Management of Peripheral Venoarterial Extracorporeal Membrane Oxygenation in Cardiogenic Shock

Temporary Mechanical Circulatory Support after Cardiac Surgery

Postcardiotomy shock in the cardiac surgical patient is a highly morbid condition characterized by profound myocardial impairment and decreased systemic perfusion inadequate to meet end-organ metabolic demand. Postcardiotomy shock is associated with significant morbidity and mortality. Poor outcomes motivate the increased use of mechanical circulatory support (MCS) to restore perfusion in an effort to prevent multiorgan injury and improve patient survival. Despite growing acceptance and adoption of MCS for postcardiotomy shock, criteria for initiation, clinical management, and future areas of clinical investigation remain a topic of ongoing debate. This article seeks to (1) define critical cardiac dysfunction in the patient after cardiotomy, (2) provide an overview of commonly used MCS devices, and (3) summarize the relevant clinical experience for various MCS devices available in the literature, with additional recognition for the role of MCS as a part of a modified approach to the cardiac arrest algorithm in the cardiac surgical patient.

Femoro-axillary versus femoro-femoral veno-arterial extracorporeal membrane oxygenation for refractory cardiogenic shock: A monocentric retrospective study

RATIONALE

For veno-arterial extracorporeal membrane oxygenation (ECMO), the femoral artery is the preferred cannulation site (femoro-femoral: Vf-Af). This results in retrograde aortic flow, which increases the left ventricular afterload and can lead to severe pulmonary edema and thrombosis of the cardiac chambers. Right axillary artery cannulation (femoral-axillary: Vf-Aa) provides partial anterograde aortic flow, which may prevent some complications. This study aimed to compare the 90-day mortality and complication rates between VF-AA and VF-AF.

METHODS

Consecutive adult patients with cardiogenic shock who received peripheral VA-ECMO between 2013 and 2019 at our institution were retrospectively included. The exclusion criteria were refractory cardiac arrest, multiple VA-ECMO implantations due to vascular access changes, weaning failure, or ICU readmission. A statistical approach using inverse probability of treatment weighting was used to estimate the effect of the cannulation site on the outcomes. The primary endpoint was the 90-day mortality. The secondary endpoints were vascular access complications, stroke, and other complications related to retrograde blood flow. Outcomes were estimated using logistic regression analysis.

RESULTS

VA-ECMO was performed on 534 patients. Patients with refractory cardiac arrest (n = 77 (14%)) and those supported by multiple VA-ECMO (n = 92, (17%)) were excluded. Out of the 333 patients studied (n = 209 Vf-Aa; n = 124 VF-AF), the main indications for VA-ECMO implantation were post-cardiotomy (33%, n = 109), dilated cardiomyopathy (20%, n = 66), post-cardiac transplantation (15%, n = 50), acute myocardial infarction (14%, n = 46) and other etiologies (18%, n = 62). The median SOFA score was 9 [7-11], and the crude 90-day mortality rate was 53% (n = 175). After IPTW, the 90-day mortality was similar in the Vf-Aa and VF-AF groups (54% vs 58%, IPTW-OR = 0.84 [0.54-1.29]). Axillary artery cannulation was associated with significantly fewer local infections (OR = 0.21, 95% CI:0.09-0.51), limb ischemia (OR = 0.37, 95% CI:0.17-0.84), bowel ischemia (OR = 0.16, 95% CI:0.05-0.51) and pulmonary edema (OR = 0.52, 95% CI:0.29-0.92) episodes, but with a higher rate of stroke (OR = 2.87, 95% CI:1.08-7.62) than femoral artery cannulation.

CONCLUSION

Compared to VF-AF, axillary cannulation was associated with similar 90-day mortality rates. The high rate of stroke associated with axillary artery cannulation requires further investigation.

