Impact of Pulsatility and Flow Rates on Hemodynamic Energy Transmission in an Adult Extracorporeal Life Support System

Preclinical Studies on Pulsatile Veno-Arterial Extracorporeal Membrane Oxygenation: A Systematic Review

Refractory cardiogenic shock is increasingly being treated with veno-arterial extracorporeal membrane oxygenation (V-A ECMO), without definitive proof of improved clinical outcomes. Recently, pulsatile V-A ECMO has been developed to address some of the shortcomings of contemporary continuous-flow devices. To describe current pulsatile V-A ECMO studies, we conducted a systematic review of all preclinical studies in this area. We adhered to PRISMA and Cochrane guidelines for conducting systematic reviews. The literature search was performed using Science Direct, Web of Science, Scopus, and PubMed databases. All preclinical experimental studies investigating pulsatile V-A ECMO and published before July 26, 2022 were included. We extracted data relating to the 1) ECMO circuits, 2) pulsatile blood flow conditions, 3) key study outcomes, and 4) other relevant experimental conditions. Forty-five manuscripts of pulsatile V-A ECMO were included in this review detailing 26 in vitro , two in silico , and 17 in vivo experiments. Hemodynamic energy production was the most investigated outcome (69%). A total of 53% of studies used a diagonal pump to achieve pulsatile flow. Most literature on pulsatile V-A ECMO focuses on hemodynamic energy production, whereas its potential clinical effects such as favorable heart and brain function, end-organ microcirculation, and decreased inflammation remain inconclusive and limited.

Ten years of our translational research in the field of veno-arterial extracorporeal membrane oxygenation

Extracorporeal life support is a treatment modality that provides prolonged blood circulation, gas exchange and can substitute functions of heart and lungs to provide urgent cardio-respiratory stabilization in patients with severe but potentially reversible cardiopulmonary failure refractory to conventional therapy. Generally, the therapy targets blood pressure, volume status, and end-organs perfusion. As there are significant differences in hemodynamic efficacy among different percutaneous circulatory support systems, it should be carefully considered when selecting the most appropriate circulatory support for specific medical conditions in individual patients. Despite severe metabolic and hemodynamic deterioration during prolonged cardiac arrest, venoarterial extracorporeal membrane oxygenation (VA ECMO) can rapidly revert otherwise fatal prognosis, thus carrying a potential for improvement in survival rate, which can be even improved by introduction of mild therapeutic hypothermia. In order to allow a rapid transfer of knowledge to clinical medicine two porcine models were developed for studying efficiency of the VA ECMO in treatments of acute cardiogenic shock and progressive chronic heart failure. These models allowed also an intensive research of adverse events accompanying a clinical use of VA ECMO and their possible compensations. The results indicated that in order to weaken the negative effects of increased afterload on the left ventricular function the optimal VA ECMO flow in cardiogenic shock should be as low as possible to allow adequate tissue perfusion. The left ventricle can be also unloaded by an ECG-synchronized pulsatile flow if using a novel pulsatile ECMO system. Thus, pulsatility of VA ECMO flow may improve coronary perfusion even under conditions of high ECMO blood flows. And last but not least, also the percutaneous balloon atrial septostomy is a very perspective method how to passively decompress overloaded left heart.

Development of a Pulsatile Flow-Generating Circulatory Assist Device (K-Beat) For Use with Veno-Arterial Extracorporeal Membrane Oxygenation in a Pig Model Study

Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) preserves the life of heart failure patients by providing an adequate oxygen supply and blood flow to vital organs. For patients with severe cardiogenic shock secondary to acute myocardial infarction or acute myocarditis, V-A ECMO is commonly used as the first choice among cardiac circulatory support devices. While V-A ECMO generates circulatory flow using a centrifugal pump, the provision of pulsatile flow is difficult. We previously reported our development of a new circulatory flow assist device (K-beat) for cardiac management with pulsatile flow. To obtain more efficient pulsatile assist flow (diastolic augmentation), an electrocardiogram (ECG)-analyzing device that can detect R waves and T waves increases the assist flow selectively in the diastole phase by controlling (opening and closing) the magnetic valve of the tamper. Here, we describe the first use of the K-beat on a large animal in combination with a clinical device. In addition, the diastolic augmentation effect of the K-beat as a circulatory flow assist device was examined in a pig V-A ECMO model. The K-beat was stopped every 60 minutes for a period of a few minutes, and blood pressure waveforms in the pulsatile and non-pulsatile phases were checked. This experiment showed that stable V-A ECMO could be achieved and that hemodynamics were managed in all animals. The pulsatile flow was provided in synchrony with the ECG in all cases. A diastolic augmentation waveform of femoral arterial pressure was confirmed in the pulsatile phase. K-beat could be useful in patients with severe heart failure.

Utilization of Percutaneous Mechanical Circulatory Support Devices in Cardiogenic Shock Complicating Acute Myocardial Infarction and High-Risk Percutaneous Coronary Interventions

Given the tremendous progress in interventional cardiology over the last decade, a growing number of older patients, who have more comorbidities and more complex coronary artery disease, are being considered for technically challenging and high-risk percutaneous coronary interventions (PCI). The success of performing such complex PCI is increasingly dependent on the availability and improvement of mechanical circulatory support (MCS) devices, which aim to provide hemodynamic support and left ventricular (LV) unloading to enable safe and successful coronary revascularization. MCS as an adjunct to high-risk PCI may, therefore, be an important component for improvement in clinical outcomes. MCS devices in this setting can be used for two main clinical conditions: patients who present with cardiogenic shock complicating acute myocardial infarction (AMI) and those undergoing technically complex and high-risk PCI without having overt cardiogenic shock. The current article reviews the advancement in the use of various devices in both AMI complicated by cardiogenic shock and complex high-risk PCI, highlights the available hemodynamic and clinical data associated with the use of MCS devices, and presents suggestive management strategies focusing on appropriate patient selection and optimal timing and support to potentially increase the clinical benefit from utilizing these devices during PCI in this high-risk group of patients.

Effects of Pulsatile Control Algorithms for Diagonal Pump on Hemodynamic Performance and Hemolysis

The objective of this study is to compare hemodynamic performances under different pulsatile control algorithms between Medos DeltaStream DP3 and i-cor diagonal pumps in simulated pediatric and adult ECLS systems. An additional pilot study was designed to test hemolysis using two pumps during 12h-ECLS. The experimental circuit consisted of parallel combined pediatric and adult ECLS circuits using an i-cor pump head and either an i-cor console or Medos DeltaStream MDC console, a Medos Hilite 2400 LT oxygenator for the pediatric ECLS circuit, and a Medos Hilite 7000 LT oxygenator for the adult ECLS circuit. The circuit was primed with lactated Ringer's solution and human packed red blood cells (hematocrit 40%). Trials were conducted at various flow rates (pediatric circuit: 0.5 and 1L/min; adult circuit: 2 and 4L/min) under nonpulsatile and pulsatile modes (pulsatile amplitude: 1000-5000rpm [1000 rpm increments] for i-cor pump, 500-2500rpm [500 rpm increments] for Medos pump) at 36°C. In an additional protocol, fresh whole blood was used to test hemolysis under nonpulsatile and pulsatile modes using the two pump systems in adult ECLS circuits. Under pulsatile mode, energy equivalent pressures (EEP) were always greater than mean pressures for the two systems. Total hemodynamic energy (THE) and surplus hemodynamic energy (SHE) levels delivered to the patient increased with increasing pulsatile amplitude and decreased with increasing flow rate. The i-cor pump outperformed at low flow rates, but the Medos pump performed superiorly at high flow rates. There was no significant difference between two pumps in percentage of THE loss. The plasma free hemoglobin level was always higher in the Medos DP3 pulsatile group at 4 L/min compared to others. Pulsatile control algorithms of Medos and i-cor consoles had great effects on pulsatility. Although high pulsatile amplitudes delivered higher levels of hemodynamic energy to the patient, the high rotational speeds increased the risk of hemolysis. Use of proper pulsatile amplitude settings and intermittent pulsatile mode are suggested to achieve better pulsatility and decrease the risk of hemolysis. Further optimized pulsatile control algorithms are needed.

