Changes in left ventricular systolic wall stress during biventricular circulatory assistance

The physiology of venoarterial extracorporeal membrane oxygenation - A comprehensive clinical perspective

Venoarterial extracorporeal membrane oxygenation (VA ECMO) has become a standard of care for severe cardiogenic shock, refractory cardiac arrest and related impending multiorgan failure. The widespread clinical use of this complex temporary circulatory support modality is still contrasted by a lack of formal scientific evidence in the current literature. This might at least in part be attributable to VA ECMO related complications, which may significantly impact on clinical outcome. In order to limit adverse effects of VA ECMO as much as possible an indepth understanding of the complex physiology during extracorporeally supported cardiogenic shock states is critically important. This review covers all relevant physiological aspects of VA ECMO interacting with the human body in detail. This, to provide a solid basis for health care professionals involved in the daily management of patients supported with VA ECMO and suffering from cardiogenic shock or cardiac arrest and impending multiorgan failure for the best possible care.

Systemic Hemodynamics, Cardiac Mechanics, and Signaling Pathways Induced by Extracorporeal Membrane Oxygenation in a Cardiogenic Shock Model

Peripheral venoarterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly being used in patients suffering from refractory cardiogenic shock (CS). Although considered life-saving, peripheral VA-ECMO may also be responsible for intracardiac hemodynamic changes, including left ventricular overload and dysfunction. Venoarterial extracorporeal membrane oxygenation may also increase myocardial wall stress and stroke work, possibly affecting the cellular cardioprotective and apoptosis signaling pathways, and thus the infarct size. To test this hypothesis, we investigated the effects of increasing the peripheral VA-ECMO blood flow (25-100% of the baseline cardiac output) on systemic and cardiac hemodynamics in a closed-chest CS model. Upon completion of the experiment, the hearts were removed for assessment of infarct size, histology, apoptosis measurements, and phosphorylation statuses of p38 and protein Kinase B (Akt), and extracellular signal-regulated kinase mitogen-activated protein kinases (ERK-MAPK). Peripheral VA-ECMO restored systemic perfusion but induced a significant and blood flow-dependent increase in left ventricular preload and afterload. Venoarterial extracorporeal membrane oxygenation did not affect infarct size but significantly decreased p38-MAPK phosphorylation and cardiac myocyte apoptosis in the border zone.

Alterations in Coronary Blood Flow and the Risk of Left Ventricular Distension in Venoarterial Extracorporeal Membrane Oxygenation

Previous theoretical studies have suggested that veno-arterial extracorporeal membrane oxygenation (VA-ECMO) ought to consistently result in markedly increased left ventricular (LV) intracavitary pressures and volumes because of increased LV afterload. However, this phenomenon of LV distension does not universally occur and occurs only in a minority of cases. We sought to explain this discrepancy by considering the potential implications of VA-ECMO support on coronary blood flow and consequently improved LV contractility (the "Gregg" effect), in addition to the effects of VA-ECMO support upon LV loading conditions, in a lumped parameter-based theoretical circulatory model. We found that LV systolic dysfunction resulted in reduced coronary blood flow; VA-ECMO support augmented coronary blood flow proportionally to the circuit flow rate. On VA-ECMO support, a weak or absent Gregg effect resulted in increased LV end-diastolic pressures and volumes and increased end-systolic volume with decreased LV ejection fraction (LVEF), consistent with LV distension. In contrast, a more robust Gregg effect resulted in unaffected and/or even reduced LV end-diastolic pressure and volume, end-systolic volume, and unaffected or even increased LVEF. Left ventricular contractility augmentation proportional to coronary blood flow increased by VA-ECMO support may be an important contributory mechanism underlying why LV distension is observed only in a minority of cases.

Improving Survival in Cardiogenic Shock-A Propensity Score-Matched Analysis of the Impact of an Institutional Allocation Protocol to Short-Term Mechanical Circulatory Support

