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Heinrich Schima - One of the best experts on this subject based on the ideXlab platform.
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LVAD Pump Flow Does Not Adequately Increase With Exercise.
Artificial organs, 2018Co-Authors: Christoph Gross, Heinrich Schima, Christiane Marko, Johann Mikl, Johann Altenberger, Thomas Schlöglhofer, Daniel Zimpfer, Francesco MoscatoAbstract:Left ventricular assist devices (LVADs) restore cardiovascular circulatory demand at rest with a spontaneous increase in Pump Flow to exercise. The relevant contribution of cardiac output provided by the LVAD and ejected through the aortic valve for exercises of different intensities has been barely investigated in patients. The hypothesis of this study was that different responses in continuous recorded Pump parameters occur for maximal and submaximal intensity exercises and that the Pump Flow change has an impact on the oxygen uptake at peak exercise (pVO2 ). Cardiac and Pump parameters such as LVAD Flow rate (QLVAD ), heart rate (HR), and aortic valve (AV) opening were analyzed from continuously recorded LVAD data during physical exercises of maximal (bicycle ergometer test) and submaximal intensities (6-min walk test and regular trainings). During all exercise sessions, the LVAD speed was kept constant. Cardiac and Pump parameter responses of 16 patients for maximal and submaximal intensity exercises were similar for QLVAD : +0.89 ± 0.52 versus +0.59 ± 0.38 L/min (P = 0.07) and different for HR: +20.4 ± 15.4 versus +7.7 ± 5.8 bpm (P
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development of a Pump Flow estimator for rotary blood Pumps to enhance monitoring of ventricular function
Artificial Organs, 2012Co-Authors: Marcus Granegger, Francesco Moscato, Fernando Casas, Georg Wieselthaler, Heinrich SchimaAbstract:: Estimation of instantaneous Flow in rotary blood Pumps (RBPs) is important for monitoring the interaction between heart and Pump and eventually the ventricular function. Our group has reported an algorithm to derive ventricular contractility based on the maximum time derivative (dQ/dt(max) as a substitute for ventricular dP/dt(max) ) and pulsatility of measured Flow signals. However, in RBPs used clinically, Flow is estimated with a bandwidth too low to determine dQ/dt(max) in the case of improving heart function. The aim of this study was to develop a Flow estimator for a centrifugal Pump with bandwidth sufficient to provide noninvasive cardiac diagnostics. The new estimator is based on both static and dynamic properties of the brushless DC motor. An in vitro setup was employed to identify the performance of Pump and motor up to 20 Hz. The algorithm was validated using physiological ventricular and arterial pressure waveforms in a mock loop which simulated different contractilities (dP/dt(max) 600 to 2300 mm Hg/s), Pump speeds (2 to 4 krpm), and fluid viscosities (2 to 4 mPa·s). The mathematically estimated Pump Flow data were then compared to the datasets measured in the mock loop for different variable combinations (Flow ranging from 2.5 to 7 L/min, pulsatility from 3.5 to 6 L/min, dQ/dt(max) from 15 to 60 L/min/s). Transfer function analysis showed that the developed algorithm could estimate the Flow waveform with a bandwidth up to 15 Hz (±2 dB). The mean difference between the estimated and measured average Flows was +0.06 ± 0.31 L/min and for the Flow pulsatilities -0.27 ± 0.2 L/min. Detection of dQ/dt(max) was possible up to a dP/dt(max) level of 2300 mm Hg/s. In conclusion, a Flow estimator with sufficient frequency bandwidth and accuracy to allow determination of changes in ventricular contractility even in the case of improving heart function was developed.
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Evaluation of left ventricular relaxation in rotary blood Pump recipients using the Pump Flow waveform: a simulation study.
