Effect of Non-Uniform Tissue Configuration on Conductance Catheter Measurement for Arterial Lumen Sizing

2011 ◽  
Author(s):  
Hyo Won Choi ◽  
Ghassan S. Kassab
Keyword(s):  
Electric Field ◽  
Surrounding Tissue ◽  
Medium Size ◽  
Conductance Catheter ◽  
Cross Sectional ◽  
Tissue Properties ◽  
Arterial Lumen ◽  
Novel Approach ◽  
Parallel Conductance ◽  
The Impact

A novel approach of two bolus injections of saline solutions has been proposed for conductance catheter measurement of cross-sectional area (CSA) and parallel conductance for medium size arteries [1–2]. The parallel conductance or current leakage through surrounding tissue is dependent on how differently the combined configuration of lumen, surrounding tissue, and conductance catheter forms an electric field. Arteries have a variety of surrounding tissue geometries and electrical conductivities depending on their anatomic situations. Specifically, coronary/peripheral arteries are often characterized by their superficial anatomic positions so that surrounding tissue has asymmetric configurations. Such notions highlight the need for addressing the impact of anatomically relevant tissue properties on the performance of conductance catheter measurement. In the present study, we computationally probe how asymmetric surrounding tissue thickness and/or inhomogeneous/anisotropic electric conductivity of tissue can modulate the electric field and hence accuracy of CSA measurement for a medium size artery.

Novel method for measurement of medium size arterial lumen area with an impedance catheter: in vivo validation

2005 ◽  
Vol 288 (4) ◽  
pp. H2014-H2020 ◽  
Author(s):  
Ghassan S. Kassab ◽  
Eugen R. Lontis ◽  
Arne Hørlyck ◽  
Hans Gregersen
Keyword(s):  
Surrounding Tissue ◽  
Medium Size ◽  
Conductance Catheter ◽  
Algebraic Equations ◽  
Cross Sectional ◽  
Arterial Lumen ◽  
The Mean ◽  
The Difference ◽  
Parallel Conductance

There is no doubt that the transformation of a cardiac catheter into a conductance catheter that allows reliable and accurate assessment of lumen cross-sectional area (CSA) will provide a powerful diagnostic and treatment tool for the invasive cardiologist. The objective of this study was to develop a method based on the impedance catheter that allows accurate and reproducible measurements of CSA for medium size vessels (e.g., coronary, femoral, and carotid arteries). Two solutions of NaCl (0.5% and 1.5%) with known conductivities were injected directly into the lumen of the artery in eight swine. We showed that the CSA can be determined analytically from two Ohm's law-type algebraic equations that account for the parallel conductance of the current into the surrounding tissue. Excellent agreement was found between the conductance catheter with the proposed two-injection method and B-mode ultrasound (US). The root mean square error for the impedance measurements was 4.8% of the mean US diameter. The repeatability of the technique was assessed with duplicate measurements. The mean of the difference between the two measurements was nearly zero, and the repeatability coefficient was within 2.4% of the mean of the two measurements. The validated method was used to assess the degree of acute vasodilatation of the vessel in response to flow overload.

scholarly journals Influence of Alternative Financing on the Relationship between Managerial Competency and Efficiency of Small and Medium Enterprises in Kenya

2018 ◽  
Vol 7 (1) ◽  
pp. 13-26
Author(s):  
Jackson Njau Waweru ◽  
Kennedy M Waweru ◽  
Kenneth L Wanjau ◽  
Josphat K Kinyanjui
Keyword(s):  
Economic Growth ◽  
Multiple Regression ◽  
Structural Equation ◽  
Secondary Data ◽  
Equation Modeling ◽  
Medium Size ◽  
Cross Sectional ◽  
Managerial Competency ◽  
Alternative Finance ◽  
The Impact

Worldwide, Small and medium-size enterprises (SMEs) exhibit inimitable financial needs. While SMEs remain fundamental to economic growth, their mortality rate in Kenya approaches 90% by the second year, mainly owing to lack of credit. However, scholarly endeavors exploring the impact of alternative finance (AF) on managerial competency - efficiency nexus for manufacturing SMEs have received little attention in Kenya. To resolve this conundrum, a thorough study to investigate how AF impacts managerial competency - efficiency nexus is necessary. The study used a cross-sectional research design, employing both qualitative and quantitative research approaches. The target population was 171 SMEs registered with Kenya Association of Manufacturers. The accessible population was 136 SMEs owners/managers. A semi-structured questionnaire was used to collect primary and secondary data. Data envelopment analysis was used to measure efficiency, multiple regression modeling used to analyze the direct relationships while hierarchical moderated multiple regression analysis employed to test moderation. Partial Least Squares Structural Equation Modeling was used to test robustness of our results. The findings of this study demonstrate that managerial competency positively influences efficiency (? = 0.150, t-value =10.246, P<0.05), and that alternative finance does moderate managerial competency relationships with efficiency (R-Square change of 21.7%). We suggest trainings for manufacturing SME owners/managers in Kenya on the pivotal role of alternative finance to facilitate SMEs achieve higher efficiencies and accelerate economic growth.

