Electrocardiographic changes during therapeutic hypothermia

Management of patients with an electrical storm or clustered ventricular arrhythmias: a clinical consensus statement of the European Heart Rhythm Association of the ESC-endorsed by the Asia-Pacific Heart Rhythm Society, Heart Rhythm Society, and Latin-American Heart Rhythm Society

Electrical storm (ES) is a state of electrical instability, manifesting as recurrent ventricular arrhythmias (VAs) over a short period of time (three or more episodes of sustained VA within 24 h, separated by at least 5 min, requiring termination by an intervention). The clinical presentation can vary, but ES is usually a cardiac emergency. Electrical storm mainly affects patients with structural or primary electrical heart disease, often with an implantable cardioverter-defibrillator (ICD). Management of ES requires a multi-faceted approach and the involvement of multi-disciplinary teams, but despite advanced treatment and often invasive procedures, it is associated with high morbidity and mortality. With an ageing population, longer survival of heart failure patients, and an increasing number of patients with ICD, the incidence of ES is expected to increase. This European Heart Rhythm Association clinical consensus statement focuses on pathophysiology, clinical presentation, diagnostic evaluation, and acute and long-term management of patients presenting with ES or clustered VA.

Myocardial electrophysiological and mechanical changes caused by moderate hypothermia-A clinical study

Moderate hypothermia has been used to improve outcomes in comatose out-of-hospital cardiac arrest survivors during the past two decades, although the effects remain controversial. We have recently shown in an experimental study that myocardial electrophysiological and mechanical relationships were altered during moderate hypothermia. Electromechanical window positivity increased, and electrical dispersion of repolarization decreased, both of which are changes associated with decreased arrhythmogenicity in clinical conditions. Mechanical dispersion, a parameter also linked to arrhythmic risk, remained unaltered. Whether corresponding electrophysiological and mechanical changes occur in humans during moderate hypothermia, has not been previously explored. Twenty patients with normal left ventricular function were included. Measurements were obtained at 36 and 32°C prior to ascending aortic repair while on partial cardiopulmonary bypass and at 36°C after repair. Registrations were performed in the presence of both spontaneous and comparable paced heart rate during standardized loading conditions. The following electrical and mechanical parameters were explored: (1) Electromechanical window, measured as time difference between mechanical and electrical systole, (2) dispersion of repolarization from ECG T-wave, and (3) mechanical dispersion, measured as segmental variation in time to peak echocardiographic strain. At moderate hypothermia, mechanical systolic prolongation (425 ± 43-588 ± 67 ms, p < 0.001) exceeded electrical systolic prolongation (397 ± 49-497 ± 79 ms, p < 0.001), whereby, electromechanical window positivity increased (29 ± 30-86 ± 50 ms, p < 0.001). Dispersion of repolarization and mechanical dispersion remained unchanged. Corresponding electrophysiological and mechanical relationships were present at comparable paced heart rates. After rewarming, the increased electromechanical window was reversed in the presence of both spontaneous and paced heart rates. Moderate hypothermia increased electromechanical window positivity, while dispersion of repolarization and mechanical dispersion remained unchanged. This impact of hypothermia may be clinically relevant for selected groups of patients after cardiac arrest.

ST-Elevation Myocardial Infarction Complicated by Out-of-Hospital Cardiac Arrest

5-10% of ST-elevated myocardial infarctions (STEMI) present with out-of-hospital cardiac arrest (OHCA). Although this subgroup of patients carries the highest in-hospital mortality among the STEMI population, it is the least likely to undergo coronary angiography and revascularization. Due to the concomitant neurologic injury, patients with OHCA STEMI require prolonged hospitalization and adjustments to standard MI management. This review systematically assesses the course of patients with OHCA STEMI from development of the arrest to hospital discharge, assesses the limiting factors for their treatment access, and presents the evidence-based optimal intervention strategy for this high-risk MI population.

Post-cardiac arrest care and targeted temperature management: A consensus of scientific statement from the Taiwan Society of Emergency & Critical Care Medicine, Taiwan Society of Critical Care Medicine and Taiwan Society of Emergency Medicine

BACKGROUND

Post-cardiac arrest care is critically important in bringing cardiac arrest patients to functional recovery after the detrimental event. More high quality studies are published and evidence is accumulated for the post-cardiac arrest care in the recent years. It is still a challenge for the clinicians to integrate these scientific data into the real clinical practice for such a complicated intensive care involving many different disciplines.

METHODS

With the cooperation of the experienced experts from all disciplines relevant to post-cardiac arrest care, the consensus of the scientific statement was generated and supported by three major scientific groups for emergency and critical care in post-cardiac arrest care.

RESULTS

High quality post-cardiac arrest care, including targeted temperature management, early evaluation of possible acute coronary event and intensive care for hemodynamic and respiratory care are inevitably needed to get full recovery for cardiac arrest. Management of these critical issues were reviewed and proposed in the consensus CONCLUSION: The goal of the statement is to provide help for the clinical physician to achieve better quality and evidence-based care in post-cardiac arrest period.

