Resuscitation from out-of-hospital cardiac arrest: implications for cardiac enzyme estimation

High-sensitivity troponin T for detection of culprit lesions in patients with out-of-hospital cardiac arrest

BACKGROUND

Patients with an out-of-hospital cardiac arrest (OHCA) often undergo coronary angiography, although a culprit lesion is found in only 30%-40% of patients. The aim of this study was to investigate high-sensitivity troponin T (hsTnT) levels in post cardiac arrest patients with and without coronary culprit lesions; factors affecting hsTnT levels after return of spontaneous circulation (ROSC); and the diagnostic ability of hsTnT in identifying patients with culprit lesions. We hypothesized that peak hsTnT levels were higher during the initial 48 h after cardiac arrest in patients with a coronary culprit lesion.

METHODS

This was a retrospective observational study, which included patients admitted to the Intensive Care Unit after an OHCA and who received a coronary angiography. Peak values and dynamic changes in hsTnT were analyzed in relation to the presence of a culprit lesion at coronary angiography.

RESULTS

A total of 238 patients were studied, of whom 140 had a culprit lesion. HsTnT levels during the initial 48 h were higher in patients with culprit lesions, longer time to ROSC and an unwitnessed cardiac arrest. At 6 to 12 h after ROSC, a hsTnT cut-off level of 1690 ng/L had a sensitivity of 64% and specificity of 84% to identify a culprit lesion. In patients without ST-elevations, hsTnT measured between 6 and 12 h after ROSC had a specificity above 90%, with a sensitivity of 46%.

CONCLUSION

HsTnT levels after cardiac arrest are higher in patients with coronary culprit lesions. Presence of a culprit lesion, witnessed status and the duration of CPR are important factors affecting hsTnT levels. Repeated measurement of hsTnT within the first 12 h after admission improved diagnostic accuracy but the value of hsTnT as a predictor of culprit lesions early after OHCA is limited.

Association of Timing of Electrocardiogram Acquisition After Return of Spontaneous Circulation With Coronary Angiography Findings in Patients With Out-of-Hospital Cardiac Arrest

IMPORTANCE

Electrocardiography (ECG) is an important tool to triage patients with out-of-hospital cardiac arrest (OHCA) after return of spontaneous circulation (ROSC). An immediate coronary angiography after ROSC is recommended only in patients with an ECG that is diagnostic of ST-segment elevation myocardial infarction (STEMI). To date, the benefit of this approach has not been demonstrated in patients with a post-ROSC ECG that is not diagnostic of STEMI.

OBJECTIVE

To assess whether the time from ROSC to ECG acquisition is associated with the diagnostic accuracy of ECG for STEMI.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective, multicenter cohort study (the Post-ROSC Electrocardiogram After Cardiac Arrest study) analyzed consecutive patients older than 18 years who were resuscitated from OHCA between January 1, 2015, and December 31, 2018, and were admitted to 1 of the 3 participating centers in Europe (Pavia, Italy; Lugano, Switzerland; and Vienna, Austria).

EXPOSURE

Only patients who underwent coronary angiography during hospitalization and who acquired a post-ROSC ECG before the angiography were enrolled. Patients with a nonmedical cause of OHCAs were excluded.

MAIN OUTCOMES AND MEASURES

The primary end point was false-positive ECG findings, defined as the percentage of patients with post-ROSC ECG findings that met STEMI criteria but who did not show obstructive coronary artery disease on angiography that was worthy of percutaneous coronary angioplasty.

RESULTS

Of 586 consecutive patients who were admitted to the 3 participating centers, 370 were included in the analysis (287 men [77.6%]; median age, 62 years [interquartile range, 53-70 years]); 121 (32.7%) were enrolled in the participating center in Pavia, Italy; 38 (10.3%) in Lugano, Switzerland; and 211 (57.0%) in Vienna, Austria. The percentage of false-positive ECG findings in the first tertile of ROSC to ECG time (≤7 minutes) was significantly higher than that in the second (8-33 minutes) and third (>33 minutes) tertiles: 18.5% in the first tertile vs 7.2% in the second (odds ratio [OR], 0.34; 95% CI, 0.13-0.87; P = .02) and 5.8% in the third (OR, 0.27; 95% CI, 0.15-0.47; P < .001). These differences remained significant when adjusting for sex (≤7 minutes: reference; 8-33 minutes: OR, 0.32; 95% CI, 0.12-0.85; P = .02; >33 minutes: OR, 0.26; 95% CI, 0.14-0.47; P < .001), age (≤7 minutes: reference; 8-33 minutes: OR, 0.34; 95% CI, 0.13-0.89; P = .03; >33 minutes: OR, 0.27; 95% CI, 0.15-0.46; P < .001), number of segments with ST-elevation (≤7 minutes: reference; 8-33 minutes: OR, 0.35; 95% CI, 0.15-0.81; P = .01; >33 minutes: OR, 0.28; 95% CI, 0.15-0.52; P < .001), QRS duration (≤7 minutes: reference; 8-33 minutes: OR, 0.35; 95% CI, 0.14-0.87; P = .02; >33 minutes: OR, 0.27; 95% CI, 0.15-0.48; P < .001), heart rate (≤7 minutes: reference; 8-33 minutes: OR, 0.35; 95% CI, 0.13-0.93; P = .04; >33 minutes: OR, 0.29; 95% CI, 0.15-0.55; P < .001), epinephrine administered (≤7 minutes: reference; 8-33 minutes: OR, 0.35; 95% CI, 0.13-0.98; P = .045; >33 minutes: OR, 0.27; 95% CI, 0.16-0.48; P < .001), shockable initial rhythm (≤7 minutes: reference; 8-33 minutes: OR, 0.35; 95% CI, 0.13-0.96; P = .04; >33 minutes: OR, 0.26; 95% CI, 0.15-0.46; P < .001), and 3 or more shocks administered (≤7 minutes: reference; 8-33 minutes: OR, 0.36; 95% CI, 0.13-1.00; P = .05; >33 minutes: OR, 0.27; 95% CI, 0.16-0.48; P < .001) in bivariable analyses.