Artificial organs, 2011Co-Authors: Francesco Moscato, Marcus Granegger, Georg Wieselthaler, Phornphop Naiyanetr, Heinrich SchimaAbstract:In heart failure, diastolic dysfunction is responsible for about 50% of the cases, with higher prevalence in women and elderly persons and contributing similarly to mortality as systolic dysfunction. Whereas the cardiac systolic diagnostics in ventricular assist device patients from Pump parameters have been investigated by several groups, the diastolic behavior has been barely discussed. This study focuses on the determination of ventricular relaxation during early diastole in rotary blood Pump (RBP) recipients. In conventional cardiology, relaxation is usually evaluated by the minimum rate and the time constant of left ventricular pressure decrease, dP/dt(min) and τ(P) . Two new analogous indices derived from the Pump Flow waveform were investigated in this study: the minimum rate and the time constant of Pump Flow decrease, dQ/dt(min) and τ(Q) . The correspondence between the indices was investigated in a numerical simulation of the assisted circulation for different ventricular relaxation states (τ(P) ranging from 24 to 68 ms) and two RBP models characterized by linear and nonlinear pressure-Flow characteristics. dQ/dt(min) and τ(Q) always correlated with the dP/dt(min) and τ(P) , respectively (r>0.97). These relationships were influenced by the nonlinear Pump characteristics during partial support and by the Pump speed during full support. To minimize these influences, simulation results suggest the evaluation of dQ/dt(min) and τ(Q) at a Pump speed that corresponds to the borderline between partial and full support. In conclusion, at least in simulation, relaxation can be derived from Pump data. This noninvasively accessible information could contribute to a continuous estimation of the remaining cardiac function and its eventual recovery.
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Cardiac Contractility Assessment in Rotary Blood Pump Recipients Derived from Pump Flow
IFMBE Proceedings, 2009Co-Authors: Phornphop Naiyanetr, Francesco Moscato, Georg Wieselthaler, Michael Vollkron, Philipp Zrunek, Heinrich SchimaAbstract:A new cardiac contractility index derived from Pump Flow (IQ) has been developed for rotary blood Pumps (RBPs) recipients, to determine preservation and eventual recovery of the remaining cardiac function. Pulse Flow indices were used for comparison with IQ during Pump speed changes.
Francesco Moscato - One of the best experts on this subject based on the ideXlab platform.
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LVAD Pump Flow Does Not Adequately Increase With Exercise.
Artificial organs, 2018Co-Authors: Christoph Gross, Heinrich Schima, Christiane Marko, Johann Mikl, Johann Altenberger, Thomas Schlöglhofer, Daniel Zimpfer, Francesco MoscatoAbstract:Left ventricular assist devices (LVADs) restore cardiovascular circulatory demand at rest with a spontaneous increase in Pump Flow to exercise. The relevant contribution of cardiac output provided by the LVAD and ejected through the aortic valve for exercises of different intensities has been barely investigated in patients. The hypothesis of this study was that different responses in continuous recorded Pump parameters occur for maximal and submaximal intensity exercises and that the Pump Flow change has an impact on the oxygen uptake at peak exercise (pVO2 ). Cardiac and Pump parameters such as LVAD Flow rate (QLVAD ), heart rate (HR), and aortic valve (AV) opening were analyzed from continuously recorded LVAD data during physical exercises of maximal (bicycle ergometer test) and submaximal intensities (6-min walk test and regular trainings). During all exercise sessions, the LVAD speed was kept constant. Cardiac and Pump parameter responses of 16 patients for maximal and submaximal intensity exercises were similar for QLVAD : +0.89 ± 0.52 versus +0.59 ± 0.38 L/min (P = 0.07) and different for HR: +20.4 ± 15.4 versus +7.7 ± 5.8 bpm (P
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development of a Pump Flow estimator for rotary blood Pumps to enhance monitoring of ventricular function
Artificial Organs, 2012Co-Authors: Marcus Granegger, Francesco Moscato, Fernando Casas, Georg Wieselthaler, Heinrich SchimaAbstract:: Estimation of instantaneous Flow in rotary blood Pumps (RBPs) is important for monitoring the interaction between heart and Pump and eventually the ventricular function. Our group has reported an algorithm to derive ventricular contractility based on the maximum time derivative (dQ/dt(max) as a substitute for ventricular dP/dt(max) ) and pulsatility of measured Flow signals. However, in RBPs used clinically, Flow is estimated with a bandwidth too low to determine dQ/dt(max) in the case of improving heart function. The aim of this study was to develop a Flow estimator for a centrifugal Pump with bandwidth sufficient to provide noninvasive cardiac diagnostics. The new estimator is based on both static and dynamic properties of the brushless DC motor. An in vitro setup was employed to identify the performance of Pump and motor up to 20 Hz. The algorithm was validated using physiological ventricular and arterial pressure waveforms in a mock loop which simulated different contractilities (dP/dt(max) 600 to 2300 mm Hg/s), Pump speeds (2 to 4 krpm), and fluid viscosities (2 to 4 mPa·s). The mathematically estimated Pump Flow data were then compared to the datasets measured in the mock loop for different variable combinations (Flow ranging from 2.5 to 7 L/min, pulsatility from 3.5 to 6 L/min, dQ/dt(max) from 15 to 60 L/min/s). Transfer function analysis showed that the developed algorithm could estimate the Flow waveform with a bandwidth up to 15 Hz (±2 dB). The mean difference between the estimated and measured average Flows was +0.06 ± 0.31 L/min and for the Flow pulsatilities -0.27 ± 0.2 L/min. Detection of dQ/dt(max) was possible up to a dP/dt(max) level of 2300 mm Hg/s. In conclusion, a Flow estimator with sufficient frequency bandwidth and accuracy to allow determination of changes in ventricular contractility even in the case of improving heart function was developed.
