Radiation Response of Large-Area 4H-SiC Schottky Barrier Diodes.

We report on the effects of large-area 4H-SiC Schottky barrier diodes on the radiation response to ionizing particles. Two different diode areas were compared: 1 mm × 1 mm and 5 mm × 5 mm. 6LiF and 10B4C films, which were placed on top of the diodes, were used as thermal neutron converters. We achieved a thermal neutron efficiency of 5.02% with a 6LiF thermal neutron converter, which is one of the highest efficiencies reported to date. In addition, a temperature-dependent radiation response to alpha particles was presented. Neutron irradiations were performed in a JSI TRIGA dry chamber and an Am-241 wide-area alpha source was used for testing the alpha response of the 4H-SiC Schottky barrier diodes.

4H-SiC Schottky Barrier Diodes for Efficient Thermal Neutron Detection.

In this work, we present the improved efficiency of 4H-SiC Schottky barrier diodes-based detectors equipped with the thermal neutron converters. This is achieved by optimizing the thermal neutron converter thicknesses. Simulations of the optimal thickness of thermal neutron converters have been performed using two Monte Carlo codes (Monte Carlo N-Particle Transport Code and Stopping and Range of Ions in Matter). We have used 6LiF and 10B4C for the thermal neutron converter material. We have achieved the thermal neutron efficiency of 4.67% and 2.24% with 6LiF and 10B4C thermal neutron converters, respectively.

Is the extent of left atrial fibrosis associated with body mass index in patients undergoing pulmonary vein isolation for atrial fibrillation?

BACKGROUND: Left atrial (LA) fibrosis is associated with a higher rate of recurrence of atrial fibrillation (AF) after pulmonary vein isolation (PVI). Body mass index (BMI) is strongly associated with the prevalence of AF, but there is insufficient data about the association between BMI and LA fibrosis. AIMS: The aim of the study was to examine the association between LA fibrosis and BMI in patients with AF undergoing PVI. METHODS: In 114 patients an electro-anatomical voltage map was created using the CARTO 3 three-dimensional system before PVI. The total fibrosis area (voltage criteria ≤0.5 mV), percentage, and the number of fibrotic areas were calculated. A general linear model was used to determine the differences in BMI with confounders between groups of patients with differing extents of fibrosis and numbers of focuses. RESULTS: Advanced fibrosis was found in 53 (47%) patients, in up to 9 areas with a median of 2 and an interquartile range (IQR) of 0-3. The median total fibrotic area was 27.3 cm2 with an IQR of 0.1-30.3 cm2. Patients were stratified by percentage of fibrotic area: <5%, 5%-20%, 20%-35%, and above 35%; no significant difference in mean BMI was found between the groups (P = 0.57). When stratified by the number of fibrotic areas (0, 1, 2, and ≥3 fibrotic areas), no difference in BMI was noted between the groups (P = 0.67). CONCLUSIONS: Fibrosis of the LA, as the strongest predictor of AF recurrence after PVI, does not correlate with BMI in patients with AF where PVI is indicated.

Association of fibrinogen and plasmin inhibitor, but not coagulation factor XIII gene polymorphisms with coronary artery disease.

BACKGROUND: In the final phase of clot formation, fibrinogen constitutes frame, whereas factor XIII (FXIII) active form is responsible for the covalent cross-linking of fibrin fibres and plasmin inhibitor (PI), thus contributing to clot stability. It could be expected that any change of coagulation factors' structure affects the clot formation and modulates the atherothrombotic risk. The aim was to determine the frequency of four single nucleotide polymorphisms: (i) A > G in codon 312 of the fibrinogen α-chain gene (rs6050, Thr312AlaFGA), (ii) C > T at position 10034 of the 3 - untranslated region in the fibrinogen γ-chain gene (rs2066865, 10034C > T FGG), (iii) C > T in codon 564 of the FXIII-A subunit gene (rs5982, Pro564LeuFXIII-A), and (iv) C > T in codon 6 of the plasmin inhibitor gene (rs2070863, Arg6TrpPI) in Croatian patients and their association with coronary artery disease (CAD). METHODS: We performed the unrelated case-control association study on the consecutive sample of patients 18 years old, who had undergone coronary angiography for investigation of chest pain and suspected CAD. The cases were patients with confirmed CAD (N=201), and the controls were the subjects with no CAD (N=119). Samples were genotyped using PCR-RFLP analysis. RESULTS: Observed frequencies of the rare alleles of Thr312Ala FGA, 10034C > T FGG, Leu564Pro FXIII-A and Arg6Trp PI polymorphisms were 21%, 17%, 14%, 20%, respectively. Patients with 10034C > T FGG CC genotype had 3.5 times (95% CI 1.02-12.03) higher adjusted odds for CAD than patients with 10034C > T FGG TT genotype. Patients with Arg6Trp PI CC genotype had 3.86 times (95% CI 1.23-12.12) higher odds for CAD than patients with Arg6Trp PI TT genotype. It seems that those genotype-related higher odds are also male-gender related. No difference was observed regarding any other investigated polymorphism. CONCLUSIONS: Our finding suggests that 10034C > T FGG and Arg6Trp PI are associated with CAD.