CONCLUSIONS AND RELEVANCE

This study suggests that early ECG acquisition after ROSC in patients with OHCA is associated with a higher percentage of false-positive ECG findings for STEMI. It may be reasonable to delay post-ROSC ECG by at least 8 minutes after ROSC or repeat the acquisition if the first ECG is diagnostic of STEMI and is acquired early after ROSC.

Diagnostic and prognostic utility of cardiac troponin in post-cardiac arrest care

BACKGROUND

Cardiac troponin is routinely tested in the post-cardiac arrest setting, but its utility in identifying ischaemic aetiology and predicting left ventricular systolic dysfunction (LVSD) and survival is not known.

METHODS

In a retrospective single center registry, we identified 145 consecutive patients who had achieved return of spontaneous circulation after cardiac arrest and had undergone serial cardiac troponin T (cTnT) testing, echocardiogram, and expert adjudication of aetiology. Initial and peak cTnT were evaluated for assessing ischaemic aetiology, LVSD, and survival to discharge using area under the receiver operating characteristic curve (AUROC).

RESULTS

Mean age was 61 ± 14 years and 71% were men. Of the 145 arrests, 19% had an ischaemic aetiology, 68% had LVSD post-arrest, and 55% survived to discharge. All patients had a positive initial cTnT at 0.01 ng/mL (clinical cut-off). Even at higher cut-offs of 10×, 100× and 1000×, initial cTnT performed poorly (AUROC 0.57, 0.56, and 0.56) and peak cTnT performed modestly (AUROC 0.55, 0.61, and 0.62) as diagnostic tests for ischaemic aetiology. Similarly, even at higher cut-offs, initial (AUROC 0.60, 0.62, 0.55) and peak (AUROC 0.57, 0.61, and 0.62) cTnT performed poorly to modestly at predicting LVSD. The test performed poorly for predicting survival to discharge (AUROC for all <0.6).

CONCLUSIONS

At both current and several-fold higher thresholds, cTnT does not perform sufficiently well to guide clinical decision-making or predict patient outcomes. Routine post-cardiac arrest testing of cTnT should be reevaluated.

Kounis Syndrome During Anesthesia: Presentation of Indolent Systemic Mastocytosis: A Case Report

Mastocytosis comprises a heterogeneous group of disorders characterized by mast cell accumulation and proliferation in distinct organs. Kounis syndrome is defined as the concurrence of acute coronary syndromes with mast cell activation in a setting of allergic or hypersensitivity reactions. This is the first reported case of an intraoperative Kounis syndrome as the onset of an indolent systemic mastocytosis probably triggered by succinylated gelatin infusion during general anesthesia. The presentation of this case is intended to contribute to the knowledge of mastocytosis and Kounis syndrome at the time of diagnostic workup during intraoperative anaphylaxis or myocardial ischemia.

The association of maximum Troponin values post out-of-hospital cardiac arrest with electrocardiographic findings, cardiac reperfusion procedures and survival to discharge: A sub-study of ROC PRIMED

BACKGROUND

The role of Troponin (Tn) levels in the management of patients post out-of-hospital cardiac arrest (OHCA) is unclear.

METHODS

All OHCA patients enrolled in the Resuscitation Outcomes Consortium Prehospital Resuscitation using an IMpedance valve and Early versus Delayed analysis trial and admitted to hospital with a Tn level and a 12-lead electrocardiogram were stratified by ST elevation (STE) or no STE in a regression model for survival to discharge adjusted for Utstein predictors and site.

RESULTS

Of the 15,617 enrolled OHCA patients, 4118 (26%) survived to admission to hospital; 17% (693) were STE and 77% (3188) were no STE with 6% unknown; 83% (3460) had at least one Tn level. Reperfusion rates were higher when Tn level >2ng/ml (p>0.1ng/ml) improved with a diagnostic cardiac catheterization (p<0.001).

CONCLUSIONS

Elevated Tn levels >2ng/ml were associated with improved survival to discharge in patients post OHCA with STE. Survival in patients with no STE and Tn values >0.1ng/ml was higher when associated with diagnostic cardiac catheterization or treated with reperfusion or revascularization.

Prognostic value of high-sensitivity troponin T levels in patients with ventricular arrhythmias and out-of-hospital cardiac arrest: data from the prospective FINNRESUSCI study

Introduction

Myocardial dysfunction is common after out-of-hospital cardiac arrest (OHCA) and high-sensitivity troponin T (hs-TnT) levels may provide incremental prognostic information to established risk indices.

