Young Keun On

Samsung Medical Center, Sŏul, Seoul, South Korea

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Publications (62)148.96 Total impact

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    ABSTRACT: Most patients with idiopathic ventricular premature depolarizations (VPDs) complain of symptoms related to this arrhythmia, but some patients are asymptomatic even with a high VPD burden. Our understanding of the relationship between symptoms and cardiomyopathy related to this arrhythmia remains limited. We evaluated 801 subjects (381 men; mean age, 55 ± 17 years) who visited our outpatient clinic. All subjects were diagnosed with frequent VPDs (1% or >1000 beats/day). The patients were divided into two groups according to the presence or absence of typical VPD symptoms (palpitations or skipped beats during VPDs): symptomatic patients (n = 455) and asymptomatic patients (n = 346). Clinical and electrocardiogram parameters were compared between these two groups. In the symptomatic group, palpitations were the most frequent symptom (91%). Daily VPD burden (P = 0.90) and electrocardiogram parameters (P>0.05) did not differ significantly between groups. The incidence of frequent VPDs with left ventricular dysfunction was significantly higher in the asymptomatic group (symptomatic patients, 3.0%; asymptomatic patients, 10.5%; P < 0.001). The absence of typical VPD-related symptoms may be a risk factor for cardiomyopathy and be associated with an adverse outcome. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.
    Europace 05/2015; DOI:10.1093/europace/euv112 · 3.05 Impact Factor
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    ABSTRACT: High ventricular premature depolarization (VPD) burden is associated with left ventricular (LV) dysfunction that typically resolves after successful ablation. Some patients, however, have persistent LV dysfunction, even after successful radiofrequency (RF) ablation. Identifying factors associated with irreversibility of LV cardiomyopathy (CMP) may help predict clinical outcome.Methods and Results:Patients with frequent VPD (>10%/day) who underwent successful VPD suppression were divided into 2 groups according to transthoracic echocardiography (TTE) before and after suppression: group A (n=38) had depressed LV function that normalized after VPD suppression; group B (n=19) had depressed LV function before and after suppression. Of 57 patients (43 men; mean age, 54±15 years), RF ablation was performed in 39. Clinical, electrocardiographic, and TTE parameters were compared between groups. LV end-diastolic dimension (LVEDD; group A vs. B: 54±5 mm vs. 60±10 mm, P=0.01), end-systolic dimension (group A vs. B: 42±6 mm vs. 48±11 mm, P=0.01) before VPD suppression differed significantly between groups. Pre-suppression LVEDD was ≤66 mm in all reversible-CMP patients. LVEDD >66 mm predicted irreversible CMP with 50% sensitivity, 100% specificity, 100% positive predictive value, and 81% negative predictive value. LVEDD was a good predictor of irreversible LV CMP with frequent VPD, with 50% sensitivity and 100% specificity.
    Circulation Journal 05/2015; DOI:10.1253/circj.CJ-15-0171 · 3.69 Impact Factor
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    ABSTRACT: Atrial fibrillation (AF) is the most common heart arrhythmia. Untreated AF incurs a considerable burden of stroke and associated healthcare costs. Asians have AF risk factors similar to Caucasians and a similarly increased risk of AF-related stroke; however, with a vast and rapidly ageing population, Asia bears a disproportionately large disease burden. Urgent action is warranted to avert this potential health crisis. Antithrombotic therapy with oral anticoagulants is the most effective means of preventing stroke in AF and is a particular priority in Asia given the increasing disease burden. However, AF in Asia remains undertreated. Conventional oral anticoagulation with warfarin is problematic in Asia due to suboptimal control and a propensity among Asians to warfarin-induced intracranial haemorrhage. Partly due to concerns about intracranial haemorrhage, there are considerable gaps between AF treatment guidelines and clinical practice in Asia, in particular overuse of antiplatelet agents and underuse of anticoagulants. Compared with warfarin, new