Woohyeun Kim

Effect of Cd-annealing on the IR transmittance of CdTe wafers grown by the Bridgman method

CdTe crystals were grown by the vertical Bridgman method. CdTe wafers processed from the crystals showed p-type conductivity and low IR transmittance. Isothermal annealing in Cd atmosphere for 5 h at 600° C enhanced the IR transmittance of the wafer up to 65%. The annealed wafer showed n-type conductivity with a carrier concentration of 2.1 × 1015 cm-3. The high IR transmittance obtained is attributed to annihilation of Cd vacancies during annealing in Cd atmosphere. The IR transmittance of CdTe wafers increased with increasing annealing time from 0.5 to 5 h. Annealed thickness could be calculated from the IR transmittance by assuming an abrupt junction between the annealed surface and unannealed core. The annealed thickness followed the usual time dependence of t12.

Unusual Polymorphic Ventricular Tachycardia Originating from the Pulmonary Artery

We report a case about a 27-year-old healthy young male who developed syncope during exercise, which was subsequently identified to be attributable to non-sustained polymorphic ventricular tachycardia (VT). Occurrence of polymorphic VT was neither related to a prolonged QT interval nor a fixed short coupling interval. Standard examinations including echocardiography, coronary angiography, isoproterenol infusion study, and cardiac MRI showed no structural heart disease. On the electrophysiology study, activation mapping revealed that a discrete potential preceded the premature ventricular complex (PVC) triggered polymorphic VT, which was recorded just above the pulmonary valve. After radiofrequency ablation at this area, PVC and polymorphic VT disappeared and did not recur after a 2 month follow up.

Two Cases of High Output Heart Failure Caused by Hereditary Hemorrhagic Telangiectasia

High-output cardiac failure is a rare complication of hereditary hemorrhagic telangiectasia (HHT) usually caused by shunting of blood through atriovenous malformations (AVMs) in the liver. We describe two cases of high output heart failure due to large hepatic AVMs. Clinical suspicion of HHT based on detailed history taking and physical examination is essential for early detection and proper management of heart failure associated with HHT.

Percutaneous coronary intervention versus optimal medical therapy for chronic total coronary occlusion with well-developed collaterals

Background The impact of percutaneous coronary intervention (PCI) on chronic total occlusion in patients with well‐developed collaterals is not clear. Methods and Results A total of 640 chronic total occlusion patients with collateral flow grade ≥2 were divided into 2 groups; chronic total occlusion patients either treated with PCI (the PCI group; n=305) or optimal medical therapy (the optimal medical therapy group; n=335). To adjust for potential confounders, a propensity score matching analysis was performed. Major clinical outcomes were compared between the 2 groups up to 5 years. In the entire population, the PCI group had a lower hazard of myocardial infarction (hazard ratio [HR], 0.177; P=0.039; 95% confidence interval [CI], 0.03–0.91) and the composite of total death or myocardial infarction (HR, 0.298; P=0.017; 95% CI, 0.11–0.80); however, it showed higher hazard of target lesion revascularization (HR, 3.942; P=0.003; 95% CI, 1.58–9.81) and target vessel revascularization (HR, 4.218; P=0.001; 95% CI, 1.85–9.60). After propensity score matching, a total of 158 matched pairs were generated. Although the PCI group showed a higher hazard of target lesion revascularization (HR, 2.868; P=0.027; 95% CI, 1.13–7.31) and target vessel revascularization (HR=2.62; P=0.022; 95% CI, 1.15–5.97), it still exhibited a lower incidence of the composite of total death or myocardial infarction (HR, 0.263; P=0.017; 95% CI, 0.087–0.790). The mean ejection fraction was improved from 47.8% to 51.6% (P<0.001) after PCI. Conclusions In our study, successful revascularization by PCI for chronic total occlusion lesions with well‐developed collaterals was associated with lower incidence of death and myocardial infarction, improved left ventricular function, but increased repeat revascularization rate.

