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Chronic total occlusion (CTO) is a high-risk factor for stent thrombosis, but little is known about the difference in neointimal healing between CTO and non-CTO lesions regarding implanted stents. We investigated factors affecting neointimal healing after stent implantation for CTO and non-CTO lesions using angioscopy.We retrospectively evaluated 106 stents in 85 consecutive patients between March 2016 and July 2020. Their average age was 68 ± 11 years, and participants (73 male and 12 female) underwent follow-up angiography and angioscopy 1 year after percutaneous coronary intervention (PCI). The stents (n = 106) were divided into three groups according to the lesion status at the previous PCI: CTO (n = 17), acute coronary syndrome (ACS) (n = 35), and stable coronary artery disease without CTO or non-CTO (n = 54).The neointimal stent coverage grade was significantly lower in the CTO and ACS groups than in the non-CTO group (0.4 ± 0.5, 0.9 ± 0.8, and 1.4 ± 0.8, respectively, p 0.001). Thrombi were significantly more frequent in CTO and ACS than in non-CTO (71 %, 51 %, and 15 %, respectively, p 0.001). The yellow grade in CTO was comparable to that in ACS but significantly higher in CTO than in non-CTO (CTO vs. ACS vs. non-CTO 1.5 ± 0.7, 1.4 ± 0.6, and 0.9 ± 0.7, respectively, p = 0.007).Delayed healing occurs in stents implanted for CTO lesions. Longer dual-antithrombotic therapy may be beneficial.

We herein report a case of mitochondrial disease with heart and intestinal tract involvement resulting in hemodynamic collapse. A 66-year-old woman was transferred to our hospital because of cardiogenic shock. Vasopressors were administered, and a circulatory support device was deployed. However, her hemodynamics did not improve sufficiently, and we detected abdominal compartment syndrome caused by the aggravation of chronic intestinal pseudo-obstruction as a complication. Insertion of a colorectal tube immediately decreased the intra-abdominal pressure, improving the hemodynamics. Finally, we diagnosed her with mitochondrial disease, concluding that the resulting combination of acute heart failure and abdominal compartment syndrome had aggravated the hemodynamics.

Blood flow imaging becomes an emerging trend in cardiology with the recent progress in computer technology. It not only visualizes colorful flow velocity streamlines but also quantifies the mechanical stress on cardiovascular structures; thus, it can provide the detailed inspections of the pathophysiology of diseases and predict the prognosis of cardiovascular functions. Clinical applications include the comprehensive assessment of hemodynamics and cardiac functions in echocardiography vector flow mapping (VFM), 4D flow MRI, and surgical planning as a simulation medicine in computational fluid dynamics (CFD).For evaluation of the hemodynamics, novel mathematically derived parameters obtained using measured velocity distributions are essential. Among them, the traditional and typical parameters are wall shear stress (WSS) and its related parameters. These parameters indicate the mechanical damages to endothelial cells, resulting in degenerative intimal change in vascular diseases. Apart from WSS, there are abundant parameters that describe the strength of the vortical and/or helical flow patterns. For instance, vorticity, enstrophy, and circulation indicate the rotating flow strength or power of 2D vortical flows. In addition, helicity, which is defined as the cross-linking number of the vortex filaments, indicates the 3D helical flow strength and adequately describes the turbulent flow in the aortic root in cases with complicated anatomies. For the description of turbulence caused by the diseased flow, there exist two types of parameters based on completely different concepts, namely: energy loss (EL) and turbulent kinetic energy (TKE). EL is the dissipated energy with blood viscosity and evaluates the cardiac workload related to the prognosis of heart failure. TKE describes the fluctuation in kinetic energy during turbulence, which describes the severity of the diseases that cause jet flow. These parameters are based on intuitive and clear physiological concepts, and are suitable for in vivo flow measurements using inner velocity profiles.

