George M Pantalos

George M Pantalos
University of Louisville | UL · Department of Surgery

About

160
Publications
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1,594
Citations

Publications

Publications (160)
Article
Evidence is accumulating that blood flow patterns in the cardiovascular system and in cardiovascular devices do, in some instances, depend on blood viscoelasticity. Thus, to better understand the challenges to providing circulatory support and surgical therapies for pediatric and adult patients, viscous and elastic components of complex blood visco...
Technical Report
Surgical capabilities in human space flight, whether on a space-based platform in low Earth orbit or on a long duration planetary exploration mission, will be challenging to conduct. Some may be ameliorated by training, technology, and pre-flight planning. Early space missions did not have any surgical capability. It was not until the Skylab missio...
Article
Full-text available
The intra-aortic balloon pump (IABP) provides circulatory support through counterpulsation. The hemodynamic effects of the IABP may vary with assisting frequency and depend on IAB inflation/deflation timing. We aimed to assess in vivo the IABP benefits on coronary, aortic, and left ventricular hemodynamics at different assistance frequencies and tr...
Article
Counterpulsation with an intra-aortic balloon pump (IABP) has not achieved the same success or clinical use in pediatric patients as in adults. In a pediatric animal model, IABP efficacy was investigated to determine whether IABP timing with a high-fidelity blood pressure signal may improve counterpulsation therapy versus a low-fidelity signal. In...
Article
Despite progress with adult ventricular assist devices, limited options exist to support pediatric patients with life-threatening heart disease. Extracorporeal membrane oxygenation remains the clinical standard. To characterize (patho)physiologic responses to different modes of mechanical unloading of the failing pediatric heart, extracorporeal mem...
Article
Full-text available
The PediBooster external cardiac compression device is a minimally invasive, non-blood contacting Biventricular Assist Device (BiVAD) intended for pediatric use. It is being developed as a palliative therapy for acute Postcardiotomy Shock (PCS). The PediBooster extracardiac wrap is pneumatically actuated to circumferentially compress the heart, pro...
Article
The purpose of this study is to determine the pumping performance of Revision 7 of the Ension pediatric cardiopulmonary assist system (pCAS) when used with cannulae for venoarterial (VA) or venovenous (VV) extracorporeal membrane oxygenation (ECMO). It was hypothesized that the pCAS could deliver flow rates within recommended ranges needed to provi...
Article
Extracorporeal membrane oxygenation (ECMO) is often used to provide cardiopulmonary support for infants experiencing severe levels of cardiac or respiratory failure. In patients with two ventricles and no intra-atrial communication, ECMO is often complicated by limited venous return to the circuit and marked left atrial hypertension. This condition...
Article
The objective of this clinical study was to quantify the incidence and magnitude of intraaortic balloon pump (IABP) inflation and deflation landmark discrepancies associated with the IABP catheter arterial pressure waveform. Cardiac surgery patients with an IABP inserted prior to surgery were recruited. Following cardiac exposure, a high-fidelity p...
Article
Full-text available
During intraaortic balloon inflation, blood volume is displaced toward the heart (V(tip)), traveling retrograde in the descending aorta, passing by the arch vessels, reaching the aortic root (V(root)), and eventually perfusing the coronary circulation (V(cor)). V(cor) leads to coronary flow augmentation, one of the main benefits of the intraaortic...
Article
A mock circulation system has been developed to approximate key anatomic features and simulate the pressures and flows of an infant. Pulsatile flow is generated by 10 cc pulsatile ventricles (Utah infant ventricular assist device). Systemic vasculature is mimicked through the use of 3/8" ID bypass tubing with two flexible reservoirs to provide comp...
Article
Full-text available
An explanation of the mechanisms leading to the beneficial hemodynamic effects of the intra-aortic balloon pump (IABP) is lacking. We hypothesized that inflation and deflation of the balloon would generate a compression (BCW) and an expansion (BEW) wave, respectively, which, when analyzed with wave intensity analysis, could be used to explain the h...