In Vitro Hemodynamic Evaluation of an Adult Pulsatile Extracorporeal Membrane Oxygenation System

The objective of this study was to evaluate a pulsatile extracorporeal membrane oxygenation (ECMO) system in terms of hemodynamic energy generation and transmission under various pulsatile amplitudes, flow rates, and pseudopatient pressures in a simulated adult ECMO circuit. Surplus hemodynamic energy (SHE), a measure of the quality of pulsatility, was used to quantify pulsatile flow. The circuit consisted of an i-cor diagonal pump, an adult XLung oxygenator, a 21 Fr Medtronic Biomedicus femoral arterial cannula, a 23/25 Fr Sorin RAP femoral venous cannula, and 3/8 in ID tubing for both arterial and venous lines. The circuit was primed with lactated Ringer's solution and then packed red blood cells (hematocrit 37%). Trials were conducted at 36°C with flow rates of 2-5 L/min (1 L/min increments) under nonpulsatile and pulsatile mode with pulsatile amplitudes of 1000-5000 rpm (1000 rpm increments). The pseudopatient pressure was maintained at 40-100 mm Hg (20 mm Hg increments). Real-time pressure and flow data were recorded for analysis using a custom-made data acquisition system. There was no SHE generated by the pump under nonpulsatile mode. Under pulsatile mode, SHE levels increased with increasing pulsatile amplitude and pseudopatient pressure (P < 0.01) but decreased with increasing flow rate. SHE levels were significantly higher at flow rates of 2-4 L/min. In addition, the XLung oxygenator had acceptable pressure drops (36.1-104.9 mm Hg) and percentages of total hemodynamic energy loss (19.6-43.9%) during all trials. The novel pulsatile ECMO system can create nonpulsatile and pulsatile flow in an adult ECMO model. However, pulsatility gradually weakened with increasing flow rates. Pulsatile amplitude settings were found to have a great impact on pulsatility.

In Vitro Hemodynamic Evaluation of ECG-Synchronized Pulsatile Flow Using i-Cor Pump as Short-Term Cardiac Assist Device for Neonatal and Pediatric Population

The objective of this study was to assess the hemodynamic properties of the i-cor ECG-synchronized cardiac assist system for off-label use as a short-term cardiac assist device for neonatal and pediatric patients and compare nonpulsatile to pulsatile flow with different amplitudes. The circuit consisted of the i-cor diagonal pump with 3 feet of ¼ inch arterial and venous tubing and a soft-shell reservoir, primed with lactated Ringer's solution and human packed red blood cells (hematocrit 42%). Trials were conducted with three different sets of cannulas (8-Fr arterial 10-Fr venous, 10-Fr arterial 12 Fr-venous, and 12-Fr arterial 14-Fr venous) with increasing flow rates at varying pseudo-patient pressures (40, 60, 80, and 100 mm Hg) and under nonpulsatile mode and pulsatile mode with pulsatile amplitudes 2000, 2500, and 3000 rpm at 36°C. Pressure and flow waveforms were recorded using a custom-made data acquisition device for each trial. Energy equivalent pressure (EEP) was higher than mean pressure under pulsatile mode, and increased with increasing pseudo-patient's pressure and flow rate while EEP was the same as the mean pressure under nonpulsatile mode. Total hemodynamic energy (THE) levels increased with pressure and pulsatile amplitude and slightly decreased with increasing flow rate. The percent THE lost throughout the circuit increased with flow rate and pulsatile amplitude and decreased with pseudo-patient's pressure. SHE levels also increased with pseudo-patient pressure and pulsatile amplitude and decreased with increasing flow rate. The i-cor diagonal pump can be used as a short term cardiac assist device for neonatal and pediatric patients and is able to provide nonpulsatile as well as pulsatile flow. Compared with nonpulsatile flow, pulsatile flow can generate and deliver more hemodynamic energy to the patients.