Objective The coronavirus disease 2019 (COVID-19) pandemic has had a significant impact on global healthcare systems. Some studies have reported the negative impact of COVID-19 on ST-elevation myocardial infarction (STEMI) patients; however, the impact in Japan remains unclear. This study investigated the impact of the COVID-19 pandemic on STEMI patients admitted to an academic tertiary-care center in Tokyo, Japan. Methods In this retrospective, observational, cohort study, we included 398 consecutive patients who were admitted to our institute from January 1, 2018, to March 10, 2021, and compared the incidence of hospitalization, clinical characteristics, time course, management, and outcomes before and after March 11, 2020, the date when the World Health Organization declared COVID-19 a pandemic. Results There was a 10.7% reduction in hospitalization of STEMI patients during the COVID-19 pandemic compared with that in the previous year (117 vs. 131 cases). During the COVID-19 pandemic, the incidence of late presentation was significantly higher (26.5% vs. 12.1%, p

Few studies have investigated the clinical benefit of the long-term use of tolvaptan (TLV) for heart failure (HF). This study evaluated the long-term prognosis of patients administered TLV for > 1 year among patients who had HF with preserved ejection fraction (HFpEF) and those who had HF with reduced ejection fraction (HFrEF). Overall, 591 consecutive patients were admitted to our hospital and administered TLV for HF between 2011 and 2018. We retrospectively enrolled 147 patients who were administered TLV for > 1 year. We divided them into the HFpEF group (n = 77, 52.4%) and the HFrEF group (n = 70; 47.6%). Their clinical backgrounds and long-term prognosis were examined. Compared with the patients in the HFrEF group, the patients in the HFpEF group were significantly older and included more women. Moreover, the HFpEF group showed significantly lower all-cause mortality (38.6% vs. 24.7%; log-rank, P = 0.014) and cardiovascular mortality during the average 2.7-year follow-up. Univariate analysis revealed that all-cause mortality was correlated with male sex, HFpEF, and changes in serum creatinine levels from baseline. Multivariate analysis revealed that HFpEF was an independent influencing factor for all-cause mortality (hazard ratio, 0.44; 95% confidence interval, 0.23–0.86; P = 0.017). Long-term administration of TLV may be more beneficial for HFpEF than for HFrEF.

The turbulent kinetic energy (TKE) estimation based on 4D flow MRI has been currently developed and can be used to estimate the pressure gradient. The objective of this study was to validate the clinical value of 4D flow-based TKE measurement in patients with hypertrophic cardiomyopathy (HCM).From April 2018 to March 2019, we recruited 28 patients with HCM. Based on echocardiography, they were divided into obstructed HCM (HOCM) and non-obstructed HCM (HNCM). Triple-velocity encoding 4D flow MRI was performed. The volume-of-interest from the left ventricle to the aortic arch was drawn semi-automatically. We defined peak turbulent kinetic energy (TKETKETKE measurement based on 4D flow MRI can detect the flow alteration induced by systolic flow jet and LV outflow tract geometry, such as SAM in patients with HOCM. The elevated TKE is correlated with increasing LV mass. This indicates that increasing cardiac load, by pressure loss due to turbulence, induces progression of LV hypertrophy, which leads to a worse prognosis.

Gastrointestinal (GI) bleeding worsens the outcomes of critically ill patients in the intensive care unit (ICU). Owing to a lack of corresponding data, we aimed to investigate whether GI bleeding during cardiovascular-ICU (C-ICU) admission in acute cardiovascular (CV) disease patients is a risk factor for subsequent CV events. Totally, 492 consecutive C-ICU patients (40.9% acute coronary syndrome, 22.8% heart failure) were grouped into GI bleeding (n = 27; 12 upper GI and 15 lower GI) and non-GI bleeding (n = 465) groups. Thirty-nine patients died or developed CV events during hospitalization, and 453 were followed up from the date of C-ICU discharge to evaluate subsequent major adverse CV events. The GI bleeding group had a higher Acute Physiology and Chronic Health Evaluation II score (20.2 ± 8.2 vs. 15.1 ± 6.8, p

Background: High coronary thrombus burden has been associated with unfavorable outcomes in patients with ST-segment elevation myocardial infarction (STEMI), the optimal management of which has not yet been established. Methods: We assessed the adjunctive catheter-directed thrombolysis (CDT) during primary percutaneous coronary intervention (PCI) in patients with STEMI and high thrombus burden. CDT was defined as intracoronary infusion of tissue plasminogen activator (t-PA; monteplase). Results: Among the 1849 consecutive patients with STEMI, 263 had high thrombus burden. Moreover, 41 patients received t-PA (CDT group), whereas 222 did not receive it (non-CDT group). No significant differences in bleeding complications and in-hospital and long-term mortalities were observed (9.8% vs. 7.2%, p = 0.53; 7.3% vs. 2.3%, p = 0.11; and 12.6% vs. 17.5%, p = 0.84, CDT vs. non-CDT). In patients who underwent antecedent aspiration thrombectomy during PCI (75.6% CDT group and 87.4% non-CDT group), thrombolysis in myocardial infarction grade 2 or 3 flow rate after thrombectomy was significantly lower in the CDT group than in the non-CDT group (32.2% vs. 61.0%, p < 0.01). However, the final rates improved without significant difference (90.3% vs. 97.4%, p = 0.14). Conclusions: Adjunctive CDT appears to be tolerated and feasible for high thrombus burden. Particularly, it may be an option in cases with failed aspiration thrombectomy.

