Computational Quantification of the Cardiac Energy Consumption during Intra-Aortic Balloon Pumping Using a Cardiac Electromechanics Model

임기무,이정상,Min-Soo Gyeong,최재성,최성욱,Eun Bo Shim 대한의학회 2013 Journal of Korean medical science Vol.28 No.1

To quantify the reduction in workload during intra-aortic balloon pump (IABP) therapy,indirect parameters are used, such as the mean arterial pressure during diastole, product of heart rate and peak systolic pressure, and pressure–volume area. Therefore, we investigated the cardiac energy consumption during IABP therapy using a cardiac electromechanics model. We incorporated an IABP function into a previously developed electromechanical model of the ventricle with a lumped model of the circulatory system and investigated the cardiac energy consumption at different IABP inflation volumes. When the IABP was used at inflation level 5, the cardiac output and stroke volume increased 11%, the ejection fraction increased 21%, the stroke work decreased 1%, the mean arterial pressure increased 10%, and the ATP consumption decreased 12%. These results show that although the ATP consumption is decreased significantly, stroke work is decreased only slightly, which indicates that the IABP helps the failed ventricle to pump blood efficiently.

Mathematical Simulation of Cold Dialysate Regeneration System

임기무,심은보,김지현 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

회귀성 파동에 기인한 심방부정맥 시뮬레이션을 위한 선행 연구

임기무,김창현 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.4-4

Numerical Simulation of the Effect of Sodium Profile on Cardiovascular Response to Hemodialysis

임기무,최성욱,민병구,심은보 연세대학교의과대학 2008 Yonsei medical journal Vol.49 No.4

Purpose: We developed a numerical model that predicts cardiovascular system response to hemodialysis, focusing on the effect of sodium profile during treatment. Materials and Methods: The model consists of a 2-compartment solute kinetics model, 3-compartment body fluid model, and 12-lumped- parameter representation of the cardiovascular circulation model connected to set-point models of the arterial baroreflexes. The solute kinetics model includes the dynamics of solutes in the intracellular and extracellular pools and a fluid balance model for the intracellular, interstitial, and plasma volumes. Perturbation due to hemodialysis treatment induces a pressure change in the blood vessels and the arterial baroreceptors then trigger control mechanisms (autoregulation system). These in turn alter heart rate, systemic arterial resistance, and cardiac contractility. The model parameters are based largely on the reported values. Results: We present the results obtained by numerical simulations of cardiovascular response during hemodialysis with 3 different dialysate sodium concentration profiles. In each case, dialysate sodium concentration profile was first calculated using an inverse algorithm according to plasma sodium concentration profiles, and then the percentage changes in each compartment pressure, heart rate, and systolic ventricular compliance and systemic arterial resistance during hemodialysis were determined. A plasma concentration with an upward convex curve profile produced a cardiovascular response more stable than linear or downward convex curves. Conclusion: By conducting numerical tests of dialysis/ cardivascular models for various treatment profiles and creating a database from the results, it should be possible to estimate an optimal sodium profile for each patient.

Simulation of Reentrant Wave Dynamics in Cardiac Tissue According to the Severity of Fibrosis

임기무,최성윤,권순성,심은보 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

This study investigated the spiral wave dynamics in cardiac tissue according to the severity of fibrosis in the hypertrophic human ventricle by simulating propagation of the electric wave. We used a model of the human ventricular cell to describe the cellular electrophysiology and a twodimensional monodomain method to compute the electric wave propagation in ventricular tissue using finite element approximation. To delineate the effect of fibrosis on the wave dynamics, a model of hypertrophic cardiac tissue with randomly distributed fibroblasts was simulated. The electrical conductivity of the fibroblasts was estimated from the experimental data. In the fibrotic cardiac tissue, we generated a reentrant wave and predicted its dynamic variation according to the severity of fibrosis. Compared to the reentrant wave in normal tissue, a conduction delay was observed in the fibrotic tissue. Furthermore, one spiral wave broke into several waves when fibroblasts constituted 40 % of the tissue, causing cardiac fibrillation. This study investigated the spiral wave dynamics in cardiac tissue according to the severity of fibrosis in the hypertrophic human ventricle by simulating propagation of the electric wave. We used a model of the human ventricular cell to describe the cellular electrophysiology and a twodimensional monodomain method to compute the electric wave propagation in ventricular tissue using finite element approximation. To delineate the effect of fibrosis on the wave dynamics, a model of hypertrophic cardiac tissue with randomly distributed fibroblasts was simulated. The electrical conductivity of the fibroblasts was estimated from the experimental data. In the fibrotic cardiac tissue, we generated a reentrant wave and predicted its dynamic variation according to the severity of fibrosis. Compared to the reentrant wave in normal tissue, a conduction delay was observed in the fibrotic tissue. Furthermore, one spiral wave broke into several waves when fibroblasts constituted 40 % of the tissue, causing cardiac fibrillation.

