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Rosenbaum AN, Rossman TL, Reddy YN, Villavicencio MA, Stulak JM, Spencer PJ, Kushwaha SS, Behfar A. Pulsatile Pressure Delivery of Continuous-Flow Left Ventricular Assist Devices Is Markedly Reduced Relative to Heart Failure Patients. ASAIO J 2023; 69:445-450. [PMID: 36417497 DOI: 10.1097/mat.0000000000001859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Although continuous-flow left ventricular assist devices (CF-LVADs) provide an augmentation in systemic perfusion, there is a scarcity of in vivo data regarding systemic pulsatility on support. Patients supported on CF-LVAD therapy (n = 71) who underwent combined left/right catheterization ramp study were included. Aortic pulsatility was defined by the pulsatile power index (PPI), which was also calculated in a cohort of high-output heart failure (HOHF, n = 66) and standard HF cohort (n = 44). PPI was drastically lower in CF-LVAD-supported patients with median PPI of 0.006 (interquartile range [IQR], 0.002-0.012) compared with PPI in the HF population at 0.09 (IQR, 0.06-0.17) or HOHF population at 0.25 (IQR, 0.13-0.37; p < 0.0001 among groups). With speed augmentation during ramp, PPI values fell quickly in patients with higher PPI at baseline. PPI correlated poorly with left ventricular ejection fraction (LVEF) in all groups. In CF-LVAD patients, there was a stronger correlation with LV dP/dt (r = 0.41; p = 0.001) than LVEF (r = 0.21; p = 0.08; pint < 0.001). CF-LVAD support is associated with a dramatic reduction in arterial pulsatility as measured by PPI relative to HOHF and HF cohorts and decreases with speed. Further work is needed to determine the applicability to the next generation of device therapy.
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Affiliation(s)
- Andrew N Rosenbaum
- From the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
- William J von Liebig Center for Transplantation and Clinical Regeneration, Mayo Clinic, Rochester, Minnesota
- Van Cleve Cardiac Regenerative Medicine Program, Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota
| | | | - Yogesh N Reddy
- From the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
| | | | - John M Stulak
- Department of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota
| | - Philip J Spencer
- Department of Cardiovascular Surgery, Mayo Clinic, Rochester, Minnesota
| | - Sudhir S Kushwaha
- From the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
- William J von Liebig Center for Transplantation and Clinical Regeneration, Mayo Clinic, Rochester, Minnesota
| | - Atta Behfar
- From the Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
- William J von Liebig Center for Transplantation and Clinical Regeneration, Mayo Clinic, Rochester, Minnesota
- Van Cleve Cardiac Regenerative Medicine Program, Center for Regenerative Medicine, Mayo Clinic, Rochester, Minnesota
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2
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Alizadehghobadi S, Biglari H, Niroomand-Oscuii H, Matin MH. Numerical study of hemodynamics in a complete coronary bypass with venous and arterial grafts and different degrees of stenosis. Comput Methods Biomech Biomed Engin 2020; 24:883-896. [PMID: 33307817 DOI: 10.1080/10255842.2020.1857744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cardiovascular diseases are among the leading causes of death in the world. The coronary blockage is one of most common types of these diseases that in the majority of cases has been treated by bypass surgery. In the bypass surgery, a graft is implemented to alter the blocked coronary and allow the blood supply process. The hemodynamic characteristics of the bypass strongly depend on the geometry and mechanical properties of the graft. In the present study, the fluid-structure interaction (FSI) analysis is conducted to investigate the bypass performance for a thoracic artery as well as a saphenous vein graft. Blood flow introduces a pressure on the walls of the graft which behaves as a hyperelastic material. A complete coronary bypass with stenosis degrees of 70% and 100% is modeled. To consider the nonlinear stress-strain behavior of the grafts, a five parameter Mooney-Rivlin hyperplastic model is implemented for the structural analysis and blood is assumed to behave as a Newtonian fluid. The simulations are performed for a structured grid to solve the governing equations using finite element method (FEM). The results show that wall shear stress (WSS) for saphenous vein is larger than that of thoracic artery while the total deformation of the thoracic artery is larger compared to the saphenous vein. Also, for the venous grafts or lower stenosis degree, the oscillatory shear index (OSI) is higher at both left and right anastomoses meaning that venous grafts as well as lower degree of stenosis are more critical in terms of restenosis.