scholarly journals Competitive Drivers of Atrial Fibrillation: The Interplay Between Focal Drivers and Multiwavelet Reentry

2021 ◽  
Vol 12 ◽  
Author(s):  
Richard T. Carrick ◽  
Bryce E. Benson ◽  
Oliver R. J. Bates ◽  
Peter S. Spector
Keyword(s):  
Atrial Fibrillation ◽  
Propagation Model ◽  
Surrounding Tissue ◽  
External Boundary ◽  
Tissue Properties ◽  
Excitable Gap ◽  
The Impact ◽  
The Relationship ◽  
Human Atrial Fibrillation

BackgroundThere is debate whether human atrial fibrillation is driven by focal drivers or multiwavelet reentry. We propose that the changing activation sequences surrounding a focal driver can at times self-sustain in the absence of that driver. Further, the relationship between focal drivers and surrounding chaotic activation is bidirectional; focal drivers can generate chaotic activation, which may affect the dynamics of focal drivers.Methods and ResultsIn a propagation model, we generated tissues that support structural micro-reentry and moving functional reentrant circuits. We qualitatively assessed (1) the tissue’s ability to support self-sustaining fibrillation after elimination of the focal driver, (2) the impact that structural-reentrant substrate has on the duration of fibrillation, the impact that micro-reentrant (3) frequency, (4) excitable gap, and (5) exposure to surrounding fibrillation have on micro-reentry in the setting of chaotic activation, and finally the likelihood fibrillation will end in structural reentry based on (6) the distance between and (7) the relative lengths of an ablated tissue’s inner and outer boundaries. We found (1) focal drivers produced chaotic activation when waves encountered heterogeneous refractoriness; chaotic activation could then repeatedly initiate and terminate micro-reentry. Perpetuation of fibrillation following elimination of micro-reentry was predicted by tissue properties. (2) Duration of fibrillation was increased by the presence of a structural micro-reentrant substrate only when surrounding tissue had a low propensity to support self-sustaining chaotic activation. Likelihood of micro-reentry around the structural reentrant substrate increased as (3) the frequency of structural reentry increased relative to the frequency of fibrillation in the surrounding tissue, (4) the excitable gap of micro-reentry increased, and (5) the exposure of the structural circuit to the surrounding tissue decreased. Likelihood of organized tachycardia following termination of fibrillation increased with (6) decreasing distance and (7) disparity of size between focal obstacle and external boundary.ConclusionFocal drivers such as structural micro-reentry and the chaotic activation they produce are continuously interacting with one another. In order to accurately describe cardiac tissue’s propensity to support fibrillation, the relative characteristics of both stationary and moving drivers must be taken into account.

scholarly journals Impact of surrounding tissue on conductance measurement of coronary and peripheral lumen area

2012 ◽  
Vol 9 (76) ◽  
pp. 2971-2982 ◽  
Author(s):  
Hyo Won Choi ◽  
Benjamin Jansen ◽  
Zhen-Du Zhang ◽  
Ghassan S. Kassab
Keyword(s):  
Electrical Conductivity ◽  
Blood Vessel ◽  
Electric Current ◽  
Muscle Tissue ◽  
Surrounding Tissue ◽  
Lumen Diameter ◽  
Electrode Spacing ◽  
Conductance Catheter ◽  
Conductance Method ◽  
Parallel Conductance

Parallel conductance (electric current flow through surrounding tissue) is an important determinant of accurate measurements of arterial lumen diameter, using the conductance method. The present study is focused on the role of non-uniform geometrical/electrical configurations of surrounding tissue, which are a primary source of electric current leakage. Computational models were constructed to simulate the conductance catheter measurement with two different excitation electrodes spacings (i.e. 12 and 20 mm for coronary and peripheral sizing, respectively) for different vessel–tissue configurations: (i) blood vessel fully embedded in muscle tissue, (ii) blood vessel superficially embedded in muscle tissue, and (iii) blood vessel superficially embedded in muscle tissue with fat covering half of the arterial vessel (anterior portion). The simulations suggest that the parallel conductance and accuracy of measurement is dependent on the inhomogeneous/anisotropic configuration of surrounding tissue, including the asymmetric dimension and anisotropy in electrical conductivity of surrounding tissue. Specifically, the measurement was shown to be accurate as long as the vessel was superficial, regardless of the considerable total surrounding tissue dimension for coronary or peripheral arteries. Moreover, it was shown that the unfavourable impact of parallel conductance on the accuracy of conductance catheter measurement is decreased by the combination of a lower transverse electrical conductivity of surrounding muscle tissue, a smaller electrode spacing and a larger lumen diameter. The present findings confirm that the conductance catheter technique provides an accurate platform for sizing of clinically relevant (i.e. superficial and diseased) arteries.