Methods

A total of 155 patients with OHCA and a shockable rhythm (98% ventricular fibrillation; OHCA-VF/VT) had blood samples drawn within six hours of admission. Blood samples were also available after 24 hours, 48 hours, and 96 hours in subsets of patients. The endpoints of the study were hospital mortality and neurological status and mortality after one year.

Results

Admission hs-TnT levels were higher than the 99-percentile of the general population (14 ng/L) in all patients (range 18 to 17837 ng/L). Admission hs-TnT levels were associated with acute coronary artery occlusion, time to return of spontaneous circulation, heart failure, and renal function. Admission hs-TnT levels were higher in one-year non-survivors compared to survivors (median 747 (quartile 1 to 3, 206 to 1061) ng/L versus 345 (184 to 740) ng/L, P =0.023) and in patients with a poor versus a favorable neurological outcome (739 (191 to 1061) ng/L versus 334 (195 to 716) ng/L, P =0.028). However, hs-TnT measurements did not add prognostic information to established risk variables in multivariate analyses. hs-TnT levels measured during the hospitalization for OHCA-VF/VT correlated closely with admission levels (r ≥0.63) and were inferior to Simplified Acute Physiology Score II (SAPS II) scores for the prediction of events during follow-up. hs-TnT dynamics did not discriminate between survivors and non-survivors or between a poor versus a favorable neurological outcome.

Conclusion

hs-TnT levels are elevated in critically ill patients with OHCA-VF/VT, but do not improve risk prediction.

Prognostic relevance of plasma heart-type fatty acid binding protein after out-of-hospital cardiac arrest

OBJECTIVE

Heart-type fatty acid binding protein (H-FABP) is a tissue-specific protein which is rapidly released into the circulation when cardiomyocyte injury occurs. The aim of the study is to investigate the prognostic relevance of H-FABP for out-of-hospital cardiac arrest (OHCA) patients in the early post-cardiac arrest period.

DESIGN AND METHODS

This is a prospective cohort study enrolling non-traumatic resuscitated OHCA patients.

RESULTS

A total of 106 patients were enrolled. The H-FABP level at 24h was correlated to the duration from collapse to return of spontaneous circulation (p<0.001, R(2)=0.549). The outcomes of survival to discharge were worse in the patient group with the higher tertile of plasma H-FABP level at 24h after the event (p=0.011). Multivariate analysis demonstrated that the significant predictors for in-hospital mortality were APACHE II score (p=0.010), gender (p=0.025) and the tertiles of H-FABP at 24h with hazard ratios for the lowest, middle, and highest tertiles being 1.0, 1.157 (95% confidence interval 0.435-3.075, p=0.770), and 2.840 (95% confidence interval 1.137-7.092, p=0.025), respectively.

CONCLUSION

The plasma level of H-FABP at 24h after the event may be an early and independent factor associated with survival to discharge in OHCA patients.

Effects of potassium/lidocaine-induced cardiac standstill during cardiopulmonary resuscitation in a pig model of prolonged ventricular fibrillation

OBJECTIVES

Several studies in patients who underwent open heart surgery found that myocardial ischemic damage was reduced by potassium cardioplegia combined with lidocaine infusion. The authors evaluated the effects of potassium/lidocaine-induced cardiac standstill during conventional cardiopulmonary resuscitation (CPR) on myocardial injury and left ventricular dysfunction after resuscitation from prolonged ventricular fibrillation (VF) cardiac arrest in a pig model.

METHODS

Ventricular fibrillation was induced in 16 pigs, and circulatory arrest was maintained for 14 minutes. Animals were then resuscitated by standard CPR. Animals were randomized at the start of CPR to receive 20 mL of saline (control group) or 0.9 mEq/kg potassium chloride and 1.2 mg/kg lidocaine diluted to 20 mL (K-lido group).

RESULTS

Seven animals in each group achieved return of spontaneous circulation (ROSC; p=1.000). Four of the K-lido group animals (50%) achieved ROSC without countershock. Resuscitated animals in the K-lido group required fewer countershocks (p=0.004), smaller doses of epinephrine (p=0.009), and shorter durations of CPR (p=0.004) than did the control group. The uncorrected troponin-I at 4 hours after ROSC was lower in the K-lido group compared with the control group (2.82 ng/mL, 95% confidence interval [CI]=1.07 to 3.38 ng/mL vs. 6.55 ng/mL, 95% CI=4.84 to 13.30 ng/mL; p=0.025), although the difference was not significant after Bonferroni correction. The magnitude of reduction in left ventricular ejection fraction (LVEF) between baseline and 1 hour after ROSC was significantly lower in the K-lido group (26.5%, SD±6.1% vs. 39.1%, SD±6.8%; p=0.004).

CONCLUSIONS

In a pig model of untreated VF cardiac arrest for 14 minutes, resuscitation with potassium/lidocaine-induced cardiac standstill during conventional CPR tended to reduce myocardial injury and decreased the severity of postresuscitation myocardial dysfunction significantly.