Transcatheter patent foramen ovale closure and radiofrequency ablation of right atrial tachycardia.

Patent foramen ovale (PFO) can be found in approximately 25% of adult population. Transcatheter closure of PFO is a potential option in selected patients with PFO. We report a case of a female patient that underwent mapping and catheter ablation of atrial tachycardia and PFO closure in the same procedure.

Echocardiographic assessment of revascularization completeness impact on diastolic dysfunction in ischemic heart disease.

Diastolic dysfunction indicates a functional abnormality of diastolic relaxation, filling, or distensibility of the left ventricle (LV), regardless of whether the LVEF is normal or abnormal. Diastolic dysfunction is practically always progressive and connected with higher morbidity and mortality rates, and, if not treated may lead to a diastolic heart failure. The golden standard for evaluation of diastolic function is echocardiography. One of the most important causes of diastolic dysfunction is ischemic heart disease. The revascularization of chronic myocardial ischemia can be partial (incomplete) or complete. Previous data have shown that the completeness of revascularization could have influence on clinical outcomes. The aim of this study was to asses, by means of echocardiography, the impact of completeness of revascularization on diastolic dysfunction in ischemic heart disease. This study included 65 consecutive patients with previously recognized diastolic dysfunction that met criteria for PCI revascularization. Two groups of patients were identified; one with complete revascularization achieved and another one with incomplete one. There were no statistical differences between two groups considering gender age, arterial hypertension, hyperlipoproteinaemia, previous CABG and left ventricle systolic function. In the incomplete revascularization group, the proportion of patients that had diabetes mellitus, previous myocardial infarction and previous PCI procedure were statistically higher (p < 0.05). The diastolic function recovery was statistically significant in both groups (p < 0.001), and there was no statistically significant difference in recovery between the two groups. Lack of recovery was registered in 18.2% patients with incomplete revascularization achieved, and 15.6% in the complete group, which was not significant, but shows a trend. The causes of somewhat worse recovery in the incomplete revascularization group could be attributed to the higher proportion of diabetics, to the somewhat older population and ultimately to the incomplete revascularization. The E/A ratio on diastolic transmitral flow as well as the E/E lat ratio on tissue doppler were found as the best echocardiographic parameters in diastolic function evaluation. In follow up recovery after complete or incomplete revascularization the tissue doppler (E/E lat) was recognized as the best parameter. In conclusion, we found that echocardiographic assessment of diastolic function recovery was a safe method, and our results showed that even in incomplete revascularization group of patients the recovery of diastolic function could be as good as in the complete one, if the indication for revascularization was correct.

Evaluation of importance of door-to-balloon time and total ischemic time in acute myocardial infarction with ST-elevation treated with primary percutaneous coronary intervention.

The aim of the study was to evaluate the influence of door-to-balloon time and symptom onset-to-balloon time on the prognosis of patients with acute ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI) in the Croatian Primary PCI Network. A total of 1190 acute STEMI patients treated with primary PCI were prospectively investigated in eight centers across Croatia (677 non-transferred, 513 transferred). All patients were divided according to door-to-balloon time in three subgroups (< 90, 90-180, and > 180 minutes) and according to symptom onset-to-balloon time in three subgroups (<180, 180-360, and > 360 minutes). The postprocedural Thrombolysis in Myocardial Infarction flow, in-hospital mortality, and major adverse cardiovascular events (mortality, pectoral angina, restenosis, reinfarction, coronary artery by-pass graft and cerebrovascular accident rate) in six-month follow-up were compared between the subgroups. The Croatian Primary PCI Network ensures results of treatment of acute STEMI comparable with randomized studies and registries abroad. None of the result differences among the door-to-balloon time subgroups was statistically significant. Considering the symptom onset-to-balloon time subgroups, a statistically significant difference at multivariate level was highest for in-hospital mortality in the subgroup of patients with longest onset-to-balloon time (4.5 vs. 2.6 vs. 5.7%; p = 0.04). Door-to-balloon time is one of the metrics of organization quality of primary PCI network and targets for quality improvement, but without an impact on early and six-month follow-up results of treatment for acute STEMI. Symptom onset-to-balloon time is more accurate for this purpose; unfortunately, reduction of the symptom onset-to-balloon time is more complex than reduction of the former.

