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

In Silico Analysis of Pulsatile Flow Veno-Arterial Extracorporeal Membrane Oxygenation on Human Aorta Model

Electrocardiogram (ECG)-synchronized pulsatile veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is a recent development in extracorporeal therapy for patients with severe cardiogenic shock. Although preclinical studies have shown benefits of pulsatile flow relative to continuous ECMO flow, none have explored the effects of the timing of ECMO pulses with respect to the cardiac cycle and its possible implications on ECMO complications. This study aimed to develop a computational fluid dynamics (CFD) model of V-A ECMO in a patient-specific human aorta and evaluate the effect of ECMO timing on cardiac unloading, surplus hemodynamic energy delivery, and mixing zone position. Using direct flow measurements from cardiogenic shock patients and an ECMO device, the model revealed that maximal left ventricular (LV) unloading occurred when the ECMO pulse was in early diastole (35-40% from LV peak systolic flow). Maximum surplus hemodynamic energy transmission to aortic branches occurred at 20% from LV peak systolic flow. This indicates a trade-off between heart afterload and hemodynamic energy delivery in selecting ECMO pulse timing. The mixing zone was primarily located in the aortic arch across timing configurations. Therefore, selecting ECMO pulse timing is crucial to maximizing the benefits of pulsatile flow in V-A ECMO treatment.

Evaluation of extra-corporeal membrane oxygenator cannulae in pulsatile and non-pulsatile pediatric mock circuits

BACKGROUND

This study evaluated the hemodynamic performance of arterial and venous cannulae in a compliant pediatric extracorporeal membrane oxygenation (ECMO) mock circuit in pulsatile and non-pulsatile flow conditions.

METHODS

The ECMO setup consisted of an oxygenator, diagonal pump, and standardized-length arterial/venous tubing with pressure transducers. A validated left-heart mock loop was adapted to simulate pediatric conditions. The pulsatile flow was driven by a computer-controlled piston pump set at 120 bpm. A roller pump was used for non-pulsatile conditions. The circuit was primed with 40% glycerol-based solution. The cardiac output was set to 1 L/min and the aortic pressure to 40-50 mmHg. Four arterial cannulae (8Fr, 10Fr, 12Fr, 14Fr) and five venous cannulae (12Fr, 14Fr, 16Fr, 18Fr, 20Fr) (Medtronic, Inc., Minneapolis, MN, USA) were tested at increasing flow rate in 12 combinations.

RESULTS

The pulsatile condition required lower ECMO pump speeds for all cannulae combinations at a given flow rate, inducing a significantly smaller increase of flow in the mock loop. Under non-pulsatile conditions, the aortic and arterial pressures in the cannulae were higher (p < 0.01) while no significant differences in pressure drop and pressure-flow characteristics (M-number) were observed. The total hemodynamic energy was higher in case of non-pulsatile flow (p < 0.01).

CONCLUSION

Under non-pulsatile conditions, the system was characterized by overall higher pressures, resulting in higher support to the patient. The consequent increase of potential energy compensates for increases of kinetic energy, leading to a higher total hemodynamic energy. Pressure gradients and M number are independent of the testing conditions. Pulsatile testing conditions led to more physiological testing conditions, and it is recommended for ECMO testing.

Numerical Simulation of Fluid-Structure Interaction in Axillary Artery Venoarterial Extracorporeal Membrane Oxygenation for Heart Failure Patients

Although axillary artery venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been utilized as a mechanical circulatory support for patients with end-stage heart failure (HF), there is currently insufficient evidence to support its effectiveness and safety. The objective of this study was to analyze the hemodynamic effects of axillary artery VA-ECMO. To this end, we obtained CT angiographic imaging data of the aorta from a carefully selected heart failure patient with a cardiac output of 2.1 L/min. These data were used to construct a detailed fluid-structure interaction model of the aorta. Axillary artery VA-ECMO was then simulated within this model, maintaining a constant flow rate of 3 L/min. The intra-aortic balloon counterpulsation (IABP) balloon was simulated to inflate and deflate in synchrony with the diastolic and systolic phases of the cardiac cycle. Hemodynamic effects, including left ventricular (LV) pressure afterload, vessel wall stress, perfusion of vital organs, blood flow pulsatility, and the watershed region, were calculated using fluid-structure interaction analysis. We found that axillary artery VA-ECMO delivers well-distributed, oxygen-rich blood flow but may increase left ventricular (LV) afterload and reduce cerebral blood flow. However, when combined with IABP, it unloads LV pressure and increases cerebral blood flow. Integrating axillary artery VA-ECMO with IABP can promote cardiac function recovery and improve oxygen-rich blood perfusion to the vital organs of heart failure patients.