Electrocardiogram-synchronized pulsatile extracorporeal life support preserves left ventricular function and coronary flow in a porcine model of cardiogenic shock

Introduction

Veno-arterial extracorporeal life support (ECLS) is increasingly being used to treat rapidly progressing or severe cardiogenic shock. However, it has been repeatedly shown that increased afterload associated with ECLS significantly diminishes left ventricular (LV) performance. The objective of the present study was to compare LV function and coronary flow during standard continuous-flow ECLS support and electrocardiogram (ECG)-synchronized pulsatile ECLS flow in a porcine model of cardiogenic shock.

Methods

Sixteen female swine (mean body weight 45 kg) underwent ECLS implantation under general anesthesia and artificial ventilation. Subsequently, acute cardiogenic shock, with documented signs of tissue hypoperfusion, was induced by initiating global myocardial hypoxia. Hemodynamic cardiac performance variables and coronary flow were then measured at different rates of continuous or pulsatile ECLS flow (ranging from 1 L/min to 4 L/min) using arterial and venous catheters, a pulmonary artery catheter, an LV pressure-volume loop catheter, and a Doppler coronary guide-wire.

Results

Myocardial hypoxia resulted in declines in mean cardiac output to 1.7±0.7 L/min, systolic blood pressure to 64±22 mmHg, and LV ejection fraction (LVEF) to 22±7%. Synchronized pulsatile flow was associated with a significant reduction in LV end-systolic volume by 6.2 mL (6.7%), an increase in LV stroke volume by 5.0 mL (17.4%), higher LVEF by 4.5% (18.8% relative), cardiac output by 0.37 L/min (17.1%), and mean arterial pressure by 3.0 mmHg (5.5%) when compared with continuous ECLS flow at all ECLS flow rates (P<0.05). At selected ECLS flow rates, pulsatile flow also reduced LV end-diastolic pressure, end-diastolic volume, and systolic pressure. ECG-synchronized pulsatile flow was also associated with significantly increased (7% to 22%) coronary flow at all ECLS flow rates.

Conclusion

ECG-synchronized pulsatile ECLS flow preserved LV function and coronary flow compared with standard continuous-flow ECLS in a porcine model of cardiogenic shock.

Impact of Different Perfusion Modalities on Coronary and Carotid Blood Flow Velocities in an Adult ECLS Swine Model

The objective of this study was to compare the effects of nonpulsatile and ECG-synchronized pulsatile extracorporeal life support on coronary and carotid blood flow velocities using transthoracic echocardiography and vascular ultrasound, respectively. Nine adult swine were randomly separated into nonpulsatile (NP, n = 5) and pulsatile (P, N = 4) groups and placed on ECLS for 24 h using an i-cor ECLS system. Noninvasive transthoracic images of the left and right coronary artery and the left carotid artery were acquired at the pre-ECLS (baseline), 30 min, 3, 6, 9, 12, and 24 h on-ECLS stages. The mean diastolic velocity of the left and right coronary arteries in the NP group significantly decreased after 24 h on ECLS compared to the baseline and 30 min ECLS stages (P < 0.05). There was no statistical difference in the mean diastolic velocity of the coronary arteries in the P group at 30 min, 3-, 6-, 9-, 12-, and 24-h ECLS compared to baseline. The P group showed a smaller decrease in the mean diastolic velocity of coronary arteries between the 30-min ECLS and 3-, 6-, 9-, 13-, 24-h ECLS stages compared to the NP group. The diastolic velocity of the left carotid artery in the NP group significantly decreased during 24-h ECLS compared to the P group (P < 0.05). An ECG-synchronized pulsatile ECLS system appeared to maintain coronary and carotid artery diastolic velocities better than conventional nonpulsatile ECLS. Further investigation of the perfusion modes during ECLS is warranted.

