A pooled analysis of the effect of endovascular cooling on infarct size in patients with ST-elevation myocardial infarction

Cardioprotective Strategies After Ischemia-Reperfusion Injury

Acute myocardial infarction (AMI) is associated with high morbidity and mortality worldwide. Although early reperfusion is the most effective strategy to salvage ischemic myocardium, reperfusion injury can develop with the restoration of blood flow. Therefore, it is important to identify protection mechanisms and strategies for the heart after myocardial infarction. Recent studies have shown that multiple intracellular molecules and signaling pathways are involved in cardioprotection. Meanwhile, device-based cardioprotective modalities such as cardiac left ventricular unloading, hypothermia, coronary sinus intervention, supersaturated oxygen (SSO2), and remote ischemic conditioning (RIC) have become important areas of research. Herein, we review the molecular mechanisms of cardioprotection and cardioprotective modalities after ischemia-reperfusion injury (IRI) to identify potential approaches to reduce mortality and improve prognosis in patients with AMI.

Differences in Outcome of Patients with Cardiogenic Shock Associated with In-Hospital or Out-of-Hospital Cardiac Arrest

Cardiogenic Shock (CS) complicated by in-hospital (IHCA) or out-of-hospital cardiac arrest (OHCA) has a poor outcome. However, studies regarding the prognostic differences between IHCA and OHCA in CS are limited. In this prospective, observational study, consecutive patients with CS were included in a monocentric registry from June 2019 to May 2021. The prognostic impact of IHCA and OHCA on 30-day all-cause mortality was tested within the entire group and in the subgroups of patients with acute myocardial infarction (AMI) and coronary artery disease (CAD). Statistical analyses included univariable t-test, Spearman's correlation, Kaplan-Meier analyses, as well as uni- and multivariable Cox regression analyses. A total of 151 patients with CS and cardiac arrest were included. IHCA on ICU admission was associated with higher 30-day all-cause mortality compared to OHCA in univariable COX regression and Kaplan-Meier analyses. However, this association was solely driven by patients with AMI (77% vs. 63%; log rank p = 0.023), whereas IHCA was not associated with 30-day all-cause mortality in non-AMI patients (65% vs. 66%; log rank p = 0.780). This finding was confirmed in multivariable COX regression, in which IHCA was solely associated with higher 30-day all-cause mortality in patients with AMI (HR = 2.477; 95% CI 1.258-4.879; p = 0.009), whereas no significant association could be seen in the non-AMI group and in the subgroups of patients with and CAD. CS patients with IHCA showed significantly higher all-cause mortality at 30 days compared to patients with OHCA. This finding was primarily driven by a significant increase in all-cause mortality at 30 days in CS patients with AMI and IHCA, whereas no difference could be seen when differentiated by CAD.

Therapeutic Hypothermia Inhibits Hypoxia-Induced Cardiomyocyte Apoptosis Via the MiR-483-3p/Cdk9 Axis

Background Therapeutic hypothermia has a beneficial effect on cardiac function after acute myocardial infarction, but the exact mechanism is still unclear. Recent research has suggested that microRNAs participate in acute myocardial infarction to regulate cardiomyocyte survival. This study aimed to explore the ability of hypothermia-regulated microRNA-483-3p (miR-483-3p) to inhibit hypoxia-induced myocardial infarction. Methods and Results Primary cardiomyocytes were cultured under hypoxia at 32 °C to mimic therapeutic hypothermia, and the differentially expressed microRNAs were determined by RNA sequencing. Therapeutic hypothermia recovered hypoxia-induced increases in apoptosis, decreases in ATP levels, and decreases in miR-483-3p expression. Overexpression of miR-483-3p exhibited effects similar to those of therapeutic hypothermia on hypoxia in the treatment of cardiomyocytes to associate with maintaining the mitochondrial membrane potential, and cyclin-dependent kinase 9 (Cdk9) was identified as a target gene with downregulated expression by miR-483-3p. Knockdown of Cdk9 also promoted cardiac survival, ATP production, and mitochondrial membrane potential stability under hypoxia. In vivo, the expression of miR-483-3p and Cdk9 was tested in the cardiac tissue of the mice with acute myocardial infarction, and the expression of miR-483-3p decreased and Cdk9 increased in the region of myocardial infarction. However, miR-483-3p was overexpressed with lentivirus, which suppressed apoptosis, infarct size (miR-483-3p, 22.00±4.04% versus negative control, 28.57±5.44%, P<0.05), and Cdk9 expression to improve cardiac contractility. Conclusions MiR-483-3p antagonizes hypoxia, leading to cardiomyocyte injury by targeting Cdk9, which is a new mechanism of therapeutic hypothermia.

Novel therapeutic strategies to reduce reperfusion injury after acute myocardial infarction

For almost 30 years, urgent revascularization termed primary percutaneous coronary intervention (pPCI) has been a cornerstone of modern care for acute myocardial infarction (AMI). It lowers mortality and improved cardiovascular outcome compared to conservative therapy including thrombolysis. Reperfusion injury, which occurs after successful re-opening of the formerly occluded coronary artery, had been exploited as a potential therapeutic target. When revascularisation became faster and pPCI was successfully performed within 60-90 minutes of symptom onset, the interest in a potential additive effect of targeting reperfusion injury vanished. More recently, several meta-analyses indicated that limiting reperfusion injury prevents microvascular obstruction and reduces final infarct size, thereby lowering the probability of heart failure events and improving quality of life in AMI survivors. Here, we describe the current strategies to limit reperfusion injury and to improve post-AMI outcomes such as systemic or intracoronary hypothermia, left-ventricular unloading, intracoronary infusion of super-saturated oxygen, intermittent coronary sinus occlusion, and C-reactive protein apharesis.

