Duration of Untreated Cardiac Arrest and Clinical Relevance of Animal Experiments: The Relationship Between the “No-Flow” Duration and the Severity of Post-Cardiac Arrest Syndrome in a Porcine Model

Dodecafluoropentane improves neuro-behavioral outcomes and return of spontaneous circulation rate in a swine model of cardiac arrest

INTRODUCTION

Dodecafluoropentane emulsion (DDFPe) administration has previously demonstrated improved gas exchange in single-organ perfusion models. This could translate to prevention of brain injury in cardiac arrest.

METHODS

We induced cardiac arrest in 12 pigs, performing CPR after 5-minute downtime. Pigs were randomly assigned to DDFPe (n = 7) or saline placebo (n = 5) groups. Neurologic injury biomarkers were measured at baseline, after return of spontaneous circulation (ROSC), and every 24 hours in survivors. Blinded Neurological Alertness Score, Neurological Dysfunction Score, and Overall Performance Score was performed in addition to histopathological scoring of parietal and hippocampal sections.

RESULTS

One placebo and four DDFPe pigs survived the 96-hour observation period. The odds ratio for ROSC was 7.2 (p = 0.22). Survival odds ratio was 4.6 (p = 0.29). All surviving animals had impaired motor responses that recovered by 72 hours. DDFPe animals showed better neuro-behavioral scores than placebo.

CONCLUSION

The findings of this novel study provide a proof of concept and early signal toward efficacy of intravenous DDFPe in cardiac arrest. The trend toward improved ROSC and functional survival may reflect improved microcirculatory gas exchange in DDFPe animals. Improving gas exchange in brain microcirculation during resuscitation from cardiac arrest may provide a significant therapeutic benefit.

Hypothermia After Cardiac Arrest in Large Animals (HACA-LA): Study protocol of a randomized controlled experimental trial

Background

Induced hypothermia post-cardiac arrest is neuroprotective in animal experiments, but few high-quality studies have been performed in larger animals with human-like brains. The neuroprotective effect of postischemic hypothermia has recently been questioned in human trials. Our aim is to investigate whether hypothermia post-cardiac arrest confers a benefit compared to normothermia in large adult animals. Our hypothesis is that induced hypothermia post cardiac arrest is neuroprotective and that the effect diminishes when delayed two hours.

Methods

Adult female pigs were anesthetized, mechanically ventilated and kept at baseline parameters including normothermia (38 °C). All animals were subjected to ten minutes of cardiac arrest (no-flow) by induced ventricular fibrillation, followed by four minutes of cardiopulmonary resuscitation with mechanical compressions, prior to the first countershock. Animals with sustained return of spontaneous circulation (systolic blood pressure >60 mmHg for ten minutes) within fifteen minutes from start of life support were included and randomized to three groups; immediate or delayed (2 h) intravenous cooling, both targeting 33 °C, or intravenously controlled normothermia (38 °C). Temperature control was applied for thirty hours including cooling time, temperature at target and controlled rewarming (0.5 °C/h). Animals were extubated and kept alive for seven days. The primary outcome measure is histological brain injury on day seven. Secondary outcomes include neurological and neurocognitive recovery, and the trajectory of biomarkers of brain injury.

Conclusion

High-quality animal experiments in clinically relevant large animal models are necessary to close the gap of knowledge regarding neuroprotective effects of induced hypothermia after cardiac arrest.Trial registration:Preclinicaltrials.eu (PCTE0000272), published 2021-11-03.

Biomarkers for neuroprognostication after standard versus extracorporeal cardiopulmonary resuscitation - A sub-analysis of Prague-OHCA study

BACKGROUND

Limited evidence exists for prognostic performance of biomarkers in patients resuscitated from out-of-hospital cardiac arrest (OHCA) with extracorporeal CPR (ECPR). We hypothesized that (1) the time course and (2) prognostic performance of biomarkers might differ between CPR and ECPR in a sub-analysis of Prague-OHCA study.

METHODS

Patients received either CPR (n = 164) or ECPR (n = 92). The primary outcome was favorable neurologic survival at 180 days [cerebral performance category (CPC) 1-2]. Secondary outcomes included biomarkers of neurologic injury, inflammation and hemocoagulation.