Weak diagnostic performance of troponin, creatine kinase and creatine kinase-MB to diagnose or exclude myocardial infarction after successful resuscitation

BACKGROUND

The aim of this study is to evaluate the diagnostic accuracy of the cardiac injury markers troponin (TNT), creatine kinase (CK) and creatine kinase-MB (CK-MB) to diagnose or exclude acute myocardial infarction after cardiac arrest.

METHODS

226 patients who underwent diagnostic coronary angiography after sudden cardiac arrest were analyzed retrospectively. Levels of TNT, CK and CK-MB on admission and 6h, 24h and 36 h later were retrieved from the files and compared with the results of coronary angiography.

RESULTS

Acute myocardial infarction (AMI) as well as non-AMI patients showed increasing levels of TNT and CK after resuscitation, although the AMI group showed significantly higher TNT and CK levels. Receiver operator curves were calculated to determine the diagnostic precision of TNT, CK and CK-MB to differentiate AMI and non-AMI patients. All analyzed markers yielded mediocre diagnostic precision with an area under the ROC curve of 0.7020, 0.6802 and 0.6508 for 6h TNT, CK and CK-MB, respectively. Applying a modified cut-off of 1 μg/l the 6h TNT measurement had a sensitivity of 70.9% and specificity of 61.2% to diagnose AMI after cardiac arrest. Using CK 800 U/l as cut-off level resulted in a sensitivity of 62.5% and specificity of 73.7%, CK-MB levels higher than 100 U/l yielded a sensitivity of 58.8% and specificity of 72.7%.

CONCLUSION

Cardiac injury markers cannot be used to reliably diagnose or rule out AMI after resuscitation. Consequently we propose that indication for coronary angiography should be extended to all patients without a certain alternative diagnosis explaining the occurrence of cardiac arrest.

Effect of cardiac compressions and hypothermia treatment on cardiac troponin I in newborns with perinatal asphyxia

BACKGROUND

The American Heart Association, the European Resuscitation and the International Liaison Committee issued new neonatal resuscitation guidelines (2010) where therapeutic hypothermia is introduced after hypoxic-ischaemic encephalopathy (HIE) in term infants to prevent brain injury. Our study aimed to investigate whether hypothermia can reduce the release of a cardiac cellular marker, cardiac troponin I (cTnI), in HIE infants compared to normothermia care, if cTnI can be used as a prognostic marker for long term neuro-developmental outcome and if cardiac compression at birth affects the level of cTnI.

METHODS

We retrospectively collected resuscitation data at birth and cTnI levels for the first 3 days in HIE infants who fulfilled cooling entry criteria. These infants received either normothermia care or induced hypothermia treatment in the neonatal period and were then followed up and tested by standard cognitive and motor assessments. The outcome is defined as death, disability or good.

RESULTS

We confirmed an increase in cTnI after cardiac compressions (p=0.003, Mann-Whitney test). We found that hypothermia significantly reduced the release of cTnI (peak level and area under the curve within 24h of age), p=0.002, linear regression. Receiver operating characteristic curves showed a level of cTnI at 24 h of age <0.22 ng/ml for normothermic and <0.15 ng/ml for hypothermic infants predicts a good outcome.

CONCLUSIONS

Our results suggest that hypothermia is cardio protective after HIE. The level of cTnI at 24h of age is a good prognostic marker for neuro-developmental outcome at 18-22 months in both normothermia and hypothermia infants.

Evaluation of acute cardiac and chest wall damage after shocks with a subcutaneous implantable cardioverter defibrillator in Swine

BACKGROUND

A subcutaneous implantable cardioverter defibrillator (S-ICD) could ease placement and reduce complications of transvenous ICDs, but requires more energy than transvenous ICDs. Therefore we assessed cardiac and chest wall damage caused by the maximum energy shocks delivered by both types of clinical devices.

METHODS

During sinus rhythm, anesthetized pigs (38 ± 6 kg) received an S-ICD (n = 4) and five 80-Joule (J) shocks, or a transvenous ICD (control, n = 4) and five 35-J shocks. An inactive S-ICD electrode was implanted into the same control pigs to study implant trauma. All animals survived 24 hours. Troponin I and creatine kinase muscle isoenzyme (CK-MM) were measured as indicators of myocardial and skeletal muscle injury. Histopathological injury of heart, lungs, and chest wall was assessed using semiquantitative scoring.

RESULTS

Troponin I was significantly elevated at 4 hours and 24 hours (22.6 ± 16.3 ng/mL and 3.1 ± 1.3 ng/mL; baseline 0.07 ± 0.09 ng/mL) in control pigs but not in S-ICD pigs (0.12 ± 0.11 ng/mL and 0.13 ± 0.13 ng/mL; baseline 0.06 ± 0.03 ng/mL). CK-MM was significantly elevated in S-ICD pigs after shocks (6,544 ± 1,496 U/L and 9,705 ± 6,240 U/L; baseline 704 ± 398 U/L) but not in controls. Electrocardiogram changes occurred postshock in controls but not in S-ICD pigs. The myocardium and lungs were histologically normal in both groups. Subcutaneous injury was greater in S-ICD compared to controls.