Conductance catheter measurements of lumen area of stenotic coronary arteries: theory and experiment

2011 ◽  
Vol 111 (3) ◽  
pp. 758-765 ◽  
Author(s):  
Hyo Won Choi ◽  
Neil D. Farren ◽  
Zhen-Du Zhang ◽  
Yunlong Huo ◽  
Ghassan S. Kassab
Keyword(s):  
Electric Field ◽  
Coronary Arteries ◽  
Saline Solution ◽  
Recirculation Region ◽  
Lumen Area ◽  
Conductance Catheter ◽  
Cross Sectional ◽  
Flow Recirculation ◽  
Conductance Method ◽  
Catheter Size

An injection of saline solution is required for the measurement of vessel lumen area using a conductance catheter. The injection of room temperature saline to displace blood in a vessel inevitably involves mass and heat transport and electric field conductance. The objective of the present study is to understand the accuracy of conductance method based on the phenomena associated with the saline injection into a stenotic blood vessel. Computational fluid dynamics were performed to simulate flow and its relation to transport and electric field in a stenotic artery for two different sized conductance catheters (0.9 and 0.35 mm diameter) over a range of occlusions [56–84% cross-sectional area (CSA) stenosis]. The results suggest that the performance of conductance catheter is dependent on catheter size and severity of stenosis more significantly for 0.9 mm than for 0.35 mm catheter. Specifically, the time of detection of 95% of injected saline solution at the detection electrodes was shown to range from 0.67 to 3.7 s and 0.82 to 0.94 s for 0.9 mm and 0.35 mm catheter, respectively. The results also suggest that the detection electrodes of conductance catheter should be placed outside of flow recirculation region distal to the stenosis to minimize the detection time. Finally, the simulations show that the accuracy in distal CSA measurements, however, is not significantly altered by whether the position of detection electrodes is inside or outside of recirculation zone (error was within 12% regardless of detection electrodes position). The results were experimentally validated for one lesion geometry and the simulation results are within 8% of actual measurements. The simulation of conductance catheter injection method may lead to further optimization of device and method for accurate sizing of diseased coronary arteries, which has clinical relevance to percutaneous intervention.

scholarly journals Influence of Alternative Financing on the Relationship between Managerial Competency and Efficiency of Small and Medium Enterprises in Kenya

2018 ◽  
Vol 7 (1) ◽  
pp. 13
Author(s):  
Jackson Njau Waweru ◽  
Kennedy M. Waweru ◽  
Kenneth L. Wanjau ◽  
Josphat K. Kinyanjui
Keyword(s):  
Economic Growth ◽  
Multiple Regression ◽  
Structural Equation ◽  
Secondary Data ◽  
Equation Modeling ◽  
Medium Size ◽  
Cross Sectional ◽  
Managerial Competency ◽  
Alternative Finance ◽  
The Impact

<p><em>Worldwide, Small and medium-size enterprises (SMEs) exhibit inimitable financial needs. While SMEs remain fundamental to economic growth, their mortality rate in Kenya approaches 90% by the second year, mainly owing to lack of credit. However, scholarly endeavors exploring the impact of alternative finance (AF) on managerial competency - efficiency nexus for manufacturing SMEs have received little attention in Kenya. To resolve this conundrum, a thorough study to investigate how AF impacts managerial competency - efficiency nexus is necessary. The study used a cross-sectional research design, employing both qualitative and quantitative research approaches. The target population was 171 SMEs registered with Kenya Association of Manufacturers. The accessible population was 136 SMEs owners/managers. A semi-structured questionnaire was used to collect primary and secondary data. Data envelopment analysis was used to measure efficiency, multiple regression modeling used to analyze the direct relationships while hierarchical moderated multiple regression analysis employed to test moderation. Partial Least Squares Structural Equation Modeling was used to test robustness of our results. The findings of this study demonstrate that managerial competency positively influences efficiency (β = 0.150, t-value =10.246, P&lt;0.05), and that alternative finance does moderate managerial competency relationships with efficiency (R-Square change of 21.7%).We suggest trainings for manufacturing SME owners/managers in Kenya on the pivotal role of alternative finance to facilitate SMEs achieve higher efficiencies and accelerate economic growth.</em></p>