Background: High coronary thrombus burden has been associated with unfavorable outcomes in patients with ST-segment elevation myocardial infarction (STEMI), the optimal management of which has not yet to be established. Methods: We evaluated the safety and efficacy of adjunctive catheter-directed thrombolysis (CDT) during primary percutaneous coronary intervention (PCI) in patients with STEMI and high thrombus burden. Results: Among the 1,849 consecutive patients with STEMI, 263 had high thrombus burden. Moreover, 41 patients received intracoronary infusion of tissue plasminogen activator during primary PCI (CDT group), whereas 222 did not receive (non-CDT group). No significant differences in bleeding complications and in-hospital and long-term mortalities were observed (9.8% vs. 7.2%, p=0.53; 7.3% vs. 2.3%, p=0.11; and 12.6% vs. 17.5%, p=0.84, CDT vs. non-CDT). In patients who underwent antecedent aspiration thrombectomy during PCI (75.6%; CDT group and 87.4%; non-CDT group), thrombolysis in myocardial infarction grade 2 or 3 flow rate after thrombectomy was significantly lower in the CDT group than in the non-CDT group (32.2% vs. 61.0%, p

Background Non-cardiac surgery for hypertrophic obstructive cardiomyopathy (HOCM) is considered to require meticulous perioperative care. β-blockers are considered the first-line drugs for patients with HOCM, and they play a key role in preventing cardiovascular complications in perioperative care. The bisoprolol transdermal patch has recently become available in Japan, and it is useful for patients who are unable to take oral medication during perioperative care. The aim of this case series was to assess the hemodynamic features of patients with HOCM who used the bisoprolol transdermal patch during perioperative care for non-cardiac surgery. Methods Between August 2016 and August 2018, we retrospectively analyzed 10 consecutive cases of HOCM with the patients using the bisoprolol transdermal patch during perioperative care. Hemodynamic and echocardiographic features were evaluated before and after patients were switched from oral bisoprolol to transdermal patch therapy or started transdermal patch therapy as a new β-blocker medication. In addition, cardiovascular complications (all-cause death, cardiac death, heart failure, ventricular tachycardia, and ventricular fibrillation) during the perioperative period were evaluated. Results There was no significant change in the patients’ heart rate, blood pressure, ejection fraction, and pressure gradient in the left ventricle after switching from oral bisoprolol to the transdermal patch therapy. On the other hand, patients who started using the bisoprolol transdermal patch as a new ß-blocker medication tended to have a decreased heart rate and pressure gradient thereafter, but there was no significant difference in blood pressure or ejection fraction. No cardiovascular complications occurred during the perioperative period. Conclusions We described the utilization of the bisoprolol transdermal patch during perioperative care for non-cardiac surgery in patients with HOCM. We determined that the hemodynamic features of these patients did not change significantly after switching to patch therapy. Further, initiation of the bisoprolol transdermal patch as a new ß-blocker medication sufficiently tended to decrease the pressure gradient. This unique approach can be an alternate treatment option for HOCM. Trial registration The registry was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN000036703). The date of registration was 10/5/2019 and it was “Retrospectively registered”.

Percutaneous transluminal septal myocardial ablation (PTSMA) has become a significant treatment for symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM) despite maximal medical therapy. The target septal arteries usually arise from the left anterior descending artery (LAD). However, when septal perforators do not originate from the LAD, non-LAD septal perforators should be included as candidate-target septal branches that feed the hypertrophic septal myocardium, causing left ventricular outflow tract (LVOT) obstruction. Data pertaining to the procedure remain limited. We aimed to investigate PTSMA through the non-LAD septal perforators in patients with HOCM. In this case series review, we evaluated the baseline characteristics, echocardiographic features, and angiographic features, as well as symptoms and pressure gradient before and after PTSMA through the non-LAD septal perforators. Among 202 consecutive patients who underwent PTSMA for HOCM with LVOT obstruction, 21 had non-LAD septal branches that fed the hypertrophic septal myocardium and received alcohol ablation. Non-LAD septal perforators could be used as an alternative route for PTSMA in patients who experienced ineffective ablation of the septal branch that arises from the LAD. This unique procedure may improve response rates and overall outcomes of patients with HOCM.