CONCLUSION

Although CK-MM suggested more skeletal muscle injury in S-ICD pigs, significant cardiac, lung, and chest wall histopathological changes were not detected in either group. Troponin I data indicate significantly less cardiac injury from 80-J S-ICD shocks than 35-J transvenous shocks.

Biomarkers as predictors of outcome after cardiac arrest

Cardiac arrest (CA) is a major health and economic problem. Management of patients resuscitated from CA is challenging for clinicians, and the mortality rate of those who achieve return of spontaneous circulation remains high. Hypoxic brain injury, cardiovascular abnormalities and systemic ischemia/reperfusion response characterize the so-called 'postcardiac arrest syndrome', which could lead to multiple organ failure and poor outcome after CA. The magnitude of these disorders differs in individual patients, mainly based on the cause and duration of CA and on the severity of the ischemic episode. Prognostication of outcome after CA is of importance because it could help physicians on triage decisions and readdress the overall management. A number of factors are thought to influence the prognosis of patients after CA, but due to the heterogeneity of CA population and scenarios no single factor has been identified as a reliable predictor of outcome and the timing and optimal approach to prognostication is still controversial. Biomarkers represent a growing area of interest in this field, as they may provide clinicians with early information on the severity of organ dysfunction to make a decision on clinical strategies and prognosticate outcome. In this article, the authors will focus on cardiac, neurological and inflammatory biomarkers as potential predictors of outcome after CA.

Can early cardiac troponin I measurement help to predict recent coronary occlusion in out-of-hospital cardiac arrest survivors?

OBJECTIVE

Recent guidelines recommend the immediate performance of a coronary angiography when an acute myocardial infarction is suspected as a cause of out-of-hospital cardiac arrest. However, prehospital factors such as postresuscitation electrocardiogram pattern or clinical features are poorly sensitive in this setting. We searched to evaluate if an early measurement of cardiac troponin I can help to detect a recent coronary occlusion in out-of-hospital cardiac arrest.

DESIGN

Retrospective analysis of a prospective electronic registry database.

SETTING

University cardiac arrest center.

PATIENTS

Between January 2003 and December 2008, 422 out-of-hospital cardiac arrest survivors without obvious extra-cardiac cause have been consecutively studied. An immediate coronary angiography has been systematically performed. The primary outcome was the finding of a recent coronary occlusion.

INTERVENTION

First, blood cardiac troponin I levels at admission were analyzed to assess the optimum cutoff for identifying a recent coronary occlusion. Second, a logistic regression was performed to determine early predictive factors of a recent coronary occlusion (including cardiac troponin I) and their respective contribution.

MEASUREMENTS AND MAIN RESULTS

An ST-segment elevation was present in 127 of 422 patients (30%). During coronary angiography, a recent occlusion has been detected in 193 of 422 patients (46%). The optimum cardiac troponin I threshold was determined at 4.66 ng·mL(-1) (sensitivity 66.7%, specificity 66.4%). In multivariate analyses, in addition of smoking and epinephrine initial dose, cardiac troponin I (odds ratio 3.58 [2.03-6.32], p < .001) and ST-segment elevation (odds ratio 10.19 [5.39-19.26], p < .001) were independent predictive factors of a recent coronary occlusion.

CONCLUSIONS

In this large cohort of out-of-hospital cardiac arrest patients, isolated early cardiac troponin I measurement is modestly predictive of a recent coronary occlusion. Furthermore, the contribution of this parameter even in association with other factors does not seem helpful to predict recent occlusion. As a result and given the high benefit of percutaneous coronary intervention for such patients, the dosage of cardiac troponin I at admission could not help in the decision of early coronary angiogram.

Cardiac troponin I concentrations in neonates with hypoxic-ischaemic encephalopathy

AIM

Myocardial dysfunction is a frequent sequel of perinatal asphyxia. Cardiac troponin I (cTnI) is a marker of myocardial injury and a surrogate marker of myocardial dysfunction in adults, but there are few data in neonates. Our aim was to compare serum cTnI concentrations with clinical severity of encephalopathy and with duration of inotropic support in asphyxiated neonates.

METHODS

Retrospective study of 60 neonates admitted with hypoxic-ischaemic encephalopathy (HIE). cTnI concentrations measured within 36 h of birth were compared with clinical grade of HIE (Sarnat-Sarnat classification) and with duration of inotropic support.

RESULTS

Serum cTnI concentrations and duration of inotropic support were significantly greater with increasing severity of HIE. Median (95% CI) cTnI concentrations were 0.04 μg/L (0.02-0.07 μg/L) in grade 1 HIE, 0.12 μg/L (0.08-0.20 μg/L) in grade 2 HIE and 0.67 μg/L (0.41-1.35 μg/L) in grade 3 HIE. Median (95% CI) duration of inotropic support required was 0 h (0-24 h) in grade 1 HIE, 28 h (0-118 h) in grade 2 HIE and 48 h (0-140 h) in grade 3 HIE.

CONCLUSION

In asphyxiated neonates, cTnI concentrations within 36 h of birth correlate strongly with clinical grade of HIE and with duration of inotropic support. Early cTnI concentrations may provide a useful proxy marker for the anticipated severity of myocardial dysfunction.