Article
In the last 40 years, mechanical circulatory support devices have become an effective option for the treatment of end-stage heart failure in adults. Few possibilities, however, are available for pediatric cardiopulmonary support. Ension Inc. (Pittsburgh, PA) is developing a pediatric cardiopulmonary assist system (pCAS) intended to address the limi...
Article
Direct measurement of blood flow output has been incorporated into ventricular assist devices (VADs), but long-term reliability of the additional device components has raised concerns regarding sensor drift and failure. As an alternative approach, the HeartMate II axial VAD (Thoratec Corp, Pleasanton, CA) estimates device flow output from power con...
Article
Advanced therapies for heart failure (HF), such as mechanical circulatory support (MCS) devices and xenotransplantation, are usually tested in bovine and porcine models. This approach assumes a priori that animal (patho)physiology will closely match that of humans. Systemic aortic input impedance (Z(ART)) is an important physiologic determinant of...
Article
Pediatric mechanical circulatory devices are currently being developed by several programs. Along with the engineering and testing challenges to be considered is the regulatory process which will be used to review applications to the Food and Drug Administration (FDA) to initiate clinical trials with these devices. This paper considers the appropri...
Article
The acute hemodynamic efficacy of an implantable counterpulsation device (CPD) was evaluated. The CPD is a valveless single port, 32-ml stroke volume blood chamber designed to be connected to the human axillary artery using a simple surface surgical procedure. Blood is drawn into the pump during systole and ejected during diastole. The acute hemody...
Article
For a mechanical heart valve, a strong spike in pressure during closing is associated with valve wear and erythrocyte damage; thus, for valid in vitro testing, the mock circulation system should replicate the conditions, including pressure spikes, expected in vivo. To address this issue, a study was performed to investigate how mock circulation inp...
Conference Paper
Motivated by questions related to flow in pediatric cardiovascular devices, the purpose of this study was to compare pediatric and adult complex viscoelasticity η* = ηV − iηE, where ηV and ηE are viscous and elastic components, respectively, measured in oscillatory flow in a capillary tube [Thurston 1972]. For normal blood, viscosity is increased a...
Article
Pediatric ventricular assist devices are being developed that can produce pulsatile flow (PF) or continuous flow (CF). An important aspect of choosing between these two modes is understanding the consequences of each mode on pediatric vascular pulsatility. Differences in vascular pulsatility generated by PF and CF operation of the 3-inch pediatric...
Article
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. Eight patients with normal ventricular function and 22 patients with heart failure were studied....
Article
The intra-aortic balloon pump has been widely and successfully used as a treatment for cardiac dysfunction, but it only has short-term applications. To overcome this limitation, a superficial counterpulsation device (CPD) is being developed to provide extended counterpulsation support to promote myocardial recovery. The CPD is a valveless, monoport...
Article
An abstract is unavailable. This article is available as HTML full text and PDF.
Article
Lumped parameter computer models of the pediatric circulatory systems for 1- and 4-year-olds were developed to predict hemodynamic responses to mechanical circulatory support devices. Model parameters, including resistance, compliance and volume, were adjusted to match hemodynamic pressure and flow waveforms, pressure-volume loops, percent systole,...
Article
A volume-displacement counterpulsation device (CPD) intended for chronic implantation via a superficial surgical approach is proposed. The CPD is a pneumatically driven sac that fills during native heart systole and empties during diastole through a single, valveless cannula anastomosed to the subclavian artery. Computer simulation was performed to...
Article
Echocardiographic measurements of astronaut cardiac function have documented an initial increase, followed by a progressive reduction in both left ventricular end-diastolic volume index and stroke volume with entry into microgravity (micro-G). The investigators hypothesize that the observed reduction in cardiac filling may, in part, be due to the a...
Article
Although continuous flow (CF) and pulsatile flow (PF) ventricular assist devices (VADs) are being clinically used, their effects on aortic blood flow, as a measure of overall blood distribution, remain unclear. In acute VAD support animal experiments, our group has described a zone of turbulent mixing in the aortic arch. The objective of this study...
