The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary... more The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary arteries using a computer heart model is described here. The goal was to correlate the simulated body surface potential map patterns corresponding to these occlusions with clinically-observed patterns recorded in patients undergoing percutaneous transluminal coronary angioplasty
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1988
A whole-heart model is proposed for the simulation of normal and pathological propagation of card... more A whole-heart model is proposed for the simulation of normal and pathological propagation of cardiac activation. The definition of heart anatomy is based on the use of computerized tomography and image processing. The specialized conduction system of the heart as well as myocardial fiber anisotropy are included. Ventricular propagation is based on assuming local plane-wave activation. Accurate simulations of normal and abnormal isochrones are possible.<>
Present-day computer models of the entire heart, capable of simulating the activation isochrones ... more Present-day computer models of the entire heart, capable of simulating the activation isochrones and subsequently the body surface potentials, focus on considerations of myocardial anisotropy. Myocardial anisotropy enters into play at two levels, first by affecting the spatial pattern of activation owing to faster propagation along cardiac fibers and second by altering the equivalent dipole sources used to calculate the surface potentials. The construction of a new and detailed model of the human heart is described, based on 132 transverse sections obtained following a computed tomography scan of a frozen human heart whose chambers were inflated with pressurized air. The entire heart anatomy was reconstructed as a three-dimensional array of approximately 250,000 points spaced 1 mm apart. Conduction in the thin-walled atria was assumed isotropic from the sinus node region to the atrioventricular node, where it was subject to a 50 ms delay. A two-tier representation of the specialized conduction system was used, with the initial segments of the left and right bundles represented by a system of cables that feeds to the second tier, which is a sheet of conduction tissue representing the distal Purkinje system. Approximately 1,120 &quot;Purkinje-myocardium&quot; junctions present at the terminations of the cables and sprinkled uniformly over the sheet, transmit the excitation to the ventricles. A stylized representation of myocardial fiber rotation was incorporated into the ventricles and the local fiber direction at each model point used to compute the velocity of propagation to its nearest neighbors. Accordingly, the activation times of the entire ventricular myocardium could be determined using the 1,120 or so Purkinje-myocardium junctions as start points. While myocardial anisotropy was considered in the ventricular propagation process, it was ignored in the computation of the equivalent dipole sources. Nevertheless, the computed electrocardiogram, vectorcardiogram, and body surface potential maps obtained with the new heart model properly positioned inside an inhomogeneous torso model were all within normal limits.
This paper begins with a brief review of the different types of computer models of the heart, the... more This paper begins with a brief review of the different types of computer models of the heart, then touches upon solution methodologies for solving the forward problem of electrocardiography, and finally describes the results obtained with forward problem simulations of the WoIff-Parkinson-White syndrome using a particular example of a computer model of the heart.
The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary... more The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary arteries using a computer heart model is described here. The goal was to correlate the simulated body surface potential map patterns corresponding to these ...
A whole-heart model is proposed for the simulation of normal and pathological propagation of card... more A whole-heart model is proposed for the simulation of normal and pathological propagation of cardiac activation. The definition of heart anatomy is based on the use of computerized tomography and image processing. The specialized conduction system of the heart as well as myocardial fiber anisotropy are included. Ventricular propagation is based on assuming local plane-wave activation. Accurate simulations of normal and abnormal isochrones are possible.<>
Canadian Journal of Anaesthesia-journal Canadien D Anesthesie, 1993
This study was designed in order to validate the respiratory mechanical variables measured by the... more This study was designed in order to validate the respiratory mechanical variables measured by the Puritan-Bennett 7200a ventilator equipped with the 30/40 module. Two ventilators were connected to a lung model and submitted to several breathing patterns by modifying the respiratory rate, the tidal volume, the inspiratory flowrate and the model resistance. The inspiratory flowrate (V), tidal volume (Vt), peak inspiratory pressure (Pmax), plateau pressure (Pplat) and PEEP measured by the ventilators were compared with the same variables measured at the connection between the breathing circuit and the lung model. The compliance (C30/40) and the resistance (R30/40) calculated by the 30/40 module were compared with those calculated by using the variables measured by the reference equipment. Both ventilators made a constant underestimation of V by 2.8 and 3.7 L · min−1, respectively. The V t was measured with a mean error of less than 10 ml but did not reflect the preselected values in the presence of an intrinsic PEEP. The Pplat was overestimated by 7 and 10%, respectively. The same