Human atrial natriuretic peptide, known as carperitide, is approved for early relief of dyspnea in patients with acute heart failure (AHF). However, the diuretic effect of carperitide is sometimes insufficient for controlling volume overload. We investigated predictors for the carperitide response in patients with AHF. Forty-seven patients (age: 74 ± 10 years; left ventricular ejection fraction: 42.0% ± 15.9%) with AHF were enrolled and treated with carperitide monotherapy at a dose of 0.0125 μg/kg/min. Patients without sufficient diuresis (

BACKGROUND Alcohol septal ablation (ASA) is a treatment option in patients with drug-refractory symptomatic hypertrophic obstructive cardiomyopathy (HOCM). In many patients, right bundle branch block (RBBB) develops during ASA because septal branches supply the right bundle branch. However, the clinical significance of procedural RBBB is uncertain.Methods and Results:We retrospectively reviewed 184 consecutive patients with HOCM who underwent ASA. We excluded 40 patients with pre-existing RBBB (n=10), prior pacemaker implantation (n=15), mid-ventricular obstruction type (n=10), and those lost to follow-up (n=5), leaving 144 patients for analysis. Patients were divided into 2 groups according to the development (n=95) or not (n=49) of procedural RBBB. ASA conferred significant decreases in the left ventricular pressure gradient (LVPG) in both the RBBB and no-RBBB group (from 74±48 to 27±27 mmHg [P

BACKGROUND Because development of acute coronary syndrome (ACS) worsens the prognosis of patients with coronary artery disease, preventing recurrent ACS is crucial. However, the degree to which secondary prevention treatment goals are achieved in patients with recurrent ACS is unknown. METHODS 214 consecutive ACS patients were classified as having First ACS (n=182) or Recurrent ACS (n=32), and the clinical characteristics of these groups were compared. Fifteen patients died or developed cardiovascular (CV) events during hospitalization, and the remaining 199 patients were followed from the date of hospital discharge to evaluate subsequent CV events. RESULTS Patients in the Recurrent ACS group were older than those in the First ACS group (76.8±10.8 years vs 68.8±13.4 years, p=0.002) and had a higher rate of diabetes mellitus (DM) (65.6% vs 36.8%, p=0.003). The rate of achieving a low-density lipoprotein cholesterol (LDL-C) level of

After alcohol septal ablation (ASA), regression of left ventricular hypertrophy (LVH) has been observed in several studies using echocardiography or cardiac magnetic resonance, and favorable changes of myocardial excitation have been expected. However, no studies have focused on the alteration of electrocardiography (ECG) findings after ASA. Therefore, we evaluated serial changes in ECG parameters during the chronic phase after ASA for drug-refractory hypertrophic obstructive cardiomyopathy (HOCM). From 1998 to 2014, we performed 187 ASA procedures in 157 drug-refractory HOCM patients. After excluding patients who underwent dual-chamber pacing therapy and who underwent staged or repeat ASA within 2 years after the index ASA, 25 patients without bundle branch block and additional pacemaker implantation were enrolled in the main study group. ECGs, echocardiograms, and clinical follow-up data were evaluated at baseline and, 1, 6, 12, and 24 months after ASA. Patients with bundle branch block or additional pacemaker implantation were assigned in a referential group (n = 79), in which the echocardiographic changes between baseline and at 1 year were evaluated. Sokolow–Lyon index (SLi), Cornell index, and total 12-lead QRS amplitude significantly decreased during 2-year follow-up after ASA. SLi and Cornell index significantly decreased from 6 to 12 months (p