QTc interval in survivors of out of hospital cardiac arrest

BACKGROUND

QTc interval (QTc) prolongation is seen on the post-arrest electrocardiogram (ECG) of many out of hospital cardiac arrest (OHCA) survivors. It remains unclear whether this is a transient phenomenon or a manifestation of an underlying arrhythmic substrate. This observational study assessed the trend of QTc in an unselected group of patients presenting with OHCA. We sought to identify any relationship between QTc, gender and aetiology of arrest. We observed whether targeted temperature management (TTM) is associated with malignant arrhythmia.

METHOD

We analysed 60 patients presenting with OHCA to the Bristol Heart Institute during a 20-month period. We measured QTc on admission and assessed for persistence, development and resolution of prolongation at up to 5 time points post-OHCA. Aetiology of arrest was divided into coronary, non-coronary or primary arrhythmic to investigate for patterns in QTc behaviour.

RESULTS

81.7% (49/60) of arrests were attributed to an acute coronary event. 55% (33/60) had QTc prolongation on admission, of which 79% resolved. There were no significant differences in QTc behaviour by aetiology. One patient presenting with a normal QTc, developed prolongation during admission and received a genetic diagnosis of Long QT Syndrome. TTM was employed in 57/60, with no increased incidence of malignant arrhythmia.

CONCLUSIONS

Prolonged QTc on admission does not imply a primary arrhythmic aetiology and resolves in the majority pre-discharge. However, an initial normal QTc post-OHCA does not preclude a diagnosis of Long QT syndrome, highlighting the importance of thorough investigations in these patients. TTM appears safe from a cardiac perspective.

Electrocardiographic changes in patients undergoing targeted temperature management

OBJECTIVES

Targeted temperature management is the recommended therapy for comatose patients after an out-of-hospital cardiac arrest resuscitation due to the reduction in neurological damage and improved outcomes. However, there may result in electrocardiographic instability depending on the degree of targeted temperature management, including minor or life-threatening dysrhythmias or conduction delays. This project aims to describe the frequency of ECG interval changes and clinically relevant dysrhythmias in targeted temperature management patients.

METHODS

This is a retrospective observational study from January 2009 to December 2015. Patients who qualified for the study had a non-traumatic cardiac arrest with a return of spontaneous circulation, received targeted temperature management at 33.5°C for 24 hours followed by 16 hours of rewarming. ECG interval changes and dysrhythmias were recorded immediately after return of spontaneous circulation, and at 24 and 48 hours post return of spontaneous circulation.

RESULTS

A total of 322 patients (age 61.0 ± 16.9 years) had targeted temperature management initiated during the study period, of which 169 had complete data and 13 died prior to completing 24 hours of hypothermia. There were statistically significant changes during targeted temperature management in heart rate (96.7 ± 26.0/min before targeted temperature management; 69.5 ± 19.1/min during, P < 0.001), QRS duration (115.1 ± 32.6 ms before targeted temperature management; 107.8 ± 27.9 ms during targeted temperature management, P < 0.001), and QTc (486.3 ± 52.8 ms before targeted temperature management; 526.9 ± 61.7 ms during targeted temperature management, P < 0.001). There were cardiac dysrhythmias that received treatment during cooling and rewarming.

CONCLUSION

During the period of targeted temperature management and rewarming, we observed few self-limiting ECG interval changes and no clinically significant dysrhythmias in this population during the period of targeted temperature management.

Hypothermia and cardiac electrophysiology: a systematic review of clinical and experimental data

Moderate therapeutic hypothermia procedures are used in post-cardiac arrest care, while in surgical procedures, lower core temperatures are often utilized to provide cerebral protection. Involuntary reduction of core body temperature takes place in accidental hypothermia and ventricular arrhythmias are recognized as a principal cause for a high mortality rate in these patients. We assessed both clinical and experimental literature through a systematic literature search in the PubMed database, to review the effect of hypothermia on cardiac electrophysiology. From included studies, there is common experimental and clinical evidence that progressive cooling will induce changes in cardiac electrophysiology. The QT interval is prolonged and appears more sensitive to decreases in temperature than the QRS interval. Severe hypothermia is associated with more pronounced changes, some of which are proarrhythmic. This is supported clinically where severe accidental hypothermia is commonly associated with ventricular fibrillation or asystole. J-waves in human electrocardiogram recordings are regularly but not always observed in hypothermia. Its relation to ventricular repolarization and arrhythmias is not obvious. Little clinical data exist on efficacy of anti-arrhythmic drugs in hypothermia, while experimental data show the potential of some agents, such as the class III antiarrhythmic bretylium. It is apparent that QT-prolonging drugs should be avoided.