Electrical conduction of polyimide films prepared from polyamic acid (PAA) and pre-imidized polyimide (PI) solution

Abstract Electrical conduction characteristics in two different polyimide films prepared by the imidization of polyamic acid (PAA) and pre-imidized polyimide (PI) solution were investigated. It is found that the current density of the polyimide film from PAA was higher than that of the polyimide film from PI at the same electric field, even though the conduction mechanism in both polyimide films follows the ionic hopping model. The hopping distance was calculated to be 2.8 nm for PAA type and 3.2 nm for PI type polyimide film. It is also found that the decay rate of the residual electrostatic charges on the polyimide films becomes faster in the PAA type than in the PI type polyimide film.

Three-year follow-up of patients with acetylcholine-induced coronary artery spasm combined with insignificant coronary stenosis

BACKGROUND Coronary artery spasm (CAS) and significant coronary stenosis are known to be major causes of myocardial ischemia. However, their association and the impact of insignificant coronary stenosis (ICS) on long-term clinical outcomes of CAS patients are largely unknown. METHODS A total of 2797 patients without significant coronary artery disease (CAD) who underwent the acetylcholine (ACH) provocation test between November 2004 and October 2010 were enrolled. Significant CAS was defined as having ≥70% of temporary narrowing by ACH test and ICS as having <70% of fixed stenosis on angiography. Patients were divided into two groups: ICS group (n=764) and non-ICS group (n=845). To adjust potential confounders, a propensity score matching (PSM) analysis was performed using the logistic regression model. Primary endpoint was the composite of total death, myocardial infraction (MI), de novo percutaneous coronary intervention (PCI), and cerebrovascular accidents (CVA). Secondary endpoint was the incidence of recurrent angina requiring repeat coronary angiography (CAG) at 3years. RESULTS After PSM analysis, two well-balanced groups (548 pairs, total=1096) were generated. The baseline clinical characteristics were similar between the two groups. During the ACH test, compared with the non-ICS group, the ICS group had smaller spastic narrowing diameter (0.69±0.35 vs. 0.73±0.37, P=0.039) and incidence of ST-segment depression (4.0% vs. 0.9%, P=0.001). The incidence of primary and secondary endpoints was similar between the two groups up to 3years. CONCLUSIONS Although, the ICS group was expected to have more adverse long-term clinical outcomes, it was not associated with the increased incidence of major adverse clinical outcomes compared with the non-ICS group up to 3years. Longer term follow-up studies are needed.

Heart Failure as a Risk Factor for Stroke

Heart failure (HF) is one of the major causes of death worldwide. Despite the high incidence of stroke in patients with HF, there has been a controversy as to whether HF itself is a risk factor for stroke. Recently, there is a great deal of evidence that HF itself increases the risk of stroke. In previous studies, the benefit of warfarin for stroke prevention in patients with HF was offset by the risk of bleeding. In the era of non-vitamin K antagonist oral anticoagulants with low bleeding profiles, we can expect a more effective stroke prevention in patients with HF by selective anticoagulation. The purpose of this review is to describe the relationship between stroke and HF, which could be an unconventional risk factor and a potential intervention target for stroke prevention.

Routine Angiographic Follow-Up versus Clinical Follow-Up after Percutaneous Coronary Intervention in Acute Myocardial Infarction

Purpose Differences in the utility of routine angiographic follow-up (RAF) and clinical follow-up (CF) after percutaneous coronary intervention (PCI) in acute myocardial infarction (AMI) are not well understood. The present study aimed to compare the 3-year clinical outcomes of RAF and CF in AMI patients who underwent PCI with drug-eluting stents (DES). Materials and Methods A total of 774 consecutive AMI patients who underwent PCI with DES were enrolled. RAF was performed at 6 to 9 months after index PCI (n=425). The remaining patients were medically managed and clinically followed (n=349); symptom-driven events were captured. To adjust for any potential confounders, a propensity score matched analysis was performed using a logistic regression model, and two propensity-matched groups (248 pairs, n=496, C-statistic=0.739) were generated. Cumulative clinical outcomes up to 3 years were compared between RAF and CF groups. Results During the 3-year follow-up period, the cumulative incidences of revascularization [target lesion revascularization: hazard ratio (HR), 2.40; 95% confidence interval (CI), 1.18–4.85; p=0.015, target vessel revascularization (TVR): HR, 3.33; 95% CI, 1.69–6.58; p=0.001, non-TVR: HR, 5.64; 95% CI, 1.90–16.6; p=0.002] and major adverse cardiac events (MACE; HR, 3.32; 95% CI, 1.92–5.73; p<0.001) were significantly higher in the RAF group than the CF group. However, the 3-year incidences of death and myocardial infarction were not different between the two groups. Conclusion RAF following index PCI with DES in AMI patients was associated with increased incidences of revascularization and MACE. Therefore, CF seems warranted for asymptomatic patients after PCI for AMI.

