OBJECTIVES: The escalating burden of cardiovascular disease (CVD) is a critical public health issue worldwide. CVD, especially acute myocardial infarction (AMI) and stroke, is the leading contributor to morbidity and mortality in Korea. We aimed to develop algorithms for identifying AMI and stroke events from the National Health Insurance Service (NHIS) database and validate these algorithms through medical record review. METHODS: We first established a concept and definition of “hospitalization episode,” taking into account the unique features of health claims-based NHIS database. We then developed first and recurrent event identification algorithms, separately for AMI and stroke, to determine whether each hospitalization episode represents a true incident case of AMI or stroke. Finally, we assessed our algorithms’ accuracy by calculating their positive predictive values (PPVs) based on medical records of algorithm- identified events. RESULTS: We developed identification algorithms for both AMI and stroke. To validate them, we conducted retrospective review of medical records for 3,140 algorithm-identified events (1,399 AMI and 1,741 stroke events) across 24 hospitals throughout Korea. The overall PPVs for the first and recurrent AMI events were around 92% and 78%, respectively, while those for the first and recurrent stroke events were around 88% and 81%, respectively. CONCLUSIONS We successfully developed algorithms for identifying AMI and stroke events. The algorithms demonstrated high accuracy, with PPVs of approximately 90% for first events and 80% for recurrent events. These findings indicate that our algorithms hold promise as an instrumental tool for the consistent and reliable production of national CVD statistics in Korea.

Background and Objectives: We investigated whether extra-pulmonary vein (PV) ablation targeting a high maximal slope of the action potential duration restitution curve (Smax) improves the rhythm outcome of persistent atrial fibrillation (PeAF) ablation. Methods: In this open-label, multi-center, randomized, and controlled trial, 178 PeAF patients were randomized with 1:1 ratio to computational modeling-guided virtual Smax ablation (V-Smax) or empirical ablation (E-ABL) groups. Smax maps were generated by computational modeling based on atrial substrate maps acquired during clinical procedures in sinus rhythm. Smax maps were generated during the clinical PV isolation (PVI). The V-Smax group underwent an additional extra-PV ablation after PVI targeting the virtual high Smax sites. Results: After a mean follow-up period of 12.3±5.2 months, the clinical recurrence rates (25.6% vs. 23.9% in the V-Smax and the E-ABL group, p=0.880) or recurrence appearing as atrial tachycardia (11.1% vs. 5.7%, p=0.169) did not differ between the 2 groups. The postablation cardioversion rate was higher in the V-Smax group than E-ABL group (14.4% vs. 5.7%, p=0.027). Among antiarrhythmic drug-free patients (n=129), the AF freedom rate was 78.7% in the V-Smax group and 80.9% in the E-ABL group (p=0.776). The total procedure time was longer in the V-Smax group (p=0.008), but no significant difference was found in the major complication rates (p=0.497) between the groups. Conclusions Unlike a dominant frequency ablation, the computational modeling-guided V-Smax ablation did not improve the rhythm outcome of the PeAF ablation and had a longer procedure time.

Background: The purpose of this study was to review the nationwide emergency care-related health policies during the coronavirus disease 2019 (COVID-19) pandemic disaster in Korea and to analyze the effects of the policies on the safety of patients who visit emergency departments (EDs) during this period. Methods: This study is a quasi-experiment study. The study population was patients who visited all 402 EDs in Korea between December 31, 2019 and May 13, 2020, using the National Emergency Department Information System (NEDIS) database. The study period was classified into 5 phases according to the level of national crisis warning of infectious disease and the implementation of emergency care-related health policies, and all study phases were 27 days. The primary outcome was in-hospital mortality, and the secondary outcome was length of stay (LOS) in the ED during the COVID-19 outbreak. Results: The number of ED visits during the study period was 2,636,341, and the in-hospital mortality rate was 1.4%. The number of ED visits decreased from 803,160 in phase 1 to 496,619 in phase 5 during the study period. For in-hospital mortality, the adjusted odds ratio (OR) (95% confidence interval) was 0.77 (0.74–0.79) in phase 5 compared to phase 3. Additionally, by subgroup, the ORs were 0.69 (0.57–0.83) for the patients with acute myocardial infarction and 0.76 (0.67–0.87) for severe trauma in phase 5 compared to phase 3. The ED LOS increased while the number of ED visits decreased as the COVID-19 pandemic progressed, and the ED LOS declined after policy implementation (beta coefficient: −5.3 [−6.5 to −4.2] minutes in phase 5 compared to phase 3). Conclusion Implementing appropriate emergency care policies in the COVID-19 pandemic would have contributed to improving the safety of all emergency patients and reducing inhospital mortality by preventing excessive deaths.