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Affiliation(s)
| | - Hasan Biglari
- Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran
| | | | - Meisam H Matin
- Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, USA
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Freundlich RE, Kingeter AJ. When Managing Patients with Left Ventricular Assist Devices Undergoing Noncardiac Surgery, Less Is Not More. Anesthesiology 2017; 127:901-902. [PMID: 29040105 DOI: 10.1097/aln.0000000000001852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Capoccia M. Mechanical Circulatory Support for Advanced Heart Failure: Are We about to Witness a New "Gold Standard"? J Cardiovasc Dev Dis 2016; 3:E35. [PMID: 29367578 PMCID: PMC5715724 DOI: 10.3390/jcdd3040035] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2016] [Revised: 12/03/2016] [Accepted: 12/06/2016] [Indexed: 01/08/2023] Open
Abstract
The impact of left ventricular assist devices (LVADs) for the treatment of advanced heart failure has played a significant role as a bridge to transplant and more recently as a long-term solution for non-eligible candidates. Continuous flow left ventricular assist devices (CF-LVADs), based on axial and centrifugal design, are currently the most popular devices in view of their smaller size, increased reliability and higher durability compared to pulsatile flow left ventricular assist devices (PF-LVADs). The trend towards their use is increasing. Therefore, it has become mandatory to understand the physics and the mathematics behind their mode of operation for appropriate device selection and simulation set up. For this purpose, this review covers some of these aspects. Although very successful and technologically advanced, they have been associated with complications such as pump thrombosis, haemolysis, aortic regurgitation, gastro-intestinal bleeding and arterio-venous malformations. There is perception that the reduced arterial pulsatility may be responsible for these complications. A flow modulation control approach is currently being investigated in order to generate pulsatility in rotary blood pumps. Thrombus formation remains the most feared complication that can affect clinical outcome. The development of a preoperative strategy aimed at the reduction of complications and patient-device suitability may be appropriate. Patient-specific modelling based on 3D reconstruction from CT-scan combined with computational fluid dynamic studies is an attractive solution in order to identify potential areas of stagnation or challenging anatomy that could be addressed to achieve the desired outcome. The HeartMate II (axial) and the HeartWare HVAD (centrifugal) rotary blood pumps have been now used worldwide with proven outcome. The HeartMate III (centrifugal) is now emerging as the new promising device with encouraging preliminary results. There are now enough pumps on the market: it is time to focus on the complications in order to achieve the full potential and selling-point of this type of technology for the treatment of the increasing heart failure patient population.
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Affiliation(s)
- Massimo Capoccia
- Scottish National Advanced Heart Failure Service, Golden Jubilee National Hospital, Glasgow G81 4DY, UK.
- Biomedical Engineering, University of Strathclyde, Glasgow G4 0NW, UK.
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Kleinheyer M, Timms DL, Tansley GD, Nestler F, Greatrex NA, Frazier OH, Cohn WE. Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller. Artif Organs 2016; 40:824-33. [DOI: 10.1111/aor.12827] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 07/05/2016] [Accepted: 07/06/2016] [Indexed: 12/25/2022]
Affiliation(s)
- Matthias Kleinheyer
- School of Engineering; Griffith University; Southport Queensland Australia
- Department of Engineering; BiVACOR Inc.; Houston TX USA
| | | | | | - Frank Nestler
- Department of Engineering; BiVACOR Inc.; Houston TX USA
- School of Information Technology and Electrical Engineering; The University of Queensland; St. Lucia, Queensland Australia
| | | | - O. Howard Frazier
- Department of Engineering; BiVACOR Inc.; Houston TX USA
- Department of Cardiovascular Surgery; Texas Heart Institute; Houston TX USA
| | - William E. Cohn
- Department of Engineering; BiVACOR Inc.; Houston TX USA
- Department of Cardiovascular Surgery; Texas Heart Institute; Houston TX USA
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Song Z, Gu K, Gao B, Wan F, Chang Y, Zeng Y. Hemodynamic effects of various support modes of continuous flow LVADs on the cardiovascular system: a numerical study. Med Sci Monit 2014; 20:733-41. [PMID: 24793178 PMCID: PMC4020910 DOI: 10.12659/msm.890824] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background The aim of this study was to determine the hemodynamic effects of various support modes of continuous flow left ventricular assist devices (CF-LVADs) on the cardiovascular system using a numerical cardiovascular system model. Material/Methods Three support modes were selected for controlling the CF-LVAD: constant flow mode, constant speed mode, and constant pressure head mode of CF-LVAD. The CF-LVAD is established between the left ventricular apex and the ascending aorta, and was incorporated into the numerical model. Various parameters were evaluated, including the blood assist index (BAI), the left ventricular external work (LVEW), the energy of blood flow (EBF), pulsatility index (PI), and surplus hemodynamic energy (SHE). Results The results show that the constant flow mode, when compared to the constant speed mode and the constant pressure head mode, increases LVEW by 31% and 14%, and EBF by 21% and 15%, respectively, indicating that this mode achieved the best ventricular unloading among the 3 support modes. As BAI is increased, PI and SHE are gradually decreased, whereas PI of the constant pressure head reaches the maximum value. Conclusions The study demonstrates that the continuous flow control mode of the CF-LVAD may achieve the highest ventricular unloading. In contrast, the constant rotational speed mode permits the optimal blood perfusion. Finally, the constant pressure head strategy, permitting optimal pulsatility, should optimize the vascular function.