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Evaluation of left ventricular relaxation in rotary blood Pump recipients using the Pump Flow waveform: a simulation study.
Artificial organs, 2011Co-Authors: Francesco Moscato, Marcus Granegger, Georg Wieselthaler, Phornphop Naiyanetr, Heinrich SchimaAbstract:In heart failure, diastolic dysfunction is responsible for about 50% of the cases, with higher prevalence in women and elderly persons and contributing similarly to mortality as systolic dysfunction. Whereas the cardiac systolic diagnostics in ventricular assist device patients from Pump parameters have been investigated by several groups, the diastolic behavior has been barely discussed. This study focuses on the determination of ventricular relaxation during early diastole in rotary blood Pump (RBP) recipients. In conventional cardiology, relaxation is usually evaluated by the minimum rate and the time constant of left ventricular pressure decrease, dP/dt(min) and τ(P) . Two new analogous indices derived from the Pump Flow waveform were investigated in this study: the minimum rate and the time constant of Pump Flow decrease, dQ/dt(min) and τ(Q) . The correspondence between the indices was investigated in a numerical simulation of the assisted circulation for different ventricular relaxation states (τ(P) ranging from 24 to 68 ms) and two RBP models characterized by linear and nonlinear pressure-Flow characteristics. dQ/dt(min) and τ(Q) always correlated with the dP/dt(min) and τ(P) , respectively (r>0.97). These relationships were influenced by the nonlinear Pump characteristics during partial support and by the Pump speed during full support. To minimize these influences, simulation results suggest the evaluation of dQ/dt(min) and τ(Q) at a Pump speed that corresponds to the borderline between partial and full support. In conclusion, at least in simulation, relaxation can be derived from Pump data. This noninvasively accessible information could contribute to a continuous estimation of the remaining cardiac function and its eventual recovery.
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Cardiac Contractility Assessment in Rotary Blood Pump Recipients Derived from Pump Flow
IFMBE Proceedings, 2009Co-Authors: Phornphop Naiyanetr, Francesco Moscato, Georg Wieselthaler, Michael Vollkron, Philipp Zrunek, Heinrich SchimaAbstract:A new cardiac contractility index derived from Pump Flow (IQ) has been developed for rotary blood Pumps (RBPs) recipients, to determine preservation and eventual recovery of the remaining cardiac function. Pulse Flow indices were used for comparison with IQ during Pump speed changes.
Mitsuo Umezu - One of the best experts on this subject based on the ideXlab platform.
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The role of diastolic Pump Flow in centrifugal blood Pump hemodynamics.
Artificial organs, 2001Co-Authors: Takehide Akimoto, Philip Litwak, Osamu Tagusari, Kenji Yamazaki, Mary J Watach, Kenneth N Litwak, Marina V. Kameneva, Shin ' Ichiro Kihara, Shun Ich Yamazaki, Mitsuo UmezuAbstract:We tried to verify the hypothesis that increases in Pump Flow during diastole are matched by decreases in left ventricular (LV) output during systole. A calf (80 kg) was implanted with an implantable centrifugal blood Pump (EVAHEART, SunMedical Technology Research Corp., Nagano, Japan) with left ventricle to aorta (LV-Ao) bypass, and parameters were recorded at different Pump speeds under general anesthesia. Pump inFlow and outFlow pressure, arterial pressure, systemic and pulmonary blood Flow, and electrocardiogram (ECG) were recorded on the computer every 5 ms. All parameters were separated into systolic and diastolic components and analyzed. The pulmonary Flow was the same as the systemic Flow during the study (p > 0.1). Systemic Flow consisted of Pump Flow and LV output through the aortic valve. The ratio of systolic Pump Flow to pulmonary Flow (51.3%) did not change significantly at variable Pump speeds (p > 0.1). The other portions of the systemic Flow were shared by the left ventricular output and the Pump Flow during diastole. When Pump Flow increased during diastole, there was a corresponding decrease in the LV output (Y = -1.068X + 51.462; R(insert)(2) = 0.9501). These show that Pump diastolic Flow may regulate expansion of the left ventricle in diastole.