Relationship of genetic markers for atherosclerosis and long-term outcome after percutaneous coronary intervention with stenting.

The aim of the study was to describe the relationship of clinical outcome after percutaneous coronary intervention (PCI) with stenting and genetic polymorphisms (GP) which are known to relate to the incidence of in-stent restenosis and late thrombotic complications. The study included 190 patients with standardized clinical follow-up over 5 years, which were initially treated with PCI. We investigated clinical data, angiographic characteristics, 10 polymorphisms involved in neointimal hyperplasia and late thrombosis at 6 different levels and their relationship with the major adverse cardiac events (MACE). The long-term clinical outcome was defined by MACE: death, target vessel revascularization (PCI or coronary bypass grafting, CABG) and myocardial infarction. Angiotensin receptor type I (AGTR A1166C) and angiotensinogen (AGT MET235THR) GPs correlated with repeat revascularization and total MACE. Carriers of G allele for NOS3 A922G GP were shown to have a significantly lower repeat revascularization rate in comparison with the AA genotype, as did the T allele carriers in the NOS3 C690T GP analysis when compared to the CC genotype. The Asp genome carriers with the NOS3 GLU298ASP GP were also shown to have significantly less re-PCI in contrast to the Glu/Glu genotype. The study could document the protective influence of the 4G/5G GP for plasminogen inhibitor activator-1, which carried the lowest rate of re-PCI and total MACE during the follow-up. GPs for beta-1 G-protein subunit GNB3 C825T, fibrinogen FGB G455A and E-selectins Ser128Arg and Leu554Phe did not show statistical correlation with the clinical outcome. The results illustrate the potential use of genetic markers in defining patients with possibly worse clinical outcome after PCI, who may profit from more aggressive prevention of restenosis and late thrombotic complications.

Angiographic control and percutaneous treatment of myocardial ischemia immediately after CABG.

Perioperative myocardial ischemia is rare but serious complication of CABG. Graft dysfunction, coronary artery thrombosis and incomplete revascularization are main causes. Pharmacological treatment, intra aortic counter pulsation and immediate additional grafting have limited results. Treatment strategy based on coronary angiography findings could lessen the burden of high mortality rate in these patients. The purpose of this study was to analyze the causes of perioperative ischemia and angiography based treatment strategy including percutaneous intervention. We enrolled all 55 consecutive patients that went early coronary angiography for perioperative myocardial ischemia in a prospective longitudinal study. Incorrect graft anastomosis, graft spasm, displacement and dissection were found in 49%, 7%, 5% and 4% of patients, respectively. Acute coronary artery thrombotic occlusion was found in 5% of patients and ischemia due to incomplete revascularization in 6% of patients. In 22% of patients no cause of myocardial ischemia could be detected. There were no complications of coronary angiography. Based on coronary angiography findings percutaneous intervention was performed in 30 patients, additional grafting in 8 patients and no action was taken in 17 patients. Percutaneous intervention with stenting was performed on coronary arteries (78%) and graft anastomosis (22%) with primary success 97%. One anastomosis rupture with treatable tamponade and one lethal stent thrombosis were complications of percutaneous treatment. Overall in hospital mortality was 30%. We concluded that graft dysfunction is usual cause of myocardial ischemia due to incorrect anastomosis and that percutaneous intervention on bypass graft or coronary artery can lessen high mortality rate in these patients.

Impact of FXIII-A Val34Leu polymorphism on coronary artery disease in Croatian patients.