Therapeutic hypothermia for acute myocardial infarction: a narrative review of evidence from animal and clinical studies

Myocardial infarction (MI) is the leading cause of death from coronary heart disease and requires immediate reperfusion therapy with thrombolysis, primary percutaneous coronary intervention, or coronary artery bypass grafting. However, myocardial reperfusion therapy is often accompanied by cardiac ischemia/reperfusion (I/R) injury, which leads to myocardial injury with detrimental consequences. The causes of I/R injury are unclear, but are multifactorial, including free radicals, reactive oxygen species, calcium overload, mitochondria dysfunction, inflammation, and neutrophil-mediated vascular injury. Mild hypothermia has been introduced as one of the potential inhibitors of myocardial I/R injury. Although animal studies have demonstrated that mild hypothermia significantly reduces or delays I/R myocardium damage, human trials have not shown clinical benefits in acute MI (AMI). In addition, the practice of hypothermia treatment is increasing in various fields such as surgical anesthesia and intensive care units. Adequate sedation for anesthetic procedures and protection from body shivering has become essential during therapeutic hypothermia. Therefore, anesthesiologists should be aware of the effects of therapeutic hypothermia on the metabolism of anesthetic drugs. In this paper, we review the existing data on the use of therapeutic hypothermia for AMI in animal models and human clinical trials to better understand the discrepancy between perceived benefits in preclinical animal models and the absence thereof in clinical trials thus far.

Intracoronary Application of Super-Saturated Oxygen to Reduce Infarct Size Following Myocardial Infarction

Optimal medical therapy for secondary prevention following acute myocardial infarction reduces non-fatal ischaemic events. Intensive antithrombotic or lipid-lowering approaches have failed to significantly lower mortality. In the past, reduction of infarct size in patients undergoing primary percutaneous revascularisation for acute myocardial infarction had been considered as a surrogate outcome marker. However, infarct size measured by magnetic resonance imaging or SPECT is strongly associated with all-cause mortality and hospitalization for heart failure within the first year after an acute myocardial infarction. Intracoronary administration of super-saturated oxygen (SSO₂) immediately after revascularisation is an approach that can be used to reduce infarct size and, therefore, improve cardiovascular outcome in patients with acute myocardial infarction. In this article, we describe the modulation of pathophysiology by SSO₂, review the existing trial data and present our first impressions with the technique in real clinical practice.

Optimum Blood Pressure in Patients With Shock After Acute Myocardial Infarction and Cardiac Arrest

BACKGROUND

In patients with shock after acute myocardial infarction (AMI), the optimal level of pharmacologic support is unknown. Whereas higher doses may increase myocardial oxygen consumption and induce arrhythmias, diastolic hypotension may reduce coronary perfusion and increase infarct size.

OBJECTIVES

This study aimed to determine the optimal mean arterial pressure (MAP) in patients with AMI and shock after cardiac arrest.

METHODS

This study used patient-level pooled analysis of post-cardiac arrest patients with shock after AMI randomized in the Neuroprotect (Neuroprotective Goal Directed Hemodynamic Optimization in Post-cardiac Arrest Patients; NCT02541591) and COMACARE (Carbon Dioxide, Oxygen and Mean Arterial Pressure After Cardiac Arrest and Resuscitation; NCT02698917) trials who were randomized to MAP 65 mm Hg or MAP 80/85 to 100 mm Hg targets during the first 36 h after admission. The primary endpoint was the area under the 72-h high-sensitivity troponin-T curve.

RESULTS

Of 235 patients originally randomized, 120 patients had AMI with shock. Patients assigned to the higher MAP target (n = 58) received higher doses of norepinephrine (p = 0.004) and dobutamine (p = 0.01) and reached higher MAPs (86 ± 9 mm Hg vs. 72 ± 10 mm Hg, p < 0.001). Whereas admission hemodynamics and angiographic findings were all well-balanced and revascularization was performed equally effective, the area under the 72-h high-sensitivity troponin-T curve was lower in patients assigned to the higher MAP target (median: 1.14 μg.72 h/l [interquartile range: 0.35 to 2.31 μg.72 h/l] vs. median: 1.56 μg.72 h/l [interquartile range: 0.61 to 4.72 μg. 72 h/l]; p = 0.04). Additional pharmacologic support did not increase the risk of a new cardiac arrest (p = 0.88) or atrial fibrillation (p = 0.94). Survival with good neurologic outcome at 180 days was not different between both groups (64% vs. 53%, odds ratio: 1.55; 95% confidence interval: 0.74 to 3.22).

CONCLUSIONS

In post-cardiac arrest patients with shock after AMI, targeting MAP between 80/85 and 100 mm Hg with additional use of inotropes and vasopressors was associated with smaller myocardial injury.

Minimal Invasive Pericardial Perfusion Model in Swine: A Translational Model for Cardiac Remodeling After Ischemia/Reperfusion Injury

Rationale

Adverse remodeling leads to heart failure after myocardial infarction (MI), with important impact on morbidity and mortality. New therapeutic approaches are needed to further improve and broaden heart failure therapy. We established a minimally invasive, reproducible pericardial irrigation model in swine, as a translational model to study the impact of temperature on adverse cardiac remodeling and its molecular mechanisms after MI.