The effect of intra-aortic balloon pump on survival and neurological outcome in patients treated with extracorporeal cardiopulmonary resuscitation: A meta-analysis and systematic review

INTRODUCTION

Extracorporeal cardiopulmonary resuscitation (ECPR) is increasingly used to treat refractory cardiac arrest, although with variable results in survival and neurological outcomes. The intra-aortic balloon pump (IABP) showed mixed effects on survival in veno-arterial extracorporeal membrane oxygenation. Furthermore, the impact of IABP on survival and neurological outcomes in ECPR recipients has yet to be fully investigated.

METHODS

We searched relevant databases for studies concerning ECPR recipients and intra-aortic balloon pump with information on survival and neurological outcomes. The inverse variance method (95 % confidence intervals) was used to determine the odds ratios of outcomes. We decided on a priori use of the random-effects model with the Hartung-Knapp adjustment.

RESULTS

We included in our analysis nine cohort studies dealing with a total of 4994 patients. The association of IABP with ECPR was associated with a survival benefit compared to ECPR alone: 1029/3124 (32.9 %) patients survived in the ECPR+IABP group versus 379/1870 (20.2 %) in the ECPR group, OR 1.94, 95 % CI [1.36 to 2.77]. Survival with good neurological outcome was analyzed in 4 studies for 4018 patients. The association of ECPR and IABP was associated with a not significant advantage in survival with favorable neurological outcome compared with ECPR alone: 555/2687 (20.7 %) patients with good neurological outcome in the group of ECPR+IABP versus 149/1331 (11.2 %) patients in the group of ECPR, OR 1.33, 95 % CI [0.61 to 2.92].

CONCLUSIONS

The association of IABP and ECPR significantly increases survival rates compared to ECPR alone. Nevertheless, the impact on favorable neurological outcomes remains uncertain.

Preclinical Proof-of-Concept of a Minimally Invasive Direct Cardiac Compression Device for Pediatric Heart Support

PURPOSE

For pediatric patients, extracorporeal membrane oxygenation (ECMO) remains the predominant mechanical circulatory support (MCS) modality for heart failure (HF) although survival to discharge rates remain between 50 and 60% for these patients. The device-blood interface and disruption of physiologic hemodynamics are significant contributors to poor outcomes.

METHODS

In this study, we evaluate the preclinical feasibility of a minimally invasive, non-blood-contacting pediatric DCC prototype for temporary MCS. Proof-of-concept is demonstrated in vivo in an animal model of HF. Hemodynamic pressures and flows were examined.

RESULTS

Minimally invasive deployment on the beating heart was successful without cardiopulmonary bypass or anticoagulation. During HF, device operation resulted in an immediate 43% increase in cardiac output while maintaining pulsatile hemodynamics. Compared to the pre-HF baseline, the device recovered up to 95% of ventricular stroke volume. At the conclusion of the study, the device was easily removed from the beating heart.

CONCLUSIONS

This preclinical proof-of-concept study demonstrated the feasibility of a DCC device on a pediatric scale that is minimally invasive and non-blood contacting, with promising hemodynamic support and durability for the initial intended duration of use. The ability of DCC to maintain pulsatile MCS without blood contact represents an opportunity to mitigate the mortality and morbidity observed in non-pulsatile, blood-contacting MCS.

Generation of Pulsatile Flow using Clinical Continuous Flow Pumps

Background

With the increasing use of mechanical circulatory support for long-term augmentation of cardiopulmonary function, the need for safer devices is apparent. Pump thrombosis and failure, inadequate ventricular unloading, progressive right-sided dysfunction, and end-organ hypoperfusion are seen with long-term mechanical circulatory support devices. Generation of pulsatile flow has been proposed to mitigate some of these risks by providing physiologic flow and pressure profiles to the vascular system and end-organs. Modification of continuous flow devices to provide pulsatility may prove a cheap and effective way to achieve physiologic flow; however, effective use of such a technique has yet to be demonstrated. This work aims to describe these efforts, as well as mechanical arguments regarding the challenges to be overcome in achieving this goal.