Theoretical Estimation of Cannulation Methods for Left Ventricular Assist Device Support as a Bridge to Recovery

임기무,이정상,송진호,윤찬현,최재성,심은보 대한의학회 2011 Journal of Korean medical science Vol.26 No.12

Left ventricular assist device (LVAD) support under cannulation connected from the left atrium to the aorta (LA-AA) is used as a bridge to recovery in heart failure patients because it is non-invasive to ventricular muscle. However, it has serious problems, such as valve stenosis and blood thrombosis due to the low ejection fraction of the ventricle. We theoretically estimated the effect of the in-series cannulation, connected from ascending aorta to descending aorta (AA-DA), on ventricular unloading as an alternative to the LAAA method. We developed a theoretical model of a LVAD-implanted cardiovascular system that included coronary circulation. Using this model, we compared hemodynamic responses according to various cannulation methods such as LA-AA, AA-DA, and a cannulation connected from the left ventricle to ascending aorta (LV-AA), under continuous and pulsatile LVAD supports. The AA-DA method provided 14% and 18% less left ventricular peak pressure than the LA-AA method under continuous and pulsatile LVAD conditions, respectively. The LA-AA method demonstrated higher coronary flow than AADA method. Therefore, the LA-AA method is more advantageous in increasing ventricular unloading whereas the AA-DA method is a better choice to increase coronary perfusion.

혈액투석 중 심혈관계 응답의 수치적 연구

임기무(K. M. Lim),민병구(B. G. Min),고형종(H. J. Ko),심은보(E. B. Shim) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

The object of this study is to develop a model of the cardiovascular system capable of simulating the short-term transient and steady-state hemodynamic responses such as hypotention and disequilibrium syndrome during hemodialysis or hemofiltration. The model consists of a closed loop 12 lumped-parameter representation of the cardiovascular circulation connected to set-point models of the arterial and cardiopulmonary baroreflexes and 3 compartmental body fluid and solute kinetic model. The hemodialysis model includes the dynamics of sodium, urea, and potassium in the intracellular and extracellular pools, fluid balance equations for the intracellular, interstitial, and plasma volumes. We have presented the results of many different simulations performed by changing a few model parameters with respect to their basal values.

동악어문학회 주최 제1회 한·중 국제학술회의 발표 요지

임기중,장민,태평무,묘춘매,황종연,김갑기,김혜숙 동악어문학회 1996 동악어문학 Vol.31 No.-

3차원 심장조직 모델과 체표면전위맵을 이용한 부정맥 예측 시뮬레이션

김유석,임기무 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.바이오공학 No.-

KCNQ1 S140G 돌연변이 발현과 심실세동과의 상관관계 분석을 위한 컴퓨터 시뮬레이션 연구

정다운,임기무,Jeong, Daun,Lim, Ki Moo 대한의용생체공학회 2017 의공학회지 Vol.38 No.3

Background and aims: The KCNQ1 S140G mutation involved in $I_{ks}$ channel is a typical gene mutation affecting atrial fibrillation. However, despite the possibility that the S140G gene mutation may affect not only atrial but also ventricular action potential shape and ventricular responses, there is a lack of research on the relationship between this mutation and ventricular fibrillation. Therefore, in this study, we analyzed the correlation and the influence of the KCNQ1 S140G mutant gene on ventricular fibrillation through computer simulation studies. Method: This study simulated a 3-dimensional ventricular model of the wild type(WT) and the S140G mutant conditions. It was performed by dividing into normal sinus rhythm simulation and reentrant wave propagation simulation. For the sinus rhythm, a ventricular model with Purkinje fiber was used. For the reentrant propagation simulation, a ventricular model was used to confirm the occurrence of spiral wave using S1-S2 protocol. Results: The result showed that 41% shortening of action potential duration(APD) was observed due to augmented $I_{ks}$ current in S140G mutation group. The shortened APD contributed to reduce wavelength 39% in sinus rhythm simulation. The shortened wavelength in cardiac tissue allowed re-entrant circuits to form and increased the probability of sustaining ventricular fibrillation, while ventricular electrical propagation with normal wavelength(20.8 cm in wild type) are unlikely to initiate re-entry. Conclusion: In conclusion, KCNQ1 S140G mutation can reduce the threshold of the re-entrant wave substrate in ventricular cells, increasing the spatial vulnerability of tissue and the sensitivity of the fibrillation. That is, S140G mutation can induce ventricular fibrillation easily. It means that S140G mutant can increase the risk of arrhythmias such as cardiac arrest due to heart failure.