direct thrombin inhibitors and Factor Xa inhibitors are non-inferior in preventing stroke and significantly reduce the risk of life-threatening bleeding, particularly intracranial bleeding. These agents may therefore provide an appropriate alternative to warfarin in Asian patients. There is considerable scope to improve stroke prevention in AF in Asia. Key priorities include: early detection of AF and identification of asymptomatic patients; assessment of stroke and bleeding risk for all AF patients; evidence-based pharmacotherapy with direct-acting oral anticoagulant agents or vitamin K antagonists for AF patients at risk of stroke; controlling hypertension; and awareness-raising, education and outreach among both physicians and patients. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    International journal of cardiology 03/2015; 191:244-253. DOI:10.1016/j.ijcard.2015.03.369 · 6.18 Impact Factor
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    ABSTRACT: An implantable cardioverter-defibrillator (ICD) is the only proven effective therapeutic strategy for patients with Brugada syndrome (BS). However, it is controversial whether the device should be replaced even in patients who had never experienced appropriate ICD therapy until the time of generator replacement. This was a nationwide, multicenter retrospective study that enrolled patients who were diagnosed with BS and had an ICD implantation between January 1998 and April 2014. Appropriate ICD therapies administered for ventricular tachyarrhythmia were evaluated during follow-up. A total of 117 patients (age 43±12years, male 115 [98.3%]) were enrolled, and the mean follow-up duration was 6.0±4.1years. Thirty-seven (31.6%) patients had experienced appropriate ICD therapy during follow-up. Of all patients, 46 underwent replacement of the device. After the first generator replacement, the incidence of appropriate ICD therapy remained as high as 65.2% in patients who previously experienced appropriate ICD therapy before generator replacement. In 30 patients who did not experience any cardiac events until the first generator change, two (8.7%) had an episode of appropriate ICD therapy afterwards. No episode of ICD therapy before generator replacement could not guarantee a safe clinical course. ICD generator replacement should be considered even in patients without ICD therapy before. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    International journal of cardiology 03/2015; 187:340-344. DOI:10.1016/j.ijcard.2015.03.262 · 6.18 Impact Factor
  • International journal of cardiology 03/2015; 186:213-215. DOI:10.1016/j.ijcard.2015.03.229 · 6.18 Impact Factor
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    ABSTRACT: Statin pretreatment in patients undergoing cardiac surgery is understood to prevent postoperative atrial fibrillation (AF). However, this is based on observational and limited randomized trial evidence, resulting in uncertainty about any genuine anti-arrhythmic benefits of these agents in this setting. We therefore aimed to quantify precisely the association between statin pretreatment and postoperative AF among patients undergoing cardiac surgery. A detailed search of MEDLINE and PubMed databases (1st January 1996 to 31st July 2012) was conducted, followed by a review of the reference lists of published studies and correspondence with trial investigators to obtain individual-participant data for meta-analysis. Evidence was combined across prospective, randomized clinical trials that compared the risk of postoperative AF among individuals randomized to statin pretreatment or placebo/control medication before elective cardiac surgery. Postoperative AF was defined as episodes of AF lasting ≥5 min. Overall, 1105 participants from 11 trials were included; of them, 552 received statin therapy preoperatively. Postoperative AF occurred in 19% of these participants when compared with 36% of those not treated with statins (odds ratio 0.41, 95% confidence interval 0.31-0.54, P < 0.00001, using a random-effects model). Atrial fibrillation prevention by statin pretreatment was consistent across different subgroups. Short-term statin pretreatment may reduce the risk of postoperative AF among patients undergoing cardiac surgery. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.