Methods

Prior literature and textbooks were used to develop the theoretical basis for the paper.

Results

Attempts at generating pulsatile flow with continuous flow devices have been marred by difficulty in mitigating viscous effects on oscillating mechanical systems. Currently available devices and research setups have been unable to generate truly physiologic pulsatile flow systems. New devices are needed that utilize various forms of positive displacement in order to generate true pulsatile flow that mimic native waveforms generated by the heart.

Conclusions

The mechanical challenges in generating pulsatile flow with continuous flow devices have precluded their widespread adoption in clinical practice. New pulsatile pumps are needed to achieve adequate physiologic pulsatility with improved side-effect profile.

Pneumatic driven pulsatile ECMO in vitro evaluation with oxygen tanks

Extracorporeal membrane oxygenation device is a procedure in which mechanical systems circulate blood and supply oxygen to patients with impaired cardiopulmonary function. Current venoarterial systems are associated with low patient survival rates and new treatments are needed to avoid left ventricular dilation, which is a major cause of death. In this study, a new mobile pulsatile ECMO with a pump structure that supplies pulsatile flow by using an oxygen tank as a power source is proposed. In vitro experiments conducted under mock circulation system as like patient conditions demonstrated that 2.8 L oxygen can sustain the outflow of 1 L/min of pulsatile blood flow for 53 min, while a 4.6 L tank was able to sustain the same flow for 85 min. The energy equivalent pressure evaluation index of the pulsatile blood pump shows that the mobile pulsatile ECMO could supply sufficient pulsatile blood flow compared to the existing pulsatile ECMO. Through in vitro experiments performed under mock circulation conditions, this new system was proven to supply sufficient oxygen and pulsatile blood flow using the pressure of an oxygen tank even while transporting a patient.

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.

Hemodynamic Effect of Pulsatile on Blood Flow Distribution with VA ECMO: A Numerical Study

The pulsatile properties of arterial flow and pressure have been thought to be important. Nevertheless, a gap still exists in the hemodynamic effect of pulsatile flow in improving blood flow distribution of veno-arterial extracorporeal membrane oxygenation (VA ECMO) supported by the circulatory system. The finite-element models, consisting of the aorta, VA ECMO, and intra-aortic balloon pump (IABP) are proposed for fluid-structure interaction calculation of the mechanical response. Group A is cardiogenic shock with 1.5 L/min of cardiac output. Group B is cardiogenic shock with VA ECMO. Group C is added to IABP based on Group B. The sum of the blood flow of cardiac output and VA ECMO remains constant at 4.5 L/min in Group B and Group C. With the recovery of the left ventricular, the flow of VA ECMO declines, and the effective blood of IABP increases. IABP plays the function of balancing blood flow between left arteria femoralis and right arteria femoralis compared with VA ECMO only. The difference of the equivalent energy pressure (dEEP) is crossed at 2.0 L/min to 1.5 L/min of VA ECMO. PPI’ (the revised pulse pressure index) with IABP is twice as much as without IABP. The intersection with two opposing blood generates the region of the aortic arch for the VA ECMO (Group B). In contrast to the VA ECMO, the blood intersection appears from the descending aorta to the renal artery with VA ECMO and IABP. The maximum time-averaged wall shear stress (TAWSS) of the renal artery is a significant difference with or not IABP (VA ECMO: 2.02 vs. 1.98 vs. 2.37 vs. 2.61 vs. 2.86 Pa; VA ECMO and IABP: 8.02 vs. 6.99 vs. 6.62 vs. 6.30 vs. 5.83 Pa). In conclusion, with the recovery of the left ventricle, the flow of VA ECMO declines and the effective blood of IABP increases. The difference between the equivalent energy pressure (EEP) and the surplus hemodynamic energy (SHE) indicates the loss of pulsation from the left ventricular to VA ECMO. 2.0 L/min to 1.5 L/min of VA ECMO showing a similar hemodynamic energy loss with the weak influence of IABP.