Objective

Chronic heart failure remains a leading cause of death in western industrialized countries, with a tremendous economic impact on the health care system. Previously, many studies have investigated mechanisms to reduce infarct size after ischemia/reperfusion injury, including therapeutic hypothermia. Nonetheless, the molecular mechanisms of adverse remodeling after MI remain poorly understood. By deciphering the latter, new therapeutic strategies can be developed to not only reduce rehospitalization of heart failure patients but also reduce or prevent adverse remodeling in the first place.

Methods and Results

After 90 min of MI, a 12Fr dual lumen dialysis catheter was place into the pericardium via minimal invasive, sub-xiphoidal percutaneous puncture. We performed pericardial irrigation with cold or warm saline for 60 min in 25 female farm pigs after ischemia and reperfusion. After one week of survival the heart was harvested for further studies. After cold pericardial irrigation we observed a significant decrease of systemic body temperature measured with a rectal probe in the cold group, reflecting that the heart was chilled throughout its entire thickness. The temperature remained stable in the control group during the procedure. We did not see any difference in arrhythmia or hemodynamic stability between both groups.

Conclusion

We established a minimally invasive, reproducible and translational model of pericardial irrigation in swine. This method enables the investigation of mechanisms involved in myocardial adverse remodeling after ischemia/reperfusion injury in the future.

Myocardial hypothermia increases autophagic flux, mitochondrial mass and myocardial function after ischemia-reperfusion injury

Animal studies have demonstrated beneficial effects of therapeutic hypothermia on myocardial function, yet exact mechanisms remain unclear. Impaired autophagy leads to heart failure and mitophagy is important for mitigating ischemia/reperfusion injury. This study aims to investigate whether the beneficial effects of therapeutic hypothermia are due to preserved autophagy and mitophagy. Under general anesthesia, the left anterior descending coronary artery of 19 female farm pigs was occluded for 90 minutes with consecutive reperfusion. 30 minutes after reperfusion, we performed pericardial irrigation with warm or cold saline for 60 minutes. Myocardial tissue analysis was performed one and four weeks after infarction. Therapeutic hypothermia induced a significant increase in autophagic flux, mitophagy, mitochondrial mass and function in the myocardium after infarction. Cell stress, apoptosis, inflammation as well as fibrosis were reduced, with significant preservation of systolic and diastolic function four weeks post infarction. We found similar biochemical changes in human samples undergoing open chest surgery under hypothermic conditions when compared to the warm. These results suggest that autophagic flux and mitophagy are important mechanisms implicated in cardiomyocyte recovery after myocardial infarction under hypothermic conditions. New therapeutic strategies targeting these pathways directly could lead to improvements in prevention of heart failure.

Successful Re-Initiation of Therapeutic Hypothermia as Adjunctive Salvage Therapy in a Case of Refractory Cardiogenic Shock Due to Acute Myocardial Infarction

BACKGROUND Acute myocardial infarction (AMI) complicated by cardiogenic shock has a high mortality rate, despite prompt revascularization, advanced medical therapy and the use of mechanical circulatory support devices. Therapeutic hypothermia is associated with physiological cellular changes in the ischemic myocardium, and a trend towards improved hemodynamics in patients with AMI and cardiogenic shock, but is currently not considered to be a therapeutic modality. A case is presented that supports the role of therapeutic hypothermia as salvage therapy in patients with cardiogenic shock following AMI. CASE REPORT A 37-year-old man who presented with cardiac arrest following an anterior wall AMI due to occlusion of the left anterior descending coronary artery complicated by cardiogenic shock, underwent emergent percutaneous revascularization with placement of a stent, a percutaneous left ventricular-assist device (LVAD), and a pulmonary artery catheter. Therapeutic hypothermia was initiated to achieve a target core body temperature of between 32-34°C for 24 hours, followed by slow re-warming. However, after rewarming, the patient developed refractory cardiogenic shock, despite revascularization, pharmacological and mechanical circulatory support. A second cycle of therapeutic hypothermia was initiated as salvage therapy, leading to clinical improvement. The patient had a favorable outcome, was discharged from hospital and was able to return to work. CONCLUSIONS The first successful case is described in which therapeutic hypothermia was re-initiated as salvage therapy for cardiogenic shock where no other hemodynamic support resources were available.

Mechano-chronotropic Unloading During the Acute Phase of Myocardial Infarction Markedly Reduces Infarct Size via the Suppression of Myocardial Oxygen Consumption

The oxygen supply-demand imbalance is the fundamental pathophysiology of myocardial infarction (MI). Reducing myocardial oxygen consumption (MVO₂) in acute MI (AMI) reduces infarct size. Since left ventricular (LV) mechanical work and heart rate are major determinants of MVO₂, we hypothesized that the combination of LV mechanical unloading and chronotropic unloading during AMI can reduce infarct size via synergistic suppression of MVO₂. In a dog model of ischemia-reperfusion, as we predicted, the combination of mechanical unloading by Impella and bradycardic agent, ivabradine (IVA), synergistically reduced MVO₂. This was translated into the striking reduction of infarct size with Impella + IVA administered 60 min after the onset of ischemia compared to no treatment (control) and Impella groups (control 56.3 ± 6.5, Impella 39.9 ± 7.4 and Impella + IVA 23.7 ± 10.6%, p < 0.001). In conclusion, Impella + IVA during AMI reduced infarct size via marked suppression of MVO₂. The mechano-chronotropic unloading may serve as a powerful therapeutic option for AMI.