Multidisciplinary team decision is rare and decreasing in percutaneous vascular interventions despite positive impact on in-hospital outcomes

VASA ◽  
2019 ◽  
Vol 48 (3) ◽  
pp. 262-269 ◽  
Author(s):  
Christian-Alexander Behrendt ◽  
Tilo Kölbel ◽  
Thea Schwaneberg ◽  
Holger Diener ◽  
Ralf Hohnhold ◽  
...  
Keyword(s):  
Multidisciplinary Team ◽  
Positive Impact ◽  
Cross Sectional Study ◽  
Invasive Treatment ◽  
Cross Sectional ◽  
Hospital Outcomes ◽  
Vascular Intervention ◽  
Medical Specialties ◽  
Team Decision ◽  
The Impact

Abstract. Background: Worldwide prevalence of peripheral artery disease (PAD) is increasing and peripheral vascular intervention (PVI) has become the primary invasive treatment. There is evidence that multidisciplinary team decision-making (MTD) has an impact on in-hospital outcomes. This study aims to depict practice patterns and time changes regarding MTD of different medical specialties. Methods: This is a retrospective cross-sectional study design. 20,748 invasive, percutaneous PVI of PAD conducted in the metropolitan area of Hamburg (Germany) were consecutively collected between January 2004 and December 2014. Results: MTD prior to PVI was associated with lower odds of early unsuccessful termination of the procedures (Odds Ratio 0.662, p < 0.001). The proportion of MTD decreased over the study period (30.9 % until 2009 vs. 16.6 % from 2010, p < 0.001) while rates of critical limb-threatening ischemia (34.5 % vs. 42.1 %), patients´ age (70 vs. 72 years), PVI below-the-knee (BTK) (13.2 % vs. 22.4 %), and rates of severe TASC C/D lesions BTK (43.2 % vs. 54.2 %) increased (all p < 0.001). Utilization of MTD was different between medical specialties with lowest frequency in procedures performed by internists when compared to other medical specialties (7.1 % vs. 25.7 %, p < 0.001). Conclusions: MTD prior to PVI is associated with technical success of the procedure. Nonetheless, rates of MTD prior to PVI are decreasing during the study period. Future studies should address the impact of multidisciplinary vascular teams on long-term outcomes.

Factors Influencing Academic Stress on Students of University of Economics and Business - Vietnam National University

2020 ◽  
Vol 36 (3) ◽  
Author(s):  
Nham Phong Tuan ◽  
Nguyen Ngoc Quy ◽  
Nguyen Thi Thanh Huyen ◽  
Hong Tra My ◽  
Tran Nhu Phu
Keyword(s):  
Academic Stress ◽  
Stress Factors ◽  
Negative Effects ◽  
Cross Sectional ◽  
Stress Scale ◽  
Perceptions And Attitudes ◽  
National University ◽  
Questionnaire Surveys ◽  
The University ◽  
The Impact

The objective of this study is to investigate the impact of seven factors causing academic stress on students of University of Economics and Business - Vietnam National University: Lack of leisure time, Academic performance, Fear of failure, Academic overload, Finances, Competition between students, Relationships with university faculty. Based on the results of a practical survey of 185 students who are attending any courses at the University of Economics and Business - Vietnam National University, the study assesses the impact of stress factors on students. The thesis focuses on clarifying the concept of "stress" and the stress level of students, while pointing out its negative effects on students. This study includes two cross-sectional questionnaire surveys. The first survey uses a set of 16 questions to assess students’ perceptions and attitudes based on an instrument to measure academic stress - Educational Stress Scale for Adolescents (ESSA). The second survey aims to test internal consistency, the robustness of the previously established 7-factor structure. Henceforth, the model was brought back and used qualitatively, combined with Cronbach’s Alpha measurement test and EFA discovery factor analysis. This study was conducted from October 2019 to December 2019. From these practical analyzes, several proposals were made for the society, the school and the students themselves.

The impact of the use of a footrest on the quality of chest compressions. A prospective, randomized, cross-sectional study

2018 ◽  
Vol 31 (3) ◽  
Author(s):  
Jolanta Majer ◽  
Sandra Pyda ◽  
Jerzy Robert Ladny ◽  
Antonio Rodriguez-Nunez ◽  
Lukasz Szarpak
Keyword(s):  
Cross Sectional Study ◽  
Sectional Study ◽  
Chest Compressions ◽  
Cross Sectional ◽  
The Impact
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