Steady Flow Left Ventricle Unloading Is Superior to Pulsatile Pressure Augmentation Venting During Venoarterial Extracorporeal Membrane Oxygenation Support

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) shunts venous blood to the systemic arterial circulation to provide end-organ perfusion while increasing afterload that may impede left ventricle (LV) ejection and impair cardiac recovery. To maintain flow across the aortic valve and reduce risk of lethal clot formation, secondary mechanical circulatory support (MCS) devices are increasingly used despite limited understanding of their effects on cardiac function. This study sought to quantify the effects of VA-ECMO and combined with either intraaortic balloon pump (IABP) or percutaneous ventricular assist device (pVAD) on LV physiologic state and perfusion metrics in a porcine model of acute cardiogenic shock. Shock was induced through serial left anterior descending artery microbead embolization followed by initiation of VA-ECMO support and then placement of either IABP or pVAD. Hemodynamic measurements, LV pressure-volume loops, and carotid artery blood flow were evaluated before and after institution of combined MCS. The IABP decreased LV end-diastolic pressure by a peak of 15% while slightly increasing LV stroke work compared with decreases of more than 60% and 50% with the pVAD, respectively. The pVAD also demonstrated increased coronary perfusion and systemic pressure gradients in comparison to the IABP. Combined support with VA-ECMO and pVAD improves cardiovascular state in comparison to IABP.

Extracorporeal Membrane Oxygenation (VA-ECMO) in Management of Cardiogenic Shock

Cardiogenic shock is a critical condition of low cardiac output resulting in insufficient systemic perfusion and end-organ dysfunction. Though significant advances have been achieved in reperfusion therapy and mechanical circulatory support, cardiogenic shock continues to be a life-threatening condition associated with a high rate of complications and excessively high patient mortality, reported to be between 35% and 50%. Extracorporeal membrane oxygenation can provide full cardiopulmonary support, has been increasingly used in the last two decades, and can be used to restore systemic end-organ hypoperfusion. However, a paucity of randomized controlled trials in combination with high complication and mortality rates suggest the need for more research to better define its efficacy, safety, and optimal patient selection. In this review, we provide an updated review on VA-ECMO, with an emphasis on its application in cardiogenic shock, including indications and contraindications, expected hemodynamic and echocardiographic findings, recommendations for weaning, complications, and outcomes. Furthermore, specific emphasis will be devoted to the two published randomized controlled trials recently presented in this setting.

Simulation of Fluid-Structure Interaction in Extracorporeal Membrane Oxygenation Circulatory Support Systems

Extracorporeal membrane oxygenation (ECMO) is a vital mechanical circulatory support modality capable of restoring perfusion for the patient in circulatory failure. Despite increasing adoption of ECMO, there is incomplete understanding of its effects on systemic hemodynamics and how the vasculature responds to varying levels of continuous retrograde perfusion. To gain further insight into the complex ECMO:failing heart circulation, computational fluid dynamics simulations focused on perfusion distribution and hemodynamic flow patterns were conducted using a patient-derived aorta geometry. Three case scenarios were simulated: (1) healthy control; (2) 90% ECMO-derived perfusion to model profound heart failure; and, (3) 50% ECMO-derived perfusion to model the recovering heart. Fluid-structure interface simulations were performed to quantify systemic pressure and vascular deformation throughout the aorta over the cardiac cycle. ECMO support alters pressure distribution while decreasing shear stress. Insights derived from computational modeling may lead to better understanding of ECMO support and improved patient outcomes.

Effect of anatomical variation on extracorporeal membrane oxygenation circulatory support: A computational study

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) via femoral cannulation is a vital intervention capable of rapidly restoring perfusion for patients in shock. Despite increasing use to provide circulatory support, its hemodynamic effects are poorly understood and the impact of patient-specific anatomical variation on perfusion is unknown. This study investigates the complex failing heart-mechanical circulatory support circulation and analyzes the effect of patient-specific vascular anatomical variations on hemodynamics and end-organ perfusion.

METHODS

Patient-specific vascular geometries were constructed from segmenting clinical computerized tomography angiography images and quantitatively compared using tortuosity, curvature, torsion, and lumen diameter. Computational fluid dynamic simulations were performed on a subset of geometries selected to represent a range of anatomical variation. Heart failure severity was modeled by varying the relative fraction of total flow provided by the heart and the extracorporeal circuit. A 3-element lumped parameter model was applied to accurately and dynamically model distal perfusion boundary conditions. Hemodynamic parameters and end-organ perfusion were analyzed and compared to assess the effect of anatomical variation.

RESULTS

Pulsatile antegrade cardiac perfusion and ECMO retrograde perfusion collide in the aorta to form a dynamic watershed region. The size, position, and variation of this region over the cardiac cycle is substantially altered by patient anatomical region. Increased vascular tortuosity reduces the proximal extent of flow from circulatory support and decreases the size of the watershed region.

CONCLUSIONS

Patient vascular anatomy is a key determinant of the ECMO-failing heart circulation that alters the location and extent of the watershed region and affects the tissues at risk for differential hypoxia and circuit-derived thromboemboli for a given level of support.