Clinical translation of myocardial conditioning

Rapid admission and acute interventional treatment combined with modern antithrombotic pharmacologic therapy have improved outcomes in patients with ST elevation myocardial infarction. The next major target to further advance outcomes needs to address ischemia-reperfusion injury, which may contribute significantly to the final infarct size and hence mortality and postinfarction heart failure. Mechanical conditioning strategies including local and remote ischemic pre-, per-, and postconditioning have demonstrated consistent cardioprotective capacities in experimental models of acute ischemia-reperfusion injury. Their translation to the clinical scenario has been challenging. At present, the most promising mechanical protection strategy of the heart seems to be remote ischemic conditioning, which increases myocardial salvage beyond acute reperfusion therapy. An additional aspect that has gained recent focus is the potential of extended conditioning strategies to improve physical rehabilitation not only after an acute ischemia-reperfusion event such as acute myocardial infarction and cardiac surgery but also in patients with heart failure. Experimental and preliminary clinical evidence suggests that remote ischemic conditioning may modify cardiac remodeling and additionally enhance skeletal muscle strength therapy to prevent muscle waste, known as an inherent component of a postoperative period and in heart failure. Blood flow restriction exercise and enhanced external counterpulsation may represent cardioprotective corollaries. Combined with exercise, remote ischemic conditioning or, alternatively, blood flow restriction exercise may be of aid in optimizing physical rehabilitation in populations that are not able to perform exercise practice at intensity levels required to promote optimal outcomes.

Novel cardioprotective and regenerative therapies in acute myocardial infarction: a review of recent and ongoing clinical trials

Following the original large-scale randomized trials of aspirin and β-blockade, there have been a number of major advances in pharmacological and mechanical treatments for acute myocardial infarction. Despite this progress, myocardial infarction remains a major global cause of mortality and morbidity, driving a quest for novel treatments in this area. As the understanding of mitochondrial dynamics and the pathophysiology of reperfusion injury has evolved, the last three decades have seen advances in ischemic conditioning, pharmacological and metabolic cardioprotection, as well as biological and stem-cell therapies. The aim of this review is to provide a synopsis of adjunctive cardioprotective and regenerative therapies currently undergoing or entering early clinical trials in the treatment of patients with acute myocardial infarction.

Editor's Choice- Inside the cold heart: A review of therapeutic hypothermia cardioprotection

Targeted temperature management has been originally used to reduce neurological injury and improve outcome in patients after out-of-hospital cardiac arrest. Myocardial infarction remains a major cause of death in the world and several investigators are studying the effect of mild therapeutic hypothermia during an acute cardiac ischemic injury. A search on MEDLINE, Scopus and EMBASE databases was conducted to obtain data regarding the cardioprotective properties of therapeutic hypothermia. Preclinical studies have shown that therapeutic hypothermia provides a cardioprotective effect in animals. The proposed pathways for the cardioprotective effects of therapeutic hypothermia include stabilization of mitochondrial permeability, production of nitric oxide, equilibration of reactive oxygen species, and calcium channels homeostasis. Clinical trials in humans have yielded controversial results. Current trials are therefore seeking to combine therapeutic hypothermia with other treatment modalities in order to improve the outcomes of patients with acute ischemic injury. This article provides a review of the hypothermia effects on the cardiovascular system, from the basic science of physiological changes in the human body and molecular mechanisms of cardioprotection to the bench of clinical trials with therapeutic hypothermia in patients with acute ischemic injury.

Improving myocardial injury, infarct size, and myocardial salvage in the era of primary PCI for STEMI

ST-segment elevation myocardial infarction (STEMI) is a major cause of mortality and disability worldwide. Reperfusion therapy by thrombolysis or primary percutaneous coronary intervention (PPCI) improves survival and quality of life in patients with STEMI. Despite the proven efficacy of timely reperfusion, mortality from STEMI remains high, particularly among patients with suboptimal reperfusion. Reperfusion injury following opening of occluded coronary arteries mitigates the efficacy of PPCI by further accentuating ischemic damage and increasing infarct size (IS). On the basis of experimental studies, it is assumed that nearly 50% of the final IS is because of the reperfusion injury. IS is a marker of ischemic damage and adequacy of reperfusion that is strongly related to mortality in reperfused patients with STEMI. Many therapeutic strategies including pharmacological and conditioning agents have been proven effective in reducing reperfusion injury and IS in preclinical research. Mechanistically, these agents act either by inhibiting reperfusion injury cascades or by activating cellular prosurvival pathways. Although most of these agents/strategies are at the experimental stage, some of them have been tested clinically in patients with STEMI. This review provides an update on key pharmacological agents and postconditioning used in the setting of PPCI to reduce reperfusion injury and IS. Despite intensive research, no strategy or intervention has been shown to prevent reperfusion injury or enhance myocardial salvage in a consistent manner in a clinical setting. A number of novel therapeutic strategies to reduce reperfusion injury in the setting of PPCI in patients with STEMI are currently under investigation. They will lead to a better understanding of reperfusion injury and to more efficient strategies for its prevention.