RESULTS

Favorable neurologic outcome was not different between groups: CPR 29.3% vs. ECPR 21.7%; p = 0.191. Biomarkers exhibited similar trajectories in both groups, with better values in patients with CPC 1-2. Procalcitonin (PCT) was higher in ECPR group at 24-72 h (all p < 0.01). Neuron-specific enolase (NSE), C-reactive protein and neutrophil-to-lymphocyte ratio did not differ between groups. Platelets, D-dimers and fibrinogen were lower in ECPR vs. CPR groups at 24-72 h (all p < 0.001). ROC analysis (24-48-72 h) showed the best performance of NSE in both CPR and ECPR groups (AUC 0.89 vs. 0.78; 0.9 vs. 0.9; 0.91 vs. 0.9). PCT showed good performance specifically in ECPR (0.72 vs. 0.84; 0.73 vs. 0.87; 0.73 vs. 0.86). Optimal cutoff points of NSE and PCT were higher in ECPR vs. CPR.

CONCLUSIONS

Biomarkers exhibited similar trajectories although absolute values tended to be higher in ECPR. NSE had superior performance in both groups. PCT showed a good performance specifically in ECPR. Additional biomarkers may have modest incremental value. Prognostication algorithms should reflect the resuscitation method.

Feasibility of Magnetic Resonance-Based Conductivity Imaging as a Tool to Estimate the Severity of Hypoxic-Ischemic Brain Injury in the First Hours After Cardiac Arrest

BACKGROUND

Early identification of the severity of hypoxic-ischemic brain injury (HIBI) after cardiac arrest can be used to help plan appropriate subsequent therapy. We evaluated whether conductivity of cerebral tissue measured using magnetic resonance-based conductivity imaging (MRCI), which provides contrast derived from the concentration and mobility of ions within the imaged tissue, can reflect the severity of HIBI in the early hours after cardiac arrest.

METHODS

Fourteen minipigs were resuscitated after 5 min or 12 min of untreated cardiac arrest. MRCI was performed at baseline and at 1 h and 3.5 h after return of spontaneous circulation (ROSC).

RESULTS

In both groups, the conductivity of cerebral tissue significantly increased at 1 h after ROSC compared with that at baseline (P = 0.031 and 0.016 in the 5-min and 12-min groups, respectively). The increase was greater in the 12-min group, resulting in significantly higher conductivity values in the 12-min group (P = 0.030). At 3.5 h after ROSC, the conductivity of cerebral tissue in the 12-min group remained increased (P = 0.022), whereas that in the 5-min group returned to its baseline level.

CONCLUSIONS

The conductivity of cerebral tissue was increased in the first hours after ROSC, and the increase was more prominent and lasted longer in the 12-min group than in the 5-min group. Our findings suggest the promising potential of MRCI as a tool to estimate the severity of HIBI in the early hours after cardiac arrest.

Wolf Creek XVII Part 8: Neuroprotection

Introduction

Post-cardiac arrest brain injury (PCABI) is the primary determinant of clinical outcomes for patients who achieve return of spontaneous circulation after cardiac arrest (CA). There are limited neuroprotective therapies available to mitigate the acute pathophysiology of PCABI.

Methods

Neuroprotection was one of six focus topics for the Wolf Creek XVII Conference held on June 14-17, 2023 in Ann Arbor, Michigan, USA. Conference invitees included international thought leaders and scientists in the field of CA resuscitation from academia and industry. Participants submitted via online survey knowledge gaps, barriers to translation, and research priorities for each focus topic. Expert panels used the survey results and their own perspectives and insights to create and present a preliminary unranked list for each category that was debated, revised and ranked by all attendees to identify the top 5 for each category.

Results

Top 5 knowledge gaps included developing therapies for neuroprotection; improving understanding of the pathophysiology, mechanisms, and natural history of PCABI; deploying precision medicine approaches; optimizing resuscitation and CPR quality; and determining optimal timing for and duration of interventions. Top 5 barriers to translation included patient heterogeneity; nihilism & lack of knowledge about cardiac arrest; challenges with the translational pipeline; absence of mechanistic biomarkers; and inaccurate neuro-triage and neuroprognostication. Top 5 research priorities focused on translational research and trial optimization; addressing patient heterogeneity and individualized interventions; improving understanding of pathophysiology and mechanisms; developing mechanistic and outcome biomarkers across post-CA time course; and improving implementation of science and technology.