Electrocardiographic changes during therapeutic hypothermia: observational data from a single centre

Background

Therapeutic hypothermia is recommended to reduce the risk of hypoxic brain damage and improve short-term survival after cardiac arrest. It also temporarily affects the cardiac conduction system. The aim of this study was to evaluate electrocardiographic changes during therapeutic hypothermia and their impact on the outcome.

Materials and methods

This retrospective analysis involved 26 patients who underwent therapeutic hypothermia after cardiac arrest in Vilnius University Hospital Santaros Klinikos from 2011 to 2015.

Results

During cooling, a significant reduction in the heart rate (p = 0.013), shortening of QRS complex duration (p = 0.041), and prolongation of the QTc interval (p < 0.001) were observed. During the cooling period, five patients had subtle Osborn waves, which disappeared after rewarming. The association between electrocardiographic changes during cooling and unfavourable neurological outcome or in-hospital mortality was non-significant.

Conclusions

Therapeutic hypothermia after cardiac arrest causes reversible electrocardiographic changes that do not increase the risk of in-hospital mortality or unfavourable neurological outcomes.

Therapy-Resistant Ventricular Arrhythmias Developed More Often in Advanced Than in Therapeutic Mild Hypothermic Condition

Therapy-resistant ventricular arrhythmias can occur during accidental advanced hypothermic conditions. On the other hand, hypothermic therapy using mild cooling has been successfully accomplished with infrequent ventricular arrhythmia events.To further clarify the therapeutic-resistant arrhythmogenic substrate which develops in hypothermic conditions, an experimental study was performed using a perfusion wedge preparation model of porcine ventricle, and electrophysiological characteristics, inducibility of ventricular arrhythmias, and effects of therapeutic interventions were assessed at 3 target temperatures (37, 32 and 28°C).As the myocardial temperature decreased, myocardial contractions and the number of spontaneous beats deceased. Depolarization (QRS width, stimulus-QRS interval) and repolarization (QT interval, ERP) parameters progressively increased, and dispersion of the ventricular repolarization increased. At 28°C, VF tended to be inducible more frequently (1/11 at 37°C, 1/11 at 32°C, and 5/11 hearts at 28°C), and some VFs at 28°C required greater defibrillation energy to resume basic rhythm.An advanced but not a mild hypothermic condition had an enhanced arrhythmogenic potential in our model. In the advanced hypothermic condition, VF with relatively prolonged F-F intervals and a greater defibrillation energy were occasionally inducible based on the arrhythmogenic substrate characterized as slowed conduction and prolonged repolarization of the ventricle.

Determinants of cardiac repolarization and risk for ventricular arrhythmias during mild therapeutic hypothermia

PURPOSE

We aimed to investigate the factors that modulate the extent of QTc prolongation and potential arrhythmogenic consequences during mild therapeutic hypothermia (MTH).

METHODS

We studied 205 patients after out-of-hospital cardiac arrest (131 underwent MTH). QTc was measured at baseline, 3h, 6h, 12h, 24h (end of hypothermia), 48h and 72h, and ventricular arrhythmias quantified.

RESULTS

During MTH, the QTc interval increased progressively peaking at 12h (mean increase 42ms, 95% CI 30-55). There was a strong gender effect (P<0.001) and a significant gender-by-MTH interaction (P=0.004). At 12h, the QTc interval was markedly longer in women as compared with men (mean difference 50ms [95% CI 27-73]. Anoxic brain injury (P=0.002) was also positively associated with QTc prolongation. The risk for ventricular arrhythmic events was not higher with MTH compared with no hypothermia (incidence rate ratio 0.57, 95% CI 0.32-1.02, P=0.06). However, typical cases of Torsade de pointes occurred in association with AV block and LQT2.

CONCLUSION

QTc prolongation during MTH is strongly affected by female gender and moderately by concomitant anoxic brain injury. Although the overall risk for ventricular arrhythmias is not greater with MTH, Torsade de pointes may develop when other contributing factors coexist.

Effect of Prophylactic Amiodarone Infusion on the Recurrence of Ventricular Arrhythmias in Out-of-Hospital Cardiac Arrest Survivors: A Propensity-Matched Analysis