Therapeutic Hypothermia for Cardioprotection in Acute Myocardial Infarction

Mild therapeutic hypothermia of 32-35°C improved neurologic outcomes in outside hospital cardiac arrest survivor. Furthermore, in experimental studies on infarcted model and pilot studies on conscious patients with acute myocardial infarction, therapeutic hypothermia successfully reduced infarct size and microvascular resistance. Therefore, mild therapeutic hypothermia has received an attention as a promising solution for reduction of infarction size after acute myocardial infarction which are not completely solved despite of optimal reperfusion therapy. Nevertheless, the results from randomized clinical trials failed to prove the cardioprotective effects of therapeutic hypothermia or showed beneficial effects only in limited subgroups. In this article, we reviewed rationale for therapeutic hypothermia and possible mechanisms from previous studies, effective methods for clinical application to the patients with acute myocardial infarction, lessons from current clinical trials and future directions.

Therapeutic hypothermia in ST elevation myocardial infarction: a systematic review and meta-analysis of randomised control trials

OBJECTIVE

Our objective is to gain a better understanding of the efficacy and safety of therapeutic hypothermia (TH) in patients with acute ST elevation myocardial infarction (STEMI) through an analysis of randomised controlled trials (RCTs).

BACKGROUND

Several RCTs have suggested a positive outcome with the use of TH in the prevention of myocardial injury in the setting of an acute STEMI. However, there are currently no clinical trials that have conclusively shown any significant benefit.

METHODS

Electronic databases were used to identify RCTs of TH in the patient population with STEMI. The primary efficacy end point was major adverse cardiovascular event (MACE). Secondary efficacy end points included all-cause mortality, infarct size, new myocardial infarction and heart failure/pulmonary oedema (HF/PO). All-bleeding, ventricular arrhythmias and bradycardias were recorded as the safety end points.

RESULTS

Six RCTs were included in this meta-analysis, enrolling a total of 819 patients. There was no significant benefit from TH in preventing MACE (OR, 01.04; 95% CI 0.37 to 2.89), all-cause mortality (OR, 1.48; 95% CI 0.68 to 3.19), new myocardial infarction (OR, 0.99; 95% CI 0.20 to 4.94), HF/PO (OR, 0.52; 95% CI 0.15 to 1.77) or infarct size (standard difference of the mean (SDM), -0.1; 95% CI -0.23 to 0.04). However, a significant reduction of infarct size was observed with TH utilisation in anterior wall myocardial infarction (SDM, -0.23; 95% CI -0.45 to -0.02). There was no significant difference seen for the safety end points all-bleeding (OR 1.32; 95% CI 0.77 to 2.24), ventricular arrhythmias (OR, 0.85; 95% CI 0.54 to 1.36) or bradycardias (OR, 1.16; 95% CI 0.74 to 1.83).

CONCLUSIONS

Although TH appears to be safe in patients with STEMI, meta-analysis of published RCTs indicates that benefit is limited to reduction of infarct size in patients with anterior wall involvement with no demonstrable effect on all-cause mortality, recurrent myocardial infarction or HF/PO.

Early targeted brain COOLing in the cardiac CATHeterisation laboratory following cardiac arrest (COOLCATH)

INTRODUCTION

Trials demonstrate significant clinical benefit in patients receiving therapeutic hypothermia (TH) after cardiac arrest. However, incidence of mortality and morbidity remains high in this patient group. Rapid targeted brain hypothermia induction, together with prompt correction of the underlying cause may improve outcomes in these patients. This study investigates the efficacy of Rhinochill, an intranasal cooling device over Blanketrol, a surface cooling device in inducing TH in cardiac arrest patients within the cardiac catheter laboratory.

METHODS

70 patients were randomized to TH induction with either Rhinochill or Blanketrol. Primary outcome measures were time to reach tympanic ≤34 °C from randomisation as a surrogate for brain temperature and oesophageal ≤34 °C from randomisation as a measurement of core body temperature. Secondary outcomes included first hour temperature drop, length of stay in intensive care unit, hospital stay, neurological recovery and all-cause mortality at hospital discharge.

RESULTS

There was no difference in time to reach ≤34 °C between Rhinochill and Blanketrol (Tympanic ≤34 °C, 75 vs. 107 mins; p=0.101; Oesophageal ≤34 °C, 85 vs. 115 mins; p=0.151). Tympanic temperature dropped significantly with Rhinochill in the first hour (1.75 vs. 0.94 °C; p<0.001). No difference was detected in any other secondary outcome measures. Catheter laboratory-based TH induction resulted in a survival to hospital discharge of 67.1%.

CONCLUSION

In this study, Rhinochill was not found to be more efficient than Blanketrol for TH induction, although there was a non-significant trend in favour of Rhinochill that potentially warrants further investigation with a larger trial.

Hypothermia in the setting of experimental acute myocardial infarction: a comprehensive review

A door-to-balloon time of less than 90 minutes is the gold standard for reperfusion therapy to treat acute myocardial infarction (MI). Because 30-day mortality remains ∼ 10%, new methods must be cultivated to limit myocardial injury. Therapeutic hypothermia has long been experimentally used to attenuate myocardial necrosis during MI with promising results, but the treatment has yet to gain popularity among most clinicians. Hypothermia, in the basic science setting, has been achieved using many techniques. In our review, we examine past and current methods of inducing hypothermia, benefits and setbacks of such methods, current and future clinical trials, and potential mechanisms.

