Human, Bovine and Porcine Systematic Vascular Input Impedances Are Not Equivalent: Implications for Device Testing and Xenotransplantation in Heart Failure

Koenig, Steven C.; Giridharan, Guruprasad A.; Ewart, Daniel L.; Schroeder, Mark J.; Ionan, Constantine; Slaughter, Mark S.; Sobieski, Michael A.; Pantalos, George M.; Dowling, Robert D.; Prabhu, Sumanth D.

doi:10.1016/j.healun.2008.08.009

Cited by 17 publications

(11 citation statements)

References 29 publications

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“…However, the increase in ΔP′ with asynchronous modulation was greater in the mock flow loop model (53 mm Hg) than the IHF bovine model (32 mm Hg), which may have been due to effects from anesthesia and/or a much higher aortic compliance (calf). 27 These pilot animal experiments demonstrate feasibility of asynchronous pump speed modulation with CF LVAD for generating vascular pulsatility and variation in ventricular volume, which warrant further investigation.…”

Section: Discussionmentioning

confidence: 80%

Feasibility of Pump Speed Modulation for Restoring Vascular Pulsatility with Rotary Blood Pumps

Ising¹,

Sobieski²,

Slaughter³

et al. 2015

ASAIO Journal

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Continuous flow (CF) left ventricular assist devices (LVAD) diminish vascular pressure pulsatility, which may be associated with clinically reported adverse events including gastrointestinal bleeding, aortic valve insufficiency, and hemorrhagic stroke. Three candidate CF LVAD pump speed modulation algorithms designed to augment aortic pulsatility were evaluated in mock flow loop and ischemic heart failure (IHF) bovine models by quantifying hemodynamic performance as a function of mean pump speed, modulation amplitude, and timing. Asynchronous and synchronous copulsation (high revolutions per minute [RPM] during systole, low RPM during diastole) and counterpulsation (low RPM during systole, high RPM during diastole) algorithms were tested for defined modulation amplitudes (±300, ±500, ±800, and ±1,100 RPM) and frequencies (18.75, 37.5, and 60 cycles/minute) at low (2,900 RPM) and high (3,200 RPM) mean LVAD speeds. In the mock flow loop model, asynchronous, synchronous copulsation, and synchronous counterpulsation algorithms each increased pulse pressure (ΔP = 931%, 210%, and 98% and reduced left ventricular external work (LVEW = 20%, 22%, 16%). Similar improvements in vascular pulsatility (1,142%) and LVEW (40%) were observed in the IHF bovine model. Asynchronous modulation produces the largest vascular pulsatility with the advantage of not requiring sensor(s) for timing pump speed modulation, facilitating potential clinical implementation.

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Section: Discussionmentioning

confidence: 80%

Feasibility of Pump Speed Modulation for Restoring Vascular Pulsatility with Rotary Blood Pumps

Ising¹,

Sobieski²,

Slaughter³

et al. 2015

ASAIO Journal

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“…17 Similarly, animal models have significantly different aortic and arterial compliance values than humans. 18 These altered compliance values would lead to an inaccurate estimation of aortic pressure pulsatility. Further, in vitro mock circulation systems typically underestimate the reduction in left ventricular peak pressures due to pneumatic/hydraulic drivers, which may lead to inaccurate estimation of LVEW.…”

Section: Discussionmentioning

confidence: 99%

Flow Modulation Algorithms for Continuous Flow Left Ventricular Assist Devices to Increase Vascular Pulsatility: A Computer Simulation Study