Amiodarone is recommended for shock-refractory ventricular arrhythmia during resuscitation; however, it is unknown whether amiodarone is effective for preventing ventricular arrhythmia recurrence in out-of-hospital cardiac arrest (OHCA) survivors treated with targeted temperature management (TTM). We investigated the effectiveness of prophylactic amiodarone in preventing ventricular arrhythmia recurrence in OHCA survivors. Data of consecutive adult non-traumatic OHCA survivors treated with TTM between 2010 and 2016 were extracted from prospective cardiac arrest registries of four tertiary care hospitals. The prophylactic amiodarone group was matched in a 1:1 ratio by using propensity scores. The primary outcome was ventricular arrhythmia recurrence requiring defibrillation during TTM. Among 295 patients with an initially shockable rhythm and 149 patients with initially non-shockable-turned-shockable rhythm, 124 patients (27.9%) received prophylactic amiodarone infusion. The incidence of ventricular arrhythmia recurrence was 11.26% (50/444). Multivariate analysis showed prophylactic amiodarone therapy to be the independent factor associated with ventricular arrhythmia recurrence (odds ratio 1.95, 95% CI 1.04–3.65, p = 0.04), however, no such association was observed (odds ratio 1.32, 95% CI 0.57–3.04, p = 0.51) after propensity score matching. In this propensity-score-matched study, prophylactic amiodarone infusion had no effect on preventing ventricular arrhythmia recurrence in OHCA survivors with shockable cardiac arrest. Prophylactic amiodarone administration must be considered carefully.

Electrocardiographic and echocardiographic changes during therapeutic hypothermia in encephalopathic infants with long-term adverse outcome

AIM

To assess the electrocardiography and echocardiography changes during therapeutic hypothermia and rewarming period in encephalopathic infants with long-term adverse neurological outcome.

METHODS

Prospective multicentre longitudinal study. We included 64 consecutive infants with moderate or severe hypoxic ischaemic encephalopathy undergoing therapeutic hypothermia who had 18-24 month-outcome data. We analysed electrocardiography and heart rate changes before, during and after therapeutic hypothermia. Superior vena cava flow, left ventricular cardiac output and stroke volume were studied using echocardiography during and immediately after therapeutic hypothermia. An abnormal outcome was defined as death or moderate/severe disability at 18-24 months.

RESULTS

Neonates with higher superior vena cava flow pre-rewarming had significantly higher odds of documented long-term adverse outcome when compared to newborns with good outcome (OR 1.57; 95%CI, 1.1-1.78; p = 0.01 after adjustment). QTc and RR intervals were significantly longer at 12, 24, 36 and 48 h in infants with good outcome compared with those with adverse outcome (p < 0.001). During therapeutic hypothermia, infants with poor outcome had a higher heart rate at 12, 24, 36, 48, 60 h after birth compared with those with good outcome (p < 0.001). From 36 h on, heart rate gradually increased and RR and QTc intervals progressively shortened with values back to normal after rewarming.

CONCLUSIONS

Infants with hypoxic ischaemic encephalopathy who have adverse neurological outcome show a preferential cerebral blood flow redistribution during therapeutic hypothermia. Infants with poor outcome have higher heart rate and shorter RR and QTc intervals during therapeutic hypothermia.

Cardiopulmonary Resuscitation in Infants and Children With Cardiac Disease: A Scientific Statement From the American Heart Association

Cardiac arrest occurs at a higher rate in children with heart disease than in healthy children. Pediatric basic life support and advanced life support guidelines focus on delivering high-quality resuscitation in children with normal hearts. The complexity and variability in pediatric heart disease pose unique challenges during resuscitation. A writing group appointed by the American Heart Association reviewed the literature addressing resuscitation in children with heart disease. MEDLINE and Google Scholar databases were searched from 1966 to 2015, cross-referencing pediatric heart disease with pertinent resuscitation search terms. The American College of Cardiology/American Heart Association classification of recommendations and levels of evidence for practice guidelines were used. The recommendations in this statement concur with the critical components of the 2015 American Heart Association pediatric basic life support and pediatric advanced life support guidelines and are meant to serve as a resuscitation supplement. This statement is meant for caregivers of children with heart disease in the prehospital and in-hospital settings. Understanding the anatomy and physiology of the high-risk pediatric cardiac population will promote early recognition and treatment of decompensation to prevent cardiac arrest, increase survival from cardiac arrest by providing high-quality resuscitations, and improve outcomes with postresuscitation care.

Electrocardiographic Findings in Patients With Acute Coronary Syndrome Presenting With Out-of-Hospital Cardiac Arrest

We sought to characterize presenting electrocardiographic findings in patients with acute coronary syndromes (ACSs) and out-of-hospital cardiac arrest (OHCA). In the Global Registry of Acute Coronary Events and Canadian ACS Registry I, we examined presenting and 24- to 48-hour follow-up ECGs (electrocardiogram) of ACS patients who survived to hospital admission, stratified by presentation with OHCA. We assessed the prevalence of ST-segment deviation and bundle branch blocks (assessed by an independent ECG core laboratory) and their association with in-hospital and 6-month mortality among those with OHCA. Of the 12,040 ACS patients, 215 (1.8%) survived to hospital admission after OHCA. Those with OHCA had higher presenting rates of ST-segment elevation, ST-segment depression, T-wave inversion, precordial Q-waves, left bundle branch block (LBBB), and right bundle branch block (RBBB) than those without. Among patients with OHCA, those with ST-segment elevation had significantly lower in-hospital mortality (20.9% vs 33.0%, p = 0.044) and a trend toward lower 6-month mortality (27% vs 39%, p = 0.060) compared with those without ST-segment elevation. Conversely, among OCHA patients, LBBB was associated with significantly higher in-hospital and 6-month mortality rates (58% vs 22%, p <0.001, and 65% vs 28%, p <0.001, respectively). ST-segment depression and RBBB were not associated with either outcome. Sixty-three percent of bundle branch blocks (RBBB or LBBB) on the presenting ECG resolved by 24 to 48 hours. In conclusion, compared with ACS patients without cardiac arrest, those with OHCA had higher rates of ST-segment elevation, LBBB, and RBBB on admission. Among OHCA patients, ST-segment elevation was associated with lower in-hospital mortality, whereas LBBB was associated with higher in-hospital and 6-month mortality.