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Affiliation(s)
- Zhiming Song
- Department of Cardiac Surgery, Peking University Third Hospital, Beijing, China (mainland)
| | - Kaiyun Gu
- School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland)
| | - Bin Gao
- School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland)
| | - Feng Wan
- Department of Cardiac Surgery, Peking University Third Hospital, Beijing, China (mainland)
| | - Yu Chang
- School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland)
| | - Yi Zeng
- School of Life Science and Bio-Engineering, Beijing University of Technology, Beijing, China (mainland)
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Wever-Pinzon O, Selzman CH, Drakos SG, Saidi A, Stoddard GJ, Gilbert EM, Labedi M, Reid BB, Davis ES, Kfoury AG, Li DY, Stehlik J, Bader F. Pulsatility and the risk of nonsurgical bleeding in patients supported with the continuous-flow left ventricular assist device HeartMate II. Circ Heart Fail 2013; 6:517-26. [PMID: 23479562 DOI: 10.1161/circheartfailure.112.000206] [Citation(s) in RCA: 173] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Bleeding is an important cause of morbidity and mortality in patients with continuous-flow left ventricular assist devices (LVADs). Reduced pulsatility has been implicated as a contributing cause. The aim of this study was to assess the effects of different degrees of pulsatility on the incidence of nonsurgical bleeding. METHODS AND RESULTS The Utah Transplantation Affiliated Hospitals (U.T.A.H.) heart failure and transplant program databases were queried for patients with end-stage heart failure who required support with the continuous-flow LVAD HeartMate II (Thoratec Corp, Pleasanton, CA) between 2004 and 2012. Pulsatility was evaluated by means of the LVAD parameter pulsatility index (PI) and by the echocardiographic assessment of aortic valve opening during the first 3 months of LVAD support. PI was analyzed as a continuous variable and also stratified according to tertiles of all the PI measurements during the study period (low PI: <4.6, intermediate PI: 4.6-5.2, and high PI: >5.2). Major nonsurgical bleeding associated with a decrease in hemoglobin ≥2 g/dL (in the absence of hemolysis) was the primary end point. A total of 134 patients (median age of 60 [interquartile range: 49-68] years, 78% men) were included. Major bleeding occurred in 33 (25%) patients (70% gastrointestinal, 21% epistaxis, 3% genitourinary, and 6% intracranial). In multivariable analysis, PI examined either as a categorical variable, low versus high PI (hazard ratio, 4.06; 95% confidence interval, 1.35-12.21; P=0.04), or as a continuous variable (hazard ratio, 0.60; 95% confidence interval, 0.40-0.92; P=0.02) was associated with an increased risk of bleeding. CONCLUSIONS Reduced pulsatility in patients supported with the continuous-flow LVAD HeartMate II is associated with an increased risk of nonsurgical bleeding, as evaluated by PI.
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Affiliation(s)
- Omar Wever-Pinzon
- Utah Transplantation Affiliated Hospitals, Cardiac Transplant Program, Salt Lake City, UT, USA.