Background and Objectives: Prior studies have shown that stroke patients treated with percutaneous left atrial appendage occlusion (LAAO) for non-valvular atrial fibrillation (NVAF) experience better outcomes than similar patients treated with warfarin. We investigated the impact of percutaneous left atrial appendage closure on post-stroke neurological outcomes in NVAF patients, compared with non-vitamin K antagonist oral anticoagulant (NOAC) therapy. Methods: Medical records for 1,427 patients in multiple registries and for 1,792 consecutive patients at 6 Korean hospitals were reviewed with respect to LAAO or NOAC treatment.Stroke severity in patients who experienced ischemic stroke or transient ischemic attack after either treatment was assessed with modified Rankin Scale (mRS) scoring at hospital discharge and at 3 and 12 months post-stroke. Results: mRS scores were significantly lower in LAAO patients at 3 (p<0.01) and 12 months (p<0.01) post-stroke, despite no significant differences in scores before the ischemic cerebrovascular event (p=0.22). The occurrences of disabling ischemic stroke in the LAAO and NOAC groups were 36.7% and 44.2% at discharge (p=0.47), 23.3% and 44.2% at 3 months post-stroke (p=0.04), and 13.3% and 43.0% at 12 months post-stroke (p=0.01), respectively.Recovery rates for disabling ischemic stroke at discharge to 12 months post-stroke were significantly higher for LAAO patients (50.0%) than for NOAC patients (5.6%) (p<0.01). Conclusions Percutaneous LAAO was associated with more favorable neurological outcomes after ischemic cerebrovascular event than NOAC treatment.

Background: The purpose of this study was to review the nationwide emergency care-related health policies during the coronavirus disease 2019 (COVID-19) pandemic disaster in Korea and to analyze the effects of the policies on the safety of patients who visit emergency departments (EDs) during this period. Methods: This study is a quasi-experiment study. The study population was patients who visited all 402 EDs in Korea between December 31, 2019 and May 13, 2020, using the National Emergency Department Information System (NEDIS) database. The study period was classified into 5 phases according to the level of national crisis warning of infectious disease and the implementation of emergency care-related health policies, and all study phases were 27 days. The primary outcome was in-hospital mortality, and the secondary outcome was length of stay (LOS) in the ED during the COVID-19 outbreak. Results: The number of ED visits during the study period was 2,636,341, and the in-hospital mortality rate was 1.4%. The number of ED visits decreased from 803,160 in phase 1 to 496,619 in phase 5 during the study period. For in-hospital mortality, the adjusted odds ratio (OR) (95% confidence interval) was 0.77 (0.74–0.79) in phase 5 compared to phase 3. Additionally, by subgroup, the ORs were 0.69 (0.57–0.83) for the patients with acute myocardial infarction and 0.76 (0.67–0.87) for severe trauma in phase 5 compared to phase 3. The ED LOS increased while the number of ED visits decreased as the COVID-19 pandemic progressed, and the ED LOS declined after policy implementation (beta coefficient: −5.3 [−6.5 to −4.2] minutes in phase 5 compared to phase 3). Conclusion Implementing appropriate emergency care policies in the COVID-19 pandemic would have contributed to improving the safety of all emergency patients and reducing inhospital mortality by preventing excessive deaths.