Novel Uses of Targeted Temperature Management

Targeted temperature management has an established role in treating the post-cardiac arrest syndrome after out-of-hospital cardiac arrest with an initial rhythm of ventricular tachycardia/ventricular fibrillation. There is less certain benefit if the initial rhythm is pulseless electrical activity/asystole or for in-hospital cardiac arrest. Targeted temperature management may have a role as salvage modality for conditions causing intracranial hypertension, such as traumatic brain injury, hepatic encephalopathy, intracerebral hemorrhage, and acute stroke. There is variable evidence for its use early in these disorders to minimize secondary neurologic injury.

Setting Up an Efficient Therapeutic Hypothermia Team in Conscious ST Elevation Myocardial Infarction Patients: A UK Heart Attack Center Experience

Patients presenting with ST elevation myocardial infarction (STEMI) are routinely treated with percutaneous coronary intervention to restore blood flow in the occluded artery to reduce infarct size (IS). However, there is evidence to suggest that the restoration of blood flow can cause further damage to the myocardium through reperfusion injury (RI). Recent research in this area has focused on minimizing damage to the myocardium caused by RI. Therapeutic hypothermia (TH) has been shown to be beneficial in animal models of coronary artery occlusion in reducing IS caused by RI if instituted early in an ischemic myocardium. Data in humans are less convincing to date, although exploratory analyses suggest that there is significant clinical benefit in reducing IS if TH can be administered at the earliest recognition of ischemia in anterior myocardial infarction. The Essex Cardiothoracic Centre is the first UK center to have participated in administering TH in conscious patients presenting with STEMI as part of the COOL-AMI case series study. In this article, we outline our experience of efficiently integrating conscious TH into our primary percutaneous intervention program to achieve 18 minutes of cooling duration before reperfusion, with no significant increase in door-to-balloon times, in the setting of the clinical trial.

Activity of antimicrobial drugs against bacterial pathogens under mild hypothermic conditions

BACKROUND

Infections are a common problem in cardiac arrest survivors. Antimicrobial drugs are often administered in routine care during treatment of patients with mild therapeutic hypothermia (MTH). Because there is to date no evidence for the pharmacodynamics of antimicrobial drugs under MTH conditions, we investigated the in vitro activity of common antimicrobials against clinically relevant bacterial pathogens.

MATERIAL AND METHODS

Activities of antimicrobial drugs against clinically relevant bacterial pathogens were assessed in vitro by disk diffusion and broth microdilution assays at normothermic (37°C) and hypothermic (32°C) conditions.

RESULTS

Seventy-three bacterial isolates were tested in disk diffusion and 15 in broth microdilution assays. Mean differences in zone diameters and minimal inhibitory concentration ratios were 0.6 mm (95% confidence interval, 0.3-0.9 mm) and 0.98 (95% confidence interval, 0.95-1.02), respectively, meeting predefined criteria for equivalence of in vitro antimicrobial activity.

CONCLUSIONS

The presented data provide reassuring evidence that the intrinsic activity of antimicrobials seems to be unaltered in MTH. However, further studies evaluating the pharmacokinetics including target site concentrations of the respective drugs and in vivo pharmacodynamics are necessary to complement our understanding of the appropriate use of antimicrobials in MTH.

Therapeutic hypothermia for the treatment of acute myocardial infarction-combined analysis of the RAPID MI-ICE and the CHILL-MI trials

In the randomized rapid intravascular cooling in myocardial infarction as adjunctive to percutaneous coronary intervention (RAPID MI-ICE) and rapid endovascular catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction CHILL-MI studies, hypothermia was rapidly induced in conscious patients with ST-elevation myocardial infarction (STEMI) by a combination of cold saline and endovascular cooling. Twenty patients in RAPID MI-ICE and 120 in CHILL-MI with large STEMIs, scheduled for primary percutaneous coronary intervention (PCI) within <6 hours after symptom onset were randomized to hypothermia induced by rapid infusion of 600-2000 mL cold saline combined with endovascular cooling or standard of care. Hypothermia was initiated before PCI and continued for 1-3 hours after reperfusion aiming at a target temperature of 33°C. The primary endpoint was myocardial infarct size (IS) as a percentage of myocardium at risk (IS/MaR) assessed by cardiac magnetic resonance imaging at 4±2 days. Patients randomized to hypothermia treatment achieved a mean core body temperature of 34.7°C before reperfusion. Although significance was not achieved in CHILL-MI, in the pooled analysis IS/MaR was reduced in the hypothermia group, relative reduction (RR) 15% (40.5, 28.0-57.6 vs. 46.6, 36.8-63.8, p=0.046, median, interquartile range [IQR]). IS/MaR was predominantly reduced in early anterior STEMI (0-4h) in the hypothermia group, RR=31% (40.5, 28.8-51.9 vs. 59.0, 45.0-67.8, p=0.01, median, IQR). There was no mortality in either group. The incidence of heart failure was reduced in the hypothermia group (2 vs. 11, p=0.009). Patients with large MaR (>30% of the left ventricle) exhibited significantly reduced IS/MaR in the hypothermia group (40.5, 27.0-57.6 vs. 55.1, 41.1-64.4, median, IQR; hypothermia n=42 vs. control n=37, p=0.03), while patients with MaR<30% did not show effect of hypothermia (35.8, 28.3-57.5 vs. 38.4, 27.4-59.7, median, IQR; hypothermia n=15 vs. control n=19, p=0.50). The prespecified pooled analysis of RAPID MI-ICE and CHILL-MI indicates a reduction of myocardial IS and reduction in heart failure by 1-3 hours with endovascular cooling in association with primary PCI of acute STEMI predominantly in patients with large area of myocardium at risk. (ClinicalTrials.gov id NCT00417638 and NCT01379261).