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9
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Lim CH, Yang S, Choi JW, Sun K. Optimizing the Circuit of a Pulsatile Extracorporeal Life Support System in Terms of Energy Equivalent Pressure and Surplus Hemodynamic Energy. Artif Organs 2009; 33:1015-20. [DOI: 10.1111/j.1525-1594.2009.00887.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Jeong GS, Hwang CM, Nam KW, Ahn CB, Kim HC, Lee JJ, Choi J, Son HS, Fang YH, Son KH, Lim CH, Sun K. Development of a closed air loop electropneumatic actuator for driving a pneumatic blood pump. Artif Organs 2009; 33:657-62. [PMID: 19624584 DOI: 10.1111/j.1525-1594.2009.00783.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this study, we developed a small pneumatic actuator that can be used as an extracorporeal biventricular assist device. It incorporated a bellows-transforming mechanism to generate blood-pumping pressure. The cylindrical unit is 88 +/- 0.1 mm high, has a diameter of 150 +/- 0.1 mm, and weighs 2.4 +/- 0.01 kg. In vitro, maximal outflow at the highest pumping rate (PR) exceeded 8 L/min when two 55 mL blood sacs were used under an afterload pressure of 100 mm Hg. At a pumping rate of 100 beats per minute (bpm), maximal hydraulic efficiency was 9.34% when the unit supported a single ventricle and 13.8% when it supported both ventricles. Moreover, pneumatic efficiencies of the actuator were 17.3% and 33.1% for LVAD and BVAD applications, respectively. The energy equivalent pressure was 62.78 approximately 208.10 mm Hg at a PR of 60 approximately 100 bpm, and the maximal value of dP/dt during systole was 1269 mm Hg/s at a PR of 60 bpm and 979 mm Hg/s at a PR of 100 bpm. When the unit was applied to 15 calves, it stably pumped 3 approximately 4 L/min of blood at 60 bpm, and no mechanical malfunction was experienced over 125 days of operation. We conclude that the presently developed pneumatic actuator can be utilized as an extracorporeal biventricular assist device.
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Affiliation(s)
- Gi Seok Jeong
- Department of Biomedical Engineering, College of Medicine, Korea University, Seoul, Korea
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Kaebnick BW, Giridharan GA, Koenig SC. Quantification of Pulsatility as a Function of Vascular Input Impedance: An In Vitro Study. ASAIO J 2007; 53:115-21. [PMID: 17413547 DOI: 10.1097/01.mat.0000250265.69542.80] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The physiological benefits of pulsatility generated by ventricular assist device (VAD) support continue to be heavily debated as application of VAD support has been expanded to include destination and recovery therapies. In this study, the relationship between input impedance (Zart) and vascular pulsatility during continuous flow (CF) or pulsatile flow (PF) VAD support was investigated. Hemodynamic waveforms were recorded at baseline failure and with 50%, 75%, and 100% CF or PF VAD support for nine different Zart test conditions (combination of three different resistance and compliance settings) in a mock circulatory system simulating left ventricular failure. High-fidelity hemodynamic pressure and flow waveforms were recorded to calculate mean arterial pressure (MAP), Zart, energy equivalent pressure (EEP), and surplus hemodynamic energy (SHE) as metrics for quantifying vascular pulsatility. MAP and EEP were elevated with increasing resistance whereas SHE was reduced with increasing compliance. Vascular pulsatility was restored with increasing PF VAD support, but diminished by up to 90% with increasing CF VAD support. The nonpulsatile energy component (MAP) of the pressure waveform is dependent on resistance whereas the pulsatile energy component (SHE) is dependent on compliance. The impact of Zart and vascular pulsatility on patient recovery with VAD support warrants further investigation.
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Affiliation(s)
- Brian W Kaebnick
- Cardiovascular Innovation Institute, Department of Bioengineering, University of Louisville, Louisville, Kentucky, USA
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Kar B, Delgado RM, Radovancevic B, Myers TJ, Wadia Y, Letsou GV, Riaz I, Metcalfe R, Gregoric I, Harting MT. Vascular Thrombosis During Support With Continuous Flow Ventricular Assist Devices: Correlation With Computerized Flow Simulations. ACTA ACUST UNITED AC 2007; 11:182-7. [PMID: 16106119 DOI: 10.1111/j.1527-5299.2005.04474.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Continuous flow pumps are increasingly used to treat severe heart failure. These pumps alter flow physiology by lowering pulsatility in the arterial circulation. In patients with peripheral stenosis, continuous flow pumps may lead to thrombosis of peripheral vessels, possibly predisposing to vascular thrombosis in areas of non-flow-limiting stenosis. The authors performed a computerized flow modeling simulation to analyze the effects of altered hemodynamics in a stenotic area. Drawing on previous clinical experience, we modeled a stenotic area in the common carotid artery. Computerized flow modeling revealed blood stagnation zones with low shear stress and velocity adjacent to the stenotic area during nonpulsatile flow. Such stagnation was not present during pulsatile flow. These results indicate a mechanism by which altered physiologic flow may accelerate occlusion of arterial conduits in patients with preexisting stenosis. This finding may be important for patients with continuous flow devices who have peripheral vascular disease; therefore, further study is warranted.