Renal haemodynamics and oxygenation during and after cardiac surgery and cardiopulmonary bypass

Acute kidney injury (AKI) is a common complication following cardiac surgery performed on cardiopulmonary bypass (CPB) and has important implications for prognosis. The aetiology of cardiac surgery-associated AKI is complex, but renal hypoxia, particularly in the medulla, is thought to play at least some role. There is strong evidence from studies in experimental animals, clinical observations and computational models that medullary ischaemia and hypoxia occur during CPB. There are no validated methods to monitor or improve renal oxygenation during CPB, and thus possibly decrease the risk of AKI. Attempts to reduce the incidence of AKI by early transfusion to ameliorate intra-operative anaemia, refinement of protocols for cooling and rewarming on bypass, optimization of pump flow and arterial pressure, or the use of pulsatile flow, have not been successful to date. This may in part reflect the complexity of renal oxygenation, which may limit the effectiveness of individual interventions. We propose a multi-disciplinary pathway for translation comprising three components. Firstly, large-animal models of CPB to continuously monitor both whole kidney and regional kidney perfusion and oxygenation. Secondly, computational models to obtain information that can be used to interpret the data and develop rational interventions. Thirdly, clinically feasible non-invasive methods to continuously monitor renal oxygenation in the operating theatre and to identify patients at risk of AKI. In this review, we outline the recent progress on each of these fronts.

In Vitro Evaluation of ECG-Synchronized Pulsatile Flow Using the i-cor Diagonal Pump in Neonatal and Pediatric ECLS Systems

The objective was to assess the i-cor electrocardiogram-synchronized diagonal pump in terms of hemodynamic energy properties for off-label use in neonatal and pediatric extracorporeal life support (ECLS) circuits. The neonatal circuit consisted of an i-cor pump and console, a Medos Hilite 800 LT oxygenator, an 8Fr arterial cannula, a 10Fr venous cannula, 91 cm of 0.6-cm ID arterial tubing, and 91 cm of 0.6-cm ID venous tubing. The pediatric circuit was identical except it included a 12Fr arterial cannula, a 14Fr venous cannula, and a Medos Hilite 2400 LT oxygenator. Neonatal trials were conducted at 36°C with hematocrit 40% using varying flow rates (200-600 mL/min, 200 mL increments) and postarterial cannula pressures (40-100 mm Hg, 20 mm Hg increments) under nonpulsatile mode and pulsatile mode with various pulsatile amplitudes (1000-4000 rpm, 1000 rpm increments). Pediatric trials were conducted at different flow rates (800-1600 mL/min, 400 mL/min increments). Mean pressure and energy equivalent pressure increased with increasing postarterial cannula pressure, flow rate, and pulsatile amplitude. Physiologic-like pulsatility was achieved between pulsatile amplitudes of 2000-3000 rpm. Pressure drops were greatest across the arterial cannula. Pulsatile flow generated significantly higher total hemodynamic energy (THE) levels than nonpulsatile flow. THE levels at postarterial cannula site increased with increasing postarterial cannula pressure, pulsatile amplitude, and flow rate. No surplus hemodynamic energy (SHE) was generated under nonpulsatile mode. Under pulsatile mode, preoxygenator SHE increased with increasing postarterial cannula pressure and pulsatile amplitude, but decreased with increasing flow rate. The i-cor system can provide nonpulsatile and pulsatile flow for neonatal and pediatric ECLS. Pulsatile amplitudes of 2000-3000 rpm are recommended for use in neonatal and pediatric patients.

Evaluation of Combined Extracorporeal Life Support and Continuous Renal Replacement Therapy on Hemodynamic Performance and Gaseous Microemboli Handling Ability in a Simulated Neonatal ECLS System

