Concomitant Respiratory Failure Can Impair Myocardial Oxygenation in Patients with Acute Cardiogenic Shock Supported by VA-ECMO

Development of idealized human aortic models for in vitro and in silico hemodynamic studies

Background

The aorta, a central component of the cardiovascular system, plays a pivotal role in ensuring blood circulation. Despite its importance, there is a notable lack of idealized models for experimental and computational studies.

Objective

This study aims to develop computer-aided design (CAD) models for the idealized human aorta, intended for studying hemodynamics or solid mechanics in both in vitro and in silico settings.

Methods

Various parameters were extracted from comprehensive literature sources to evaluate major anatomical characteristics of the aorta in healthy adults, including variations in aortic arch branches and corresponding dimensions. The idealized models were generated based on averages weighted by the cohort size of each study for several morphological parameters collected and compiled from image-based or cadaveric studies, as well as data from four recruited subjects. The models were used for hemodynamics assessment using particle image velocimetry (PIV) measurements and computational fluid dynamics (CFD) simulations.

Results

Two CAD models for the idealized human aorta were developed, focusing on the healthy population. The CFD simulations, which align closely with the PIV measurements, capture the main global flow features and wall shear stress patterns observed in patient-specific cases, demonstrating the capabilities of the designed models.

Conclusions

The collected statistical data on the aorta and the two idealized aorta models, covering prevalent arch variants known as Normal and Bovine types, are shown to be useful for examining the hemodynamics of the aorta. They also hold promise for applications in designing medical devices where anatomical statistics are needed.

Left ventricular hemodynamics with veno-arterial extracorporeal membrane oxygenation

BACKGROUND

There is considerable debate about the hemodynamic effects of veno-arterial extracorporeal membrane oxygenation (VA-ECMO).

AIMS

To evaluate the changes in left ventricular (LV) function, volumes, and work in patients treated with VA-ECMO using invasive LV catheterization and three-dimensional echocardiographic volumes.

METHODS

Patients on VA-ECMO underwent invasive hemodynamic evaluation due to concerns regarding candidacy for decannulation. Hemodynamic parameters were reported as means±standard deviations or medians (interquartile ranges) after evaluating for normality. Paired comparisons were done to evaluate hemodynamics at the baseline (highest) and lowest tolerated levels of VA-ECMO support.

RESULTS

Twenty patients aged 52.3 ± 15.8 years were included. All patients received VA-ECMO for refractory cardiogenic shock (5/20 SCAI stage D, 15/20 SCAI stage E). At 3.0 (2.0, 4.0) days after VA-ECMO cannulation, the baseline LV ejection fraction was 20% (15%, 27%). The baseline and lowest VA-ECMO flows were 4.0 ± 0.6 and 1.5 ± 0.6 L/min, respectively. Compared to the lowest flow, full VA-ECMO support reduced LV end-diastolic volume [109 ± 81 versus 134 ± 93 mL, p = 0.001], LV end-diastolic pressure (14 ± 9 vs. 19 ± 9 mmHg, p < 0.001), LV stroke work (1858 ± 1413 vs. 2550 ± 1486 mL*mmHg, p = 0.002), and LV pressure-volume area (PVA) (4507 ± 1910 vs. 5193 ± 2388, p = 0.03) respectively. Mean arterial pressure was stable at the highest and lowest flows (80 ± 16 vs. 75 ± 14, respectively; p = 0.08) but arterial elastance was higher at the highest VA-ECMO flow (4.9 ± 2.2 vs lowest flow 2.7 ± 1.6; p < 0.001).

CONCLUSIONS

High flow VA-ECMO support significantly reduced LV end-diastolic pressure, end-diastolic volume, stroke work, and PVA compared to minimal support. The Ea was higher and MAP was stable or minimally elevated on high flow.

Extracorporeal Membrane Oxygenation

The utilization of extracorporeal membrane oxygenation (ECMO) for cardiopulmonary support continues to increase globally, with > 190,000 ECMO cases reported to the international Extracorporeal Life Support Organization Registry. The present review aims to synthesize important contributions to the literature surrounding the management of mechanical ventilation, prone positioning, anticoagulation, bleeding complications, and neurologic outcomes for infants, children, and adults undergoing ECMO in 2022. Additionally, issues related to cardiac ECMO, Harlequin syndrome, and anticoagulation during ECMO will be discussed.

The effect of arterial cannula tip position on differential hypoxemia during venoarterial extracorporeal membrane oxygenation

Interaction between native ventricular output and venoarterial extracorporeal membrane oxygenation (VA ECMO) flow may hinder oxygenated blood flow to the aortic arch branches, resulting in differential hypoxemia. Typically, the arterial cannula tip is placed in the iliac artery or abdominal aorta. However, the hemodynamics of a more proximal arterial cannula tip have not been studied before. This study investigated the effect of arterial cannula tip position on VA ECMO blood flow to the upper extremities using computational fluid dynamics simulations. Four arterial cannula tip positions (P1. common iliac, P2. abdominal aorta, P3. descending aorta and P4. aortic arch) were compared with different degrees of cardiac dysfunction and VA ECMO support (50%, 80% and 90% support). P4 was able to supply oxygenated blood to the arch vessels at all support levels, while P1 to P3 only supplied the arch vessels during the highest level (90%) of VA ECMO support. Even during the highest level of support, P1 to P3 could only provide oxygenated VA-ECMO flow at 0.11 L/min to the brachiocephalic artery, compared with 0.5 L/min at P4. This study suggests that cerebral perfusion of VA ECMO flow can be increased by advancing the arterial cannula tip towards the aortic arch.