Conference Paper
Full-text available
Rotary blood pumps (RBP) are currently being used as a bridge to transplantation as well as for myocardial recovery and destination therapy for patients with heart failure. Physiologic control systems for RBP that can automatically and autonomously adjust the pump flow to match the physiologic requirement of the patient while avoiding suction for v...
Article
Experiments were performed to test the hypothesis that viscoelastic properties of the swine myocardium are independent of heart rate (HR), preload (PL), and afterload (AL). Left ventricular pressure and aortic flow (AoF) waveforms were recorded in 13 swine. At different paced heart rates, an inferior vena caval occlusion (IVC) was used to reduce PL...
Article
Although continuous flow (CFVAD) and pulsatile (PVAD) ventricular assist devices (VADs) are being clinically used, their effects upon aortic blood flow as a measure of overall blood distribution remain unclear. The objective of this study was to compare the effects of CFVAD and PVAD support for ascending (AscA) and descending (DA) aorta outflow can...
Article
Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. In a few cases, patients have been successfully weaned from these devices after myocardial recovery. To promote myocardial recovery and alleviate the demand for donor organs...
Article
In seeking approval from the US Food and Drug Administration (FDA) for clinical trial evaluation of an experimental medical device, a sponsor is required to submit experimental findings and support documentation to demonstrate device safety and efficacy that are in compliance with Good Laboratory Practices (GLP). The objective of this project was t...
Article
Alternative therapies for treating heart failure patients are being explored to provide effective options for patients with progressive heart failure. Cardiac assist devices that promote myocardial recovery may be a potential solution. Ventricular assist devices (VAD) have demonstrated long-term efficacy and intraaortic balloon pumps (IABP) have sh...
Article
Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. An artificial vasculature device (AVD) that may better facilitate myocardial recovery than VAD by controlling the afterload seen by the ejecting heart is being developed. Th...
Article
This study investigated the hemodynamic and left ventricular (LV) pressure-volume loop responses to continuous versus pulsatile assist techniques at 50% and 100% bypass flow rates during simulated ventricular pathophysiologic states (normal, failing, recovery) with Starling response behavior in an adult mock circulation. The rationale for this appr...
Article
A need exists for a mock circulation that behaves in a physiologic manner for testing cardiac devices in normal and pathologic states. To address this need, an integrated mock cardiovascular system consisting of an atrium, ventricle, and systemic and coronary vasculature was developed specifically for testing ventricular assist devices (VADs). This...
Article
The aim of this study was to evaluate the function of the AbioCor artificial heart implanted in calves that underwent treadmill exercise testing and to investigate the cardiovascular and metabolic responses during exercise. Six calves were implanted with the AbioCor. One week after surgery, exercise training was undertaken and animals were put on a...
Article
Rotary blood pumps (RBPs) are currently being used as a bridge to transplantation as well as for myocardial recovery and destination therapy for patients with heart failure. Physiologic control systems for RBPs that can automatically and autonomously adjust the pump flow to match the physiologic requirement of the patient are needed to reduce human...
Article
Rotary blood pumps (RBPs) are currently being used as a bridge to transplantation as well as for myocardial recovery and destination therapy for patients with heart failure. Physiologic control systems for RBPs that can automatically and autonomously adjust the pump flow to match the physiologic requirement of the patient are needed to reduce human...
Article
Full-text available
This article presents an integrated model of the human circulatory system that incorporates circulatory support by a brushless DC axial flow ventricular assist device (VAD), and a feedback VAD controller designed to maintain physiologically sufficient perfusion. The developed integrated model combines a network type model of the circulatory system...
Article
Full-text available
A numerical model of the cardiovascular system was used to quantify the influences on cardiac function of intrathoracic pressure and intravascular and intraventricular hydrostatic pressure, which are fundamental biomechanical stimuli for orthostatic response. The model included a detailed arterial circulation with lumped parameter models of the atr...