Arterial thrombosis is the major reason for severe complications of coronary artery disease (CAD). Recently it has been suggested that the FXIII-A Val34Leu polymorphism, affecting clot stability, provides protection against thrombosis. Results published up to date implicate that there is a significant correlation between geographical area and the Leu34 allele prevalence and that its contribution to arterial thrombosis is different in different populations. The purpose of this study was to determine frequency of Leu34 allele in Croatian subjects as well as to estimate its association with a CAD. FXIII-A Val34Leu genotyping was carried out by real-time PCR method on the LightCycler using melting curve analysis with forward 5'-AACTTCCAGGACCGGCTTT-3' and reverse 5'-ACCCAGAGTGGTGGGGAA-3' primers. The Leu34 allele frequency in studied Croatian subjects was 24.3%. No significant differences were found in the prevalence of FXIII-A Val34Leu genotype or Leu34 allele distribution between studied subjects (P > 0.05). Carriage of the Leu34 allele was not significantly associated with CAD or MI risk reduction (P > 0.05). This is the first report that studies the prevalence of the Leu34 allele frequency in Croatian subjects and our results suggest that possession of the Leu 34 alele does not provide protection against MI.

C-reactive protein gene polymorphisms affect plasma CRP and homocysteine concentrations in subjects with and without angiographically confirmed coronary artery disease.

Human C-reactive protein (CRP) is a reactant involved in the acute phase response and one of the many molecular factors involved in pathogenesis of coronary artery disease (CAD). CRP gene variants potentially mediate CRP plasma concentrations and the development of CAD. 220 Croatian subjects with angiographically confirmed CAD and 132 control subjects were included in the study. CRP gene polymorphisms 1059G/C and -717G/A were determined by RFLPs, using MaeIII and KspI endonuclease, respectively. Plasma concentrations of CRP and homocysteine were determined by immunoturbidimetry and FPIA, respectively. CRP 1059G/C gene variants were significantly associated with CAD (OR = 0.50; 95% CI = 0.27, 0.94; P = 0.032). Wild GG genotype and rare allele C carrier genotypes were 184 and 22 in CAD(+) group, and 101 and 24 in CAD(-) group, respectively. Multivariate analysis with age, gender, BMI, smoking status, hypertension and diabetes as covariates showed that 1059C carriers had lower CRP concentrations in CAD(-) (P = 0.010) and CAD(+) subjects (P = 0.028). This allele was also significantly associated with lower plasma homocysteine concentrations in both groups (P = 0.018 for CAD(-) and 0.002 for CAD(+). There was no significant difference between CAD(+) and CAD(-) subjects in absolute frequencies for CRP -717A/G gene variant, but multivariate analysis showed that carriers of the rarer G allele had significantly higher CRP plasma concentrations in CAD(-) subjects (P = 0.031) and higher homocysteine concentrations in CAD(+) group (P < 0.001). Atherosclerosis is an inflammatory disease resulting from different genetic and environmental factors. Results presented here support the contribution of CRP genetic variations in the development of CAD.

Micro-scale socioeconomic inequalities and health indicators in a small isolated community of Vis Island, Croatia.

AIM: To investigate whether socioeconomic inequalities at a micro-scale, through their effect on major health risk factors and other health indicators, contribute to health status in an isolated island population with demonstrated reduced genetic and environmental variability. METHODS: This cross-sectional study was performed in 2003 and 2004 in the adult population of the island of Vis, Croatia. Participants were recruited from the electoral register. A total of 1024 participants were included in the study, which represented a response rate of approximately 70%. The level of education and household socioeconomic status were used as the socioeconomic status indicators. Associations of these indicators with hypertension, obesity, hyperlipidaemia, smoking, diet indicators, and supplementary vitamins and calcium intake were investigated. Data analysis was performed by multivariate methods. RESULTS: Age and gender were most commonly associated with the presence of major health risk factors. Level of education did not show significant association with any of the investigated risk factors, supplements intake, or with dietary habits. Household socioeconomic status was significantly associated only with excessive alcohol intake (logistic regression odds ratio [OR], 1.85; 95% confidence interval [CI], 1.12-3.07, P=0.016), obesity (OR, 1.78; 95% CI, 1.13-2.81 P=0.013), and high-fat diet (multiple linear modeling F=2.75, P=0.042). CONCLUSION: In isolated communities, socioeconomic stratification may be a less important health determinant than in large general populations, making these populations favorable resource for biomedical research into other health risk factors.