Conclusion

This overview can serve as a guide to transform the care and outcome of patients with PCABI. Addressing these topics has the potential to improve both research and clinical care in the field of neuroprotection for PCABI.

Assessment of the Effects of Sodium Nitroprusside Administered Via Intracranial Subdural Catheters on the Cerebral Blood Flow and Lactate Using Dynamic Susceptibility Contrast Magnetic Resonance Imaging and Proton Magnetic Resonance Spectroscopy in a Pig Cardiac Arrest Model

Background Cerebral blood flow (CBF) is impaired in the early phase after return of spontaneous circulation. Sodium nitroprusside (SNP) administration via intracranial subdural catheters improves cerebral cortical microcirculation. We determined whether the SNP treatment improves CBF in the subcortical tissue and evaluated the effects of this treatment on cerebral lactate. Methods and Results Sixty minutes after return of spontaneous circulation following 14 minutes of untreated cardiac arrest, 14 minipigs randomly received 4 mg SNP or saline via intracranial subdural catheters. CBF was measured in regions of interest within the cerebrum and thalamus using dynamic susceptibility contrast-magnetic resonance imaging. After return of spontaneous circulation, CBF was expressed as a percentage of the baseline value. In the saline group, the %CBF in the regions of interest within the cerebrum remained at approximately 50% until 3.5 hours after return of spontaneous circulation, whereas %CBF in the thalamic regions of interest recovered to approximately 73% at this time point. The percentages of the baseline values in the cortical gray matter and subcortical white matter were higher in the SNP group (group effect P=0.026 and 0.025, respectively) but not in the thalamus. The cerebral lactate/creatine ratio measured using magnetic resonance spectroscopy increased over time in the saline group but not in the SNP group (group-time interaction P=0.035). The thalamic lactate/creatine ratio was similar in the 2 groups. Conclusions SNP administered via intracranial subdural catheters improved CBF not only in the cortical gray matter but also in the subcortical white matter. The CBF improvement by SNP was accompanied by a decrease in cerebral lactate.

Current animal models of extracorporeal cardiopulmonary resuscitation: A scoping review

Aim

Animal models of Extracorporeal Cardiopulmonary Resuscitation (ECPR) focusing on neurological outcomes are required to further the development of this potentially life-saving technology. The aim of this review is to summarize current animal models of ECPR.

Methods

A comprehensive database search of PubMed, EMBASE, and Web of Science was undertaken. Full-text publications describing animal models of ECPR between January 1, 2000, and June 30, 2022, were identified and included in the review. Data describing the conduct of the animal models of ECPR, measured variables, and outcomes were extracted according to pre-defined definitions.

Results

The search strategy yielded 805 unique reports of which 37 studies were included in the final analysis. Most studies (95%) described using a pig model of ECPR with the remainder (5%) describing a rat model. The most common method for induction of cardiac arrest was a fatal ventricular arrhythmia through electrical stimulation (70%). 10 studies reported neurological assessment of animals using physical examination, serum biomarkers, or electrophysiological findings, however, only two studies described a multimodal assessment. No studies reported the use of brain imaging as part of the neurological assessment. Return of spontaneous circulation was the most reported primary outcome, and no studies described the neurological status of the animal as the primary outcome.

Conclusion

Current animal models of ECPR do not describe clinically relevant neurological outcomes after cardiac arrest. Further work is needed to develop models that more accurately mimic clinical scenarios and can test innovations that can be translated to the application of ECPR in clinical medicine.

Hypertonic sodium lactate infusion reduces vasopressor requirements and biomarkers of brain and cardiac injury after experimental cardiac arrest

INTRODUCTION

Prognosis after resuscitation from cardiac arrest (CA) remains poor, with high morbidity and mortality as a result of extensive cardiac and brain injury and lack of effective treatments. Hypertonic sodium lactate (HSL) may be beneficial after CA by buffering severe metabolic acidosis, increasing brain perfusion and cardiac performance, reducing cerebral swelling, and serving as an alternative energetic cellular substrate. The aim of this study was to test the effects of HSL infusion on brain and cardiac injury in an experimental model of CA.