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Relationship of blood pressure and Pump Flow in an implantable centrifugal blood Pump during hypertension.
ASAIO journal (American Society for Artificial Internal Organs : 1992), 2000Co-Authors: Takehide Akimoto, Philip Litwak, Osamu Tagusari, James F. Antaki, Kenji Yamazaki, Mary J Watach, Kenneth N Litwak, Marina V. Kameneva, Toshio Mori, Mitsuo UmezuAbstract:The purpose of this study was to evaluate the real time relationship between Pump Flow and Pump differential pressure (D-P) during experimentally induced hypertension (HT). Two calves (80 and 68 kg) were implanted with the EVAHEART centrifugal blood Pump (SunMedical Technology Research Corp., Nagano, Japan) under general anesthesia. Blood pressure (BP) in diastole was increased to 100 mm Hg by norepinephrine to simulate HT. Pump Flow, D-P, ECG, and BP were measured at Pump speeds of 1,800, 2,100, and 2,300 rpm. All data were separated into systole and diastole, and Pump Flow during HT was compared with normotensive (NT) conditions at respective Pump speeds. Diastolic BP was increased to 99.3 ± 4.1 mm Hg from 66.5 ± 4.4mm Hg (p < 0.01). D-P in systole was under 40 mm Hg (range of change was 10 to 40 mm Hg) even during HT. During NT, the average systolic Pump Flow volume was 60% of the total Pump Flow. However, during HT, the average systolic Pump Flow was 100% of total Pump Flow volume, although the Pump Flow volume in systole during HT decreased (33.1 ± 5.7 vs 25.9 ± 4.0 ml/systole, p < 0.01). In diastole, the average Flow volume through the Pump was 19.6± 6.9 ml/diastole during NT and -2.2 ± 11.1 ml/diastole during HT (p < 0.01). The change in Pump Flow volume due to HT, in diastole, was greater than the change in Pump Flow in systole at each Pump speed (p < 0.001). This study suggests that the decrease of mean Pump Flow during HT is mainly due to the decrease of the diastolic Pump Flow and, to a much lesser degree, systolic Pump Flow.
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rotary blood Pump Flow spontaneously increases during exercise under constant Pump speed results of a chronic study
Artificial Organs, 1999Co-Authors: Takehide Akimoto, Philip Litwak, Osamu Tagusari, James F. Antaki, Kenji Yamazaki, Mary J Watach, Kenneth N Litwak, Marina V. Kameneva, Toshio Mori, Mitsuo UmezuAbstract:Many types of rotary blood Pumps and Pump control methods have recently been developed with the goal of clinical use. From experiments, we know that Pump Flow spontaneously increases during exercise without changing Pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long-term observation of calves implanted with centrifugal blood Pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), Pump speed, and Pump Flow. The Pump Flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 ± 5.2 vs. 106 ± 9.7 bpm), mean Pump Flow (4.8 ± 0.2 vs. 7.0 ± 0.3 L/min), and volume of Pump Flow in diastole (26.0 ± 1.8 vs. 13.5 ± 2.5 ml). During exercise, the volume of Pump Flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and Pump speed did not change significantly from rest to exercise. These results suggested that the mean Pump Flow depends on the systolic Pump Flow. Therefore, the increase in the mean Pump Flow during exercise under constant Pump speed was caused by an increase in the heart rate.
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a miniature intraventricular axial Flow blood Pump that is introduced through the left ventricular apex
Asaio Journal, 1992Co-Authors: Kenji Yamazaki, Osamu Tagusari, Mitsuo Umezu, H Koyanagi, Masaya Kitamura, K Eishi, Akihiko Kawai, H Niinami, Tetsu Akimoto, Chisato NojiriAbstract:A new intraventricular axial Flow blood Pump has been designed and developed as an implantable left ventricular assist device (LVAD). The Pump consists of a tube housing (10 cm in length and 14 mm in diameter), a three-vane impeller combined with a guide vane, and a DC motor. This Pump is introduced into the LV cavity through the LV apex, and the outlet cannula is passed antegrade across the aortic valve. Blood is withdrawn from the LV through the inlet ports at the Pump base, and discharged into the ascending aorta. A Pump Flow of > 8 L/min was obtained against 90 mmHg differential pressure in the mock circulatory system. In an acute dog model, this Pump could produce a sufficient output of 200 ml/kg/min. In addition, the Pump Flow profile demonstrated a pulsatile pattern, although the rotation speed was fixed. This is mainly due to the changes in Flow rate during a cardiac cycle--that is, during systole, the Flow rate increases to the maximum, while the differential pressure between the LV and the aorta decreases to the minimum. Thus, this simple and compact axial Flow blood Pump can be a potential LVAD, with prompt accessibility and need for less invasive surgical procedures.