[Hypothermia-induced ECG changes: characteristic, but not specific]

Hypothermia-induced J‑ or so-called Osborn waves can be detected under therapeutic hypothermia in approximately 20-40% of cases. The occurrence of J‑waves in the context of the targeted temperature management after cardiopulmonary resuscitation is characteristic, but not pathognomonic for hypothermia. An electrocardiographic diagnosis under hypothermia after cardiac arrest should always be done with caution due to the various hypothermia-associated electromechanical changes of the myocardium.

Prevalence and Prognostic Implications of Bundle Branch Block in Comatose Survivors of Out-of-Hospital Cardiac Arrest

This study reports the prevalence and prognostic impact of right bundle branch block (RBBB) and left bundle branch block (LBBB) in the admission electrocardiogram (ECG) of comatose survivors of out-of-hospital cardiac arrest (OHCA). The present study is part of the predefined electrocardiographic substudy of the prospective randomized target temperature management trial, which found no benefit of targeting 33°C over 36°C in terms of outcome. Six-hundred eighty-two patients were included in the substudy. An admission ECG, which defined the present study population, was available in 602 patients (88%). These ECGs were stratified by the presence of LBBB, RBBB, or no-BBB (reference) on admission. End points were mortality and neurologic outcome 6 months after OHCA. RBBB was present in 79 patients (13%) and LBBB in 65 patients (11%), and the majority of BBBs (92%) had resolved 4 hours after admission. RBBB was associated with significantly higher 6 months mortality (RBBB: hazard ratio [HR]_unadjusted 1.78, 95% confidence interval [CI] 1.30 to 2.43; LBBB: HR_unadjusted 1.26, 95% CI 0.87 to 1.81), but this did not reach a level of significance in the adjusted model (HR_adjusted 1.33, 95% CI 0.94 to 1.87). Similar findings were seen for neurologic outcome in the unadjusted and adjusted analyses. RBBB was further independently associated with higher odds of unfavorable neurologic outcome (RBBB: adjusted odds ratio 1.97, 95% CI 1.05 to 3.71). In conclusion, BBBs after OHCA were transient in most patients, and RBBB was directly associated with higher mortality and independently associated with higher odds of unfavorable neurologic outcome. RBBB is seemingly an early indicator of an unfavorable prognosis after OHCA.

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.

Accidental hypothermia in severe trauma

Hypothermia, along with acidosis and coagulopathy, is part of the lethal triad that worsen the prognosis of severe trauma patients. While accidental hypothermia is easy to identify by a simple measurement, it is no less pernicious if it is not detected or treated in the initial phase of patient care. It is a multifactorial process and is a factor of mortality in severe trauma cases. The consequences of hypothermia are many: it modifies myocardial contractions and may induce arrhythmias; it contributes to trauma-induced coagulopathy; from an immunological point of view, it diminishes inflammatory response and increases the chance of pneumonia in the patient; it inhibits the elimination of anaesthetic drugs and can complicate the calculation of dosing requirements; and it leads to an over-estimation of coagulation factor activities. This review will detail the pathophysiological consequences of hypothermia, as well as the most recent principle recommendations in dealing with it.

[Corrected QT interval during therapeutic hypothermia in hypoxic ischaemic encephalopathy]

INTRODUCTION

Therapeutic hypothermia is the standard treatment for hypoxic ischaemic encephalopathy (HIE), despite not knowing all its effects and complications. Sinus bradycardia is one of the consequences of cooling that has been previously documented in the literature, but little is known about the cardiac electrical activity in these patients.

OBJECTIVE

To determine the corrected QT (QTc) interval in newborns treated with therapeutic hypothermia for HIE.

MATERIAL AND METHODS

A prospective observational study was conducted in all patients treated with hypothermia for HIE that were admitted to our Unit between November 2012 and October 2013. ECGs were performed during hypothermia (every 24h), during the re-warming period (at 34.5°C, 35.5°C, 36.5°C), and on the 7th day of life.

