Blood flow and emboli transport patterns during venoarterial extracorporeal membrane oxygenation: A computational fluid dynamics study.

PROBLEM: Despite advances in Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO), a significant mortality rate persists due to complications. The non-physiological blood flow dynamics of VA-ECMO may lead to neurological complications and organ ischemia. Continuous retrograde high-flow oxygenated blood enters through a return cannula placed in the femoral artery which opposes the pulsatile deoxygenated blood ejected by the left ventricle (LV), which impacts upper body oxygenation and subsequent hyperoxemia. The complications underscore the critical need to comprehend the impact of VA-ECMO support level and return cannula size, as mortality remains a significant concern. AIM: The aim of this study is to predict and provide insights into the complications associated with VA-ECMO using computational fluid dynamics (CFD) simulations. These complications will be assessed by characterising blood flow and emboli transport patterns through a comprehensive analysis of the influence of VA-ECMO support levels and arterial return cannula sizes. METHODS: Patient-specific 3D aortic and major branch models, derived from a male patient's CT scan during VA-ECMO undergoing respiratory dysfunction, were analyzed using CFD. The investigation employed species transport and discrete particle tracking models to study ECMO blood (oxygenated) mixing with LV blood (deoxygenated) and to trace emboli transport patterns from potential sources (circuit, LV, and aorta wall). Two cannula sizes (15 Fr and 19 Fr) were tested alongside varying ECMO pump flow rates (50%, 70%, and 90% of the total cardiac output). RESULTS: Cannula size did not significantly affect oxygen transport. At 90% VA-ECMO support, all arteries distal to the aortic arch achieved 100% oxygen saturation. As support level decreased, oxygen transport to the upper body also decreased to a minimum saturation of 73%. Emboli transport varied substantially between emboli origin and VAECMO support level, with the highest risk of cerebral emboli coming from the LV with a 15 Fr cannula at 90% support. CONCLUSION: Arterial return cannula sizing minimally impacted blood oxygen distribution; however, it did influence the distribution of emboli released from the circuit and aortic wall. Notably, it was the support level alone that significantly affected the mixing zone of VA-ECMO and cardiac blood, subsequently influencing the risk of embolization of the cardiogenic source and oxygenation levels across various arterial branches.

Effect of RVAD Cannulation Length on Right Ventricular Thrombosis Risk: An In Silico Investigation.

Left ventricular assist devices (LVADs) have been used off-label as long-term support of the right heart due to the lack of a clinically approved durable right VAD (RVAD). Whilst various techniques to reduce RVAD inflow cannula protrusion have been described, the implication of the protrusion length on right heart blood flow and subsequent risk of thrombosis remains poorly understood. This study investigates the influence of RVAD diaphragmatic cannulation length on right ventricular thrombosis risk using a patient-specific right ventricle in silico model validated with particle image velocimetry. Four cannulation lengths (5, 10, 15 and 25 mm) were evaluated in a one-way fluid-structure interaction simulation with boundary conditions generated from a lumped parameter model, simulating a biventricular supported condition. Simulation results demonstrated that the 25-mm cannulation length exhibited a lower thrombosis risk compared to 5-, 10- and 15-mm cannulation lengths due to improved flow energy distribution (25.2%, 24.4% and 17.8% increased), reduced stagnation volume (72%, 68% and 49% reduction), better washout rate (13.0%, 11.6% and 9.1% faster) and lower blood residence time (6% reduction). In the simulated scenario, our findings suggest that a longer RVAD diaphragmatic cannulation length may be beneficial in lowering thrombosis risk; however, further clinical studies are warranted.

ECMO PAL: using deep neural networks for survival prediction in venoarterial extracorporeal membrane oxygenation.