Temporary mechanical circulatory support (tMCS) is a life-saving treatment option for patients in cardiogenic shock (CS), but many aspects such as patient selection, initiation threshold and optimal modality selection remain unclear. This study describes a standard operating procedure (SOP) for tMCS allocation for CS patients and presents outcome data before and after implementation. Data from 421 patients treated for CS with tMCS between 2018 and 2021 were analyzed. In 2019, we implemented a new SOP for allocating CS patients to tMCS modalities. The association between the time of SOP implementation and the 30-day and 1-year survival as well as hospital discharge was evaluated. Of the 421 patients included, 189 were treated before (pre-SOP group) and 232 after implementation of the new SOP (SOP group). Causes of CS included acute myocardial infarction (n = 80, 19.0%), acute-on-chronic heart failure in patients with dilated or chronic ischemic heart failure (n = 139, 33.0%), valvular cardiomyopathy (n = 14, 3.3%) and myocarditis (n = 5, 1.2%); 102 patients suffered from postcardiotomy CS (24.2%). The SOP group was further divided into an SOP-adherent (SOP-A) and a non-SOP-adherent group (SOP-NA). The hospital discharge rate was higher in the SOP group (41.7% vs. 29.7%), and treating patients according to the SOP was associated with an improved 30-day survival (56.9% vs. 38.9%, OR 2.21, 95% CI 1.01-4.80, p = 0.044). Patient allocation according to the presented SOP significantly improved 30-day survival.

Patient Selection for Protected Percutaneous Coronary Intervention: Who Benefits the Most?

The evolution of percutaneous coronary intervention (PCI) enables a complete revascularization of complex coronary lesions. However, simultaneously, patients are presenting nowadays with higher rates of comorbidities, which may lead to a lower physiologic tolerance for complex PCI. To avoid hemodynamic instability during PCI and achieve safe complete revascularization, protected PCI using mechanical circulatory support devices has been developed. However, which patients would benefit from the protected PCI is still in debate. Hence, this review provides practical approaches for the selection of patients by outlining current clinical data assessing utility of protected PCI in high-risk patients.

Cardiogenic Shock Management and Research: Past, Present, and Future Outlook

Although great strides have been made in the pathophysiological understanding, diagnosis and management of cardiogenic shock (CS), morbidity and mortality in patients presenting with the condition remain high. Acute MI is the commonest cause of CS; consequently, most existing literature concerns MI-associated CS. However, there are many more phenotypes of patients with acute heart failure. Medical treatment and mechanical circulatory support are well-established therapeutic options, but evidence for many current treatment regimens is limited. The issue is further complicated by the fact that implementing adequately powered, randomized controlled trials are challenging for many reasons. In this review, the authors discuss the history, landmark trials, current topics of medical therapy and mechanical circulatory support regimens, and future perspectives of CS management.

Modalities of Left Ventricle Decompression during VA-ECMO Therapy

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used to sustain circulatory and respiratory support in patients with severe cardiogenic shock or refractory cardiac arrest. Although VA-ECMO allows adequate perfusion of end-organs, it may have detrimental effects on myocardial recovery. Hemodynamic consequences on the left ventricle, such as the increase of afterload, end-diastolic pressure and volume, can lead to left ventricular (LV) distention, increase of myocardial oxygen consumption and delayed LV function recovery. LV distention occurs in almost 50% of patients supported with VA-ECMO and is associated with an increase in morbidity and mortality. Thus, recognizing, preventing and treating LV distention is key in the management of these patients. In this review, we aim to discuss the pathophysiology of LV distention and to describe the strategies to unload the LV in patients supported with VA-ECMO.

Evaluation of Extracorporeal Membrane Oxygenation Therapy as a Bridging Method

BACKGROUND

With the implementation of the new heart allocation system, heart transplantation teams are prompted to reevaluate management of patients requiring mechanical circulatory support. The purpose of our study is to compare the outcomes of patients supported with extracorporeal membrane oxygenation (ECMO) before transplantation.

METHODS

The United Network for Organ Sharing database was queried for all adult patients (aged 18 years or more) who required support with ECMO before heart transplantation from 2001 to 2018. Patients were stratified into patients who did not require ECMO before transplantation, who were weaned off ECMO before transplantation, who were bridged immediately to transplantation from ECMO, and who were bridged to a left ventricular assist device (LVAD) before transplantation. Demographics and outcomes including 1-year survival, postoperative stroke, postoperative renal failure requiring dialysis, episodes of rejection, and graft failure were compared.

RESULTS

Overall, 29,370 patients did not require ECMO before transplantation, 101 patients were weaned off ECMO before transplantation, 118 were bridged from ECMO directly to transplantation, and 55 patients were successfully bridged from ECMO to LVAD before transplantation. Kaplan-Meier survival estimates found a statistically significant decrease in 1-year survival for patients who were bridged from ECMO to transplantation compared with patients who were bridged to LVAD before subsequent transplantation (P < .001).

CONCLUSIONS

Our study suggests bridging ECMO patients to an LVAD before transplantation will result in improved 1-year survival compared with patients bridged to immediate transplantation. With the new heart allocation system, continued evaluation of outcomes is required to inform management strategies.