Conference Paper
A need exists for a mock ventricle and vasculature that behaves in a physiological manner for testing cardiac devices in normal pathologic states. To this end, an integrated mock cardiovascular system consisting of a mock atrium, mock ventricle, and mock systemic and coronary vasculature was developed specifically for testing ventricular assist dev...
Article
OBJECTIVES: To evaluate the effect of aortic compliance on pediatric intra-aortic balloon pumping (IABP). DESIGN: In vitro study using a mechanical model of the pediatric left heart circulation. SETTING: Cardiovascular fluid dynamics research laboratory. SUBJECT: Pulsatile flow system simulating the pediatric left heart circulation and two differen...
Article
Objectives: To evaluate the effect of aortic compliance on pediatric intra-aortic balloon pumping (IABP). Design: In vitro study using a mechanical model of the pediatric left heart circulation. Setting: Cardiovascular fluid dynamics research laboratory. Subject: Pulsatile flow system simulating the pediatric left heart circulation and two differen...
Article
Full-text available
Flow and pressure measurements were performed in the ascending aortas of six pediatric patients ranging in age from 1 to 4 yr and in weight from 7.2 to 16.4 kg. From these measurements, input impedance was calculated. It was found that total vascular resistance decreased with increasing patient weight and was approximately one to three times higher...
Article
With increasing durations of left ventricular assist device (LVAD) support, patients are pursuing greater levels of independence. To improve quality of life, we have introduced a selective approach to allow patients to drive. We have developed a protocol to test a patient's ability to enact emergency procedures within two minutes following LVAD mal...
Article
The TCI VE HeartMate LVAD (Woburn, MA) supports a variety of individuals, each unique by virtue of age, strength, size, sex and body shape. The standard approaches for managing the patient's wearable LVAD accessories (controller, batteries, etc.) are not always desirable, effective or even possible. Patients supported by the TCI VE LVAD were survey...
Article
Continuous flow blood pumps with magnetically suspended rotors have been under consideration for almost 2 decades. In this paper, a description is given of progress toward meeting the full potential of magnetic suspension in a left ventricular assist device. By combining creative system integration with innovative component design, the HeartQuest L...
Article
Two clinical goals for recipients of left ventricular assist systems (LVAS) are independence and a better quality of life. The ability to travel, including commercial airline travel, is a vital part of these goals. Patients implanted with an LVAS (Thermo Cardiosystems VE HeartMate) have recently initiated regional and transcontinental travel that h...
Article
The need to remove an implanted left ventricular assist device (LVAD) in the event of recovery of LV function or device malfunction prompted the development of a plug for the LV apical insertion site. The plug is intended to be left in place following LVAD removal or be removed for easy uptake cannula re-insertion in the event that long-term left v...
Article
The response of total artificial hearts (TAH) to changes in recipient posture needs to be characterized and considered for automatic control intervention. Observations of cardiac output (CO) were periodically made in a recipient of a pneumatic TAH (C-70, CardioWest) during maneuvers that altered alignment to the gravitational vector. After starting...
Article
A cardiovascular model incorporating variable elastance ventricles, finite difference model of major systemic arteries and lumped parameter representations of systemic veins and pulmonary system was developed to study cardiovascular response to gravity. Results were obtained in supine, launch, sitting and standing postures for influences of intrath...
Article
Input impedance was calculated from flow and pressure waveforms recorded from the ascending aortas of six pediatric patients ranging in age from 1 to 4 years and weight from 7.2 to 6.4 kg. Impedance curve fits were compared for two four-element lumped parameter models and the three-element modified Windkessel model. The results suggested that Rp de...
Article
Orbital measurements of the cardiac function of Space Shuttle crew members have shown an initial increase in cardiac stroke volume upon entry into weightlessness, followed by a gradual reduction in stroke volume to a level approximately 15% less than preflight values. In an effort to explain this response, it was hypothesized that gravity plays a r...