Georg Wieselthaler - One of the best experts on this subject based on the ideXlab platform.
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development of a Pump Flow estimator for rotary blood Pumps to enhance monitoring of ventricular function
Artificial Organs, 2012Co-Authors: Marcus Granegger, Francesco Moscato, Fernando Casas, Georg Wieselthaler, Heinrich SchimaAbstract:: Estimation of instantaneous Flow in rotary blood Pumps (RBPs) is important for monitoring the interaction between heart and Pump and eventually the ventricular function. Our group has reported an algorithm to derive ventricular contractility based on the maximum time derivative (dQ/dt(max) as a substitute for ventricular dP/dt(max) ) and pulsatility of measured Flow signals. However, in RBPs used clinically, Flow is estimated with a bandwidth too low to determine dQ/dt(max) in the case of improving heart function. The aim of this study was to develop a Flow estimator for a centrifugal Pump with bandwidth sufficient to provide noninvasive cardiac diagnostics. The new estimator is based on both static and dynamic properties of the brushless DC motor. An in vitro setup was employed to identify the performance of Pump and motor up to 20 Hz. The algorithm was validated using physiological ventricular and arterial pressure waveforms in a mock loop which simulated different contractilities (dP/dt(max) 600 to 2300 mm Hg/s), Pump speeds (2 to 4 krpm), and fluid viscosities (2 to 4 mPa·s). The mathematically estimated Pump Flow data were then compared to the datasets measured in the mock loop for different variable combinations (Flow ranging from 2.5 to 7 L/min, pulsatility from 3.5 to 6 L/min, dQ/dt(max) from 15 to 60 L/min/s). Transfer function analysis showed that the developed algorithm could estimate the Flow waveform with a bandwidth up to 15 Hz (±2 dB). The mean difference between the estimated and measured average Flows was +0.06 ± 0.31 L/min and for the Flow pulsatilities -0.27 ± 0.2 L/min. Detection of dQ/dt(max) was possible up to a dP/dt(max) level of 2300 mm Hg/s. In conclusion, a Flow estimator with sufficient frequency bandwidth and accuracy to allow determination of changes in ventricular contractility even in the case of improving heart function was developed.
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Evaluation of left ventricular relaxation in rotary blood Pump recipients using the Pump Flow waveform: a simulation study.
Artificial organs, 2011Co-Authors: Francesco Moscato, Marcus Granegger, Georg Wieselthaler, Phornphop Naiyanetr, Heinrich SchimaAbstract:In heart failure, diastolic dysfunction is responsible for about 50% of the cases, with higher prevalence in women and elderly persons and contributing similarly to mortality as systolic dysfunction. Whereas the cardiac systolic diagnostics in ventricular assist device patients from Pump parameters have been investigated by several groups, the diastolic behavior has been barely discussed. This study focuses on the determination of ventricular relaxation during early diastole in rotary blood Pump (RBP) recipients. In conventional cardiology, relaxation is usually evaluated by the minimum rate and the time constant of left ventricular pressure decrease, dP/dt(min) and τ(P) . Two new analogous indices derived from the Pump Flow waveform were investigated in this study: the minimum rate and the time constant of Pump Flow decrease, dQ/dt(min) and τ(Q) . The correspondence between the indices was investigated in a numerical simulation of the assisted circulation for different ventricular relaxation states (τ(P) ranging from 24 to 68 ms) and two RBP models characterized by linear and nonlinear pressure-Flow characteristics. dQ/dt(min) and τ(Q) always correlated with the dP/dt(min) and τ(P) , respectively (r>0.97). These relationships were influenced by the nonlinear Pump characteristics during partial support and by the Pump speed during full support. To minimize these influences, simulation results suggest the evaluation of dQ/dt(min) and τ(Q) at a Pump speed that corresponds to the borderline between partial and full support. In conclusion, at least in simulation, relaxation can be derived from Pump data. This noninvasively accessible information could contribute to a continuous estimation of the remaining cardiac function and its eventual recovery.