Patient Selection for Protected Percutaneous Coronary Intervention: Who Benefits the Most?

The evolution of percutaneous coronary intervention (PCI) enables a complete revascularization of complex coronary lesions. However, simultaneously, patients are presenting nowadays with higher rates of comorbidities, which may lead to a lower physiologic tolerance for complex PCI. To avoid hemodynamic instability during PCI and achieve safe complete revascularization, protected PCI using mechanical circulatory support devices has been developed. However, which patients would benefit from the protected PCI is still in debate. Hence, this review provides practical approaches for the selection of patients by outlining current clinical data assessing utility of protected PCI in high-risk patients.

Left ventricle unloading strategies in ECMO: A single-center experience

INTRODUCTION

Extracorporeal membrane oxygenation (ECMO) is a life-saving technology capable of restoring perfusion but is not without significant complications that limit its realizable therapeutic benefit. ECMO-induced hemodynamics increase cardiac afterload risking left ventricular distention and impaired cardiac recovery. To mitigate potentially harmful effects, multiple strategies to unload the left ventricle (LV) are used in clinical practice but data supporting the optimal approach is presently lacking.

MATERIALS & METHODS

We reviewed outcomes of our ECMO population from September 2015 through January 2019 to determine if our LV unloading strategies were associated with patient outcomes. We compared reactive (Group 1, n = 30) versus immediate (Group 2, n = 33) LV unloading and then compared patients unloaded with an Impella CP (n = 19) versus an intra-aortic balloon pump (IABP, n = 16), analyzing survival and ECMO-related complications.

RESULTS

Survival was similar between Groups 1 and 2 (33 vs 42%, P = .426) with Group 2 experiencing more clinically-significant hemorrhage (40 vs. 67%, P = .034). Survival and ECMO-related complications were similar between patients unloaded with an Impella versus an IABP. However, the Impella group exhibited a higher rate of survival (37%) than predicted by their median SAVE score (18%).

DISCUSSION

Based on this analysis, reactive unloading appears to be a viable strategy while venting with the Impella CP provides better than anticipated survival. Our findings correlate with recent large cohort studies and motivate further work to design clinical guidelines and future trial design.

Advanced Pulmonary and Cardiac Support of COVID-19 Patients: Emerging Recommendations From ASAIO-A "Living Working Document"

The severe acute respiratory syndrome (SARS)-CoV-2 is an emerging viral pathogen responsible for the global coronavirus disease 2019 (COVID)-19 pandemic resulting in significant human morbidity and mortality. Based on preliminary clinical reports, hypoxic respiratory failure complicated by acute respiratory distress syndrome is the leading cause of death. Further, septic shock, late-onset cardiac dysfunction, and multiorgan system failure are also described as contributors to overall mortality. Although extracorporeal membrane oxygenation and other modalities of mechanical cardiopulmonary support are increasingly being utilized in the treatment of respiratory and circulatory failure refractory to conventional management, their role and efficacy as support modalities in the present pandemic are unclear. We review the rapidly changing epidemiology, pathophysiology, emerging therapy, and clinical outcomes of COVID-19; and based on these data and previous experience with artificial cardiopulmonary support strategies, particularly in the setting of infectious diseases, provide consensus recommendations from ASAIO. Of note, this is a "living document," which will be updated periodically, as additional information and understanding emerges.

Advanced Pulmonary and Cardiac Support of COVID-19 Patients: Emerging Recommendations From ASAIO-a Living Working Document

The severe acute respiratory syndrome-CoV-2 is an emerging viral pathogen responsible for the global coronavirus disease 2019 pandemic resulting in significant human morbidity and mortality. Based on preliminary clinical reports, hypoxic respiratory failure complicated by acute respiratory distress syndrome is the leading cause of death. Further, septic shock, late-onset cardiac dysfunction, and multiorgan system failure are also described as contributors to overall mortality. Although extracorporeal membrane oxygenation and other modalities of mechanical cardiopulmonary support are increasingly being utilized in the treatment of respiratory and circulatory failure refractory to conventional management, their role and efficacy as support modalities in the present pandemic are unclear. We review the rapidly changing epidemiology, pathophysiology, emerging therapy, and clinical outcomes of coronavirus disease 2019; and based on these data and previous experience with artificial cardiopulmonary support strategies, particularly in the setting of infectious diseases, provide consensus recommendations from American Society for Artificial Internal Organs. Of note, this is a living document, which will be updated periodically, as additional information and understanding emerges.