METHODS

After a 10-min electrically induced CA followed by 5 min of cardiopulmonary resuscitation maneuvers, adult swine (n = 35) were randomly assigned to receive either balanced crystalloid (controls, n = 11) or HSL infusion started during cardiopulmonary resuscitation (CPR, Intra-arrest, n = 12) or after return of spontaneous circulation (Post-ROSC, n = 11) for the subsequent 12 h. In all animals, extensive multimodal neurological and cardiovascular monitoring was implemented. All animals were treated with targeted temperature management at 34 °C.

RESULTS

Thirty-four of the 35 (97.1%) animals achieved ROSC; one animal in the Intra-arrest group died before completing the observation period. Arterial pH, lactate and sodium concentrations, and plasma osmolarity were higher in HSL-treated animals than in controls (p < 0.001), whereas potassium concentrations were lower (p = 0.004). Intra-arrest and Post-ROSC HSL infusion improved hemodynamic status compared to controls, as shown by reduced vasopressor requirements to maintain a mean arterial pressure target > 65 mmHg (p = 0.005 for interaction; p = 0.01 for groups). Moreover, plasma troponin I and glial fibrillary acid protein (GFAP) concentrations were lower in HSL-treated groups at several time-points than in controls.

CONCLUSIONS

In this experimental CA model, HSL infusion was associated with reduced vasopressor requirements and decreased plasma concentrations of measured biomarkers of cardiac and cerebral injury.

Thiamine for the Treatment of Cardiac Arrest-Induced Neurological Injury: A Randomized, Blinded, Placebo-Controlled Experimental Study

Background Thiamine supplementation has demonstrated protective effects in a mouse model of cardiac arrest. The aim of this study was to investigate the neuroprotective effects of thiamine in a clinically relevant large animal cardiac arrest model. The hypothesis was that thiamine reduces neurological injury evaluated by neuron-specific enolase levels. Methods and Results Pigs underwent myocardial infarction and subsequently 9 minutes of untreated cardiac arrest. Twenty minutes after successful resuscitation, the pigs were randomized to treatment with either thiamine or placebo. All pigs underwent 40 hours of intensive care and were awakened for assessment of functional neurological outcome up until 9 days after cardiac arrest. Nine pigs were included in both groups, with 8 in each group surviving the entire intensive care phase. Mean area under the curve for neuron-specific enolase was similar between groups, with 81.5 μg/L per hour (SD, 20.4) in the thiamine group and 80.5 μg/L per hour (SD, 18.3) in the placebo group, with an absolute difference of 1.0 (95% CI, -57.8 to 59.8; P=0.97). Likewise, there were no absolute difference in neurological deficit score at the end of the protocol (2 [95% CI, -38 to 42]; P=0.93). There was no absolute mean group difference in lactate during the intensive care period (1.1 mmol/L [95% CI, -0.5 to 2.7]; P=0.16). Conclusions In this randomized, blinded, placebo-controlled trial using a pig cardiac arrest model with myocardial infarction and long intensive care and observation for 9 days, thiamine showed no effect in changes to functional neurological outcome or serum levels of neuron-specific enolase. Thiamine treatment had no effect on lactate levels after successful resuscitation.

Effects of Sodium Nitroprusside Administered Via a Subdural Intracranial Catheter on the Microcirculation, Oxygenation, and Electrocortical Activity of the Cerebral Cortex in a Pig Cardiac Arrest Model

Background

Postischemic cerebral hypoperfusion has been indicated as an important contributing factor to secondary cerebral injury after cardiac arrest. We evaluated the effects of sodium nitroprusside administered via a subdural intracranial catheter on the microcirculation, oxygenation, and electrocortical activity of the cerebral cortex in the early postresuscitation period using a pig model of cardiac arrest.

Methods and Results

Twenty‐nine pigs were resuscitated with closed cardiopulmonary resuscitation after 14 minutes of untreated ventricular fibrillation. Thirty minutes after restoration of spontaneous circulation, 24 pigs randomly received either 4 mg of sodium nitroprusside (IT‐SNP group) or saline placebo (IT‐saline group) via subdural intracranial catheters and were observed for 5 hours. The same dose of sodium nitroprusside was administered intravenously in another 5 pigs. Compared with the IT‐saline group, the IT‐SNP group had larger areas under the curve for tissue oxygen tension and percent changes of arteriole diameter and number of perfused microvessels from baseline (all P<0.05) monitored on the cerebral cortex during the 5‐hour period, without severe hemodynamic instability. This group also showed faster recovery of electrocortical activity measured using amplitude‐integrated electroencephalography. Repeated‐measures analysis of variance revealed significant group–time interactions for these parameters. Intravenously administered sodium nitroprusside caused profound hypotension but did not appear to increase the cerebral parameters.