Ising

Warren

Sobieski

et al. 2011

Cardiovasc Eng Tech

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Continuous flow (CF) left ventricular assist devices (LVAD) support diminishes vascular pressure pulsatility. Despite its recent clinical success CF LVAD support has been associated with a higher incidence of gastrointestinal bleeding, aortic valve dysfunction and hemorrhagic strokes. To overcome this limitation, we are developing algorithms to provide vascular pulsatility using a CF LVAD. The effects of timing and synchronizing the CF LVAD flow modulation to the native myocardium, modulation amplitude, and modulation widths were studied on the native ventricle and vasculature using a computer simulation model of the circulatory system simulating heart failure. A total of over 150 combinations of varying pulse widths, beat frequencies, time shifts, and amplitudes to modulate CF LVAD flow were tested. All control algorithms maintained a mean CF LVAD flow of 5.0 ± 0.1 L/min (full support) or 2.5 ± 0.1 L/min (partial support). These algorithms resulted in an increased arterial pressure pulsatility of up to 59 mmHg, reduced left ventricular external work (LVEW) by 10-75%, and increased myocardial perfusion by up to 44% from baseline heart failure condition. Importantly, reduction in LVEW and increase in pulsatility may be adjusted to userdefined values while maintaining the same average CF LVAD flow rate. These methods of CF LVAD flow modulation may enable tailored unloading of the native ventricle to provide rest and rehabilitation (maximal unloading to rest followed by gradual reloading to wean), which may promote sustainable myocardial recovery. Further, these LVAD flow modulation patterns may reduce the incidence of adverse events associated with the CF LVAD therapy by increasing vascular pulsatility.

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“…First, counterpulsation therapy is most effective when the displaced blood volume and ventricular stroke volume are comparable and aortic compliance is low (29). This study was performed in calves (80 kg) which have a substantially higher cardiac output (calf: 8-12 L/min vs. human: 4-6 L/min), stroke volume (calf: 100-120 mL, human: 35-50 mL), and greater arterial compliance than humans (30). As a result, the potential improvement in hemodynamics during CPD support in a human may actually be more pronounced than was observed in this study.…”

Section: Limitationsmentioning

confidence: 99%

A Novel Subcutaneous Counterpulsation Device: Acute Hemodynamic Efficacy During Pharmacologically Induced Hypertension, Hypotension, and Heart Failure

et al. 2010

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The miniaturization of mechanical assist devices and less invasive implantation techniques may lead to earlier intervention in patients with heart failure. As such, we evaluated the effectiveness of a novel, minimally invasive, implantable counterpulsation device (CPD) in augmenting cardiac function during impaired hemodynamics. We compared the efficacy of a 32-mL stroke volume CPD with a standard 40-mL intra-aortic balloon pump (IABP) over a range of clinically relevant pathophysiological conditions. Male calves were instrumented via thoracotomy, the CPD was anastomosed to the left carotid artery, and the IABP was positioned in the descending aorta. Hemodynamic conditions of hypertension, hypotension, and heart failure were pharmacologically simulated and data were recorded during CPD and IABP support (off, 1:2, 1:1 modes) for each condition. In all three pathophysiological conditions, the CPD and IABP produced similar and statistically significant (P < 0.05) increases in coronary artery blood flow normalized to the left ventricular (LV) workload. During hypotension and heart failure conditions, however, the CPD produced significantly greater reductions in LV workload and myocardial oxygen consumption as compared with the IABP. A novel 32-mL CPD connected to a peripheral artery produced equivalent or greater hemodynamic benefits than a standard 40-mL IABP during pharmacologically induced hypertension, hypotension, and heart failure conditions.

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Human, Bovine and Porcine Systematic Vascular Input Impedances Are Not Equivalent: Implications for Device Testing and Xenotransplantation in Heart Failure

Cited by 17 publications

References 29 publications

Feasibility of Pump Speed Modulation for Restoring Vascular Pulsatility with Rotary Blood Pumps

Feasibility of Pump Speed Modulation for Restoring Vascular Pulsatility with Rotary Blood Pumps

Flow Modulation Algorithms for Continuous Flow Left Ventricular Assist Devices to Increase Vascular Pulsatility: A Computer Simulation Study

A Novel Subcutaneous Counterpulsation Device: Acute Hemodynamic Efficacy During Pharmacologically Induced Hypertension, Hypotension, and Heart Failure

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