Interatrial Shunting for Treating Acute and Chronic Left Heart Failure

The creation of an interatrial shunt has emerged as a new therapy to decompress the left atrium in patients with acute and chronic left heart failure (HF). Current data support the safety of this therapy, and promising preliminary efficacy results have been reported in patients who are refractory to optimal medical/device therapy. This article aims to provide an updated overview and clinical perspective on interatrial shunting for treating different HF conditions, and highlights the potential challenges and future directions of this therapy.

Increasing venoarterial extracorporeal membrane oxygenation flow puts higher demands on left ventricular work in a porcine model of chronic heart failure

Background

Venoarterial extracorporeal membrane oxygenation (VA ECMO) is widely used in the treatment of circulatory failure, but repeatedly, its negative effects on the left ventricle (LV) have been observed. The purpose of this study is to assess the influence of increasing extracorporeal blood flow (EBF) on LV performance during VA ECMO therapy of decompensated chronic heart failure.

Methods

A porcine model of low-output chronic heart failure was developed by long-term fast cardiac pacing. Subsequently, under total anesthesia and artificial ventilation, VA ECMO was introduced to a total of five swine with profound signs of chronic cardiac decompensation. LV performance and organ specific parameters were recorded at different levels of EBF using a pulmonary artery catheter, a pressure–volume loop catheter positioned in the LV, and arterial flow probes on systemic arteries.

Results

Tachycardia-induced cardiomyopathy led to decompensated chronic heart failure with mean cardiac output of 2.9 ± 0.4 L/min, severe LV dilation, and systemic hypoperfusion. By increasing the EBF from minimal flow to 5 L/min, we observed a gradual increase of LV peak pressure from 49 ± 15 to 73 ± 11 mmHg (P = 0.001) and an improvement in organ perfusion. On the other hand, cardiac performance parameters revealed higher demands put on LV function: LV end-diastolic pressure increased from 7 ± 2 to 15 ± 3 mmHg, end-diastolic volume increased from 189 ± 26 to 218 ± 30 mL, end-systolic volume increased from 139 ± 17 to 167 ± 15 mL (all P < 0.001), and stroke work increased from 1434 ± 941 to 1892 ± 1036 mmHg*mL (P < 0.05). LV ejection fraction and isovolumetric contractility index did not change significantly.

Conclusions

In decompensated chronic heart failure, excessive VA ECMO flow increases demands and has negative effects on the workload of LV. To protect the myocardium from harm, VA ECMO flow should be adjusted with respect to not only systemic perfusion, but also to LV parameters.

Simultaneous Venoarterial Extracorporeal Membrane Oxygenation and Percutaneous Left Ventricular Decompression Therapy with Impella Is Associated with Improved Outcomes in Refractory Cardiogenic Shock

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been used for refractory cardiogenic shock; however, it is associated with increased left ventricular afterload. Outcomes associated with the combination of a percutaneous left ventricular assist device (Impella) and VA-ECMO remains largely unknown. We retrospectively reviewed patients treated for refractory cardiogenic shock with VA-ECMO (2014-2016). The primary outcome was all-cause mortality within 30 days of VA-ECMO implantation. Secondary outcomes included duration of support, stroke, major bleeding, hemolysis, inotropic score, and cardiac recovery. Outcomes were compared between the VA-ECMO cohort and VA-ECMO + Impella (ECPELLA cohort). Sixty-six patients were identified: 36 VA-ECMO and 30 ECPELLA. Fifty-eight percent of VA-ECMO patients (n = 21) had surgical venting, as compared to 100% of the ECPELLA cohort (n = 30) which had Impella (±surgical vent). Both cohorts demonstrated relatively similar baseline characteristics except for higher incidence of ST-elevation myocardial infarction (STEMI) and percutaneous coronary intervention (PCI) in the ECPELLA cohort. Thirty-day all-cause mortality was significantly lower in the ECPELLA cohort (57% vs. 78%; hazard ratio [HR] 0.51 [0.28-0.94], log rank p = 0.02), and this difference remained intact after correcting for STEMI and PCI. No difference between secondary outcomes was observed, except for the inotrope score which was greater in VA-ECMO group by day 2 (11 vs. 0; p = 0.001). In the largest US-based retrospective study, the addition of Impella to VA-ECMO for patients with refractory cardiogenic shock was associated with lower all-cause 30 day mortality, lower inotrope use, and comparable safety profiles as compared with VA-ECMO alone.