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Affiliation(s)
- Biswajit Kar
- Cardiopulmonary Transplant Service, Texas Heart Institute, Houston, TX 77030, USA.
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Travis AR, Giridharan GA, Pantalos GM, Dowling RD, Prabhu SD, Slaughter MS, Sobieski M, Undar A, Farrar DJ, Koenig SC. Vascular pulsatility in patients with a pulsatile- or continuous-flow ventricular assist device. J Thorac Cardiovasc Surg 2007; 133:517-24. [PMID: 17258591 DOI: 10.1016/j.jtcvs.2006.09.057] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 07/07/2006] [Accepted: 09/25/2006] [Indexed: 11/21/2022]
Abstract
OBJECTIVE We sought to investigate differences in indices of pulsatility between patients with normal ventricular function and patients with heart failure studied at the time of implantation with continuous-flow or pulsatile-flow left ventricular assist devices. METHODS Eight patients with normal ventricular function and 22 patients with heart failure were studied. A high-fidelity aortic and left ventricular pressure catheter was inserted retrograde through the aortic valve into the left ventricle, and transit-time flow probes were placed on the aorta and device outflow graft. Hemodynamic waveforms were recorded at native heart rate before cardiopulmonary bypass and over a range of device flow rates controlled by adjusting beat rate or rpm. These data were used to calculate vascular input impedance and 2 indices of vascular pulsatility: energy-equivalent pressure and surplus hemodynamic energy. RESULTS At low support levels, pulsatile support restored surplus hemodynamic energy to within 2.5% of normal values, whereas continuous support diminished surplus energy by more than 93%. At high support levels, pulsatile support augmented surplus energy by 49% over normal values, whereas continuous support further diminished surplus energy by 97%. Pulsatile support diminished vascular impedance from baseline failure values, whereas continuous support increased impedance. Vascular impedances at baseline for patients undergoing pulsatile and continuous support and during pulsatile support revealed normal vascular compliance, whereas impedance during continuous support indicated a loss of compliance (or "stiffening") of the vasculature. CONCLUSION These results suggest that selection of device type and flow rate can influence vascular pulsatility and input impedance, which might affect clinical outcomes.
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Affiliation(s)
- Adam R Travis
- Cardiovascular Innovation Institute, University of Louisville, Louisville, Ky 40202, USA
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Ündar A, Rosenberg G, Myers JL. Part 2: Principles of Research on Pulsatile and Nonpulsatile Perfusion. ASAIO J 2005. [DOI: 10.1097/01.mat.0000161941.85873.96] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Thalmann M, Schima H, Wieselthaler G, Wolner E. Physiology of continuous blood flow in recipients of rotary cardiac assist devices. J Heart Lung Transplant 2005; 24:237-45. [PMID: 15737748 DOI: 10.1016/j.healun.2004.04.018] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2003] [Revised: 03/16/2004] [Accepted: 04/05/2004] [Indexed: 11/30/2022] Open
Abstract
The beating heart and the resultant pulse wave have been a symbol of life for centuries. The development history of roller pumps for cardiopulmonary bypass shows that the human body tolerates non-pulsatile blood flow, at least for short-term support. Over the last few years, many types of rotary blood pumps have been developed for clinical use in patients requiring mid- to long-term support. Although early clinical experiences in patients with long-term support have been promising, the matter of whether pulsatile flow is needed or not remains controversial. Therefore, this review summarizes the observed clinical consequences of continuous blood flow in patients supported by rotary blood pumps and relates these consequences to underlying experimental studies.