Conclusions

Sodium nitroprusside administered via a subdural intracranial catheter increased post–restoration of spontaneous circulation cerebral cortical microcirculation and oxygenation and hastened electrocortical activity recovery in a pig model of cardiac arrest. Further studies are required to determine its impact on the long‐term neurologic outcomes.

A comprehensive neuromonitoring approach in a large animal model of cardiac arrest

BACKGROUND

Anoxic brain injuries represent the main determinant of poor outcome after cardiac arrest (CA). Large animal models have been described to investigate new treatments during CA and post-resuscitation phase, but a detailed model that includes extensive neuromonitoring is lacking.

METHOD

Before an electrically-induced 10-minute CA and resuscitation, 46 adult pigs underwent neurosurgery for placement of a multifunctional probe (intracranial pressure or ICP, tissue oxygen tension or PbtO2 and cerebral temperature) and a bolt-based technique for the placement and securing of a regional blood flow probe and two sEEG electrodes; two modified cerebral microdialysis (CMD) probes were also inserted in the frontal lobes and accidental misplacement was prevented using a perforated head support.

RESULT

42 animals underwent the CA procedure and 41 achieved the return of spontaneous circulation (ROSC). In 4 cases (8.6%) an adverse event took place during preparation, but only in two cases (4.3%) this was related to the neurosurgery. In 6 animals (13.3%) the minor complications that occurred resolved after probe repositioning.

CONCLUSION

Herein we provide a detailed comprehensive neuromonitoring approach in a large animal model of CA that might help future research.

Cardiac Arrest in Pigs With 48 hours of Post-Resuscitation Care Induced by 2 Methods of Myocardial Infarction: A Methodological Description

Background

Systematic reviews have disclosed a lack of clinically relevant cardiac arrest animal models. The aim of this study was to develop a cardiac arrest model in pigs encompassing relevant cardiac arrest characteristics and clinically relevant post‐resuscitation care.

Methods and Results

We used 2 methods of myocardial infarction in conjunction with cardiac arrest. One group (n=7) had a continuous coronary occlusion, while another group (n=11) underwent balloon‐deflation during arrest and resuscitation with re‐inflation after return of spontaneous circulation. A sham group was included (n=6). All groups underwent 48 hours of intensive care including 24 hours of targeted temperature management. Pigs underwent invasive hemodynamic monitoring. Left ventricular function was assessed by pressure‐volume measurements. The proportion of pigs with return of spontaneous circulation was 43% in the continuous infarction group and 64% in the deflation‐reinflation group. In the continuous infarction group 29% survived the entire protocol while 55% survived in the deflation‐reinflation group. Both cardiac arrest groups needed vasopressor and inotropic support and pressure‐volume measurements showed cardiac dysfunction. During rewarming, systemic vascular resistance decreased in both cardiac arrest groups. Median [25%;75%] troponin‐I 48 hours after return of spontaneous circulation, was 88 973 ng/L [53 124;99 740] in the continuous infarction group, 19 661 ng/L [10 871;23 209] in the deflation‐reinflation group, and 1973 ng/L [1117;1995] in the sham group.

Conclusions

This article describes a cardiac arrest pig model with myocardial infarction, targeted temperature management, and clinically relevant post‐cardiac arrest care. We demonstrate 2 methods of inducing myocardial ischemia with cardiac arrest resulting in post‐cardiac arrest organ injury including cardiac dysfunction and cerebral injury.