Assistance ventriculaire gauche par Impella® : indications, gestion et complications

L’assistance monoventriculaire Impella® est une assistance microaxiale non pulsatile dépourvue de fonction d’oxygénation et/ou de décarboxylation. Sur le principe de la vis sans fin d’Archimède, elle aspire le sang dans le ventricule gauche pour le réinjecter dans la racine de l’aorte en regard des ostia coronaires. Selon le modèle utilisé, le débit d’assistance antérograde ainsi généré varie de 2,5 à 5 l/min. De par son mode de fonctionnement, l’assistance Impella® permet une décharge ventriculaire efficace. Ses indications sont l’angioplastie coronaire à haut risque et le choc cardiogénique réfractaire aux agents cardiovasoactifs. Chez le patient assisté par une extracorporeal life support (ECLS), la pompe Impella® permet de limiter le risque de surcharge ventriculaire. Chez le patient exclusivement assisté par Impella® soit d’emblée ou après une association avec l’ECLS, la voie d’abord axillaire permet sa réhabilitation active y compris la déambulation et l’activité physique. Elle se révèle alors une mise à l’épreuve cliniquement pertinente du ventricule droit en vue d’une assistance de longue durée de type left ventricular assist device.

Cardiac catheterization and percutaneous intervention procedures on extracorporeal membrane oxygenation support

Extracorporeal membrane oxygenation (ECMO) is used to support critically ill patients when conventional therapies have failed. ECMO has been available for four decades and has gained use as a rescue therapy in severe refractory hypoxic disorders and in patients with refractory cardiogenic shock (RCS). Over recent years, several percutaneous cardiac interventions and implant devices have been developed that are now used frequently in conjunction with ECMO in order to maintain organ perfusion. Here, we review the literature on VA-ECMO cannulation location, the use of VA-ECMO in interventions (e.g., coronary interventions and structural heart interventions) and percutaneous cardiac device implantation in VA-ECMO recipients with RCS.

Experience with Uni- (LVAD) and Biventricular (ECMO) Circulatory Support in Postcardiotomy Pediatric Patients

In six pediatric patients with postoperative low-output-syndrome (LOS), uni-(LVAD) and biventricular (ECMO) assist systems with Biomedicus centrifugal pump were used. ECMO was applied in 5 children aged between 3 days and 16 years, one infant with an age of 16 months was implanted with LVAD. One patient from the ECMO-group and the patient with LVAD-support survived. Analysis of vital organ functions during ECMO and LVAD support are presented and characteristics of both support systems for use in pediatric patients with postcardiotomy LOS based on worldwide experience discussed. In conclusion, both, uni- (LVAD) and biventricular circulatory support (ECMO) using Biomedicus centrifugal pump can be safely applied for management of postcardiotomy LOS even in neonates, however, ECMO support in comparison to LVAD is a more aggressive approach associated with a higher complication rate.

Tachycardia-Induced Cardiomyopathy As a Chronic Heart Failure Model in Swine

A stable and reliable model of chronic heart failure is required for many experiments to understand hemodynamics or to test effects of new treatment methods. Here, we present such a model by tachycardia-induced cardiomyopathy, which can be produced by rapid cardiac pacing in swine. A single pacing lead is introduced transvenously into fully anaesthetized healthy swine, to the apex of the right ventricle, and fixated. Its other end is then tunneled dorsally to the paravertebral region. There, it is connected to an in-house modified heart pacemaker unit that is then implanted in a subcutaneous pocket. After 4 - 8 weeks of rapid ventricular pacing at rates of 200 - 240 beats/min, physical examination revealed signs of severe heart failure - tachypnea, spontaneous sinus tachycardia, and fatigue. Echocardiography and X-ray showed dilation of all heart chambers, effusions, and severe systolic dysfunction. These findings correspond well to decompensated dilated cardiomyopathy and are also preserved after the cessation of pacing. This model of tachycardia-induced cardiomyopathy can be used for studying the pathophysiology of progressive chronic heart failure, especially hemodynamic changes caused by new treatment modalities like mechanical circulatory supports. This methodology is easy to perform and the results are robust and reproducible.