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Cardiac Contractility Assessment in Rotary Blood Pump Recipients Derived from Pump Flow
IFMBE Proceedings, 2009Co-Authors: Phornphop Naiyanetr, Francesco Moscato, Georg Wieselthaler, Michael Vollkron, Philipp Zrunek, Heinrich SchimaAbstract:A new cardiac contractility index derived from Pump Flow (IQ) has been developed for rotary blood Pumps (RBPs) recipients, to determine preservation and eventual recovery of the remaining cardiac function. Pulse Flow indices were used for comparison with IQ during Pump speed changes.
Marcus Granegger - One of the best experts on this subject based on the ideXlab platform.
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development of a Pump Flow estimator for rotary blood Pumps to enhance monitoring of ventricular function
Artificial Organs, 2012Co-Authors: Marcus Granegger, Francesco Moscato, Fernando Casas, Georg Wieselthaler, Heinrich SchimaAbstract:: Estimation of instantaneous Flow in rotary blood Pumps (RBPs) is important for monitoring the interaction between heart and Pump and eventually the ventricular function. Our group has reported an algorithm to derive ventricular contractility based on the maximum time derivative (dQ/dt(max) as a substitute for ventricular dP/dt(max) ) and pulsatility of measured Flow signals. However, in RBPs used clinically, Flow is estimated with a bandwidth too low to determine dQ/dt(max) in the case of improving heart function. The aim of this study was to develop a Flow estimator for a centrifugal Pump with bandwidth sufficient to provide noninvasive cardiac diagnostics. The new estimator is based on both static and dynamic properties of the brushless DC motor. An in vitro setup was employed to identify the performance of Pump and motor up to 20 Hz. The algorithm was validated using physiological ventricular and arterial pressure waveforms in a mock loop which simulated different contractilities (dP/dt(max) 600 to 2300 mm Hg/s), Pump speeds (2 to 4 krpm), and fluid viscosities (2 to 4 mPa·s). The mathematically estimated Pump Flow data were then compared to the datasets measured in the mock loop for different variable combinations (Flow ranging from 2.5 to 7 L/min, pulsatility from 3.5 to 6 L/min, dQ/dt(max) from 15 to 60 L/min/s). Transfer function analysis showed that the developed algorithm could estimate the Flow waveform with a bandwidth up to 15 Hz (±2 dB). The mean difference between the estimated and measured average Flows was +0.06 ± 0.31 L/min and for the Flow pulsatilities -0.27 ± 0.2 L/min. Detection of dQ/dt(max) was possible up to a dP/dt(max) level of 2300 mm Hg/s. In conclusion, a Flow estimator with sufficient frequency bandwidth and accuracy to allow determination of changes in ventricular contractility even in the case of improving heart function was developed.
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Evaluation of left ventricular relaxation in rotary blood Pump recipients using the Pump Flow waveform: a simulation study.
Artificial organs, 2011Co-Authors: Francesco Moscato, Marcus Granegger, Georg Wieselthaler, Phornphop Naiyanetr, Heinrich SchimaAbstract:In heart failure, diastolic dysfunction is responsible for about 50% of the cases, with higher prevalence in women and elderly persons and contributing similarly to mortality as systolic dysfunction. Whereas the cardiac systolic diagnostics in ventricular assist device patients from Pump parameters have been investigated by several groups, the diastolic behavior has been barely discussed. This study focuses on the determination of ventricular relaxation during early diastole in rotary blood Pump (RBP) recipients. In conventional cardiology, relaxation is usually evaluated by the minimum rate and the time constant of left ventricular pressure decrease, dP/dt(min) and τ(P) . Two new analogous indices derived from the Pump Flow waveform were investigated in this study: the minimum rate and the time constant of Pump Flow decrease, dQ/dt(min) and τ(Q) . The correspondence between the indices was investigated in a numerical simulation of the assisted circulation for different ventricular relaxation states (τ(P) ranging from 24 to 68 ms) and two RBP models characterized by linear and nonlinear pressure-Flow characteristics. dQ/dt(min) and τ(Q) always correlated with the dP/dt(min) and τ(P) , respectively (r>0.97). These relationships were influenced by the nonlinear Pump characteristics during partial support and by the Pump speed during full support. To minimize these influences, simulation results suggest the evaluation of dQ/dt(min) and τ(Q) at a Pump speed that corresponds to the borderline between partial and full support. In conclusion, at least in simulation, relaxation can be derived from Pump data. This noninvasively accessible information could contribute to a continuous estimation of the remaining cardiac function and its eventual recovery.