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.

Brain injury in extracorporeal cardiopulmonary resuscitation: translational to clinical research

The addition of extracorporeal membrane oxygenation (ECMO) to conventional cardiopulmonary resuscitation (CPR), termed extracorporeal cardiopulmonary resuscitation (ECPR), has significantly improved survival in selected patient populations. Despite this advancement, significant neurological impairment persists in approximately half of survivors. ECPR represents a potential advancement for patients who experience refractory cardiac arrest (CA) due to a reversible etiology and do not regain spontaneous circulation. Important risk factors for acute brain injury (ABI) in ECPR include lack of perfusion, reperfusion, and altered cerebral autoregulation. The initial hypoxic-ischemic injury caused by no-flow and low-flow states after CA and during CPR is compounded by reperfusion, hyperoxia during ECMO support, and nonpulsatile blood flow. Additionally, ECPR patients are at risk for Harlequin syndrome with peripheral cannulation, which can lead to preferential perfusion of cerebral vessels with deoxygenated blood. Lastly, the oxygenator membrane is prothrombotic and requires systemic anticoagulation. The two competing phenomena result in thrombus formation, hemolysis, and thrombocytopenia, increasing the risk of ischemic and hemorrhagic ABI. In addition to clinical studies, we assessed available ECPR animal models to identify the mechanisms underlying ABI at the cellular level. Standardized multimodal neurological monitoring may facilitate early detection of and intervention for ABI. With the increasing use of ECPR, it is critical to understand the pathophysiology of ABI, its prevention, and the management strategies for improving the outcomes of ECPR. Translational and clinical research focusing on acute ABI immediately after ECMO cannulation and its short- and long-term neurological outcomes are warranted.

Importance of pulse pressure after extracorporeal cardiopulmonary resuscitation

BACKGROUND

Recent reports have revealed better clinical outcomes for extracorporeal cardiopulmonary resuscitation (ECPR) than conventional cardiopulmonary resuscitation (CPR). In this retrospective study, we attempted to identify predictors associated with successful weaning off extracorporeal membrane oxygenation (ECMO) support after ECPR.

METHODS

The demographic and clinical data of 30 ECPR patients aged over 18 years treated between August 2016 and January 2019 were analyzed. All clinical data were retrospectively collected. The primary endpoint was successful weaning off ECMO support after ECPR. Patients were divided into two groups based on successful or unsuccessful weaning off ECMO support (Weaned (n = 14) vs. Failed (n = 16)).

RESULTS

Univariate logistic regression analysis showed that age, CPR duration, ECMO complications, and loss of pulse pressure significantly predicted the results of weaning off ECMO support. However, multivariate logistic regression analysis showed that only CPR duration and loss of pulse pressure independently predicted unsuccessful weaning from ECMO support.

CONCLUSION

We conclude that long CPR duration and loss of pulse pressure after ECPR predict unsuccessful weaning from ECMO. However, unlike CPR duration, loss of pulse pressure during post-ECPR was related to subsequent management. In patients with reduced pulse pressure after ECPR, careful management is warranted because this reduction is closely associated with unsuccessful weaning off ECMO support after ECPR.

A Computational Fluid Dynamics Study of the Extracorporeal Membrane Oxygenation-Failing Heart Circulation

Extracorporeal membrane oxygenation (ECMO) is increasingly deployed to provide percutaneous mechanical circulatory support despite incomplete understanding of its complex interactions with the failing heart and its effects on hemodynamics and perfusion. Using an idealized geometry of the aorta and its major branches and a peripherally inserted return cannula terminating in the iliac artery, computational fluid dynamic simulations were performed to (1) quantify perfusion as function of relative ECMO flow and (2) describe the watershed region produced by the collision of antegrade flow from the heart and retrograde ECMO flow. To simulate varying degrees of cardiac failure, ECMO flow as a fraction of systemic perfusion was evaluated at 100%, 90%, 75%, and 50% of total flow with the remainder supplied by the heart calculated from a patient-derived flow waveform. Dynamic boundary conditions were generated with a three-element lumped parameter model to accurately simulate distal perfusion. In profound failure (ECMO providing 90% or more of flow), the watershed region was positioned in the aortic arch with minimal pulsatility observed in the flow to the visceral organs. Modest increases in cardiac flow advanced the watershed region into the thoracic aorta with arch perfusion entirely supplied by the heart.