Esmolol during cardiopulmonary resuscitation reduces neurological injury in a porcine model of cardiac arrest

Primary vasopressor efficacy of epinephrine during cardiopulmonary resuscitation (CPR) is due to its α-adrenergic effects. However, epinephrine plays β1-adrenergic actions, which increasing myocardial oxygen consumption may lead to refractory ventricular fibrillation (VF) and poor outcome. Effects of a single dose of esmolol in addition to epinephrine during CPR were investigated in a porcine model of VF with an underlying acute myocardial infarction. VF was ischemically induced in 16 pigs and left untreated for 12 min. During CPR, animals were randomized to receive epinephrine (30 µg/kg) with either esmolol (0.5 mg/kg) or saline (control). Pigs were then observed up to 96 h. Coronary perfusion pressure increased during CPR in the esmolol group compared to control (47 ± 21 vs. 24 ± 10 mmHg at min 5, p < 0.05). In both groups, 7 animals were successfully resuscitated and 4 survived up to 96 h. No significant differences were observed between groups in the total number of defibrillations delivered prior to final resuscitation. Brain histology demonstrated reductions in cortical neuronal degeneration/necrosis (score 0.3 ± 0.5 vs. 1.3 ± 0.5, p < 0.05) and hippocampal microglial activation (6 ± 3 vs. 22 ± 4%, p < 0.01) in the esmolol group compared to control. Lower circulating levels of neuron specific enolase were measured in esmolol animals compared to controls (2[1-3] vs. 21[16-52] ng/mL, p < 0.01). In this preclinical model, β1-blockade during CPR did not facilitate VF termination but provided neuroprotection.

Mitochondrial dysfunction in fatal ventricular arrhythmias

Ventricular fibrillation (VF) and sudden cardiac arrest (SCA) remain some of the most important public health concerns worldwide. For the past 50 years, the recommendation in the Advanced Cardiac Life Support (ACLS) guidelines has been that defibrillation is the only option for shockable cardiac arrest. There is growing evidence to demonstrate that mitochondria play a vital role in the outcome of postresuscitation cardiac function. Although targeting mitochondria to improve resuscitation outcome following cardiac arrest has been proposed for many years, understanding concerning the changes in mitochondria during cardiac arrest, especially in the case of VF, is still limited. In addition, despite new research initiatives and improved medical technology, the overall survival rates of patients with SCA still remain the same. Understanding cardiac mitochondrial alterations during fatal arrhythmias may help to enable the formulation of strategies to improve the outcomes of resuscitation. The attenuation of cardiac mitochondrial dysfunction during VF through pharmacological intervention as well as ischaemic postconditioning could also be a promising target for intervention and inform a new paradigm of treatments. In this review, the existing evidence available from in vitro, ex vivo and in vivo studies regarding the roles of mitochondrial dysfunction during VF is comprehensively summarized and discussed. In addition, the effects of interventions targeting cardiac mitochondria during fatal ventricular arrhythmias are presented. Since there are no clinical reports from studies targeting mitochondria to improve resuscitation outcome available, this review will provide important information to encourage further investigations in a clinical setting.

Ventilation With Argon Improves Survival With Good Neurological Recovery After Prolonged Untreated Cardiac Arrest in Pigs

Background

Ventilation with the noble gas argon (Ar) has shown neuroprotective and cardioprotective properties in different in vitro and in vivo models. Hence, the neuroprotective effects of Ar were investigated in a severe, preclinically relevant porcine model of cardiac arrest.

Methods and Results

Cardiac arrest was ischemically induced in 36 pigs and left untreated for 12 minutes before starting cardiopulmonary resuscitation. Animals were randomized to 4‐hour post‐resuscitation ventilation with: 70% nitrogen–30% oxygen (control); 50% Ar–20% nitrogen–30% oxygen (Ar 50%); and 70% Ar–30% oxygen (Ar 70%). Hemodynamic parameters and myocardial function were monitored and serial blood samples taken. Pigs were observed up to 96 hours for survival and neurological recovery. Heart and brain were harvested for histopathology. Ten animals in each group were successfully resuscitated. Ninety‐six‐hour survival was 60%, 70%, and 90%, for the control, Ar 50%, and Ar 70% groups, respectively. In the Ar 50% and Ar 70% groups, 60% and 80%, respectively, achieved good neurological recovery, in contrast to only 30% in the control group (P<0.0001). Histology showed less neuronal degeneration in the cortex (P<0.05) but not in the hippocampus, and less reactive microglia activation in the hippocampus (P=0.007), after Ar compared with control treatment. A lower increase in circulating biomarkers of brain injury, together with less kynurenine pathway activation (P<0.05), were present in Ar‐treated animals compared with controls. Ar 70% pigs also had complete left ventricular function recovery and smaller infarct and cardiac troponin release (P<0.01).