The objective of this study was to evaluate the hemodynamic performance and gaseous microemboli (GME) handling ability of a simulated neonatal extracorporeal life support (ECLS) circuit with an in-line continuous renal replacement therapy (CRRT) device. The circuit consisted of a Maquet RotaFlow centrifugal pump or HL20 roller pump, Quadrox-iD Pediatric diffusion membrane oxygenator, 8-Fr arterial cannula, 10-Fr venous cannula, and Better-Bladder (BB) with "Y" connector. A second Quadrox-I Adult oxygenator was added postarterial cannula for GME experiments. The circuit and pseudo-patient were primed with lactated Ringer's solution and packed human red blood cells (hematocrit 40%). All hemodynamic trials were conducted at ECLS flow rates ranging from 200 to 600 mL/min and CRRT flow rate of 75 mL/min at 36°C. Real-time pressure and flow data were recorded with a data acquisition system and GME were detected and characterized using the Emboli Detection and Classification Quantifier System. CRRT was added at distinct locations such that blood entered CRRT between the pump and oxygenator (A), recirculated through the pump (B), or bypassed the pump (C). With the centrifugal pump, all CRRT positions had similar flow rates, mean arterial pressure (MAP), and total hemodynamic energy (THE) loss. With the roller pump, C demonstrated increased flow rates (293.2-686.4 mL/min) and increased MAP (59.4-75.5 mm Hg) (P < 0.01); B had decreased flow rates (129.7-529.7 mL/min), and MAP (34.2-45.0 mm Hg) (P < 0.01); A maintained the same when compared to without CRRT. At 600 mL/min C lost more THE (81.4%) (P < 0.01) with a larger pressure drop across the oxygenator (95.6 mm Hg) (P < 0.01) than without CRRT (78.3%; 49.1 mm Hg) (P < 0.01). C also demonstrated a poorer GME handling ability using the roller pump, with 87.1% volume and 17.8% count reduction across the circuit, compared to A and B with 99.9% volume and 65.8-72.3% count reduction. These findings suggest that, in contrast to A and B, adding CRRT at position C is unsafe and not advised for clinical use.

Artificial Organs 2015: A Year in Review

In this Editor's Review, articles published in 2015 are organized by category and briefly summarized. We aim to provide a brief reflection of the currently available worldwide knowledge that is intended to advance and better human life while providing insight for continued application of technologies and methods of organ Replacement, Recovery, and Regeneration. As the official journal of The International Federation for Artificial Organs, The International Faculty for Artificial Organs, the International Society for Rotary Blood Pumps, the International Society for Pediatric Mechanical Cardiopulmonary Support, and the Vienna International Workshop on Functional Electrical Stimulation, Artificial Organs continues in the original mission of its founders "to foster communications in the field of artificial organs on an international level." Artificial Organs continues to publish developments and clinical applications of artificial organ technologies in this broad and expanding field of organ Replacement, Recovery, and Regeneration from all over the world. We take this time also to express our gratitude to our authors for providing their work to this journal. We offer our very special thanks to our reviewers who give so generously of their time and expertise to review, critique, and especially provide meaningful suggestions to the author's work whether eventually accepted or rejected. Without these excellent and dedicated reviewers, the quality expected from such a journal could not be possible. We also express our special thanks to our Publisher, John Wiley & Sons for their expert attention and support in the production and marketing of Artificial Organs. We look forward to reporting further advances in the coming years.

[Importance of mechanical assist devices in acute circulatory arrest]

Mechanical assist devices are indicated for hemodynamic stabilization in acute circulatory arrest if conventional means of cardiopulmonary resuscitation are unable to re-establish adequate organ perfusion. Their temporary use facilitates further diagnostic and therapeutic options in selected patients, e.g. coronary angiography followed by revascularization.External thorax compression devices allow sufficient cardiac massage in case of preclinical or in-hospital circulatory arrest, especially under complex transfer conditions. These devices perform standardized thorax compressions at a rate of 80-100 per minute. Invasive mechanical support devices are used in the catheter laboratory or in the intensive care unit. Axial turbine pumps, e.g. the Impella, continuously pump blood from the left ventricle into the aortic root. The Impella can also provide right ventricle support by pumping blood from the vena cava into the pulmonary artery. So-called emergency systems or ECMO devices consist of a centrifugal pump and a membrane oxygenator allowing complete takeover of cardiac and pulmonary functions. Withdrawing blood from the right atrium and vena cava, oxygenated blood is returned to the abdominal aorta. Isolated centrifugal pumps provide left heart support without an oxygenator after transseptal insertion of a venous cannula into the left atrium.Mechanical assist devices are indicated for acute organ protection and hemodynamic stabilization for diagnostic and therapeutic measures as well as bridge to myocardial recovery. Future technical developments and better insights into the pathophysiology of mechanical circulatory support will broaden the spectrum of indications of such devices in acute circulatory arrest.