RESULTS

A total of 19 patients were included. A prolonged QTc was observed in all patients during hypothermia, and 84% (n=16) had prolonged QTc in all the ECGs during treatment. In 3 patients, one of the ECGs did not have a prolonged QTc. After re-warming, the QTc interval returned to normal in all patients. No statistically significant differences were seen when the degree of HIE (P=.192) or the use of inotropic support (P=.669) were considered.

CONCLUSIONS

Therapeutic hypothermia applied to asphyxiated newborns with HIE seems to induce a QTc prolongation that resolves when the patient regains physiological temperature.

Arrhythmogenic potential develops rapidly at graft reperfusion before the start of hypotension during living-donor liver transplantation

Background

Detailed profiles of acute hypothermia and electrocardiographic (ECG) manifestations of arrhythmogenicity were examined to analyze acute hypothermia and ventricular arrhythmogenic potential immediately after portal vein unclamping (PVU) in living-donor liver transplantation (LT).

Methods

We retrospectively analyzed electronically archived medical records (n = 148) of beat-to-beat ECG, arterial pressure waveforms, and blood temperature (BT) from Swan-Ganz catheters in patients undergoing living-donor LT. The ECG data analyzed were selected from the start of BT drop to the initiation of systolic hypotension after PVU.

Results

On reperfusion, acute hypothermia of < 34℃, < 33℃ and < 32℃ developed in 75.0%, 37.2% and 11.5% of patients, respectively. BT decreased from 35.0℃ ± 0.8℃ to 33.3℃ ± 1.0℃ (range 35.8℃–30.5℃). The median time to nadir of BT was 10 s after PVU. Difference in BT (ΔBT) was weakly correlated with graft-recipient weight ratio (GRWR; r = 0.22, P = 0.008). Compared to baseline, arrhythmogenicity indices such as corrected QT (QTc), Tp-e (T wave peak to end) interval, and Tp-e/QTc ratio were prolonged (P < 0.001 each). ST height decreased and T amplitude increased (P < 0.001 each). However, no correlation was found between ΔBT and arrhythmogenic indices.

Conclusions

In living-donor LT, regardless of extent of BT drop, ventricular arrhythmogenic potential developed immediately after PVU prior to occurrence of systolic hypotension.

Therapeutic hypothermia post-cardiac arrest: a clinical nurse specialist initiative in Pakistan

PURPOSE

The purpose of this project was to assess the feasibility of an evidence-based therapeutic hypothermia protocol in adult post-cardiac arrest (CA) patients in a university hospital in Pakistan.

BACKGROUND

Cardiac arrest has a deleterious effect on neurological function, and survival is associated with significant morbidity. The International Liaison Committee of Cardiopulmonary Resuscitation and the American Heart Association recommend the use of mild hypothermia in post-CA victims to mitigate brain injury caused by anoxia. In Pakistan, the survival rate in CA victims is poor. At present, there are no hospitals in the country that use the evidence-based hypothermia intervention in adult post-CA victims.

DESCRIPTION

This pilot project of therapeutic hypothermia in adult post-CA patients was implemented in a university hospital in Pakistan by a clinical nurse specialist in collaboration with the cardiopulmonary resuscitation committee and the nursing leadership of the hospital. Various clinical nurse specialist competencies and roles were used to address the 3 spheres of influence: patient, nurses, and system, while executing an evidence-based hypothermia protocol. Process and outcome indicators were monitored to evaluate the effectiveness and feasibility of hypothermia intervention in this setting.

OUTCOME

The hypothermia protocol was successfully implemented in 3 adult post-CA patients using cost-effective measures. All 3 patients were extubated within 72 hours after CA, and 2 patients were discharged home with good neurological outcome.

CONCLUSION

Adoption of an evidence-based hypothermia protocol for adult CA patients is feasible in the intensive care setting of a university hospital in Pakistan.

IMPLICATIONS

The process used in the project can serve as a road map to other hospitals in resource-limited countries such as Pakistan that are motivated to improve post-CA outcomes. This experience reveals that advanced practice nurses can be instrumental in translation of evidence into practice in a healthcare system in Pakistan.

Inducibility of ventricular fibrillation during mild therapeutic hypothermia: electrophysiological study in a swine model

INTRODUCTION

Mild therapeutic hypothermia (MTH) is being used after cardiac arrest for its expected improvement in neurological outcome. Safety of MTH concerning inducibility of malignant arrhythmias has not been satisfactorily demonstrated. This study compares inducibility of ventricular fibrillation (VF) before and after induction of MTH in a whole body swine model and evaluates possible interaction with changing potassium plasma levels.

METHODS

The extracorporeal cooling was introduced in fully anesthetized swine (n = 6) to provide MTH. Inducibility of VF was studied by programmed ventricular stimulation three times in each animal under the following: during normothermia (NT), after reaching the core temperature of 32°C (HT) and after another 60 minutes of stable hypothermia (HT60). Inducibility of VF, effective refractory period of the ventricles (ERP), QTc interval and potassium plasma levels were measured.