Coagulopathy Characterized by Rotational Thromboelastometry in a Porcine Pediatric ECMO Model

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is used to support patients with reversible cardiopulmonary insufficiency. Although it is a lifesaving technology, bleeding, inflammation, and thrombosis are well-described complications of ECMO. Adult porcine models of ECMO have been used to recapitulate the physiology and hemostatic consequences of ECMO cannulation in adults. However, these models lack the unique physiology and persistence of fetal forms of coagulation factors and fibrinogen as in human infants. We aimed to describe physiologic and coagulation parameters of piglets cannulated and supported with VA-ECMO. Four healthy piglets (5.7-6.4 kg) were cannulated via jugular vein and carotid artery by cutdown and supported for a maximum of 20 hours. Heparin was used with a goal activated clotting time of 180-220 seconds. Arterial blood gas (ABG) was performed hourly, and blood was transfused from an adult donor to maintain hematocrit (Hct) > 24%. Rotational thromboelastometry (ROTEM) was performed at seven time points. All animals achieved adequate flow with a patent circuit throughout the run (pre- and post-oxygenator pressure gradient <10 mmHg). There was slow but significant hemorrhage at cannulation, arterial line, and bladder catheter sites. All animals required the maximum blood transfusion volume available. All animals became anemic after exhaustion of blood for transfusion. ABG showed progressively declining Hct and adequate oxygenation. ROTEM demonstrated decreasing fibrin-only ROTEM (FIBTEM) clot firmness. Histology was overall unremarkable. Pediatric swine are an important model for the study of pediatric ECMO. We have demonstrated the feasibility of such a model while providing descriptions of physiologic, hematologic, and coagulation parameters throughout. Weak whole-blood clot firmness by ROTEM suggested defects in fibrinogen, and there was a clinical bleeding tendency in all animals studied. This model serves as an important means to study the complex derangements in hemostasis during 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.

Temporary right ventricular circulatory support following right ventricular infarction: results of a groin-free approach

Aims

Acute right heart failure (RHF) is a severe complication of right ventricular infarction. The management of acute RHF poses a number of challenges, such as providing haemodynamic support. Temporary circulatory support (TCS) may be required upon failing medical therapy. The ProtekDuo® dual lumen cannula provides a minimally invasive option for (TCS) through a groin‐free internal jugular vein approach. We present the largest patient series to date using the ProtekDuo® cannula as temporary right ventricular assist device (t‐RVAD) in RHF after acute myocardial infarction (MI).

Methods and results

From July 2016 to November 2019, 10 patients underwent t‐RVAD implantation for RHF following acute MI. Transthoracic and transoesophageal echocardiography were performed in all patients to assess cardiac function, with a particular focus on RV function. Cumulative 30‐day survival was 60%. Mean TAPSE was 6.4 ± 3.1 mm, mean fractional area change was 12.1 ± 4.2%, and mean right ventricular end diastolic area was 19.8 ± 2.7 cm². Mean implantation time was 32.8 ± 8.3 min. Mean interval after first cardiac intervention was 4.6 ± 5.8 days. Mean t‐RVAD time was 10.0 ± 7.4 days with a significant reduction in central venous pressure 19.3 ± 2.7 vs. 8.2 ± 2.6 mmHg, P < 0.001 and a significant increase in central venous saturation 52.8 ± 15.6 vs. 80.0 ± 6.0%, P < 0.001. Mean intensive care unit stay was 18.6 ± 12.2 days. Four patients were weaned from TCS. Two patients were bridged to a long‐term paracorporeal RVAD. There were no t‐RVAD associated complications. Causes of death (n = 4) were multiorgan failure, electromechanical dissociation, and haemorrhagic stroke. Mean follow‐up time was 96.0 ± 107.6 days. No independent predictors of mortality were identified in univariate analysis.

Conclusions

We show that groin‐free, percutaneous implantation of the ProtekDuo® cannula is a feasible and safe tool for TCS in acute RHF post‐MI. This approach provides the advantages of percutaneous implantation including complete mobilization and non‐surgical bedside explantation, as well as the option for adding an oxygenator to the t‐RVAD circuit.

