Pulsatile Venoarterial Perfusion Using a Novel Synchronized Cardiac Assist Device Augments Coronary Artery Blood Flow During Ventricular Fibrillation

Extracorporeal cardiopulmonary resuscitation: a comparison of two experimental approaches and systematic review of experimental models

BACKGROUND

In patients requiring extracorporeal cardiopulmonary resuscitation (ECPR), there is a need for studies to assess the potential benefits of therapeutic interventions to improve survival and reduce hypoxic-ischemic brain injuries. However, conducting human studies may be challenging. This study aimed to describe two experimental models developed in our laboratory and to conduct a systematic review of existing animal models of ECPR reported in the literature.

RESULTS

In our experiments, pigs were subjected to 12 min (model 1) or 5 min (model 2) of untreated ventricular fibrillation, followed by 18 min (model 1) or 25 min (model 2) of conventional cardiopulmonary resuscitation. Results showed severe distributive shock, decreased brain oxygen pressure and increased intracranial pressure, with model 1 displaying more pronounced brain perfusion impairment. A systematic review of 52 studies, mostly conducted on pigs, revealed heterogeneity in cardiac arrest induction methods, cardiopulmonary resuscitation strategies, and evaluated outcomes.

CONCLUSIONS

This review emphasizes the significant impact of no-flow and low-flow durations on brain injury severity following ECPR. However, the diversity in experimental models hinders direct comparisons, urging the standardization of ECPR models to enhance consistency and comparability across studies.

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.

Efficacy and safety of ECG-synchronized pulsatile extracorporeal membrane oxygenation in the clinical setting: The SynCor Trial

INTRODUCTION

Mechanical circulatory support (MCS) devices are increasingly used as a treatment option in resuscitation or in patients with cardiogenic shock (CS). Prophylactic implantation in high-risk percutaneous coronary interventions (HRPCI) is another upcoming indication. The i-cor ECG-synchronized cardiac assist device combines the hemodynamic support of a veno-arterial extracorporeal membrane oxygenation (VA-ECMO) with the ability to generate a pulsatile flow and thus decreasing adverse effects of VA-ECMO on myocardial function. Aim of this study was to obtain data concerning feasibility, safety and outcomes in both indications.

METHODS

A total of 47 patients (34 HRPCI, 13 CS) were included in nine German centers and participated in this study. Demographic and clinical parameters, procedural as well as follow-up data were prospectively recorded and analyzed.

RESULTS

Device implantation and initiation of ECG-synchronized cardiac assist was technical successful in all cases and no failures of the consoles or disposable parts were observed. Furthermore, intended percutaneous coronary interventions and successful weaning from cardiac assist was achieved in 97.1% of HRPCI patients. We observed a 30d-survival of 94.1% in the HRPCI group and 69.2% in the CS group. Main complications in both groups were bleeding events (14.7% HRPCI, 23.1% CS) and critical limb ischemia (2.9% HRPCI, 38.5% CS).

CONCLUSION

The i-cor ECG-synchronized cardiac assist device appears safe and feasible showing clinical outcomes comparable to existing data in the setting of high-risk percutaneous coronary interventions and acute cardiogenic shock. Further prospective trials are warranted to identify optimal patient and interventional characteristics that will benefit most of this novel kind of mechanical circulatory support.

The Pulsatile Modification Improves Hemodynamics and Attenuates Inflammatory Responses in Extracorporeal Membrane Oxygenation

Background

COVID-19 is still a worldwide pandemic and extracorporeal membrane oxygenation (ECMO) is vital for extremely critical COVID-19 patients. Pulsatile flow impacts greatly on organ function and microcirculation, however, the effects of pulsatile flow on hemodynamics and inflammatory responses during ECMO are unknown. An in vivo study was launched aiming at comparing the two perfusion modes in ECMO.

Methods

Fourteen beagles were randomly allocated into two groups: the pulsatile group (n=7) and the non-pulsatile group (n=7). ECMO was conducted using the i-Cor system for 24 hours. Hemodynamic parameters including surplus hemodynamic energy (SHE), energy equivalent pressure (EEP), oxygenator pressure drop (OPD), and circuit pressure drop (CPD) were monitored. To assess inflammatory responses during ECMO, levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8, and transforming growth factor-β1 (TGF-β1) were measured.

Results

EEP and SHE were markedly higher in pulsatile circuits when compared with the conventional circuits. Between-group differences in both OPD and CPD reached statistical significance. Significant decreases in TNF-α were seen in animals treated with pulsatile flows at 2 hours, 12 hours, and 24 hours as well as a decrease in IL-1β at 24 hours during ECMO. The TGF-β1 levels were significantly higher in pulsatile circuits from 2 hours to 24 hours. The changes in IL-6 and IL-8 levels were insignificant.

Conclusion

The modification of pulsatility in ECMO generates more hemodynamic energies and attenuates inflammatory responses as compared to the conventional non-pulsatile ECMO.