Cardiogenic shock in Taiwan from 2003 to 2017 (CSiT-15 study)

BACKGROUND

This study investigated temporal trends in the treatment and mortality of patients with cardiogenic shock (CS) in Taiwan in relation to acute myocardial infarction (AMI) accreditation implemented in 2009 and the unavailability of percutaneous ventricular assist devices.

METHODS

Data of patients diagnosed as having CS between January 2003 and December 2017 were collected from Taiwan's National Health Insurance Research Database. Each case was followed from the date of emergency department arrival or hospital admission for the first incident associated with a CS diagnosis up to a 1-year interval. Measurements included demographics, comorbidities, treatment, mortality, and medical costs. Using an interrupted time-series (ITS) design with multi-level mixed-effects logistic regression model, we assessed the impact of AMI accreditation implementation on the mortality of patients with AMI and CS overall and stratified by the hospital levels.

RESULTS

In total, 64 049 patients with CS (mean age:70 years; 62% men) were identified. The incidence rate per 10⁵ person-years increased from 17 in 2003 to 25 in 2010 and plateaued thereafter. Average inpatient costs increased from 159 125 points in 2003 to 240 993 points in 2017, indicating a 1.5-fold increase. The intra-aortic balloon pump application rate was approximately 22-25% after 2010 (p = 0.093). Overall, in-hospital, 30-day, and 1-year mortality declined from 60.3%, 63.0%, and 69.3% in 2003 to 47.9%, 50.8% and 59.8% in 2017, respectively. The decline in mortality was more apparent in patients with AMI-CS than in patients with non-AMI-CS. The ITS estimation revealed a 2% lower in-hospital mortality in patients with AMI-CS treated in district hospitals after the AMI accreditation had been implemented for 2 years.

CONCLUSIONS

In Taiwan, the burden of CS has consistently increased due to high patient complexity, advanced therapies, and stable incidence. Mortality declined over time, particularly in patients with AMI-CS, which may be attributable to advancements in AMI therapies and this quality-improving policy.

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.

Extracorporeal Membrane Oxygenation for Poisonings Reported to U.S. Poison Centers from 2000 to 2018: An Analysis of the National Poison Data System

OBJECTIVES

To assess trends in the use of extracorporeal membrane oxygenation for poisoning in the United States.

DESIGN

Retrospective cohort study.

SETTING

The National Poison Data System, the databased owned and managed by the American Association of Poison Control Centers, the organization that supports and accredits all 55 U.S. Poison Centers, 2000-2018.

PATIENTS

All patients reported to National Poison Data System treated with extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In total, 407 patients met final inclusion criteria (332 adults, 75 children). Median age was 27 years (interquartile range, 15-39 yr); 52.5% were male. Median number of ingested substances was three (interquartile range, 2-4); 51.5% were single-substance exposures. Extracorporeal membrane oxygenation use in poisoned patients in the United States has significantly increased over time (z = 3.18; p = 0.001) in both adults (age > 12 yr) and children (age ≤ 12 yr), increasing by 9-100% per year since 2008. Increase in use occurred more commonly in adults. We found substantial geographical variation in extracorporeal membrane oxygenation use by geospatially mapping the ZIP code associated with the initial call, with large, primarily rural areas of the United States reporting no cases. Overall survival was 70% and did not vary significantly over the study period for children or adults. Patients with metabolic and hematologic poisonings were less likely to survive following extracorporeal membrane oxygenation than those with other poisonings (49% vs 72%; p = 0.004).

CONCLUSIONS

The use of extracorporeal membrane oxygenation to support critically ill, poisoned patients in the United States is increasing, driven primarily by increased use in patients greater than 12 years old. We observed no trends in survival over time. Mortality was higher when extracorporeal membrane oxygenation was used for metabolic or hematologic poisonings. Large, predominantly rural regions of the United States reported no cases of extracorporeal membrane oxygenation for poisoning. Further research should focus on refining criteria for the use of extracorporeal membrane oxygenation in poisoning.

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.

Noteworthy Literature From 2019 for Cardiothoracic Critical Care

This annual article summarizes key findings from notable studies published in 2019 relevant to the practice of cardiothoracic critical care medicine. This year's article encompasses updates to the literature on enhanced recovery after cardiac surgery, extracorporeal membranous oxygenation, delirium, and primary graft dysfunction after heart transplant.