PURPOSE: Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is a complex and high-risk life support modality used in severe cardiorespiratory failure. ECMO survival scores are used clinically for patient prognostication and outcomes risk adjustment. This study aims to create the first artificial intelligence (AI)-driven ECMO survival score to predict in-hospital mortality based on a large international patient cohort. METHODS: A deep neural network, ECMO Predictive Algorithm (ECMO PAL) was trained on a retrospective cohort of 18,167 patients from the international Extracorporeal Life Support Organisation (ELSO) registry (2017-2020), and performance was measured using fivefold cross-validation. External validation was performed on all adult registry patients from 2021 (N = 5015) and compared against existing prognostication scores: SAVE, Modified SAVE, and ECMO ACCEPTS for predicting in-hospital mortality. RESULTS: Mean age was 56.8 ± 15.1 years, with 66.7% of patients being male and 50.2% having a pre-ECMO cardiac arrest. Cross-validation demonstrated an inhospital mortality sensitivity and precision of 82.1 ± 0.2% and 77.6 ± 0.2%, respectively. Validation accuracy was only 2.8% lower than training accuracy, reducing from 75.5% to 72.7% [99% confidence interval (CI) 71.1-74.3%]. ECMO PAL accuracy outperformed the ECMO ACCEPTS (54.7%), SAVE (61.1%), and Modified SAVE (62%) scores. CONCLUSIONS: ECMO PAL is the first AI-powered ECMO survival score trained and validated on large international patient cohorts. ECMO PAL demonstrated high generalisability across ECMO regions and outperformed existing, widely used scores. Beyond ECMO, this study highlights how large international registry data can be leveraged for AI prognostication for complex critical care therapies.

Impact of Concomitant Mitral Regurgitation on the Hemodynamic Indicators of Aortic Stenosis.

Background In patients with aortic stenosis (AS), the presence of mitral regurgitation (MR) can lead to underestimation of AS severity and worse clinical outcomes. The objective of this study was to characterize the magnitude of the effects of concomitant MR on hemodynamic indicators of AS severity using clinical data and a computational cardiovascular simulation. Methods and Results Echocardiographic data from 1427 patients with severe AS were used to inform a computational cardiovascular system model, and varying degrees of MR and AS were simulated. Hemodynamic data, including left ventricular and aortic pressure waveforms, were generated for all simulations. Simulated reduction in mean transaortic pressure gradient (MPG) associated with MR was then used to calculate the adjusted MPG in the clinical cohort. MR was present in 861 (60%) patients. Compared with patients without MR, patients with MR had a lower aortic-valve area (0.83±0.2 cm2 versus 0.75±0.2; P<0.001) and were more likely to have a low-gradient pattern (MPG <40 mm Hg) (45% versus 54%; P<0.001). Simulations showed that the presence of concomitant mild, moderate, and severe MR with AS was accompanied by a mean reduction in MPG of 10%, 29%, and 40%, respectively. For patients with MR, their calculated adjusted MPG was on average 24% higher than their MPG (52±22 versus 42±16 mm Hg). Of the 467 patients with low-gradient AS and MR, 240 (51%) would reclassify as high gradient based on their adjusted MPG. Conclusions Concomitant MR results in lower MPG and reduced forward flow compared with isolated AS. Careful quantitation of MR should be factored into the assessment of AS severity to mitigate for potential underestimation.

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.

Ex vivo evaluation of personal protective equipment in hands-on defibrillation.

Background: Defibrillation guidelines recommend avoiding patient contact during shock delivery. However, hands-on defibrillation (compressions during shock) and manual pressure augmentation (MPA - pushing on the defibrillator pads during shock) may lead to improved clinical outcomes. There are limited data addressing the protection provided by personal protective equipment (PPE) during hands-on defibrillation and MPA. This study investigated the hand-to-hand and hand-to-knee leakage current experienced by a simulated kneeling provider wearing different PPE. Methods: A defibrillator was used in experiments on a pork shoulder, investigating three different hands-on positions: closed fist on defibrillator pads; open palm on pads with inadvertent finger contact (overhang); and open palm on the chest. Evaluated PPE included single and double gloves (nitrile and latex) and rescuer cargo trousers in wet and dry conditions (N = 126 experiments). Results: Mean hand-to-hand leakage currents in MPA without PPE was 0.41 mA (0.2-0.74 mA) and with PPE was 0.2 mA (0.08-0.58 mA). For experiments involving finger or palm contact on the chest, wearing any PPE resulted in a >99% reduction in mean leakage currents from an average 354.58 mA (258.96-446.22 mA) to an average 0.48 mA (0.16-1.56 mA). Rescuer trousers were insulative in dry conditions even without gloves (0.2-1.2 mA). Conclusion: This study demonstrated that the tested clinical examination gloves markedly reduced leakage current to the rescuer and that the lowest levels of leakage current occurred during MPA attributed to the electrical insulation of the pads.