Primary outcomes for resuscitation science studies: a consensus statement from the American Heart Association

BACKGROUND AND PURPOSE

The guidelines presented in this consensus statement are intended to serve researchers, clinicians, reviewers, and regulators in the selection of the most appropriate primary outcome for a clinical trial of cardiac arrest therapies. The American Heart Association guidelines for the treatment of cardiac arrest depend on high-quality clinical trials, which depend on the selection of a meaningful primary outcome. Because this selection process has been the subject of much controversy, a consensus conference was convened with national and international experts, the National Institutes of Health, and the US Food and Drug Administration.

METHODS

The Research Working Group of the American Heart Association Emergency Cardiovascular Care Committee nominated subject leaders, conference attendees, and writing group members on the basis of their expertise in clinical trials and a diverse perspective of cardiovascular and neurological outcomes (see the online-only Data Supplement). Approval was obtained from the Emergency Cardiovascular Care Committee and the American Heart Association Manuscript Oversight Committee. Preconference position papers were circulated for review; the conference was held; and postconference consensus documents were circulated for review and comments were invited from experts, conference attendees, and writing group members. Discussions focused on (1) when after cardiac arrest the measurement time point should occur; (2) what cardiovascular, neurological, and other physiology should be assessed; and (3) the costs associated with various end points. The final document underwent extensive revision and peer review by the Emergency Cardiovascular Care Committee, the American Heart Association Science Advisory and Coordinating Committee, and oversight committees.

RESULTS

There was consensus that no single primary outcome is appropriate for all studies of cardiac arrest. The best outcome measure is the pairing of a time point and physiological condition that will best answer the question under study. Conference participants were asked to assign an outcome to each of 4 hypothetical cases; however, there was not complete agreement on an ideal outcome measure even after extensive discussion and debate. There was general consensus that it is appropriate for earlier studies to enroll fewer patients and to use earlier time points such as return of spontaneous circulation, simple "alive versus dead," hospital mortality, or a hemodynamic parameter. For larger studies, a longer time point after arrest should be considered because neurological assessments fluctuate for at least 90 days after arrest. For large trials designed to have a major impact on public health policy, longer-term end points such as 90 days coupled with neurocognitive and quality-of-life assessments should be considered, as should the additional costs of this approach. For studies that will require regulatory oversight, early discussions with regulatory agencies are strongly advised. For neurological assessment of post-cardiac arrest patients, researchers may wish to use the Cerebral Performance Categories or modified Rankin Scale for global outcomes.

CONCLUSIONS

Although there is no single recommended outcome measure for trials of cardiac arrest care, the simple Cerebral Performance Categories or modified Rankin Scale after 90 days provides a reasonable outcome parameter for many trials. The lack of an easy-to-administer neurological functional outcome measure that is well validated in post-cardiac arrest patients is a major limitation to the field and should be a high priority for future development.

Value of post-resuscitation electrocardiogram in the diagnosis of acute myocardial infarction in out-of-hospital cardiac arrest patients

BACKGROUND

Diagnosis of acute myocardial infarction (AMI) in out-of-hospital cardiac arrest (OHCA) patients is important because immediate coronary angiography with coronary angioplasty could improve outcome in this setting. However, the value of acute post-resuscitation electrocardiographic (ECG) data for the detection of AMI is debatable.

METHODS

We assessed the diagnostic characteristics of post-resuscitation ECG changes in a retrospective single centre study evaluating several ECG criteria of selection of patients undergoing AMI, in order to improve sensitivity, even at the expense of specificity. Immediate post resuscitation coronary angiogram was performed in all patients. AMI was defined angiographically using coronary flow and plaque morphology criteria.

RESULTS

We included 165 consecutive patients aged 56 (IQR 48-67) with sustained return of spontaneous circulation after OHCA between 2002 and 2008. 84 patients had shockable, 73 non-shockable and 8 unknown initial rhythm; 36% of the patients had an AMI. ST-segment elevation predicted AMI with 88% sensitivity and 84% specificity. The criterion including ST-segment elevation and/or depression had 95% sensitivity and 62% specificity. The combined criterion including ST-segment elevation and/or depression, and/or non-specific wide QRS complex and/or left bundle branch block provided a sensitivity and negative predictive value of 100%, a specificity of 46% and a positive predictive value of 52%.

CONCLUSION

In patients with OHCA without obvious non-cardiac causes, selection for coronary angiogram based on the combined criterion would detect all AMI and avoid the performance of the procedure in 30% of the patients, in whom coronary angiogram did not have a therapeutic role.

Low levels of the omega-3 index are associated with sudden cardiac arrest and remain stable in survivors in the subacute phase

In previous studies, low blood levels of n-3 fatty acids (FA) have been associated with increased risk of cardiac death, and the omega-3 index (red blood cell (RBC) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) expressed as weight percentage of total FA) has recently been proposed as a new risk factor for death from coronary artery disease, especially following sudden cardiac arrest (SCA). As blood samples often haven been harvested after the event, the aim of our study was to evaluate the stability of RBC fatty acids following SCA. The total FA profile, including the omega-3 index, was measured three times during the first 48 h in 25 survivors of out-of-hospital cardiac arrest (OHCA), in 15 patients with a myocardial infarction (MI) without SCA and in 5 healthy subjects. We could not demonstrate significant changes in the FA measurements in any of the groups, this also applied to the omega-6/omega-3 ratio and the arachidonic acid (AA)/EPA ratio. Furthermore, we compared the omega-3 index in 14 OHCA-patients suffering their first MI with that of 185 first-time MI-patients without SCA; mean values being 4.59% and 6.48%, respectively (p = 0.002). In a multivariate logistic regression analysis, a 1% increase of the omega-3 index was associated with a 58% (95% CI: 0.25–0.76%) reduction in risk of ventricular fibrillation (VF). In conclusion, the omega-3 index remained stable after an event of SCA and predicted the risk of VF.