    Europace 03/2015; DOI:10.1093/europace/euv001 · 3.05 Impact Factor
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    ABSTRACT: In patients with nonvalvular atrial fibrillation (AF), the risk of stroke varies considerably according to individual clinical status. The CHA2DS2-VASc score is better than the CHADS2 score for identifying truly lower risk patients with AF. With the advent of novel oral anticoagulants (NOACs), the strategy for antithrombotic therapy has undergone significant changes due to its superior efficacy, safety and convenience compared with warfarin. Furthermore, new aspects of antithrombotic therapy and risk assessment of stroke have been revealed: the efficacy of stroke prevention with aspirin is weak, while the risk of major bleeding is not significantly different from that of oral anticoagulant (OAC) therapy, especially in the elderly. Reflecting these pivotal aspects, previous guidelines have been updated in recent years by overseas societies and associations. The Korean Heart Rhythm Society has summarized the new evidence and updated recommendations for stroke prevention of patients with nonvalvular AF. First of all, antithrombotic therapy must be considered carefully and incorporate the clinical characteristics and circumstances of each individual patient, especially with regards to balancing the benefits of stroke prevention with the risk of bleeding, recommending the CHA2DS2-VASc score rather than the CHADS2 score for assessing the risk of stroke, and employing the HAS-BLED score to validate bleeding risk. In patients with truly low risk (lone AF, CHA2DS2-VASc score of 0), no antithrombotic therapy is recommended, whereas OAC therapy, including warfarin (international normalized ratio 2-3) or NOACs, is recommended for patients with a CHA2DS2-VASc score ≥2 unless contraindicated. In patients with a CHA2DS2-VASc score of 1, OAC therapy should be preferentially considered, but depending on bleeding risk or patient preferences, antiplatelet therapy or no therapy could be permitted.
    Korean Circulation Journal 01/2015; 45(1):9-19. DOI:10.4070/kcj.2015.45.1.9
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    ABSTRACT: A case of a fistula running from the pulmonary vein to the esophagus after a staged hybrid procedure combining total thoracoscopic ablation and percutaneous radiofrequency catheter ablation has not been reported previously. We describe such a case in a 37-year-old man who was successfully treated by surgery.
    12/2014; 47(6):560-2. DOI:10.5090/kjtcs.2014.47.6.560
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    ABSTRACT: We applied cardiac resynchronization therapy (CRT) for desynchronized heart failure patients. We evaluated clinical outcomes including morbidity, mortality, and echocardiographic parameters in 47 patients with implanted CRT in Korea from October 2005 to May 2013. The combined outcomes of hospitalization from heart failure, heart transplantation and death were the primary end point. Median follow-up period was 17.5 months. The primary outcomes listed above occurred in 10 (21.3%) patients. Two patients (4.3%) died after CRT and 8 (17%) patients were hospitalized for recurrent heart failure. Among patients hospitalized for heart failure, 2 (4.3%) patients underwent heart transplantation. The overall free rate of heart failure requiring hospitalization was 90.1% (95% CI, 0.81-0.99) over one year and 69.4% (95% CI, 0.47-0.91) over 3 yr. We observed improvement of the New York Heart Association classification (3.1±0.5 to 1.7±0.4), decreases in QRS duration (169.1 to 146.9 ms), decreases in left ventricular (LV) end-diastolic (255.0 to 220.1 mL) and end-systolic (194.4 to 159.4 mL) volume and increases in LV ejection fraction (22.5% to 31.1%) at 6 months after CRT. CRT improved symptoms and echocardiographic parameters in a relatively short period, resulting in low mortality and a decrease in hospitalization due to heart failure.
    Journal of Korean Medical Science 12/2014; 29(12):1651-7. DOI:10.3346/jkms.2014.29.12.1651 · 1.25 Impact Factor
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    ABSTRACT: Purpose: Recurrent syncope leads to poor functional status and psychiatric impairment in patients with syncope. The aim of the study was to prospectively analyze the risk factors attributed to syncope recurrence. Materials and Methods: Between 2009 and 2010, 289 patients with all cause of syncope visited our institution. Syncope recurrences were followed for 1 year by telephone interview every 3 months. Results: We diagnosed 181 (63%) patients with neurally mediated syncope (NMS), 39 (13%) with orthostatic hypotension, 34 (12%) with cardiac syncope, and 35 (12%) with unexplained syncope. During the 1-year follow-up period, 19 (6.6%) patients suffered recurrent syncope. Kaplan-Meier curves showed that recurrent syncope was observed more often in patients with unexplained syncope compared with those with NMS (p < 0.01), and also observed more often in patients with six previous syncopal episodes compared to those with fewer episodes (p = 0.02). Cox regression analysis showed that the recurrence of syncope was significantly associated with more than six previous syncopal episodes (HR 5.38, 95% CI 1.17-24.71, p = 0.03) and that there was a tendency for association between recurrence of syncope and unexplained syncope (HR 6.13, 95% CI 0.96-39.1, p = 0.05). Conclusions: Patients with previous frequent syncopal episodes or unexplained syncope had higher rates of syncope recurrence during the follow up period. © 2014 S. Karger AG, Basel.