Background and Objectives: Prior studies have shown that stroke patients treated with percutaneous left atrial appendage occlusion (LAAO) for non-valvular atrial fibrillation (NVAF) experience better outcomes than similar patients treated with warfarin. We investigated the impact of percutaneous left atrial appendage closure on post-stroke neurological outcomes in NVAF patients, compared with non-vitamin K antagonist oral anticoagulant (NOAC) therapy. Methods: Medical records for 1,427 patients in multiple registries and for 1,792 consecutive patients at 6 Korean hospitals were reviewed with respect to LAAO or NOAC treatment.Stroke severity in patients who experienced ischemic stroke or transient ischemic attack after either treatment was assessed with modified Rankin Scale (mRS) scoring at hospital discharge and at 3 and 12 months post-stroke. Results: mRS scores were significantly lower in LAAO patients at 3 (p<0.01) and 12 months (p<0.01) post-stroke, despite no significant differences in scores before the ischemic cerebrovascular event (p=0.22). The occurrences of disabling ischemic stroke in the LAAO and NOAC groups were 36.7% and 44.2% at discharge (p=0.47), 23.3% and 44.2% at 3 months post-stroke (p=0.04), and 13.3% and 43.0% at 12 months post-stroke (p=0.01), respectively.Recovery rates for disabling ischemic stroke at discharge to 12 months post-stroke were significantly higher for LAAO patients (50.0%) than for NOAC patients (5.6%) (p<0.01). Conclusions Percutaneous LAAO was associated with more favorable neurological outcomes after ischemic cerebrovascular event than NOAC treatment.

Purpose: To compare contrast sensitivity before and after surgery in patients who underwent laser in situ keratomileusis (LASIK)and small-incision lenticule extraction (SMILE). Methods: From February 2019 to April 2019, 20 patients who underwent LASIK, and 21 who underwent SMILE, were comparedbefore, one day, one week, and one month after surgery. Results: On postoperative day (POD) 1, contrast sensitivity was better in the LASIK group than in the SMILE group under all conditionsfor 1.6, 1, and 0.64 cycles per degree (cpd). One week after surgery, the contrast sensitivity of the LASIK group was betterthan that of the SMILE group under photopic conditions with glare for 1.6, 1, and 0.64 cpd, under photopic conditions withoutglare for 1 and 0.64 cpd, and under all scotopic conditions for 2.5, 1.6, and 0.64 cpd (p< 0.05). There was no significant differencebetween the two groups, except under the scotopic conditions without glare for 0.64 cpd at one month after surgery. In theLASIK group, the contrast sensitivity was best at one week after surgery. The SMILE group showed the poorest contrast sensitivityon POD 1, but this gradually improved. Conclusions The LASIK group had better contrast sensitivity on one day and one week after surgery than the SMILE group, butthere was no significant difference at one month after surgery. In the LASIK group, the contrast sensitivity was best at one weekafter surgery. In the SMILE group, the contrast sensitivity was worst on POD 1.

Purpose: To report a case of central toxic keratopathy after femtosecond laser in-situ keratomileusis (LASIK).Case summary: A 26-year-old male developed diffuse lamellar keratitis bilaterally on day 2 after femtosecond LASIK. He was applying topical steroid frequently, while also using topical antibiotics. On day 6 after LASIK, slit-lamp biomicroscopy showed a thick central corneal opacity on the right eye so a flap irrigation was performed. He was then treated with systemic methylprednisolone. A corneal epithelial crack and stromal striae were noted by slit-lamp biomicroscopy on postoperative day 10. Four weeks after LASIK, the refractive error was +4.25 Dsph = -1.25 Dcyl Axis 80°. He was treated with topical steroid, topical antibiotics, and oral doxycycline until eight weeks after LASIK. Eight weeks after LASIK, the patient was observed without treatment. The central corneal thickness recovered from 488 μm at eight weeks to 540 μm, and the refractive error was +1.25 Dsph = -0.75 Dcyl Axis 85° at postoperative 72 weeks. The central corneal opacity also recovered. Conclusions Because femtosecond LASIK may result in a combination of diffuse lamellar keratitis and central toxic keratopathy, the clinical characteristics and natural course of both diseases should be understood and timely treatment should be available.