Refractory Pulmonary Edema and Upper Body Hypoxemia During Veno-Arterial Extracorporeal Membrane Oxygenation-A Case for Atrial Septostomy

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) provides mechanical circulatory support for patients with advanced cardiogenic shock, facilitating myocardial recovery and limiting multi-organ failure. In patients with severely limited left ventricular ejection, peripheral VA-ECMO can further increase left ventricular and left atrial pressures (LAP). Failure to decompress the left heart under these circumstances can result in pulmonary edema and upper body hypoxemia, that is, myocardial and cerebral ischemia. Atrial septostomy can decrease LAP in these situations. However, the effects of atrial septostomy on upper body oxygenation remain unknown. After IRB approval, we identified 9 out of 242 adult VA-ECMO patients between January 2011 and June 2016 who also underwent atrial septostomy for refractory pulmonary edema/upper body hypoxemia. We analyzed LAP/pulmonary capillary wedge pressure (PCWP), right atrial pressures (RAPs), P_a O₂ /F_i O₂ ratios (blood samples from right radial artery), intrathoracic volume status, and resolution of pulmonary edema before and up to 48 h after septostomy. There were no procedure-related complications. Thirty-day survival was 44%. LAP/PCWP decreased by approximately 40% immediately following septostomy and remained so for at least 24 h. P_a O₂ /F_i O₂ ratios significantly increased from 0.49 (0.38-2.12) before to 5.35 (3.01-7.69) immediately after septostomy and continued so for 24 h, 6.6 (4.49-10.93). Radiographic measurements also indicated a significant improvement in thoracic intravascular volume status after atrial septostomy. Atrial septostomy reduces LAP and improves upper body oxygenation and intrathoracic vascular volume status in patients developing severe refractory pulmonary edema while undergoing peripheral VA-ECMO. Atrial septostomy therefore appears safe and suitable to reduce the risk of upper body ischemia under these circumstances.

Institution of Veno-arterial Extracorporeal Membrane Oxygenation Does Not Lead to Increased Wall Stress in Patients with Impaired Myocardial Function

The effect of veno-arterial extracorporeal membrane oxygenation (VA ECMO) on wall stress in patients with cardiomyopathy, myocarditis, or other cardiac conditions is unknown. We set out to determine the circumferential and meridional wall stress (WS) in patients with systemic left ventricles before and during VA ECMO. We established a cohort of patients with impaired myocardial function who underwent VA ECMO therapy from January 2000 to November 2013. Demographic and clinical data were collected and inotropic score calculated. Measurements were taken on echocardiograms prior to the initiation of VA ECMO and while on full-flow VA ECMO, in order to derive wall stress (circumferential and meridional), VCFc, ejection fraction, and fractional shortening. A post hoc sub-analysis was conducted, separating those with pulmonary hypertension (PH) and those with impaired systemic output. Thirty-three patients met inclusion criteria. The patients' median age was 0.06 years (range 0-18.7). Eleven (33%) patients constituted the organ failure group (Gr2), while the remaining 22 (66%) patients survived to discharge (Gr1). WS and all other echocardiographic measures were not different when comparing patients before and during VA ECMO. Ejection and shortening fraction, WS, and VCFc were not statistically different comparing the survival and organ failure groups. The patients' position on the VCFc-WS curve did not change after the initiation of VA ECMO. Those with PH had decreased WS as well as increased EF after ECMO initiation, while those with impaired systemic output showed no difference in those parameters with initiation of ECMO. The external workload on the myocardium as indicated by WS is unchanged by the institution of VA ECMO support. Furthermore, echocardiographic measures of cardiac function do not reflect the changes in ventricular performance inherent to VA ECMO support. These findings are informative for the interpretation of echocardiograms in the setting of VA ECMO. ECMO may improve ventricular mechanics in those with PH as the primary diagnosis.

Regional Tissue Oximetry Reflects Changes in Arterial Flow in Porcine Chronic Heart Failure Treated With Venoarterial Extracorporeal Membrane Oxygenation

Venoarterial extracorporeal membrane oxygenation (VA ECMO) is widely used in treatment of decompensated heart failure. Our aim was to investigate its effects on regional perfusion and tissue oxygenation with respect to extracorporeal blood flow (EBF). In five swine, decompensated low-output chronic heart failure was induced by long-term rapid ventricular pacing. Subsequently, VA ECMO was introduced and left ventricular (LV) volume, aortic blood pressure, regional arterial flow and tissue oxygenation were continuously recorded at different levels of EBF. With increasing EBF from minimal to 5 l/min, mean arterial pressure increased from 47±22 to 84±12 mm Hg (P<0.001) and arterial blood flow increased in carotid artery from 211±72 to 479±58 ml/min (P<0.01) and in subclavian artery from 103±49 to 296±54 ml/min (P<0.001). Corresponding brain and brachial tissue oxygenation increased promptly from 57±6 to 74±3 % and from 37±6 to 77±6 %, respectively (both P<0.01). Presented results confirm that VA ECMO is a capable form of heart support. Regional arterial flow and tissue oxygenation suggest that partial circulatory support may be sufficient to supply brain and peripheral tissue by oxygen.