    Cardiology 11/2014; 129(4):233-239. DOI:10.1159/000366267 · 2.04 Impact Factor
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    ABSTRACT: The selection of the optimal right ventricular (RV) pacing site remains unclear. We hypothesized that a normal paced QRS axis would provide a physiological ventricular activation and lead to a better long-term outcome.
    Journal of Interventional Cardiac Electrophysiology 11/2014; DOI:10.1007/s10840-014-9950-7 · 1.55 Impact Factor
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    ABSTRACT: Purpose: Our objective was to compare the efficacy of dronedarone and propafenone in maintaining sinus rhythm in patients with atrial fibrillation (AF) after electrical cardioversion. Methods: In this single-center, open-label, randomized trial, we randomly assigned patients with AF after electrical cardioversion to receive dronedarone 400 mg BID or propafenone 150 mg TID. Follow-up clinical evaluations were conducted at 1, 2, 3, and 6 months of treatment. The primary end point was the time to the first recurrence of AF. Findings: A total of 98 patients were enrolled (79 men; mean age, 59.2 years; n = 49 per group). The median times to first recurrence of AF were 31 days in the dronedarone group and 32 days in the propafenone group (P = 0.715). The median (interquartile range) ventricular rates at first recurrence of AF were 76.5 (67.3-86.5) beats/min in the dronedarone group and 83.0 (71.0-96.0) beats/min in the propafenone group (P = 0.059).
    Clinical Therapeutics 08/2014; 36(9). DOI:10.1016/j.clinthera.2014.07.013 · 2.59 Impact Factor
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    ABSTRACT: Brugada syndrome is a rare channelopathy associated with the SCN5A gene that causes fatal ventricular arrhythmias. This case of Brugada syndrome, in which ventricular tachycardia (VT) was provoked by high fever, is the first report in a Korean child. The boy had retinoblastoma of his left eye diagnosed at 16 months of age. After chemotherapy, he contracted a catheter-related infection with a high fever up to 41℃ leading to monomorphic VT. This was characterized as having right bundle branch block morphology, superior axis deviation, and a heart rate of 212/min. Direct current cardioversion recovered the VT to sinus rhythm after a lack of response to amiodarone and lidocaine. A second attack of VT that was not controlled by cardioversion, however, responded to lidocaine. The baseline electrocardiogram showed a long PR interval and QRS duration, and the patient's grandfather had a history of Brugada syndrome. A mutation in SCN5A was identified in this patient, his father, and his grandfather. The patient was treated with quinidine and followed up for 1 year.
    Korean Journal of Pediatrics 08/2014; 57(8):374-8. DOI:10.3345/kjp.2014.57.8.374
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    ABSTRACT: Atrial septal defect (ASD) is one of the most common congenital heart defects in adults. Surgical repair is the most common treatment approach, but device closure has recently become widely performed in accordance with the trend toward less invasive surgical approaches. Although surgery is recommended when ASD is accompanied by atrial fibrillation, this study reports a case in which a complete cure was achieved by closure of a device and totally thoracoscopic ablation.
    06/2014; 47(3):280-2. DOI:10.5090/kjtcs.2014.47.3.280
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    ABSTRACT: Percutaneous left atrial appendage (LAA) occlusion using the Watchman device (Atritech, Plymouth, MN) is suggested as an alternative modality to warfarin for stroke prevention in patients with nonvalvular atrial fibrillation (AF). However, peridevice leakage resulting from incomplete LAA occlusion remains 1 of the most frequent limitations. We report a case of progressive increase in peridevice leakage after Watchman device implantation on long-term transesophageal echocardiographic follow-up accompanied by stroke.