Cardio-geriatric model of care in acute heart failure: initial experience of a multidisciplinary approach in complex elderly patients.

A 'cardio-geriatric' heart failure model of care was implemented to address the high rates of readmission in elderly acute decompensated heart failure patients. Despite demonstrably intensified management in both the cardiology and geriatric domains, this study did not demonstrate a positive effect on the primary outcome of all cause readmissions at 30 days.

The impact of cultural and linguistic diversity on hospital readmission in patients hospitalized with acute heart failure.

AIMS: Health services worldwide face the challenge of providing care for increasingly culturally and linguistically diverse (CALD) populations. The aims of this study were to determine whether CALD patients hospitalized with acute heart failure (HF) are at increased risk of rehospitalization and emergency department (ED) visitation after discharge, compared to non-CALD patients, and within CALD patients to ascertain the impact of limited English proficiency (LEP) on outcomes. METHODS AND RESULTS: A cohort of 1613 patients discharged from hospital following an episode of acute HF was derived from hospital administrative datasets. CALD status was based on both country of birth and primary spoken language. Comorbidities, HF subtype, age, sex and socioeconomic status, and hospital readmission and ED visitation incidences, were compared between groups. A Cox proportional hazard model was employed to adjust for potential confounders. The majority of patients were classified as CALD [1030 (64%)]. Of these, 488 (30%) were designated as English proficient (CALD-EP) and 542 (34%) were designated CALD-LEP. Compared to non-CALD, CALD-LEP patients exhibited a greater cumulative incidence of HF-related readmission and ED visitation, as expressed by an adjusted hazard ratio (HR) [1.27 (1.02-1.57) and 1.40 (1.18-1.67), respectively]; this difference was not significant for all-cause readmission [adjusted HR 1.03 (0.88-1.20)]. CALD-EP showed a non-significant trend towards increased rehospitalization and ED visitation. CONCLUSION: This study suggests that CALD patients with HF, in particular those designated as CALD-LEP, have an increased risk of HF rehospitalization and ED visitation. Further research to elucidate the underlying reasons for this disparity are warranted.

Impact of limited English proficiency on presentation and outcomes of patients undergoing primary percutaneous coronary intervention for ST-elevation myocardial infarction.

Doctor-patient language discordance has been shown to lead to worse clinical outcomes. In this study of patients undergoing primary percutaneous coronary intervention for ST-elevation myocardial infarction at an Australian health service, we demonstrated that limited English proficiency (LEP) is an independent predictor of prolonged symptom-to-door time, but does not lead to worse 30-day mortality compared with English-proficient patients. More effort needs to be placed in providing public health education in varied languages to encourage early presentation to hospital for patients with LEP.

Inorganic nitrate as a treatment for acute heart failure: a protocol for a single center, randomized, double-blind, placebo-controlled pilot and feasibility study.

BACKGROUND: Acute heart failure (AHF) is a frequent reason for hospitalization worldwide and effective treatment options are limited. It is known that AHF is a condition characterized by impaired vasorelaxation, together with reduced nitric oxide (NO) bioavailability, an endogenous vasodilatory compound. Supplementation of inorganic sodium nitrate (NaNO3) is an indirect dietary source of NO, through bioconversion. It is proposed that oral sodium nitrate will favorably affect levels of circulating NO precursors (nitrate and nitrite) in AHF patients, resulting in reduced systemic vascular resistance, without significant hypotension. METHODS AND OUTCOMES: We propose a single center, randomized, double-blind, placebo-controlled pilot trial, evaluating the feasibility of sodium nitrate as a treatment for AHF. The primary hypothesis that sodium nitrate treatment will result in increased systemic levels of nitric oxide pre-cursors (nitrate and nitrite) in plasma, in parallel with improved vasorelaxation, as assessed by non-invasively derived systemic vascular resistance index. Additional surrogate measures relevant to the known pathophysiology of AHF will be obtained in order to assess clinical effect on dyspnea and renal function. DISCUSSION: The results of this study will provide evidence of the feasibility of this novel approach and will be of interest to the heart failure community. This trial may inform a larger study.