2015 SCAI/ACC/HFSA/STS Clinical Expert Consensus Statement on the Use of Percutaneous Mechanical Circulatory Support Devices in Cardiovascular Care (Endorsed by the American Heart Association, the Cardiological Society of India, and Sociedad Latino Americana de Cardiologia Intervencion; Affirmation of Value by the Canadian Association of Interventional Cardiology-Association Canadienne de Cardiologie d'intervention)

Although historically the intra-aortic balloon pump has been the only mechanical circulatory support device available to clinicians, a number of new devices have become commercially available and have entered clinical practice. These include axial flow pumps, such as Impella(®); left atrial to femoral artery bypass pumps, specifically the TandemHeart; and new devices for institution of extracorporeal membrane oxygenation. These devices differ significantly in their hemodynamic effects, insertion, monitoring, and clinical applicability. This document reviews the physiologic impact on the circulation of these devices and their use in specific clinical situations. These situations include patients undergoing high-risk percutaneous coronary intervention, those presenting with cardiogenic shock, and acute decompensated heart failure. Specialized uses for right-sided support and in pediatric populations are discussed and the clinical utility of mechanical circulatory support devices is reviewed, as are the American College of Cardiology/American Heart Association clinical practice guidelines.

Predictors of mortality in pediatric patients on venoarterial extracorporeal membrane oxygenation

OBJECTIVES

Currently, there are no established echocardiographic or hemodynamic predictors of mortality after weaning venoarterial extracorporeal membrane oxygenation in children. We wished to determine which measurements predict mortality.

DESIGN

Over 3 years, we prospectively assessed six echo and six hemodynamic variables at 3-5 circuit rates while weaning extracorporeal membrane oxygenation flow. Hemodynamic measurements were heart rate, inotropic score, arteriovenous oxygen difference, pulse pressure, oxygenation index, and lactate. Echo variables included shortening/ejection fraction, outflow tract Doppler-derived stroke distance (velocity-time integral), degree of atrioventricular valve regurgitation, longitudinal strain (global longitudinal strain), and circumferential strain (global circumferential strain).

SETTING

Cardiovascular ICU at Lucille Packard Children's Hospital Stanford, CA.

SUBJECTS

Patients were stratified into those who died or required heart transplant (Gr1) and those who did not (Gr2). For each patient, we compared the change for each variable between full versus minimum extracorporeal membrane oxygenation flow for each group.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We enrolled 21 patients ranging in age from 0.02 to 15 years. Five had dilated cardiomyopathy, and 16 had structural heart disease with severe ventricular dysfunction. Thirteen of 21 patients (62%) comprised Gr1, including two patients with heart transplants. Eight patients constituted Gr2. Gr1 patients had a significantly greater increase in oxygenation index (35% mean increase; p < 0.01) off extracorporeal membrane oxygenation compared to full flow, but no change in velocity-time integral or arteriovenous oxygen difference. In Gr2, velocity-time integral increased (31% mean increase; p < 0.01), with no change in arteriovenous oxygen difference or oxygenation index. Pulse pressure increased modestly with flow reduction only in Gr1 (p < 0.01).

CONCLUSION

Failure to augment velocity-time integral or an increase in oxygenation index during the extracorporeal membrane oxygenation weaning is associated with poor outcomes in children. We propose that these measurements should be performed during extracorporeal membrane oxygenation wean, as they may discriminate who will require alternative methods of circulatory support for survival.

Transfromation of percutaneous extracorporeal life support to paracorporeal ventricular assist device: a case report

Percutaneous extracorporeal life support (P-ECLS) is a useful modality for the management of refractory cardiac or pulmonary failure. However, venoarterial P-ECLS may result in a complication of left ventricular distension. In this case report, we discuss a patient with drug-induced dilated cardiomyopathy managed with venoarterial P-ECLS and a left atrial vent catheter. The venoarterial P-ECLS was modified to a paracorporeal left ventricular assist device (LVAD) by removing the femoral venous cannula. After 28 days of hospitalization, the patient was successfully weaned from the paracorporeal LVAD and discharged home from the hospital.

Extracorporeal life support with an integrated left ventricular vent in children with a low cardiac output

BACKGROUND

The aim of this study was to evaluate our experience in central extracorporeal life support with an integrated left ventricular vent in children with cardiac failure.

METHODS

Eight children acquired extracorporeal life support with a left ventricular vent, either after cardiac surgery (n = 4) or during an acute cardiac illness (n = 4). The ascending aorta and right atrium were cannulated. The left ventricular vent was inserted through the right superior pulmonary vein and connected to the venous line on the extracorporeal life support such that active left heart decompression was achieved.