Heart failure supported by veno-arterial extracorporeal membrane oxygenation (ECMO): a systematic review of pre-clinical models

OBJECTIVES

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly being used to treat patients with refractory severe heart failure. Large animal models are developed to help understand physiology and build translational research projects. In order to better understand those experimental models, we conducted a systematic literature review of animal models combining heart failure and VA-ECMO.

STUDIES SELECTION

A systematic review was performed using Medline via PubMed, EMBASE, and Web of Science, from January 1996 to January 2019. Animal models combining experimental acute heart failure and ECMO were included. Clinical studies, abstracts, and studies not employing VA-ECMO were excluded.

DATA EXTRACTION

Following variables were extracted, relating to four key features: (1) study design, (2) animals and their peri-experimental care, (3) heart failure models and characteristics, and (4) ECMO characteristics and management.

RESULTS

Nineteen models of heart failure and VA-ECMO were included in this review. All were performed in large animals, the majority (n = 13) in pigs. Acute myocardial infarction (n = 11) with left anterior descending coronary ligation (n = 9) was the commonest mean of inducing heart failure. Most models employed peripheral VA-ECMO (n = 14) with limited reporting.

CONCLUSION

Among models that combined severe heart failure and VA-ECMO, there is a large heterogeneity in both design and reporting, as well as methods employed for heart failure. There is a need for standardization of reporting and minimum dataset to ensure translational research achieve high-quality standards.

Lung-kidney interactions in critically ill patients: consensus report of the Acute Disease Quality Initiative (ADQI) 21 Workgroup

BACKGROUND

Multi-organ dysfunction in critical illness is common and frequently involves the lungs and kidneys, often requiring organ support such as invasive mechanical ventilation (IMV), renal replacement therapy (RRT) and/or extracorporeal membrane oxygenation (ECMO).

METHODS

A consensus conference on the spectrum of lung-kidney interactions in critical illness was held under the auspices of the Acute Disease Quality Initiative (ADQI) in Innsbruck, Austria, in June 2018. Through review and critical appraisal of the available evidence, the current state of research, and both clinical and research recommendations were described on the following topics: epidemiology, pathophysiology and strategies to mitigate pulmonary dysfunction among patients with acute kidney injury and/or kidney dysfunction among patients with acute respiratory failure/acute respiratory distress syndrome. Furthermore, emphasis was put on patients receiving organ support (RRT, IMV and/or ECMO) and its impact on lung and kidney function.

CONCLUSION

The ADQI 21 conference found significant knowledge gaps about organ crosstalk between lung and kidney and its relevance for critically ill patients. Lung protective ventilation, conservative fluid management and early recognition and treatment of pulmonary infections were the only clinical recommendations with higher quality of evidence. Recommendations for research were formulated, targeting lung-kidney interactions to improve care processes and outcomes in critical illness.

Acute right heart failure: future perspective with the PERKAT RV pulsatile right ventricular support device

Acute right heart failure is associated with impaired prognosis in cardiogenic shock. Since most pharmacological therapies are not evaluated for the failing right ventricle, or even contraindicated, there is a need for rapid minimal invasive circulatory right heart support. The PERKAT RV is such a device for acute therapy in congestive heart failure. It reduces the central venous pooling by pumping blood from the inferior vena cava into the pulmonary artery with flow rates of up to 4 litres/min. The device was evaluated in an animal model of acute pulmonary embolism after careful in vitro tests. PERKAT RV increased cardiac output by 59% in sheep suffering from acute right heart failure. We await the first human implantation in the near future. Based on the PERKAT concept, future devolvement will also focus on left heart support.

Numerical analysis of aortic hemodynamics under the support of venoarterial extracorporeal membrane oxygenation and intra-aortic balloon pump

BACKGROUND AND OBJECTIVE

A gap still exists in the hemodynamic effect of intra-aortic balloon pump (IABP), venoarterial extracorporeal membrane oxygenation (VA-ECMO), and VA-ECMO plus IABP on the blood perfusion of the coronary artery, brain, and lower limb; the relation between heart flow and ECMO flow; and the wall stress of vessels.