Hyperuricaemia and development of type 2 diabetes mellitus in Asian population

Recently, meta‐analysis studies reported that hyperuricaemia is associated with higher incidence of type 2 diabetes mellitus (T2DM), however, there are limited data on the Asian population. The aim of this observational study is to estimate the long‐term impact of hyperuricaemia on the new‐onset T2DM and cardiovascular events. This study is based on a single‐centre, all‐comers, and large retrospective cohort. Subjects that visited from January 2004 to February 2014 were enrolled using the electronic database of Korea University Guro Hospital. A total of 10 505 patients without a history of T2DM were analyzed for uric acid, fasting glucose and haemoglobin (Hb) A1c level. Inclusion criteria included both Hb A1c <5.7% and fasting glucose level <100 mg/dL without T2DM. Hyperuricaemia was defined as a uric acid level ≥7.0 mg/dL in men, and ≥6.5 mg/dL in women. To adjust baseline confounders, a propensity score matching (PSM) analysis was performed. The impact of hyperuricaemia on the new‐onset T2DM and cardiovascular events were compared with the non‐hyperuricaemia during the 5‐year clinical follow‐up. After PSM, baseline characteristics of both groups were balanced. In a 5‐year follow‐up, the hyperuricaemia itself was a strong independent predictor of the incidence of new‐onset T2DM (HR, 1.78; 95% CI, 1.12 to 2.8). Hyperuricaemia was a strong independent predictor of new‐onset T2DM, which suggests a substantial implication for a correlation between uric acid concentration and insulin resistance (or insulin sensitivity). Also, hyperuricaemia is substantially implicated in cardiovascular risks and the further long‐term cardiovascular events in the crude population, but it is not an independent predictor of long‐term cardiovascular mortality in the matched population.

Selective ß1-blockers are not associated with new-onset diabetes mellitus in hypertensive patients

Background: Although ß-blockers are known to increase new-onset diabetes mellitus (DM), previous evidence have been controversial. It has been suggested that newer vasodilatory ß-blockers yield better glycemic control than older nonselective agents. The aim of this study was to evaluate the diabetogenicity of currently used newer ß-blockers based on ß1 receptor selectivity in a series of Asian population. Methods: We investigated a total of 65,686 hypertensive patients without DM from 2004 to 2014. Patients with hemoglobin (Hb) A1c ⩽6.0%, fasting blood glucose ⩽110 mg/dL, and no history of diabetes or diabetic treatment were enrolled for analysis. Patients were divided into the ß-blockers group and non-ß-blockers group. Propensity score matching (PSM) analysis using a logistic regression model was performed to adjust for potential confounders. The primary end point was the cumulative incidence of new-onset DM, defined as a fasting blood glucose ≥126 mg/dL or HbA1c ≥6.5%, and major adverse cardiac and cerebral events (MACCE), defined as a composite of total death, nonfatal myocardial infarction, and cerebrovascular accidents. We investigated predictors of new-onset DM and MACCE based on 2 models, including clinical risk factors and co-medications, respectively. Results: Mean follow-up duration was 30.91 ± 23.14 months in the entire group before adjustment. The ß-blockers group had a significantly higher incidence of new-onset DM and MACCE than the non-ß-blockers group. After PSM, analysis of a total of 2284 patients (1142 pairs, C-statistic = 0.752) showed no difference between the 2 groups in new-onset DM or MACCE. In multivariate analysis after PSM, baseline HbA1c, stroke, heart failure, nonselective ß-blockers, and age were independent predictors of new-onset DM. Selective ß1-blockers did not increase new-onset DM after adjustment for other antihypertensive medication and statins. Conclusions: In the era of newer ß-blockers, selective ß1-blockers were not associated with new-onset DM. More evidence is needed to verify this relationship and the underlying mechanisms.