Mechanical Assist Device-Assisted Percutaneous Coronary Intervention: The Use of Impella Versus Extracorporeal Membrane Oxygenation as an Emerging Frontier in Revascularization in Cardiogenic Shock

The extracorporeal membrane oxygenation (ECMO) procedure aids in the provision of prolonged cardiopulmonary support, whereas the Impella device (Abiomed, Danvers, MA) is a ventricular assist device that maintains circulation by pumping blood into the aorta from the left ventricle. Blood is circulated in parallel with the heart by Impella. It draws blood straight into the aorta from the left ventricle, hence preserving the physiological flow. ECMO bypasses the left atrium and the left ventricle, and the end consequence is a non-physiological flow. In this article, we conducted a detailed analysis of various publications in the literature and examined various modalities pertaining to the use of ECMO and Impella for cardiogenic shocks, such as efficacy, clinical outcomes, cost-effectiveness, device-related complications, and limitations. The Impella completely unloads the left ventricle, thereby significantly reducing the effort of the heart. Comparatively, ECMO only stabilizes a patient with cardiogenic shock for a short stretch of time and does not lessen the efforts of the left ventricle ("unload" it). In the acute setting, both devices reduced left ventricular end-diastolic pressure and provided adequate hemodynamic support. By comparing patients on Impella to those receiving ECMO, it was found that patients on Impella were associated with better clinical results, quicker recovery, limited complications, and reduced healthcare costs; however, there is a lack of conclusive studies performed demonstrating the reduction in long-term mortality rates. Considering the effectiveness of given modalities and taking into account the various studies described in the literature, Impella has reported better clinical outcomes although more clinical trials are needed for establishing the effectiveness of these interventional approaches in revascularization in cardiogenic shock.

Drainage From Superior Vena Cava Improves Upper Body Oxygenation in Patients on Femoral Veno-Arterial Extracorporeal Membrane Oxygenation

Objective

To investigate the feasibility of drainage from the superior vena cava (SVC) to improve upper body oxygenation in patients with cardiogenic shock undergoing femoral veno-arterial extracorporeal membrane oxygenation (VA ECMO).

Methods

Seventeen adult patients receiving peripheral femoral VA ECMO for circulatory support were enrolled. The femoral drainage cannula was shifted three times (from the inferior vena cava (IVC) level to the SVC level and then the IVC level again), all under ultrasound guidance, at an interval of 15 minutes. The blood gas levels of the right radial artery (RA) and SVC and cerebral oxygen saturation (ScO₂) were measured and compared.

Results

Fifteen patients (88.2%) were successfully weaned from ECMO, and 12 patients (70.6%) survived to discharge. The oxygen saturation (SO₂) and oxygen partial pressure (PO₂) of the RA (97.0 ± 3.5% to 98.3 ± 1.5%, P < 0.05, SO₂; 127.4 ± 58.2 mmHg to 153.1 ± 67.8 mmHg, P < 0.05, PO₂) and SVC (69.5 ± 9.0% to 75.7 ± 8.5%, P < 0.05, SO₂; 38.5 ± 5.6 mmHg to 43.6 ± 6.4 mmHg, P < 0.05, PO₂) were increased; ScO₂ was also increased on both sides (left: 50.6 ± 8.6% to 55.0 ± 9.0%, P < 0.05; right: 48.7 ± 9.2% to 52.3 ± 9.8%, P < 0.05) when the femoral drainage cannula was shifted from the IVC level to the SVC level. When the femoral drainage cannula was shifted from SVC level to the IVC level again, the SO₂ and PO₂ of RA (98.3 ± 1.5% to 96.9 ± 3.2%, P <0.05, SO₂; 153.1 ± 67.8 mmHg to 125.8 ± 63.3 mmHg, P <0.05, PO₂) and SVC (75.7 ± 38.5% to 70.4 ± 7.6%, P <0.05, SO₂; 43.6 ± 6.4 mmHg to 38.9 ± 4.5 mmHg, P <0.05, PO₂) were decreased; ScO₂ was also reduced on both sides (left: 55.0 ± 9.0% to 50.7 ± 8.2%, P < 0.05; right: 52.3 ± 9.8% to 48.7 ± 9.3%, P <0.05).

Conclusion

Drainage from the SVC by shifting the cannula upward could improve upper body oxygenation in patients with cardiogenic shock undergoing femoral VA ECMO. This cannulation strategy provides an alternative solution for differential hypoxia.

Extracorporeal Life Support for Cardiac Arrest and Cardiogenic Shock

The rising incidence and recognition of cardiogenic shock has led to an increase in the use of veno-arterial extracorporeal membrane oxygenation (VA-ECMO). As clinical experience with this therapy has increased, there has also been a rapid growth in the body of observational and randomized data describing the clinical and logistical considerations required to institute a VA-ECMO program with successful clinical outcomes. The aim of this review is to summarize this contemporary data in the context of four key themes that pertain to VA-ECMO programs: the principles of patient selection; basic hemodynamic and technical principles underlying VA-ECMO; contraindications to VA-ECMO therapy; and common complications and intensive care considerations that are encountered in the setting of VA-ECMO therapy.

Overview of Veno-Arterial Extracorporeal Membrane Oxygenation (VA-ECMO) Support for the Management of Cardiogenic Shock

Cardiogenic shock accounts for ~100,000 annual hospital admissions in the United States. Despite improvements in medical management strategies, in-hospital mortality remains unacceptably high. Multiple mechanical circulatory support devices have been developed with the aim to provide hemodynamic support and to improve outcomes in this population. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is the most advanced temporary life support system that is unique in that it provides immediate and complete hemodynamic support as well as concomitant gas exchange. In this review, we discuss the fundamental concepts and hemodynamic aspects of VA-ECMO support in patients with cardiogenic shock of various etiologies. In addition, we review the common indications, contraindications and complications associated with VA-ECMO use.