calibration error was observed with Pmax which was also affected by a pressure gradient due to the resistance of the breathing circuit. Even in the absence of intrinsic PEEP, C30/40 presented an error due to the combination of the measurement errors onVt, Pplat and PEEP. Finally, R30/40 presented a high percentage of error due to the combination of the measurement errors on V, Pmax and Pplat, and to a sporadic aberrant selection of V. Due to these numerous sources of error, the two ventilators studied did not give reliable estimates of resistance and compliance. We do not recommend the use of the optional 30/40 module to measure respiratory mechanics at the bedside. Cette étude a été réalisée afin de valider les paramètres de mécanique respiratoire mesurés par le ventilateur Puritan-Bennett 7200a muni d’un module 30/40. Deux ventilateurs ont été branchés à un modèle de poumon et soumis à plusieurs conditions ventilatoires en modifiant la fréquence respiratoire, le volume courant, le débit inspiratoire et la résistance du modèle. Le débit inspiratoire (V), le volume courant (Vt), la pression inspiratoire maximale (Pmax), la pression de plateau (Pplat) et le PEEP mesurés par les ventilateurs ont été comparés aux mêmes paramètres mesurés au niveau du branchement entre le circuit respiratoire et le modèle de poumon. La compliance (C30/40) et la résistance (R30/40) calculées par le module 30/ 40 ont été comparées à celles calculées en utilisant les paramètres mesurés au moyen de l’appareillage de référence. Les deux ventilateurs ont fait une sous-estimation constante du V de 2,8 et 3,7 L · min−1, respectivement. LeVt était mesuré avec une erreur moyenne de moins de 10 ml mais, en présence d’un PEEP intrinsèque, cette mesure ne reflétait pas les valeurs présélectionnées. La Pplat était surestimée par 7 et 10%, respectivement. La même erreur de calibration était observée avec Pmax qui était de plus affectée par un gradient de pression dû à la résistance du circuit respiratoire. Même en l’absence de PEEP intrinsèque, C30/40 présentait une erreur secondaire à la combinaison des erreurs de mesure surVt, Pplat et PEEP. Finalement, R30/40 présentait un haut pourcentage d’erreur secondaire à la combinaison des erreurs de mesure sur V,Pmax et Pplat, et à une sélection sporadiquement aberrante de V. A cause de ces nombreuses sources d’erreur, les deux ventilateurs étudiés n’ont pas fourni des estimations fiables de la résistance et de la compliance. Nous ne recommandons pas l’utilisation du module optionnel 30/40 pour mesurer la mécanique respiratoire au chevet du patient.
The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary... more The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary arteries using a computer heart model is described here. The goal was to correlate the simulated body surface potential map patterns corresponding to these occlusions with clinically-observed patterns recorded in patients undergoing percutaneous transluminal coronary angioplasty
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1988
A whole-heart model is proposed for the simulation of normal and pathological propagation of card... more A whole-heart model is proposed for the simulation of normal and pathological propagation of cardiac activation. The definition of heart anatomy is based on the use of computerized tomography and image processing. The specialized conduction system of the heart as well as myocardial fiber anisotropy are included. Ventricular propagation is based on assuming local plane-wave activation. Accurate simulations of normal and abnormal isochrones are possible.<>
Present-day computer models of the entire heart, capable of simulating the activation isochrones ... more Present-day computer models of the entire heart, capable of simulating the activation isochrones and subsequently the body surface potentials, focus on considerations of myocardial anisotropy. Myocardial anisotropy enters into play at two levels, first by affecting the spatial pattern of activation owing to faster propagation along cardiac fibers and second by altering the equivalent dipole sources used to calculate the surface potentials. The construction of a new and detailed model of the human heart is described, based on 132 transverse sections obtained following a computed tomography scan of a frozen human heart whose chambers were inflated with pressurized air. The entire heart anatomy was reconstructed as a three-dimensional array of approximately 250,000 points spaced 1 mm apart. Conduction in the thin-walled atria was assumed isotropic from the sinus node region to the atrioventricular node, where it was subject to a 50 ms delay. A two-tier representation of the specialized conduction system was used, with the initial segments of the left and right bundles represented by a system of cables that feeds to the second tier, which is a sheet of conduction tissue representing the distal Purkinje system. Approximately 1,120 &quot;Purkinje-myocardium&quot; junctions present at the terminations of the cables and sprinkled uniformly over the sheet, transmit the excitation to the ventricles. A stylized representation of myocardial fiber rotation was incorporated into the ventricles and the local fiber direction at each model point used to compute the velocity of propagation to its nearest neighbors. Accordingly, the activation times of the entire ventricular myocardium could be determined using the 1,120 or so Purkinje-myocardium junctions as start points. While myocardial anisotropy was considered in the ventricular propagation process, it was ignored in the computation of the equivalent dipole sources. Nevertheless, the computed electrocardiogram, vectorcardiogram, and body surface potential maps obtained with the new heart model properly positioned inside an inhomogeneous torso model were all within normal limits.