Conclusions

Post‐resuscitation ventilation with Ar significantly improves neurologic recovery and ameliorates brain injury after cardiac arrest with long no‐flow duration. Benefits are greater after Ar 70% than Ar 50%.

Searching for Preclinical Models of Acute Decompensated Heart Failure: a Concise Narrative Overview and a Novel Swine Model

Purpose

Available animal models of acute heart failure (AHF) and their limitations are discussed herein. A novel and preclinically relevant porcine model of decompensated AHF (ADHF) is then presented.

Methods

Myocardial infarction (MI) was induced by occlusion of left anterior descending coronary artery in 17 male pigs (34 ± 4 kg). Two weeks later, ADHF was induced in the survived animals (n = 15) by occlusion of the circumflex coronary artery, associated with acute volume overload and increases in arterial blood pressure by vasoconstrictor infusion. After onset of ADHF, animals received 48-h iv infusion of either serelaxin (n = 9) or placebo (n = 6). The pathophysiology and progression of ADHF were described by combining evaluation of hemodynamics, echocardiography, bioimpedance, blood gasses, circulating biomarkers, and histology.

Results

During ADHF, animals showed reduced left ventricle (LV) ejection fraction < 30%, increased thoracic fluid content > 35%, pulmonary edema, and high pulmonary capillary wedge pressure ~ 30 mmHg (p < 0.01 vs. baseline). Other ADHF-induced alterations in hemodynamics, i.e., increased central venous and pulmonary arterial pressures; respiratory gas exchanges, i.e., respiratory acidosis with low arterial PO₂ and high PCO₂; and LV dysfunction, i.e., increased LV end-diastolic/systolic volumes, were observed (p < 0.01 vs. baseline). Representative increases in circulating cardiac biomarkers, i.e., troponin T, natriuretic peptide, and bio-adrenomedullin, occurred (p < 0.01 vs. baseline). Finally, elevated renal and liver biomarkers were observed 48 h after onset of ADHF. Mortality was ~ 50%. Serelaxin showed beneficial effects on congestion, but none on mortality.

Conclusion

This new model, resulting from a combination of chronic and acute MI, and volume and pressure overload, was able to reproduce all the typical clinical signs occurring during ADHF in a consistent and reproducible manner.

Electronic supplementary material

The online version of this article (10.1007/s10557-020-07096-5) contains supplementary material, which is available to authorized users.

Cardiac function after cardiac arrest: what do we know?

Postcardiac arrest myocardial dysfunction (PCAMD) is a frequent complication faced during post-resuscitation care that adversely impacts survival and neurological outcome. Both mechanical and electrical factors contribute to the occurrence of PCAMD. Prearrest ventricular function, the cause of cardiac arrest, global ischemia, resuscitation factors, ischemia/reperfusion injury and post-resuscitation treatments contribute to the severity of PCMAD. The pathophysiology of PCAMD is complex and include myocytes energy failure, impaired contractility, cardiac edema, mitochondrial damage, activation of inflammatory pathways and the coagulation cascade, persistent ischemic injury and myocardial stiffness. Hypotension and low cardiac output with vasopressor/inotropes need are frequent after resuscitation. However, clinical, hemodynamic and laboratory signs of shock are frequently altered by cardiac arrest pathophysiology and post-resuscitation treatment, potentially being misleading and not fully reflecting the severity of postcardiac arrest syndrome. Even if validated criteria are lacking, an extensive hemodynamic evaluation is useful to define a "benign" and a "malign" form of myocardial dysfunction and circulatory shock, potentially having treatment and prognostic implications. Cardiac output is frequently decreased after cardiac arrest, particularly in patients treated with target temperature management (TTM); however, it is not independently associated with outcome. Sinus bradycardia during TTM seems independently associated with survival and good neurological outcome, representing a promising prognostic indicator. Higher mean arterial pressure (MAP) seems to be associated with improved survival and cerebral function after cardiac arrest; however, two recent randomized clinical trials failed to replicate these results. Recommendations on hemodynamic optimization are relatively poor and are largely based on general principle of intensive care medicine.