Introduction Percutaneous coronary intervention (PCI) for complex lesions, including unprotected left main (ULM) and bifurcations, is gaining a relevant role in treating coronary artery disease with good outcomes, also thanks to new generation stents. The daily risk of adverse cardiovascular events and their temporal distribution after these procedures is not known. Methods All consecutive patients presenting with a critical lesion of ULM or bifurcation treated with very thin struts stents, enrolled in the RAIN-Cardiogroup VII study, were analyzed. The daily risk of major acute cardiovascular events (MACE), target lesion revascularization (TLR) and stent thrombosis (ST) and their temporal distribution in the first year of follow-up was the primary endpoint. Differences among subgroups (ULM, patient presentation, kind of stent polymer) were the secondary endpoint. Results 2745 patients were included, mean age 68 ± 11 years, 33.3% diabetics, 54.5% had an acute coronary syndrome (ACS); 88.5% of treated lesions were bifurcations, 27.2% ULM. Average daily risk was 0.022% for MACE, 0.005% for TLR and 0.004% for ST, in the first year. Bimodal distribution of adverse events, especially TLR, with an early peak in the first 50 days and a late one after 150 days, was observed. Patients with ULM presented a significantly higher daily risk of events, and ACS patients presented higher MACE risk. No difference emerged according to the type of stent polymer. Conclusions The daily risk of adverse events in the first year after complex PCI in our study is acceptably low. PCI on ULM carries a higher risk of complications.

Careful evaluation, including provocation tests, is needed to specify an indication for septal reduction therapy in patients with drug-refractory hypertrophic obstructive cardiomyopathy. This study aimed to evaluate the outcome of alcohol septal ablation (ASA) using an intravenous nitroglycerin test (IV-NTG). Of consecutive 156 patients, after excluding cases of severe valvular disease and repeat septal reduction therapy, we investigated the clinical characteristics of patients with labile obstruction (n = 32) and the outcomes after ASA using the IV-NTG test; comparisons were made with those exhibiting basal obstruction (a resting gradient of ≥30 mm Hg). The patients with labile obstruction had less left ventricular mass (141 ± 47 vs 182 ± 59 g, p = 0.003) and less brain natriuretic peptide values (414 ± 576 vs 744 ± 625 pg/ml, p

Background Boerhaave syndrome is a rare and often fatal syndrome. Delayed diagnosis and treatment is closely associated with prolonged morbidity and increased mortality. In general, esophagography is usually chosen as the diagnostic procedure, but it has a relatively high false-negative rate. There are no reports, to our knowledge, regarding the efficacy of thoracic drainage, although it is easier to perform and more immediate than esophagography in the emergency department. Objectives To report the efficacy of thoracic drainage for rapid diagnosis and treatment of Boerhaave syndrome. Case Report An 80-year-old woman was admitted with vomiting and sudden onset of postprandial chest pain radiating to the back. Initially, myocardial infarction or aortic dissection was suspected, but was excluded by point-of-care tests and computed tomography (CT) scan, which revealed a left-sided pneumothorax, heterogeneous left pleural effusion, and pneumomediastinum at the lower level of the esophagus. Boerhaave syndrome was suspected and confirmed by thoracic drainage, which drained off bloody fluid and residual food such as broccoli. Emergency thoracotomy was performed within 4 h after onset of symptoms. The patient made an uneventful recovery. Conclusion Findings in this case indicate that chest pain, left-sided massive effusion on chest radiography, and left-sided massive heterogeneous effusion on CT scan are important for the diagnosis of Boerhaave syndrome. Subsequent thoracic drainage is useful for confirming Boerhaave syndrome, and such a strategy might lead to a good prognosis for patients with this rare but critical disease.

A 70-year-old woman suffered from bilateral lacrimal gland enlargement from 2 years ago (figure 1). Geranium-enhanced MRI disclosed diffuse enlargement of bilateral eyelids indicating IgG4-related disease (IgG4RD), especially Mikulicz’s disease. Laboratory tests showed elevation of serum IgG4 concentration and histopathological findings of the lacrimal glands showed IgG4-positive cell infiltration and obliterated veins by inflammatory cells, which consist of lymphocytes and plasma cells (obliterative phlebitis). Figure 1 Bilateral lacrimal gland enlargement with predominance of right ones observed as a representative pathophysiological finding in this patient with IgG4-related disease. Then, she was diagnosed with IgG4RD. We performed chest CT as screening for comorbidities of Mikulicz’s disease. Chest CT revealed left circumflex artery (LCX) wall thickening. Coronary CT showed thickening of the left anterior descending artery and LCX. For suppressing physiological myocardial uptake, the patient was asked to restrict carbohydrate intake 24 hours before 18F-fluorodeoxyglucose (FDG) PET/CT and to consume a low carbohydrate high fat protein permitted (LCHFPP) diet for lunch of the day before the examination, a low-carbohydrate diet …