    The Canadian journal of cardiology 06/2014; 30(11). DOI:10.1016/j.cjca.2014.06.013 · 3.94 Impact Factor
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    ABSTRACT: Background: Although the maze procedure reduces the risk of adverse cardiac events, the clinical importance of post-maze left atrial (LA) activity on long-term surgical outcomes is not well defined. Methods and Results: Between January 2000 and December 2009, 416 consecutive patients with sinus conversion after a modified Cox III procedure with cryoablation were enrolled and subdivided into patients with restored LA activity (group ReA; n=231) and those without LA activity (group NoA; n=185) assessed using Doppler echocardiographic examination at 3-6 months after the maze procedure. During the long-term follow-up (4.6±2.6 years), the NoA group showed more frequent major adverse events (P=0.001) including cardiac death (P=0.145), heart failure events (P=0.032), and thromboembolic stroke (P=0.048) than the ReA group. In multivariate analysis, lack of LA activity was associated with a 2.2-fold increased risk for major adverse events (95% confidence interval [CI], 1.1-6.8; P=0.029) and with a 2.4-fold increased risk for late progression of tricuspid regurgitation (95% CI, 1.0-3.5; P=0.041). Conclusions: Absence of LA activity after the maze procedure was independently associated with a significantly increased risk of major adverse events and late progression of tricuspid regurgitation.
    Circulation Journal 04/2014; 78(7). DOI:10.1253/circj.CJ-13-1390 · 3.69 Impact Factor
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    ABSTRACT: Cardiac autonomic dysfunction reportedly contributes to the AF triggering and maintenance. Heart rate turbulence (HRT) is a promising noninvasive measure of cardiac autonomic function. We investigated whether ambulatory ECG-based HRT measurement could predict in-hospital new-onset atrial fibrillation (AF) after coronary artery bypass graft (CABG) surgery. HRT onset (TO) and slope (TO) were prospectively measured from 24-h Holter recording in 113 consecutive patients prior to CABG. Abnormal HRT was defined as at least one abnormal value in TO (>0%) and TS (<2.5ms/RR). Patients with abnormal HRT (n=60) showed a significantly higher AF incidence (47% versus 21%, P=0.005) and AF burden (29±9 versus 7±5h, P=0.043) than those with normal HRT (n=53). Abnormal HRT were identified as independent predictors for the new-onset postoperative AF. During the follow-up period (12.0±10.5months), the abnormal HRT group showed a worse prognosis versus the normal HRT group regarding the AF recurrence/postoperative stroke (P=0.018). Additionally, the postoperative AF incidence, in-hospital AF burden, and the rate of AF recurrence/postoperative stroke gradually elevated as the number of abnormal HRT values increased from 0 to 2. Preoperative abnormal HRT was significantly associated with worse short-term (in-hospital new-onset AF) and long-term outcomes (post-discharge AF recurrence/postoperative stroke) after CABG surgery. Additional studies incorporating preventive interventions depending on the preoperative HRT results might be worthwhile in this patient group.
    International journal of cardiology 04/2014; 174(3). DOI:10.1016/j.ijcard.2014.04.130 · 6.18 Impact Factor
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    ABSTRACT: Purpose Our study aims to analyze prognosis after implantable cardioverter-defibrillator (ICD) implantation in Korean patients with Brugada syndrome (BrS). Materials and Methods This was a retrospective study of BrS patients implanted with an ICD at one of four centers in Korea between January 1998 and April 2012. Sixty-nine patients (68 males, 1 female) were implanted with an ICD based on aborted cardiac arrest (n=38, 55%), history of syncope (n=17, 25%), or induced ven tricular tachyarrhythmia on electrophysiologic study in asymptomatic patients (n=14, 20%). A family history of sudden cardiac death and a spontaneous type 1 electrocardiography (ECG) were noted in 13 patients (19%) and 44 patients (64%), respectively. Results During a mean follow-up of 59±46 months, 4.6±5.5 appropri ate shocks were delivered in 19 patients (28%). Fourteen patients (20%) experienced 5.2±8.0 inappropriate shocks caused by supraventricular arrhythmia, lead failure, or abnormal sensing. Six patients were admitted for cardiac causes during follow-up, but no cardiac deaths occurred. An episode of aborted cardiac arrest was a significant predictor of appropriate shock, and the composite of cardiac events in the Cox pro portional hazard model [hazard ratio (95% confidence interval) was 11.34 (1.31-97.94) and 4.78 (1.41-16.22), respectively]. However, a spontaneous type 1 ECG was not a predictor of cardiac events. Conclusion Appropriate shock (28%) and inappropriate shock (20%) were noted during a mean follow-up of 59±46 months in Korean BrS patients implanted with an ICD. An episode of aborted cardiac ar rest was the most powerful predictor of cardiac events.
