CI), 1.96 to 3.72], 10.03 (95% CI, 4.39 to 22.96), and 2.04 (95% CI, 1.44 to 2.88), respectively. With adjustment, the OR of symptomatic DWI-LR was 6.44 (95% CI, 2.50 to 16.57), whereas those of any and asymptomatic DWI-LR lost their statistical significance: 1.44 (95% CI, 0.94 to 2.20) and 1.04 (95% CI, 0.65 to 1.65), respectively. Analyzing with the 1-year outcome produced similar results. This study shows that symptomatic early lesion recurrence can affect functional outcome after acute ischemic stroke, whereas an asymptomatic one may not.
    Journal of Clinical Neurology 03/2010; 6(1):19-26. · 1.69 Impact Factor
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    ABSTRACT: Cardiac multidetector computed tomography (MDCT) is less dependent upon the patient's condition and may be valuable in the diagnosis of embolic sources when the patient's cooperation is limited due to a neurologic deficit. However, its role has never been validated in acute stroke patients whose stroke mechanism is assumed to be embolic. Consecutive patients who were admitted with acute ischemic stroke from May 1, 2007 to November 30, 2007 were included in this study. Inclusion criteria were (1) any cardiac evidence of high-risk embolic sources for cerebral embolism, or (2) radiological or (3) clinical evidence of embolic stroke. All patients underwent transthoracic echocardiography first, and then cardiac MDCT or transesophageal echocardiography (TEE) was attempted, if possible. The results and feasibility of cardiac MDCT and TEE were compared. One hundred and forty-three patients met the inclusion criteria. Cardiac MDCT was performed in 124 patients (86.7%), TEE in 83 patients (57.3%), whereas 75 patients (52.4%) underwent both studies. Renal insufficiency for cardiac MDCT and lack of cooperation for TEE were found to be the most impeding factors. Among the patients with both evaluations, cardiac MDCT identified a high-risk intracardiac embolic source in 8 and an extracardiac source in 20, while TEE found an intracardiac source in 1 and an extracardiac source in 7. Statistically significant differences were found with respect to detecting cardioembolic sources and high-risk aortic atheroma. Cardiac MDCT is a feasible and accurate diagnostic tool for embolic sources in an acute stroke setting.
    Cerebrovascular Diseases 01/2010; 29(4):313-20. · 2.81 Impact Factor
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    ABSTRACT: The usefulness of 64-multidetector row computed tomography (MDCT) for the evaluation of aortic atherosclerotic disease (AAD), a potential source of cerebral emboli, has recently been suggested. We aimed to assess the significance of AAD by using MDCT in patients who are suspected to have had embolic stroke clinically or radiologically but without evident cardioembolic source (possibly embolic stroke, or PES). From 5/2007 to 10/2007, patients who were presented with acute ischemic stroke, met predefined criteria for PES, and underwent MDCT, were found in a prospective stroke registry (PES group). High-risk AAD was defined as thrombus, ulceration, and a >or=4 mm thickness of atherosclerotic plaque in the ascending aorta and aortic arch on MDCT. For comparison, patients who were hospitalized due to non-embolic stroke (NES) during the study period and who underwent MDCT for the purpose of screening of coronary artery disease were selected (NES group). Among a total of 336 patients with acute ischemic stroke, 57 (20.0%) satisfied the criteria for PES, and MDCT was performed in 50 of these 57 patients. One-hundred six patients were selected as the NES group. The PES group had significantly higher prevalence of high-risk AAD than the NES group did (38.0 vs. 13.2%, P < 0.01). The odds ratio of high-risk AAD was 4.03 (95% confidence interval, 1.81-8.98) and this result remained significant after adjustment for risk factors of atherosclerosis. This study suggests the etiologic role of aortic atherosclerosis detected by MDCT in patients who are assumed to have had embolic stroke but without evident embolic source.
    Journal of Neurology 11/2009; 257(5):699-705. · 3.58 Impact Factor
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    ABSTRACT: Results: The baseline characteristics did not differ significantly betw een patients admitted to SUs (n=195) and their matched controls (n=386). The 3-month dependency rate was 17.4% in SUs and 21.0% in GWs (p=0.31), and the case fatality rates were 1.5% and 8.0% (p
    01/2009;
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    ABSTRACT: Background: Acute intracranial large-artery occlusions (AILAOs) are detected frequently and cause severe neurological disabilities. Most studies in this field do not focus on the natural history of AILAOs, but on the individual prognosis for each intervention. The aim of this study was to elucidate the clinical profiles and outcomes of AILAOs. Methods: A consecutive series of patients hospitalized between January 2004 and October 2007 due to AILAO within 24 hours from onset were recruited. Based on a prospective stroke registry, their clinical profiles were collected. AILAO was defined as an intracranial internal carotid artery (ICA), middle cerebral artery (MCA), or basilar artery (BA) occlusion that could be confirmed by angiography, with relevant lesions on diffusion-weighted imaging (DWI). The modified Rankin Scale (MRS) score at 3 months and the recanalization rate within 14 days were recorded as outcomes. Results: Among 1,047 patients with acute ischemic stroke who were examined within 24 hours of onset, 189 (18.1%; 101 men, 88 women; age 68.6±13.0 years (mean±SD); median National Institutes of Health Stroke Scale (NIHSS) score=11). Occlusion sites were MCA M1, MCA M2, distal ICA, and BA in 99 (52.4%), 50 (26.5%), 20 (10.6%), and 20 (10.6%) of cases, respectively. Embolic sources were found in 103 (54.5%) cases. MRS scores were available for 184 (97.4%) of the patients, of which 78 had a favorable outcome (MRS: 0-2). Follow-up angiography was performed in 122 (64.6%) cases, with recanalization observed in 88 (72.1%) of these. Thrombolysis, occlusion site, presence of an embolic source, and initial glucose level were predictors of early recanalization (p
    01/2009;
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    ABSTRACT: Background: Recurrent stroke is a major cause of morbidity and mortality among stroke survivors. However, studies of the long-term prognosis after acute stroke are very rare, especially in Asia. This study aimed to provide estimates of recurrent stroke rates by age, gender, and subtype of stroke in an unselected cohort of patients hospitalized to a community-based general hospital due to acute stroke. Methods: Based on a prospective stroke registry, acute stroke patients were enrolled within 7 days of symptom onset and followed retrospectively or prospectively for up to 3 years. Information was gathered about stroke recurrence and other vascular events. The cumulative risk of recurrent stroke was calculated using the Kaplan-Meier method. Results: Two-thousand and sixty-eight patients were enrolled in this study. The cumulative risks of stroke recurrence were 2.3%, 5.5%, 8.6%, and 10.0% at 90 days and 1, 2, and 3 years, respectively. The prevalence of stroke recurrence increased with age and the presence of previous stroke history (p
    01/2009;

Publication Stats

42 Citations
45.80 Total Impact Points

Institutions

  • 2013–2014
    • Eulji University
      Daiden, Daejeon, South Korea
  • 2009–2012
    • Seoul National University Bundang Hospital
      • Department of Radiology
      Sŏul, Seoul, South Korea
  • 2010
    • Seoul National University Hospital
      • Department of Neurology
      Seoul, Seoul, South Korea