Introduction: A residual gradient and repeat septal reduction therapy are more likely to occur with alcohol seplta ablation (ASA) than with surgical myectomy. We evaluated a cohort of patients treated with ASA to identify predictive factors of repeat ASA. Methods: Of 157 patients who underwent ASA, 19 (Group R) who underwent repeat ASA procedures remained after excluding those with planned staged ablation and isolated mid-ventricular obstruction. The median time interval between both procedures was 2.1 years. We compared Group R with patients not requiring repeat procedures (n = 105, Group S) in terms of clinical characteristics, ASA procedures, and morphological cardiac magnetic resonance (CMR), which was used to diagnose regional hypertrophy (thickness ≥ 15 mm) for each left ventricular myocardial segment. Results: Compared with group S, group R had a higher peak creatine phosphokinase value at the first ASA (1250 ± 522 vs. 1028 ± 520 IU/L, p = 0.046) and number of hypertrophic segments in the basal left ventricular level (segments 0-6, 2.8 ± 1.7 vs. 1.7 ± 0.8, p = 0.009). In multivariate analysis, diuretics use [adjusted odds ratio, 9.3 (95%CI: 1.6-56.2)] and the number of extended hypertrophy segments (except the anteroseptal region at the basal left ventricular level) were independent predictors of a repeat ASA procedure (adjusted odds ratio, 6.8 (95%CI: 1.5-32.1)/segment, p = 0.010). The repeat ASA rate was only 5% (1/21) among patients without non-anteroseptal hypertrophy, and 3% (1/29) among those without posteroseptal hypertrophy; however, patients with ≥2 segments of non-anteroseptal hypertrophy had an extremely high rate (50%, 7/14). Conclusions: CMR morphological analysis elucidated the characteristics of regional hypertrophic patterns in patients who underwent repeat ASA and found non-anteroseptal extended hypertrophy (≥ 2 segments) to be a crucial predictor of repeat ASA.

Giant left atrium due to mitral stenosis with massive atelectasis: A successful case with perioperative approach☆ Atsushi Tanita , Yusuke Hosokawa ⁎, Takeshi Tomiyama , Maiko Kato , Junya Matsuda , Keisuke Sawai , Yoshie Arita , Toshiyuki Aokage , Hiroomi Suzuki , Hiroshige Murata , Hideki Miyachi , Toshiyuki Shibui , Takahito Nei , Koichi Akutsu , Takeshi Yamamoto , Shinhiro Takeda , Takashi Nitta , Kunio Tanaka , Kyoichi Mizuno , Keiji Tanaka a

Patient initials or identifier number I.T ### Relevant clinical history and physical exam A 100-year-old female, who had the history of atrial fibrillation, visited our hospital because of right lower-leg pain and pallor for several weeks. Enhanced computed tomography showed total occlusion

This paper discusses the repetitive control problem for a single-input, single-output linear digital system. The servo problem with periodic references signal and periodic disturbances is transformed into a regulator problem by using the deviation system of the augmented system. Then, the fixed-endpoint approach is applied, and the optimal control is obtained. Furthermore, the sub-optimal control which is more simple and practical than the optimal control is proposed. In both controls, the output follows the periodic reference signal without error within finite steps.

The gate leakage reduction mechanism of AlGaN/GaN metal-insulator-semiconductor (MIS) heterostructure field-effect transistors (HFETs) is investigated and compared with those of three types of HFET, namely; a conventional HFET, a standard MIS-HFET and a specially prepared MIS-HFET with a metal interlayer. It is found that the resistance of the AlGaN layer with an insulator deposited on its surface is much higher than that of the AlGaN layer with a metal. From the fitting of transconductance-frequency characteristics, the resistance of the insulator-deposited AlGaN layer is about 5 orders of magnitude higher than that of the metal-deposited AlGaN layer. From dc measurements, the resistance of the insulator-deposited AlGaN layer at a negative gate bias is higher than that of the insulator layer. From these results, it can be concluded that gate leakage is suppressed by the high resistance of the AlGaN layer in the MIS-HFET at a negative gate bias.