Purpose: This study aimed to construct a database of the effective doses (ED) from F-18 fluorodeoxyglucose (FDG) torso positron emission tomography/computed tomography (PET/CT) in Korea to provide data that supports the reduction of the CT dose of PET/CT and optimization of PET/CT protocols in Korea. Methods: We investigated data of ED and CT parameters of FDG PET/CT. The data were analyzed by body weight groups. Results: A total of 31 hospitals participated in the survey (99 adults). The mean total EDs (± SD) were 8.77 ± 2.76, 10.93 ± 3.14, and 12.57 ± 3.79 mSv for the 55-, 70-, and 85-kg groups, respectively. The FDG EDs were 4.80 ± 0.98, 6.05 ± 1.15, and 6.89 ± 1.52 mSv, and the CT EDs were 4.00 ± 2.12, 4.88 ± 2.51, and 5.68 ± 2.89 mSv, respectively. Of the enrolled hospitals, 54.5% used ultra-low-dose CT protocols, and their CT ED was significantly lower than low-dose CT group in all groups (2.9 ± 1.0, 3.2 ± 1.1, and 3.3 ± 1.0 mSv vs. 6.6 ± 1.6, 7.2 ± 2.1, and 7.9 ± 2.2 mSv, all p < 0.001, respectively). In the ultra-low-dose CT group, the CT ED with the iterative reconstruction was significantly lower than that of CT without iterative reconstruction in the 55-kg group (2.4 ± 0.9 vs. 3.3 ± 0.9, p = 0.04). Conclusions These results and current recommendations can be helpful for optimizing PET/CT diagnostic reference level (DRL) and reducing unnecessary PET/CT radiation exposure.

Objective: To compare the energy efficiency of gait with knee-ankle-foot orthosis (KAFO) and robot-assisted gait and to develop a usability questionnaire to evaluate the satisfaction of walking devices in paraplegic patients with spinal cord injuries. Methods: Thirteen patients with complete paraplegia participated and 10 completed the evaluation. They were trained to walk with KAFO (KAFO-gait) or a ReWalk robot (ReWalk-gait) for 4 weeks (20 sessions). After a 2-week wash-out period, they switched walking devices and underwent 4 additional weeks of training. Two evaluations were performed (after 2 and 4 weeks) following the training periods for each walking device, using the 6-minute walking test (6MWT) and 30-minute walking test (30MWT). The spatiotemporal variables (walking distance, velocity, and cadence) and energy expenditure (heart rate, maximal heart rate, the physiologic cost index, oxygen consumption, metabolic equivalents, and energy efficiency) were evaluated duringthe 6MWT and 30MWT. A usability evaluation questionnaire for walking devices was developed based on the International Organization for Standardization/International Electrotechnical Commission guidelines through expert consultation. Results: The ReWalk-gait presented significant advantages in energy efficiency compared to KAFO-gait in the 6MWT and 30MWT; however, there were no differences in walking distance or speed in the 30MWT between ReWalk-gait and KAFOgait. The usability test demonstrated that ReWalk-gait was not superior to KAFO-gait in terms of safety, efficacy, efficiency, or patient satisfaction. Conclusion The robot (ReWalk) enabled patients with paraplegia to walk with lower energy consumption compared to KAFO, but the ReWalk-gait was not superior to KAFO-gaitin terms of patient satisfaction.