RESULTS

No patient died while on support, seven patients were successfully weaned from it and one patient was transitioned to a biventricular assist device. The median length of support was 6 days (range 5-10 days). One patient died while in the hospital, despite successful weaning from extracorporeal life support. No intra-cardiac thrombus or embolic stroke was observed. No patient developed relevant intracranial bleeding resulting in neurological dysfunction during and after extracorporeal life support.

CONCLUSIONS

In case of a low cardiac output and an insufficient inter-atrial shunt, additional left ventricular decompression via a vent could help avoid left heart distension and might promote myocardial recovery. In pulmonary dysfunction, separate blood gas analyses from the venous cannula and the left ventricular vent help detect possible coronary hypoxia when the left ventricle begins to recover. We recommend the use of central extracorporeal life support with an integrated left ventricular vent in children with intractable cardiac failure.

Outcome evaluation of the bridge-to-bridge concept in patients with cardiogenic shock

BACKGROUND

Patients with cardiogenic shock can be stabilized by percutaneous implantation of extracorporeal membrane oxygenation (ECMO). If weaning from ECMO is impossible, the implantation of a ventricular assist device (VAD) is required. Patients either go for recovery of myocardial function (bridge to recovery) or for heart transplantation (bridge to transplant).

METHODS

One hundred thirty-one patients were supported with ECMO between March 1995 and November 2005. Reasons for ECMO implantation were acute heart failure, acute or chronic heart failure, and postcardiotomy heart failure. In 28 patients, subsequent VAD implantation was necessary (bridge to bridge concept).

RESULTS

Fourteen bridge to bridge patients (50%) became long-time survivors with a mean follow-up of 39 months. Risk factors for mortality were status post-cardiopulmonary resuscitation and elevated lactate and bilirubin levels before VAD implantation. Complications after ECMO and VAD implantation were bleeding and thromboembolic events. The most common cause of death was multiorgan failure.

CONCLUSIONS

Bridge to bridge is a successful concept for selected patients with cardiogenic shock. During ECMO support, patients can be evaluated for comorbidities. For patients with a combination of risk factors (status post-cardiopulmonary resuscitation, elevated lactate levels, and impaired liver function), VAD implantation should be considered very carefully.

Artificial lungs: a new inspiration

An estimated 16 million Americans are afflicted with some degree of chronic obstructive pulmonary disease (COPD), accounting for 100,000 deaths per year. The only current treatment for chronic irreversible pulmonary failure is lung transplantation. Since the widespread success of single and double lung transplantation in the early 1990s, demand for donor lungs has steadily outgrown the supply. Unlike dialysis, which functions as a bridge to renal transplantation, or a ventricular assist device (VAD), which serves as a bridge to cardiac transplantation, no suitable bridge to lung transplantation exists. The current methods for supporting patients with lung disease, however, are not adequate or efficient enough to act as a bridge to transplantation. Although occasionally successful as a bridge to transplant, ECMO requires multiple transfusions and is complex, labor-intensive, time-limited, costly, non-ambulatory and prone to infection. Intravenacaval devices, such as the intravascular oxygenator (IVOX) and the intravenous membrane oxygenator (IMO), are surface area limited and currently provide inadequate gas exchange to function as a bridge-to-recovery or transplant. A successful artificial lung could realize a substantial clinical impact as a bridge to lung transplantation, a support device immediately post-lung transplant, and as rescue and/or supplement to mechanical ventilation during the treatment of severe respiratory failure.

Mechanical circulatory support for infants and children with cardiac disease

Mechanical circulatory support is assuming an expanding role in the practice of congenital cardiac surgery. Extracorporeal membrane oxygenation and centrifugal ventricular assist devices are still the mainstay of mechanical circulatory support for children; however, newly developed pulsatile, paracorporeal ventricular assist devices designed for pediatric applications are achieving increased utilization. In addition, several new, continuous flow devices that are under development as fully implantable systems for adults, ultimately may be useful for pediatric patients.

Extracorporeal membrane oxygenation for severe respiratory failure

The use of extracorporeal technology to accomplish gas exchange with or without cardiac support is based on the premise that "lung rest" facilitates repair and avoids the baso- or volutrauma of mechanical ventilator management. Extracorporeal membrane oxygenation (ECMO), a modified form of cardiopulmonary bypass, has been shown to decrease mortality of neonatal, pediatric and adult respiratory failure and is capable of total gas exchange. In neonates, over 20,638 patients have been treated with an overall survival of 77% in a population thought to have 78% mortality.