METHODS

A finite-element model of the aorta, ECMO, and IABP was proposed to calculate the mechanical response via fluid-structure interaction. Heart failure (HF), IABP, ECMO, and ECMO plus IABP were utilized to study the effect of support models.

RESULTS

For the pressure curve, VA-ECMO weakened the dicrotic notch of pressure compared with HF and the pulsatile index (0.494 vs. 0.706 vs. 0.471 vs. 0.613). IABP, ECMO, and ECMO plus IABP increased the perfusion of the coronary, brain, and renal artery compared with HF. However, ECMO and ECMO plus IABP clearly reduced the blood flow of the left arteria femoralis compared to that of the right arteria femoralis (ECMO: 194.04 vs. 730.80 mL/min; ECMO plus IABP: 342.15 vs. 947.22 mL/min). In addition, the flow of ECMO accessed the renal artery more than the left ventricular flow. Greater ventricular flow perfused to the renal artery at a diastolic period for ECMO plus IABP, especially at the time points of 2.192 s and 2.304 s. Compared to the velocity distribution with ECMO, the flow of the right arteria femoralis was increased in the process of IABP-on. According to these four cases, the stress of the vascular wall was increased for ECMO support at the systolic period. The peak wall stress of ECMO is increased by 20% at 1.68 s.

CONCLUSIONS

ECMO plus IABP is more conducive to the blood supply than other cases from the result of numerical simulation. The location of blood intersection was generated in the region of the renal artery, which is estimated carefully.

The association of early post-resuscitation hypotension with discharge survival following targeted temperature management for pediatric in-hospital cardiac arrest

AIM

Approximately 40% of children who have an in-hospital cardiac arrest (IHCA) in the US survive to discharge. We aimed to evaluate the impact of post-cardiac arrest hypotension during targeted temperature management following IHCA on survival to discharge.

METHODS

This is a secondary analysis of the therapeutic hypothermia after pediatric cardiac arrest in-hospital (THAPCA-IH) trial. "Early hypotension" was defined as a systolic blood pressure less than the fifth percentile for age and sex for patients not treated with extracorporeal membrane oxygenation (ECMO) or a mean arterial pressure less than fifth percentile for age and sex for patients treated with ECMO during the first 6 h of temperature intervention. The primary outcome was survival to hospital discharge.

RESULTS

Of 299 children, 142 (47%) patients did not receive ECMO and 157 (53%) received ECMO. Forty-two of 142 (29.6%) non-ECMO patients had systolic hypotension. Twenty-three of 157 (14.7%) ECMO patients had mean arterial hypotension. After controlling for confounders of interest, non-ECMO patients who had early systolic hypotension were less likely to survive to hospital discharge (40.5% vs. 72%; adjusted OR [aOR] 0.34; 95%CI, 0.12-0.93). There was no difference in survival to discharge by blood pressure groups for children treated with ECMO (30.4% vs. 49.3%; aOR = 0.60; 95%CI, 0.22-1.63).

CONCLUSIONS

In this secondary analysis of the THAPCA-IH trial, in patients not treated with ECMO, systolic hypotension within 6 h of temperature intervention was associated with lower odds of discharge survival. Blood pressure groups in patients treated with ECMO were not associated with survival to discharge.

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.

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.

Improved Outcome in an Animal Model of Prolonged Cardiac Arrest Through Pulsatile High Pressure Controlled Automated Reperfusion of the Whole Body

The reperfusion period after extracorporeal cardiopulmonary resuscitation has been recognized as a key player in improving the outcome after cardiac arrest (CA). Our aim was to evaluate the effects of high mean arterial pressure (MAP) and pulsatile flow during controlled automated reperfusion of the whole body. Following 20 min of normothermic CA, high MAP, and pulsatile blood flow (pulsatile group, n = 10) or low MAP and nonpulsatile flow (nonpulsatile group, n = 6) controlled automated reperfusion of the whole body was commenced through the femoral vessels of German landrace pigs for 60 min. Afterwards, animals were observed for eight days. Blood samples were analyzed throughout the experiment and a species-specific neurologic disability score (NDS) was used for neurologic evaluation. In the pulsatile group, nine animals finished the study protocol, while no animal survived postoperative day four in the nonpulsatile group. NDS were significantly better at any given time in the pulsatile group and reached overall satisfactory outcome values. In addition, blood analyses revealed lower levels of lactate in the pulsatile group compared to the nonpulsatile group. This study demonstrates superior survival and neurologic outcome when using pulsatile high pressure automated reperfusion following 20 min of normothermic CA compared to nonpulsatile flow and low MAP. This study strongly supports regulating the reperfusion period after prolonged periods of CA.