This paper begins with a brief review of the different types of computer models of the heart, the... more This paper begins with a brief review of the different types of computer models of the heart, then touches upon solution methodologies for solving the forward problem of electrocardiography, and finally describes the results obtained with forward problem simulations of the WoIff-Parkinson-White syndrome using a particular example of a computer model of the heart.
The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary... more The simulation of transmural myocardial ischemia due to occlusion of the three principal coronary arteries using a computer heart model is described here. The goal was to correlate the simulated body surface potential map patterns corresponding to these ...
A whole-heart model is proposed for the simulation of normal and pathological propagation of card... more A whole-heart model is proposed for the simulation of normal and pathological propagation of cardiac activation. The definition of heart anatomy is based on the use of computerized tomography and image processing. The specialized conduction system of the heart as well as myocardial fiber anisotropy are included. Ventricular propagation is based on assuming local plane-wave activation. Accurate simulations of normal and abnormal isochrones are possible.<>
Canadian Journal of Anaesthesia-journal Canadien D Anesthesie, 1993
This study was designed in order to validate the respiratory mechanical variables measured by the... more This study was designed in order to validate the respiratory mechanical variables measured by the Puritan-Bennett 7200a ventilator equipped with the 30/40 module. Two ventilators were connected to a lung model and submitted to several breathing patterns by modifying the respiratory rate, the tidal volume, the inspiratory flowrate and the model resistance. The inspiratory flowrate (V), tidal volume (Vt), peak inspiratory pressure (Pmax), plateau pressure (Pplat) and PEEP measured by the ventilators were compared with the same variables measured at the connection between the breathing circuit and the lung model. The compliance (C30/40) and the resistance (R30/40) calculated by the 30/40 module were compared with those calculated by using the variables measured by the reference equipment. Both ventilators made a constant underestimation of V by 2.8 and 3.7 L · min−1, respectively. The V t was measured with a mean error of less than 10 ml but did not reflect the preselected values in the presence of an intrinsic PEEP. The Pplat was overestimated by 7 and 10%, respectively. The same calibration error was observed with Pmax which was also affected by a pressure gradient due to the resistance of the breathing circuit. Even in the absence of intrinsic PEEP, C30/40 presented an error due to the combination of the measurement errors onVt, Pplat and PEEP. Finally, R30/40 presented a high percentage of error due to the combination of the measurement errors on V, Pmax and Pplat, and to a sporadic aberrant selection of V. Due to these numerous sources of error, the two ventilators studied did not give reliable estimates of resistance and compliance. We do not recommend the use of the optional 30/40 module to measure respiratory mechanics at the bedside. Cette étude a été réalisée afin de valider les paramètres de mécanique respiratoire mesurés par le ventilateur Puritan-Bennett 7200a muni d’un module 30/40. Deux ventilateurs ont été branchés à un modèle de poumon et soumis à plusieurs conditions ventilatoires en modifiant la fréquence respiratoire, le volume courant, le débit inspiratoire et la résistance du modèle. Le débit inspiratoire (V), le volume courant (Vt), la pression inspiratoire maximale (Pmax), la pression de plateau (Pplat) et le PEEP mesurés par les ventilateurs ont été comparés aux mêmes paramètres mesurés au niveau du branchement entre le circuit respiratoire et le modèle de poumon. La compliance (C30/40) et la résistance (R30/40) calculées par le module 30/ 40 ont été comparées à celles calculées en utilisant les paramètres mesurés au moyen de l’appareillage de référence. Les deux ventilateurs ont fait une sous-estimation constante du V de 2,8 et 3,7 L · min−1, respectivement. LeVt était mesuré avec une erreur moyenne de moins de 10 ml mais, en présence d’un PEEP intrinsèque, cette mesure ne reflétait pas les valeurs présélectionnées. La Pplat était surestimée par 7 et 10%, respectivement. La même erreur de calibration était observée avec Pmax qui était de plus affectée par un gradient de pression dû à la résistance du circuit respiratoire. Même en l’absence de PEEP intrinsèque, C30/40 présentait une erreur secondaire à la combinaison des erreurs de mesure surVt, Pplat et PEEP. Finalement, R30/40 présentait un haut pourcentage d’erreur secondaire à la combinaison des erreurs de mesure sur V,Pmax et Pplat, et à une sélection sporadiquement aberrante de V. A cause de ces nombreuses sources d’erreur, les deux ventilateurs étudiés n’ont pas fourni des estimations fiables de la résistance et de la compliance. Nous ne recommandons pas l’utilisation du module optionnel 30/40 pour mesurer la mécanique respiratoire au chevet du patient.
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