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Affiliation(s)
- Markus Thalmann
- Department of Cardio-Thoracic Surgery, and LBI for Cardio-Surgical Research, University of Vienna, Vienna, Austria
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Undar A, Zapanta CM, Reibson JD, Souba M, Lukic B, Weiss WJ, Snyder AJ, Kunselman AR, Pierce WS, Rosenberg G, Myers JL. Precise Quantification of Pressure Flow Waveforms of a Pulsatile Ventricular Assist Device. ASAIO J 2005; 51:56-9. [PMID: 15745135 DOI: 10.1097/01.mat.0000150326.51377.a0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Unreliable quantification of flow pulsatility has hampered many efforts to assess the importance of pulsatile perfusion. Generation of pulsatile flow depends upon an energy gradient. It is necessary to quantify pressure flow waveforms in terms of hemodynamic energy levels to make a valid comparison between perfusion modes during chronic support. The objective of this study was to quantify pressure flow waveforms in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) levels in an adult mock loop using a pulsatile ventricle assist system (VAD). A 70 cc Pierce-Donachy pneumatic pulsatile VAD was used with a Penn State adult mock loop. The pump flow rate was kept constant at 5 L/min with pump rates of 70 and 80 bpm and mean aortic pressures (MAP) of 80, 90, and 100 mm Hg, respectively. Pump flows were adjusted by varying the systolic pressure, systolic duration, and the diastolic vacuum of the pneumatic drive unit. The aortic pressure was adjusted by varying the systemic resistance of the mock loop EEP (mm Hg) = (integral of fpdf)/(integral of fdt) SHE (ergs/cm3) = 1,332 [((integral of fpdt)/(integral of fdt))--MAP] were calculated at each experimental stage. The difference between the EEP and the MAP is the extra energy generated by this device. This difference is approximately 10% in a normal human heart. The EEP levels were 88.3 +/- 0.9 mm Hg, 98.1 +/- 1.3 mm Hg, and 107.4 +/- 1.0 mm Hg with a pump rate of 70 bpm and an aortic pressure of 80 mm Hg, 90 mm Hg, and 100 mm Hg, respectively. Surplus hemodynamic energy in terms of ergs/cm3 was 11,039 +/- 1,236 ergs/cm3, 10,839 +/- 1,659 ergs/cm3, and 9,857 +/- 1,289 ergs/cm3, respectively. The percentage change from the mean aortic pressure to EEP was 10.4 +/- 1.2%, 9.0 +/- 1.4%, and 7.4 +/- 1.0% at the same experimental stages. Similar results were obtained when the pump rate was changed from 70 bpm to 80 bpm. The EEP and SHE formulas are adequate to quantify different levels of pulsatility for direct and meaningful comparisons. This particular pulsatile VAD system produces near physiologic hemodynamic energy levels at each experimental stage.
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Affiliation(s)
- Akif Undar
- Department of Pediatrics, Penn State College of Medicine, Penn State Children's Hospital, Penn State Milton S. Hershey Medical Center, 500 University Drive, P.O. Box 850, Hershey, PA 17033-0850, USA
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Shyu JJ, Chou NK, Lee CJ, Chen CF, Shau YW, Wang SS, Chu SH. Acute hemodynamic study of Tai-Ta left ventricular assist device in a canine model. Artif Organs 2004; 28:1095-101. [PMID: 15554938 DOI: 10.1111/j.1525-1594.2004.07314.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A revised Tai-Ta centrifugal impeller pump was designed to study the interaction of the left ventricular assist device (LVAD) with the cardiovascular system in a canine model. Six healthy dogs weighing 12-16 kg were used. Blood flows in the aortic arch, the pulmonary artery (PA), and the LVAD outlet were measured simultaneously with the arterial blood pressure (ABP), the pump outflow pressure (POP), and the electrocardiograph (ECG). Normally, the blood flows in the aorta and the PA started at the S-wave of the ECG. When the LVAD was operated at a higher rotational speed (increased from 2900 to 5400 rpm), the ABP, POP, the pump flow, and the maximum rate of change of PA flow increased. However, the fluctuating amplitudes of ABP, POP, and the pump flow decreased significantly. The cardiovascular hemodynamics change with the pump speeds. For a typical 1.1-1.5 L/min cardiac output in canine, the revised LVAD was able to deliver a flow bypass ratio from 15% up to 100%. The LVAD outflow appeared to be pulsatile and matched the cardiac cycle, showing that the centrifugal impeller pump could be used as a pediatric assist device when cardiac function was impeded.
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Affiliation(s)
- Jeou-Jong Shyu
- Department of Veterinary Medicine, National Taiwan University, Taipei, Taiwan
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18
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Undar A. Myths and Truths of Pulsatile and Nonpulsatile Perfusion During Acute and Chronic Cardiac Support. Artif Organs 2004; 28:439-43. [PMID: 15113337 DOI: 10.1111/j.1525-1594.2004.00086.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Undar A, Fraser CD. Influence of Pulsatile and Nonpulsatile Left Heart Bypass on the Hormonal Circadian Rhythm. ASAIO J 2001; 47:305-7. [PMID: 11374778 DOI: 10.1097/00002480-200105000-00029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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