Suppression of Superoxide-Hydrogen Peroxide Production at Site IQ of Mitochondrial Complex I Attenuates Myocardial Stunning and Improves Postcardiac Arrest Outcomes

OBJECTIVES

Cardiogenic shock following cardiopulmonary resuscitation for sudden cardiac arrest is common, occurring even in the absence of acute coronary artery occlusion, and contributes to high rates of postcardiopulmonary resuscitation mortality. The pathophysiology of this shock is unclear, and effective therapies for improving clinical outcomes are lacking.

DESIGN

Laboratory investigation.

SETTING

University laboratory.

SUBJECTS

C57BL/6 adult female mice.

INTERVENTIONS

Anesthetized and ventilated adult female C57BL/6 wild-type mice underwent a 4, 8, 12, or 16-minute potassium chloride-induced cardiac arrest followed by 90 seconds of cardiopulmonary resuscitation. Mice were then blindly randomized to a single IV injection of vehicle (phosphate-buffered saline) or suppressor of site IQ electron leak, an inhibitor of superoxide production by complex I of the mitochondrial electron transport chain. Suppressor of site IQ electron leak and vehicle were administered during cardiopulmonary resuscitation.

MEASUREMENTS AND MAIN RESULTS

Using a murine model of asystolic cardiac arrest, we discovered that duration of cardiac arrest prior to cardiopulmonary resuscitation determined postresuscitation success rates, degree of neurologic injury, and severity of myocardial dysfunction. Post-cardiopulmonary resuscitation cardiac dysfunction was not associated with myocardial necrosis, apoptosis, inflammation, or mitochondrial permeability transition pore opening. Furthermore, left ventricular function recovered within 72 hours of cardiopulmonary resuscitation, indicative of myocardial stunning. Postcardiopulmonary resuscitation, the myocardium exhibited increased reactive oxygen species and evidence of mitochondrial injury, specifically reperfusion-induced reactive oxygen species generation at electron transport chain complex I. Suppressor of site IQ electron leak, which inhibits complex I-dependent reactive oxygen species generation by suppression of site IQ electron leak, decreased myocardial reactive oxygen species generation and improved postcardiopulmonary resuscitation myocardial function, neurologic outcomes, and survival.

CONCLUSIONS

The severity of cardiogenic shock following asystolic cardiac arrest is dependent on the length of cardiac arrest prior to cardiopulmonary resuscitation and is mediated by myocardial stunning resulting from mitochondrial electron transport chain complex I dysfunction. A novel pharmacologic agent targeting this mechanism, suppressor of site IQ electron leak, represents a potential, practical therapy for improving sudden cardiac arrest resuscitation outcomes.

LUCAS Versus Manual Chest Compression During Ambulance Transport: A Hemodynamic Study in a Porcine Model of Cardiac Arrest

Background Mechanical chest compression (CC) is currently suggested to deliver sustained high-quality CC in a moving ambulance. This study compared the hemodynamic support provided by a mechanical piston device or manual CC during ambulance transport in a porcine model of cardiopulmonary resuscitation. Methods and Results In a simulated urban ambulance transport, 16 pigs in cardiac arrest were randomized to 18 minutes of mechanical CC with the LUCAS (n=8) or manual CC (n=8). ECG, arterial and right atrial pressure, together with end-tidal CO2 and transthoracic impedance curve were continuously recorded. Arterial lactate was assessed during cardiopulmonary resuscitation and after resuscitation. During the initial 3 minutes of cardiopulmonary resuscitation, the ambulance was stationary, while then proceeded along a predefined itinerary. When the ambulance was stationary, CC-generated hemodynamics were equivalent in the 2 groups. However, during ambulance transport, arterial and coronary perfusion pressure, and end-tidal CO2 were significantly higher with mechanical CC compared with manual CC (coronary perfusion pressure: 43±4 versus 18±4 mmHg; end-tidal CO2: 31±2 versus 19±2 mmHg, P<0.01 at 18 minutes). During cardiopulmonary resuscitation, arterial lactate was lower with mechanical CC compared with manual CC (6.6±0.4 versus 8.2±0.5 mmol/L, P<0.01). During transport, mechanical CC showed greater constancy compared with the manual CC, as represented by a higher CC fraction and a lower transthoracic impedance curve variability ( P<0.01). All animals in the mechanical CC group and 6 (75%) in the manual one were successfully resuscitated. Conclusions This model adds evidence in favor of the use of mechanical devices to provide ongoing high-quality CC and tissue perfusion during ambulance transport.