The impact of therapeutic hypothermia on on-treatment platelet reactivity and clinical outcome in cardiogenic shock patients undergoing primary PCI for acute myocardial infarction: Results from the ISAR-SHOCK registry

INTRODUCTION

Mild therapeutic hypothermia (TH) is standard of care after cardiac arrest of any cause. However, its impact on on-treatment platelet reactivity and clinical outcome in patients with acute myocardial infarction (AMI) complicated by cardiogenic shock and undergoing PCI with P2Y12 receptor inhibitor treatment is less clear.

METHODS AND RESULTS

For the ISAR-SHOCK registry, 145 patients with AMI, cardiogenic shock and primary PCI in two centers (Deutsches Herzzentrum München and Klinikum rechts der Isar, Technical University Munich) between January 2009-May 2012 were analysed. Of these, 64 (44%) patients received TH treatment. The median [IQR] ADP-induced platelet aggregation following thienopyridine loading dose administration (clopidogrel in 95 and prasugrel in 50 patients) did not differ between the two groups (419 [283-684] for TH vs. 355 [207-710] AU x min for non-TH patients, P=0.22). After 30days follow-up, no significant differences were observed between both groups for mortality (42 vs. 44 %, HR: 0.93, 95% CI [0.56-1.53], p=0.77), MI (6 vs. 6%, HR: 0.99 95% CI [0.27-3.7], p=0.99) and TIMI minor bleedings (17 vs. 17%, HR 0.99 95% CI [0.45-2.18], p=0.98). TIMI major bleedings were numerically higher in the TH vs. non-TH cohort (25 % vs. 12 %, HR: 2.1 95% CI [0.95-4.63], p=0.07). Three definite stent thrombosis (ST) were observed in this registry and all STs occurred in the TH group of patients (p=0.09).

CONCLUSION

Results of this registry suggest that TH does not negatively impact on platelet reactivity in shock patients receiving either clopidogrel or prasugrel. The numerically higher rate of major bleedings and the clustering of STs in the TH cohort warrant further investigation.

Cardioprotection for percutaneous coronary intervention--reperfusion quality as well as quantity

Ischaemia-reperfusion (IR) injury is an important cause of myocardial damage during percutaneous coronary intervention (PCI). There are few therapies in widespread clinical use which impact on IR injury and it remains an important and underutilized target for treatment in acute myocardial infarction. This review will examine the translational scientific evidence for ischaemic conditioning and pharmacological agents including conditioning mimetics such as cyclosporine, anti-inflammatory agents, and those which modify myocardial glucose metabolism. We will address the reasons why many trials have failed to demonstrate clinical benefit and emphasize the need to deliver the right therapy to the right patient, at the right time to achieve successful translation of cardioprotection from bench-to-bedside. We critique trial design and offer advice for future translational trials in the field to ensure that effective treatments can be demonstrated clinically to improve patient outcomes during PCI.

Novel adjunctive treatments of myocardial infarction

Myocardial infarction is a major cause of death and disability worldwide and myocardial infarct size is a major determinant of prognosis. Early and successful restoration of myocardial reperfusion following an ischemic event is the most effective strategy to reduce final infarct size and improve clinical outcome, but reperfusion may induce further myocardial damage itself. Development of adjunctive therapies to limit myocardial reperfusion injury beyond opening of the coronary artery gains increasing attention. A vast number of experimental studies have shown cardioprotective effects of ischemic and pharmacological conditioning, but despite decades of research, the translation into clinical effects has been challenging. Recently published clinical studies, however, prompt optimism as novel techniques allow for improved clinical applicability. Cyclosporine A, the GLP-1 analogue exenatide and rapid cooling by endovascular infusion of cold saline all reduce infarct size and may confer clinical benefit for patients admitted with acute myocardial infarcts. Equally promising, three follow-up studies of the effect of remote ischemic conditioning (RIC) show clinical prognostic benefit in patients undergoing coronary surgery and percutaneous coronary intervention. The discovery that RIC can be performed noninvasively using a blood pressure cuff on the upper arm to induce brief episodes of limb ischemia and reperfusion has facilitated the translation of RIC into the clinical arena. This review focus on novel advances in adjunctive therapies in relation to acute and elective coronary procedures.

Rapid Induction of Hypothermia by the ThermoSuit System Profoundly Reduces Infarct Size and Anatomic Zone of No Reflow Following Ischemia-Reperfusion in Rabbit and Rat Hearts

INTRODUCTION

Although hypothermia reduces myocardial infarct size, noninvasive and rapid cooling methods are lacking. This study tests the effectiveness of a novel cooling apparatus on myocardial infarct size and no-reflow area in 2 models of coronary artery occlusion (CAO).