Microfluidic cell sorting: Towards improved biocompatibility of extracorporeal lung assist devices

Extracorporeal lung assist technology is one of the last options in critical care medicine to treat patients suffering from severe oxygenation and decarboxylation disorders. Platelet activation along with the consequent thrombus formation is a potentially life-threatening complication of this technique. To avoid platelet-dependent clot formation, this study aims at developing a microfluidic cell sorting chip that can bypass platelets prior to the membrane oxygenator of the extracorporeal lung assist device. The cell sorting chips were produced by maskless dip-in laser lithography, followed by soft lithography replication using PDMS. Citrated porcine whole blood with a clinically relevant haematocrit of 17% was used for the cell sorting experiments involving three different blood flow rates. The joint effects of flow focusing and hydrodynamic lifting forces within the cell sorting chip resulted in a reduction of up to 57% of the baseline platelet count. This cell sorting strategy is suitable for the continuous and label-free separation of red blood cells and platelets and is potentially applicable for increasing the biocompatibility and lifetime of current extracorporeal lung assist devices.

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.

Artificial Organs 2016: A Year in Review

In this Editor's Review, articles published in 2016 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 Mechanical Circulatory Support, 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 were pleased to publish our second Virtual Issue in April 2016 on "Tissue Engineering in Bone" by Professor Tsuyoshi Takato. Our first was published in 2011 titled "Intra-Aortic Balloon Pumping" by Dr. Ashraf Khir. Other peer-reviewed Special Issues this year included contributions from the 11th International Conference on Pediatric Mechanical Circulatory Support Systems and Pediatric Cardiopulmonary Perfusion edited by Dr. Akif Ündar and selections from the 23rd Congress of the International Society for Rotary Blood Pumps edited by Dr. Bojan Biocina. We take this time also to express our gratitude to our authors for offering their work to this journal. We offer our very special thanks to our reviewers who give so generously of 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.

Application of a Lumped Parameter Model to Study the Feasibility of Simultaneous Implantation of a Continuous Flow Ventricular Assist Device (VAD) and a Pulsatile Flow VAD in BIVAD Patients

The aim of this work is to develop and test a lumped parameter model of the cardiovascular system to simulate the simultaneous use of pulsatile (P) and continuous flow (C) ventricular assist devices (VADs) on the same patient. Echocardiographic and hemodynamic data of five pediatric patients undergoing VAD implantation were retrospectively collected and used to simulate the patients' baseline condition with the numerical model. Once the baseline hemodynamic was reproduced for each patient, the following assistance modalities were simulated: (a) CVAD assisting the right ventricle and PVAD assisting the left ventricle (RCF + LPF), (b) CVAD assisting the left ventricle and PVAD assisting the right ventricle (LCF + RPF). The numerical model can well reproduce patients' baseline. The cardiac output increases in both assisted configurations (RCF + LPF: +17%, LCF + RPF: +21%, P = ns), left (right) ventricular volumes decrease more evidently in the configuration LCF + RPF (RCF + LPF), left (right) atrial pressure decreases in the LCF + RPF (RCF + LPF) modality. The pulmonary arterial pressure slightly decreases in the configuration LCF + RPF and it increases with RCF + LPF. Left and right ventricular external work increases in both configurations probably because of the total cardiac output increment. However, left and right artero-ventricular coupling improves especially in the LCF + RPF (-36% for the left ventricle and -21% for the right ventricle, P = ns). The pulsatility index decreases by 8.5% in the configuration LCF + RPF and increases by 6.4% with RCF + LPF (P = 0.0001). A numerical model could be useful to tailor on patients the choice of the VAD that could be implanted to improve the hemodynamic benefits. Moreover, a model could permit to simulate extreme physiological conditions and innovative configurations, as the implantation of both CVAD and PVAD on the same patient.