Comparison of low-energy versus high-energy biphasic defibrillation shocks following prolonged ventricular fibrillation

INTRODUCTION

Since the initial development of the defibrillator, there has been concern that, while delivery of a large electric shock would stop fibrillation, it would also cause damage to the heart. This concern has been raised again with the development of the biphasic defibrillator.

OBJECTIVE

To compare defibrillation efficacy, postshock cardiac function, and troponin I levels following 150-J and 360-J shocks.

METHODS

Nineteen swine were anesthetized with isoflurane and instrumented with pressure catheters in the left ventricle, aorta, and right atrium. The animals were fibrillated for 6 minutes, followed by defibrillation with either low-energy (n = 8) or high-energy (n = 11) shocks. After defibrillation, chest compressions were initiated and continued until return of spontaneous circulation (ROSC). Epinephrine, 0.01 mg/kg every 3 minutes, was given for arterial blood pressure < 50 mmHg. Hemodynamic parameters were recorded for four hours. Transthoracic echocardiography was performed and troponin I levels were measured at baseline and four hours following ventricular fibrillation (VF).

RESULTS

Survival rates at four hours were not different between the two groups (low-energy, 5 of 8; high-energy, 7 of 11). Results for arterial blood pressure, positive dP/dt (first derivative of pressure measured over time, a measure of left ventricular contractility), and negative dP/dt at the time of lowest arterial blood pressure (ABP) following ROSC were not different between the two groups (p = not significant [NS]), but were lower than at baseline. All hemodynamic measures returned to baseline by four hours. Ejection fractions, stroke volumes, and cardiac outputs were not different between the two groups at four hours. Troponin I levels at four hours were not different between the two groups (12 +/- 11 ng/mL versus 21 +/- 26 ng/mL, p = NS) but were higher at four hours than at baseline (19 +/- 19 ng/mL versus 0.8 +/- 0.5 ng/mL, p < 0.05, groups combined).

CONCLUSION

Biphasic 360-J shocks do not cause more cardiac damage than biphasic 150-J shocks in this animal model of prolonged VF and resuscitation.

Successful use of therapeutic hypothermia in an opiate induced out-of-hospital cardiac arrest complicated by severe hypoglycaemia and amphetamine intoxication: a case report

The survival to discharge rate after unwitnessed, non-cardiac out-of-hospital cardiac arrest (OHCA) is dismal. We report the successful use of therapeutic hypothermia in a 26-year old woman with OHCA due to intentional poisoning with heroin, amphetamine and insulin.The cardiac arrest was not witnessed, no bystander CPR was initiated, the time interval from the call to ambulance arrival was 9 minutes and the initial cardiac rhythm was asystole. Eight minutes of advanced cardiac life support resulted in ROSC.Upon hospital admission, the patient's pupils were dilated. Her arterial lactate was 17 mmol/l, base excess -20, pH 6.9 and serum glucose 0.2 mmol/l. During the first 24 hours in the ICU, the patient developed maximally dilated pupils not reacting to light and became increasingly haemodynamically unstable, requiring both inotropic support and massive fluid resuscitation. After 1 week in the ICU, however, she made an uneventful recovery with a Cerebral Performance Category of 1 at hospital discharge and at a follow up examination at 6 months.

CONCLUSION

According to most prognostic factors, the patient had a statistical chance for survival of less than 1%, not taking into account her severe state of hypoglyaemia. We suggest that this case exemplifies the need for more studies on the use of TH in non-coronary causes of OHCA.

Elevated serum cardiac troponin in non-acute coronary syndrome

Cardiac troponins (CTn) are the most sensitive and specific biochemical markers of myocardial injury and risk stratification. The assay for troponin T (cTnI) is standardized, and results obtained from different institutions are comparable. This is not the case with troponin I (cTnT), and clinicians should be aware that each institution must analyze and standardize its own results. Elevated cTn levels indicate cardiac injury, but do not define the mechanical injury. The differentiation of cTn elevation caused by coronary events from those not related to an acute coronary syndrome (ACS) is tiresome, at times vexing, and often costly. Elevation of cTn in non-ACS is a marker of increased cardiac and all-cause morbidity and mortality. The cause of these elevations may involve serious medical conditions that require meticulous diagnostic evaluation and aggressive therapy. At present, there are no guidelines to treat patients with elevated troponin levels and no coronary disease. The current strategy of treatment of patients with elevated troponin and non-ACS involves treating the underlying causes.