RESULTS

Starting at normothermia of 38.7 (IQR 38.2; 39.8)°C, HT was achieved within 54 (39; 59) minutes and the core temperature was further maintained constant. Overall, the inducibility of VF was 100% (18/18 attempts) at NT, 83% (15/18) after reaching HT (P = 0.23) and 39% (7/18) at HT60 (P = 0.0001) using the same protocol. Similarly, ERP prolonged from 140 (130; 150) ms at NT to 206 (190; 220) ms when reaching HT (P < 0.001) and remained 206 (193; 220) ms at HT60. QTc interval was inversely proportional to the core temperature and extended from 376 (362; 395) at NT to 570 (545; 599) ms at HT. Potassium plasma level changed spontaneously: decreased during cooling from 4.1 (3.9; 4.8) to 3.7 (3.4; 4.1) mmol/L at HT (P < 0.01), then began to increase and returned to baseline level at HT60 (4.6 (4.4; 5.0) mmol/L, P = NS).

CONCLUSIONS

According to our swine model, MTH does not increase the risk of VF induction by ventricular pacing in healthy hearts. Moreover, when combined with normokalemia, MTH exerts an antiarrhythmic effect despite prolonged QTc interval.

Therapeutic temperature management after cardiac arrest and the risk of bleeding: systematic review and meta-analysis

AIM

Prognosis after cardiac arrest in the era of modern critical care is still poor with a high mortality of approximately 90%. Around 30% of the survivors have neurological impairments. Targeted temperature management (TTM) is the only treatment option which can improve mortality and neurological outcome. It is so far unclear if bleeding complications occur more often in patients undergoing TTM treatment.

METHODS

We conducted a systematic literature research in September 2013 including three major databases i.e. MEDLINE, EMBASE and CENTRAL. All studies were rated in respect to the ILCOR Guidelines and concerning their level of evidence and quality. We then performed a meta-analysis on bleeding disposition under TTM.

RESULTS

We initially found 941 studies out of which 34 matched our requirements and were thus included in our overview. Five studies including 599 patients were summarized in a meta-analysis concerning bleeding complications of all severities. There was a trend toward higher bleeding in patients treated with TTM (RR: 1.30, 95% CI: 0.97-1.74) which did not reach significance (p=0.085). Seven studies with an overall 599 patients were included in our meta-analysis on bleeding requiring transfusion. There was no significant difference in the incidence of severe bleeding with a risk ratio of 0.97 (95% CI: 0.61-1.56, p=0.909).

CONCLUSIONS

The data included in our meta-analysis indicate that, concerning the risk of bleeding, TTM is a safe method for patients after cardiac arrest. We did not observe a significantly higher risk for bleeding in patients undergoing TTM.

Managing the Complications of Mild Therapeutic Hypothermia in the Cardiac Arrest Patient

Mild therapeutic hypothermia (MTH) is used to lower the core body temperature of cardiac arrest (CA) patients to 32°C from 34°C to provide improved survival and neurologic outcomes after resuscitation from in-hospital or out-of-hospital CA. Despite the improved benefits of MTH, there are potentially unforeseen complications associated during management. Although the adverse effects are transient, the clinician should be aware of the associated complications when managing the patient receiving MTH. We aim to provide the medical community comprehensive information related to the potential complications of survivors of CA receiving MTH, as it is imperative for the clinician to understand the physiologic changes that take place in the patient receiving MTH and how to prepare for them and manage them if they do occur. We hope to provide information of how to manage these potential complications through both a review of the current literature and a reflection of our own experience.

Therapeutic hypothermia-induced electrocardiographic changes and relations to in-hospital mortality

BACKGROUND

Therapeutic hypothermia improves survival for selected patients who remain comatose after cardiac arrest. Hypothermia triggers changes in electrocardiographic (ECG) parameters; however, the association of these changes to in-hospital mortality remains unclear.

HYPOTHESIS

QT interval changes induced by therapeutic hypothermia are not associated with in-hospital mortality.

METHODS

We retrospectively compared precooling ECG parameters to ECG parameters during hypothermia on all consecutive patients with available information who received hypothermia at our academic medical center between December 2006 and July 2012 (N = 101; 24% women). Paired 2-sample t test was used to compare precooling vs cooling ECG parameters. In-hospital mortality related to ECG parameter changes was compared using the Pearson χ(2) test.