Abnormal systolic blood pressure during treadmill test and brachial artery flow-mediated vasodilatation impairment.

The aim of the study was to assess the relationship between systolic blood pressure during maximal treadmill test (SBP9mtt)) and flow-mediated vasodilation (FMD). Abnormal rise of SBP(mtt) is the phenomenon more frequent in hypertensive persons but it could be found in normotensive subjects too. 199 subjects referred to treadmill test were enrolled in the study. Four groups were formed: hypertensives with abnormal SBP(mtt) (group A), hypertensives with normal SBP(mtt) (group B), normotensives with abnormal SBP(mtt) (group C) and normotensives with normal SBP(mtt) (group D). Rise of SBP(mtt) above 200 mmHg was considered abnormal reaction. Simple linear regression analysis showed significant inverse relationship between SBP(mtt) and FMD (F = 20.2036, p < 0.001, R2 = 0.0956). Mean FMD index was worst in hypertensive subjects with abnormal SBP(mtt) (group A), followed by normotensives with abnormal SBP(mtt) (group C), hypertensives with normal SBP(mtt) (group B) and the best was in normotensives with normal SBP(mtt) (3.56 +/- 5.17, 4.19 +/- 5.14, 6.81 +/- 8.43 and 10.92 +/- 7.48%, respectively). In multivariate regression analysis FMD showed significant association with abnormal SBP(mtt) (p < 0.001) along with brachial artery diameter (p < 0.001), male gender (p < 0.001), but not with hypertension (p = 0.073), BMI (p = 0.137) and total cholesterol (p = 0.23) (coefficients: -0.26, -0.40, -0.27, -0.13, -0.11 and -0.07, respectively). There was a significant inverse relationship between SBP(mtt) and FMD. An impairment of FMD exists in normotensive subjects with abnormal SBP(mtt). In hypertensives with abnormal SBP(mtt) an additional impairment of FMD exists when compared to hypertensives with normal SBP(mtt). Abnormal SBP(mtt) should be taken into account in global cardiovascular risk assessment.

[Myocardial revascularization strategy in patients with acute coronary syndrome]. / Strategija revaskularizacije miokarda u bolesnika s akutnim koronarnim sindromom.

Acute coronary syndrome (ACS) represents a spectrum of conditions caused by activated malignant coronary disease, with one of the following outcomes: stabilization, myocardial infarction or sudden death. The strategies of diagnostic procedures and treatment for ACS have been developed on the basis of differentiation between the two main groups of patients: those with unstable angina pectoris (UAP) and non-ST-segment elevation myocardial infarction (NSTEMI), and those with ST-elevation myocardial infarction (STEMI). The diagnosis and treatment of STEMI patients have both temporal and spatial limitations, where rapid identification and use of revascularization strategy, generally from 6 to not more than 12 hours, are the mainstay of the respective algorithm. In contrast to this, in UAP/NSTEMI patients the nature of the disease usually allows for more time for the diagnosis and choice of most appropriate therapy, whereas the chance of saving practically the entire myocardial area is much greater. Proposals of the possible algorithms for the procedures to be used in the diagnosis and management of ACS, based on the real possibilities available in the Republic of Croatia, and some our own results are presented in this review.

Long-term results and learning curve for radio frequency ablation of accessory pathways.

Radio frequency (RF) catheter ablation of accessory pathways represents an interventional method in modern cardiology that has become the first-line treatment for patients with symptomatic WPW-syndrome. The aim of this study was to analyze: (1) the learning curve for the ablation procedure; (2) procedural parameters and success; and (3) personal assessment of the treatment by the patients. Learning curve analysis included 195 consecutive patients, who underwent ablation between 1991 and 1996. The follow-up survey included 65 consecutive patients. The analysis of the procedural parameters showed significant improvement after 100 cases, implying a completion of the learning curve at this point. Long-term follow-up showed a high success rate for all pathways (95.4%). All procedure parameters indicated significantly higher degree of difficulty for right free-wall and septal pathways, with lowest long-term success rate for right-sided pathways (78.6%). Personal assessment survey showed high acceptance of the treatment; the procedure was described as a significant improvement of overall quality-of-life by 92.3% of patients. The results of this study confirm the catheter ablation of accessory pathways--in particular after completion of the learning curve--as a low-risk and highly efficient treatment for symptomatic WPW-syndrome, with a high degree of patient-related acceptance.