Hemodynamic adaptation of heart failure to percutaneous venoarterial extracorporeal circulatory supports

Extracorporeal life support (ECLS) is a treatment modality that provides prolonged blood circulation, gas exchange and can partially support or fully substitute functions of heart and lungs in patients with severe but potentially reversible cardiopulmonary failure refractory to conventional therapy. Due to high-volume bypass, the extracorporeal flow is interacting with native cardiac output. The pathophysiology of circulation and ECLS support reveals significant effects on arterial pressure waveforms, cardiac hemodynamics, and myocardial perfusion. Moreover, it is still subject of research, whether increasing stroke work caused by the extracorporeal flow is accompanied by adequate myocardial oxygen supply. The left ventricular (LV) pressure-volume mechanics are reflecting perfusion and loading conditions and these changes are dependent on the degree of the extracorporeal blood flow. By increasing the afterload, artificial circulation puts higher demands on heart work with increasing myocardial oxygen consumption. Further, this can lead to LV distention, pulmonary edema, and progression of heart failure. Multiple methods of LV decompression (atrial septostomy, active venting, intra-aortic balloon pump, pulsatility of flow) have been suggested to relieve LV overload but the main risk factors still remain unclear. In this context, it has been recommended to keep the rate of circulatory support as low as possible. Also, utilization of detailed hemodynamic monitoring has been suggested in order to avoid possible harm from excessive extracorporeal flow.

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.

Impact of Heart Rate on Pulsatile Hemodynamic Performance in a Neonatal ECG-Synchronized ECLS System

The experimental circuit consisted of an i-cor diagonal pump, a Medos Hilite 800 LT oxygenator, an 8Fr Biomedicus arterial cannula, a 10Fr Biomedicus venous cannula, and six feet of 1/4 in ID tubing for arterial and venous lines. The circuit was primed with lactated Ringer's solution and packed red blood cells (hematocrit 40%). Trials were conducted at various heart rates (90, 120, and 150 bpm) and flow rates (200, 400, and 600mL/min) under nonpulsatile and pulsatile mode with pulsatile amplitudes of 1000-4000rpm (1000 rpm increments). Real-time pressure and flow data were recorded for analysis. The i-cor pump was capable of creating nonpulsatile and electrocardiography (ECG)-synchronized pulsatile flow, and automatically reducing pulsatile frequency by increasing the assist ratio at higher heart rates. Reduced pulsatile frequency led to lower hemodynamic energy generation but did not affect circuit pressure drop. Pulsatile flow delivered more hemodynamic energy to the pseudopatient when compared with nonpulsatile flow. The pump generated more hemodynamic energy with higher pulsatile amplitudes. The i-cor pump can automatically adjust the pulsatile assist ratio to create pulsatile flow at higher heart rates, although this caused some hemodynamic energy loss. Compared with nonpulsatile flow, pulsatile flow generated and transferred more hemodynamic energy to the neonate during ECLS (200-600mL/min), especially at high pulsatile amplitudes and low flow rates.

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.

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.

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.

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.

Effect of the Pulsatile Extracorporeal Membrane Oxygenation on Hemodynamic Energy and Systemic Microcirculation in a Piglet Model of Acute Cardiac Failure

The objective of this study was to compare the effects of pulsatile and nonpulsatile extracorporeal membrane oxygenation (ECMO) on hemodynamic energy and systemic microcirculation in an acute cardiac failure model in piglets. Fourteen piglets with a mean body weight of 6.08 ± 0.86 kg were divided into pulsatile (N = 7) and nonpulsatile (N = 7) ECMO groups. The experimental ECMO circuit consisted of a centrifugal pump, a membrane oxygenator, and a pneumatic pulsatile flow generator system developed in-house. Nonpulsatile ECMO was initiated at a flow rate of 140 mL/kg/min for the first 30 min with normal heart beating, with rectal temperature maintained at 36°C. Ventricular fibrillation was then induced with a 3.5-V alternating current to generate a cardiac dysfunction model. Using this model, we collected the data on pulsatile and nonpulsatile groups. The piglets were weaned off ECMO at the end of the experiment (180 min after ECMO was initiated). The animals did not receive blood transfusions, inotropic drugs, or vasoactive drugs. Blood samples were collected to measure hemoglobin, methemoglobin, blood gases, electrolytes, and lactic acid levels. Hemodynamic energy was calculated using the Shepard's energy equivalent pressure. Near-infrared spectroscopy was used to monitor brain and kidney perfusion. The pulsatile ECMO group had a higher atrial pressure (systolic and mean), and significantly higher regional saturation at the brain level, than the nonpulsatile group (for both, P < 0.05). Additionally, the pulsatile ECMO group had higher methemoglobin levels within the normal range than the nonpulsatile group. Our study demonstrated that pulsatile ECMO produces significantly higher hemodynamic energy and improves systemic microcirculation, compared with nonpulsatile ECMO in acute cardiac failure.