RESULTS

Therapeutic hypothermia resulted in increases in PR and QTc intervals and decreases in heart rate and QRS intervals (P for all <0.02). During hospitalization, 45 of the 101 patients died. Survivors vs nonsurvivors did not differ in heart rate change (P = 0.74), PR change (P = 0.57), QRS change (P = 0.09), or QTc change (P = 0.67). Comparing patients who had reduced QTc intervals with hypothermia to those who had prolonged QTc with hypothermia, 14 out of 30 died in the former group, whereas 31 out of 71 died in the latter group (46.7% vs 43.7%, odds ratio [OR]: 1.13, 95% CI: 0.48-2.66). Patients presenting with right bundle branch block (RBBB) had a higher risk of in-hospital death compared to those without RBBB (72.2% vs 38.6%, OR: 4.14, 95% CI: 1.35-12.73).

CONCLUSIONS

Therapeutic hypothermia prolonged QTc interval with no association to in-hospital mortality. Presence of RBBB on initial presentation was related to increased mortality.

Long QT interval in a patient after out-of-hospital cardiac arrest with hypocalcaemia, undergoing therapeutic hypothermia

A 53-year-old woman was hospitalized after out-of-hospital cardiac arrest due to ventricular fibrillation. Initial electrocardioagram showed sinus rhythm of 117 beats per minute, 452 ms QTc interval, ST-segment depression up to 1 mm in V(2)-V(6), and ST-elevation in lead aVR. Patient was treated with primary coronary angioplasty and therapeutic hypothermia, during which QTc interval prolonged up to 616 ms and Osborn wave was seen in lead V(4), along with elevation of ST-segment in I, II, III, aVF, V(5) and V(6); negative T waves in I, II, aVL, aVF, and V(2)-V(6). Laboratory test results showed hypocalcaemia. After rewarming and ion correction QT abnormalities resolved.

[Early repolarisation. A dilemma of risk stratification]

Early repolarization, involving infero-lateral ST segment elevation and prominent J waves at the QRS-ST junction has been considered a normal ECG variant for more than 80 years. More recent studies suggest that this phenomenon is not as benign as earlier believed and may represent a risk for subsequent ventricular fibrillation in patients with and without structural heart disease. However, based on current data it seems unjustified to consider these often accidental ECG findings a marker for high risk of sudden cardiac death. The concept of a reduced repolarization reserve developed for the Long QT syndrome can be transformed to early repolarization syndrome. In general a "fibrillation reserve" is relatively high but if triggers such as a genetic background, age, gender, influences of the autonomous nervous system, changes in body temperature, or an acute coronary syndrome act together ventricular fibrillation may occur. A combination of an "early repolarization ECG" with syncope and/or a positive family history of sudden cardiac death may justify defibrillator therapy just on an individual basis. This review intends to summarize actual aspects of early repolarizations syndrome and focuses on the dilemma of risk stratification.

State-of-the-art paper: Therapeutic hypothermia in out of hospital cardiac arrest survivors

Out of hospital cardiac arrest (OHCA) is associated with an extremely poor survival rate, with mortality in most cases being related to neurological injury. Among patients who experience return of spontaneous circulation (ROSC), therapeutic hypothermia (TH) is the only proven intervention shown to reduce mortality and improve neurological outcome. First described in 1958, the field of TH has rapidly evolved in recent years. While recent technological advances in TH will likely improve outcomes in OHCA survivors, several fundamental questions remain to be answered including the optimal speed of cooling, which patients benefit from an early invasive strategy, and whether technological advances will facilitate application of TH in the field. An increased awareness and understanding of TH strategies, devices, monitoring, techniques, and complications will allow for a more widespread adoption of this important treatment modality.

Temperature affects thrombolytic efficacy using rt-PA and eptifibatide, an in vitro study

The potential for hypothermia as a neuroprotectant during stroke has led to its increase in clinical use. At the same time, combination pharmaceutical therapies for ischemic stroke using recombinant tissue plasminogen activator (rt-PA), and GP IIb-IIIa inhibitors, such as Eptifibatide (Epf ), are under study. However, there is little data on how the reactions triggered by these agents are impacted by temperature. Here, clot lysis during exposure to the combination of rt-PA and Epf is measured in an in vitro human clot model at hypothermic temperatures. The hypothesis is that lytic efficacy of rt-PA and Epf decreases with decreasing temperature. Whole blood clots from 31 volunteers were exposed to rt-PA (0.5 μg/mL) and Epf (0.63 μg/mL) in human fresh-frozen plasma (rt-PA+Epf ), rt-PA alone in plasma (rt-PA Alone), or to plasma alone (Control), at temperatures from 30°C to 37°C, for 30 minutes. Clot lysis was measured using a microscopic imaging technique; the mean fractional clot loss (FCL) at 30 minutes was used to determine lytic efficacy. Temperature had a significant impact on FCL in clots exposed to rt-PA+Epf, with the FCL being lower at 30°C to 36°C than at 37°C. The FCL remained significantly higher for rt-PA+Epf–treated clots than Controls regardless of temperature, with the exception of measurements made at 30°C when no significant differences in the FCL were observed between groups. The use of hypothermia as a neuroprotectant may negatively impact the therapeutic benefit of thrombolytic agents.