METHODS AND RESULTS

Animals were randomized to normothermic (N) or hypothermic (H) groups after isolation of a proximal coronary artery. Animals were subjected to 30 minutes CAO and 3 hours reperfusion. In protocol 1 (rabbit, n = 8 per group), hypothermia was initiated, using the ThermoSuit apparatus (convective-immersion cooling), 5 minutes after the onset of CAO to a goal temperature of ∼32°C. In protocol 2 (rat, n = 5 per group), hypothermia was initiated 2 minutes after the onset of CAO to a goal temperature of ∼30°C. Goal temperature was reached in ∼20 minutes. In protocol 1, hypothermia caused an 82% reduction in infarct size as a percentage of the ischemic risk zone (N, 44% ± 5%; H; 8% ± 2%, P < 0.001) and an 89% reduction in the no-reflow area (N, 44% ± 4%; H, 5% ± 1%, P < 0.001). In protocol 2, hypothermia caused a 73% infarct size reduction (N, 51% ± 5%; H, 14% ± 6%, P < 0.01) and a 99% reduction in the no-reflow area (N, 33% ± 5%; H, 0.4% ± 0.3%, P < 0.01).

CONCLUSION

The ThermoSuit device induced rapid hypothermia and limited infarct size and no reflow to the greatest extent ever observed in this laboratory with a single intervention.

High rates of prasugrel and ticagrelor non-responder in patients treated with therapeutic hypothermia after cardiac arrest

INTRODUCTION

After cardiac arrest due to acute coronary syndromes (ACS) therapeutic hypothermia (HT) is the standard care to reduce neurologic damage. Additionally, the concomitant medical treatment with aspirin and a P2Y12 receptor inhibitor like clopidogrel (Cl), prasugrel (Pr) or ticagrelor (Ti) is mandatory. The platelet inhibitory effect of these drugs under hypothermia remains unclear.

METHODS

164 patients with ACS were prospectively enrolled in this study. 84 patients were treated with HT, 80 patients were under normothermia (NT). All patients were treated with aspirin and one of the P2Y12 receptor inhibitors Cl, Pr or Ti. 24h after the initial loading dose the platelet reactivity index (PRI/VASP-index) was determined to achieve the platelet inhibitory effect.

RESULTS

In the HT-group the PRI/VASP-index was significantly higher compared to the NT-group (54.86%±25.1 vs. 28.98%±22.8; p<0.001). In patients under HT receiving Cl, the platelet inhibition was most markedly reduced (HT vs. NT: 66.39%±19.1 vs. 33.36%±22.1; p<0.001) compared to Pr (HT vs. NT: 37.6%±25.0 vs. 27.04%±25.5; p=0.143) and Ti (HT vs. NT: 41.5%±21.0 vs. 17.83%±14.5; p=0.009). The rate of non-responder defined as PRI/VASP-index>50% was increased in HT compared to NT (60.7% vs. 22.5%; p<0.001) with the highest rates in the group receiving Cl (CL: 82% vs. 26%, p<0.001; Pr: 32% vs. 23%; n.s.; Ti: 30% vs. 8%, n.s.).

CONCLUSION

The platelet inhibitory effect in patients treated with HT after cardiac arrest is significantly reduced. This effect was most marked with the use of Cl. The new P2Y12-inhibitors Pr and Ti improved platelet inhibition in HT, but could not completely prevent non-responsiveness.

Rapid endovascular catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction. The CHILL-MI trial: a randomized controlled study of the use of central venous catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction

OBJECTIVES

The aim of this study was to confirm the cardioprotective effects of hypothermia using a combination of cold saline and endovascular cooling.

BACKGROUND

Hypothermia has been reported to reduce infarct size (IS) in patients with ST-segment elevation myocardial infarctions.

METHODS

In a multicenter study, 120 patients with ST-segment elevation myocardial infarctions (<6 h) scheduled to undergo percutaneous coronary intervention were randomized to hypothermia induced by the rapid infusion of 600 to 2,000 ml cold saline and endovascular cooling or standard of care. Hypothermia was initiated before percutaneous coronary intervention and continued for 1 h after reperfusion. The primary end point was IS as a percent of myocardium at risk (MaR), assessed by cardiac magnetic resonance imaging at 4 ± 2 days.

RESULTS

Mean times from symptom onset to randomization were 129 ± 56 min in patients receiving hypothermia and 132 ± 64 min in controls. Patients randomized to hypothermia achieved a core body temperature of 34.7°C before reperfusion, with a 9-min longer door-to-balloon time. Median IS/MaR was not significantly reduced (hypothermia: 40.5% [interquartile range: 29.3% to 57.8%; control: 46.6% [interquartile range: 37.8% to 63.4%]; relative reduction 13%; p = 0.15). The incidence of heart failure was lower with hypothermia at 45 ± 15 days (3% vs. 14%, p < 0.05), with no mortality. Exploratory analysis of early anterior infarctions (0 to 4 h) found a reduction in IS/MaR of 33% (p < 0.05) and an absolute reduction of IS/left ventricular volume of 6.2% (p = 0.15).

CONCLUSIONS

Hypothermia induced by cold saline and endovascular cooling was feasible and safe, and it rapidly reduced core temperature with minor reperfusion delay. The primary end point of IS/MaR was not significantly reduced. Lower incidence of heart failure and a possible effect in patients with early anterior ST-segment elevation myocardial infarctions need confirmation. (Efficacy of Endovascular Catheter Cooling Combined With Cold Saline for the Treatment of Acute Myocardial Infarction [CHILL-MI]; NCT01379261).