    Yonsei medical journal 01/2014; 55(1):37-45. DOI:10.3349/ymj.2014.55.1.37 · 1.26 Impact Factor
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    ABSTRACT: Atrial fibrillation (AF) is the most common arrhythmia. Gain-of-function mutations in KCNQ1, the pore-forming α-subunit of the slow delayed rectifier K current (I Ks) channel, have been associated with AF. The purpose of this study was functional assessment of a mutation in KCNQ1 identified in a family with persistent AF and sinus bradycardia. We investigated whether this KCNQ1 missense mutation could form the genetic basis for AF and bradycardia simultaneously in this family. Sanger sequencing in a family with hereditary persistent AF identified a novel KCNQ1 variant (V241F) in a highly conserved region of S4 domain. The proband and her son developed bradycardia and persistent AF in an age-dependent fashion. The other son was a mutation carrier but he showed sinus bradycardia and not AF. Whole-cell patch clamp electrophysiology showed that V241F mutation in KCNQ1 shifted the activation curve to the left and dramatically slowed deactivation, leading to a constitutively open-like phenotype. Computer modeling showed that V241F would slow pacemaker activity. Also, simulations of atrial excitation predicted that V241F results in extreme shortening of action potential duration, possibly resulting in AF. Our study indicates that V241F might cause sinus bradycardia by increasing I Ks. Additionally, V241F likely shortens atrial refractoriness to promote a substrate for reentry. KCNQ1 mutations have previously been described in AF, yet this is the first time a mutation in KCNQ1 is associated with age-dependent bradycardia and persistent AF. This finding further supports the hypothesis that sinus node dysfunction contributes to the development of AF.
    Pflügers Archiv - European Journal of Physiology 08/2013; DOI:10.1007/s00424-013-1337-6 · 3.07 Impact Factor
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    ABSTRACT: Mutation or common intronic variants in cardiac ion channel genes have been suggested to be associated with sudden cardiac death caused by idiopathic ventricular tachyarrhythmia. This study aimed to find mutations in cardiac ion channel genes of Korean sudden cardiac arrest patients with structurally normal heart and to verify association between common genetic variation in cardiac ion channel and sudden cardiac arrest by idiopathic ventricular tachyarrhythmia in Koreans. Study participants were Korean survivors of sudden cardiac arrest caused by idiopathic ventricular tachycardia or fibrillation. All coding exons of the SCN5A, KCNQ1, and KCNH2 genes were analyzed by Sanger sequencing. Fifteen survivors of sudden cardiac arrest were included. Three male patients had mutations in SCN5A gene and none in KCNQ1 and KCNH2 genes. Intronic variant (rs2283222) in KCNQ1 gene showed significant association with sudden cardiac arrest (OR 4.05). Four male sudden cardiac arrest survivors had intronic variant (rs11720524) in SCN5A gene. None of female survivors of sudden cardiac arrest had SCN5A gene mutations despite similar frequencies of intronic variants between males and females in 55 normal controls. Common intronic variant in KCNQ1 gene is associated with sudden cardiac arrest caused by idiopathic ventricular tachyarrhythmia in Koreans.
    Journal of Korean medical science 07/2013; 28(7):1021-6. DOI:10.3346/jkms.2013.28.7.1021 · 1.25 Impact Factor

Publication Stats

327 Citations
148.96 Total Impact Points

Institutions

  • 2010–2015
    • Samsung Medical Center
      • Department of Cardiology
      Sŏul, Seoul, South Korea
    • Indiana University-Purdue University Indianapolis
      Indianapolis, Indiana, United States
    • Seoul Medical Center
      Sŏul, Seoul, South Korea
  • 2005–2015
    • Sungkyunkwan University
      • • School of Medicine
      • • Samsung Medical Center
      Sŏul, Seoul, South Korea