Cardiac catheterization is underutilized after in-hospital cardiac arrest

BACKGROUND

Indications for immediate cardiac catheterization in cardiac arrest survivors without ST elevation myocardial infarction (STEMI) are uncertain as electrocardiographic and clinical criteria may be challenging to interpret in this population. We sought to evaluate rates of early catheterization after in-hospital ventricular fibrillation (VF) arrest and the association with survival.

METHODS

Using a billing database we retrospectively identified cases with an ICD-9 code of cardiac arrest (427.5) or VF (427.41). Discharge summaries were reviewed to identify in-hospital VF arrests. Rates of catheterization on the day of arrest were determined by identifying billing charges. Unadjusted analyses were performed using Chi-square, and adjusted analyses were performed using logistic regression.

RESULTS

One hundred and ten in-hospital VF arrest survivors were included in the analysis. Cardiac catheterization was performed immediately or within 1 day of arrest in 27% (30/110) of patients and of these patients, 57% (17/30) successfully received percutaneous coronary intervention. Of those who received cardiac catheterization the indication for the procedure was STEMI or new left bundle branch block (LBBB) in 43% (13/30). Therefore, in the absence of standard ECG data suggesting acute myocardial infarction, 57% (17/30) received angiography. Patients receiving cardiac catheterization were more likely to survive than those who did not receive catheterization (80% vs. 54%, p<.05).

CONCLUSION

In patients receiving cardiac catheterization, more than half received this procedure for indications other than STEMI or new LBBB. Cardiac catheterization was associated with improved survival. Future recommendations need to be established to guide clinicians on which arrest survivors might benefit from immediate catheterization.

Use and Misuse of Cardiac Troponins in Clinical Practice

Cardiac troponins are very sensitive and specific markers of myocardial injury. Elevated troponin levels in the setting of acute coronary syndrome are diagnostic of acute myocardial infarction and provide guidance to clinicians with regard to appropriate use of intensive medical and revascularization therapies. However, elevated troponin levels are commonly seen in several noncoronary ischemia presentations and create considerable confusion among clinicians in these settings. In this review article, we discuss the utility of troponins in various clinical settings and present a "common sense" approach to interpreting troponin elevation outside the setting of acute coronary syndrome.

Cardiac troponin I as a predictor of mortality for pediatric submersion injuries requiring out-of-hospital cardiopulmonary resuscitation

BACKGROUND

It is difficult to predict ultimate survivors to hospital discharge in children who are successfully resuscitated after a cardiorespiratory arrest associated with a submersion injury. Serum measurements of organ injury or dysfunction may serve as a surrogate marker of the degree of hypoxic injury. We designed a prospective study whose purpose was to assess the predictive value for outcome of serum cardiac troponin I measurements after submersion injury and cardiorespiratory arrest.

METHODS

This is a prospective, observational study of children admitted to a postintensive care unit after experiencing an out-of-hospital cardiorespiratory arrest associated with a submersion event. Cardiac troponin I measurements were examined upon admission to the postoperative intensive care unit after successful emergency department resuscitation.

RESULTS

Nine patients were admitted, and 2 patients (22%) survived to hospital discharge. The area under the receiver operating characteristic curve is 0.786 (95% confidence interval, 0.481-1.0). This suggests that cardiac troponin I has a moderate degree of discriminatory power in selecting children who did not survive to hospital discharge.

The influence of cardiopulmonary resuscitation without defibrillation on serum levels of cardiac enzymes: A time course study of out-of-hospital cardiac arrest survivors

BACKGROUND

The serum concentration of cardiac enzymes may be influenced by mechanical and electrical trauma due to cardiopulmonary resuscitation (CPR) attempts. This could complicate the determination of whether an acute myocardial infarction (AMI) had occurred. In this study, only patients without any of the known confounding factors affecting cardiac enzyme release were included, and the specific time course and patterns of serum cardiac enzyme levels after resuscitation were evaluated. The purpose is to help clinicians distinguish between spontaneous myocardial damage and that induced by CPR.

METHODS AND RESULTS

This prospective, observational study was performed in the emergency department on eight patients surviving cardiac arrest. They were selected for not having heart disease, chest trauma or septic shock; and not receiving defibrillation. The median (range) duration of return of spontaneous circulation (ROSC) was 13 min (5-30 min). Cardiac enzyme measurements were taken immediately after ROSC and every 6h thereafter. Although cardiac troponin I (cTnI) level reached as high as 62.6 ng/ml at 24 h in one patient, five of the eight (62.5%) patients had their cTnI level fall below the normal reference range (i.e. 2 ng/ml) by 30 h. The time to maximum and peak concentration of cTnI was 16.50+/-10.99 h and 16.85+/-21.50 ng/ml, respectively. Both MB creatine kinase (CKMB) and total creatine kinase (CK) levels were above their normal reference ranges. In addition, the CKMB/CK ratio exceeded 5% in all patients at any time point during this study.

CONCLUSION

In this study, the influence of resuscitative procedures - defibrillation excluded - on the release of cardiac enzymes were examined. During 30 h after ROSC cTnI level exhibited a bell-shaped configuration, which is distinct from that after AMI; whereas the enzymatic activities of CKMB and CK, as well as CKMB/CK ratio, were constantly higher than normal. This chronological pattern of cardiac enzyme levels may help physicians differentiate primary cardiac disease from other aetiologies in out-of-hospital cardiac arrests.

Recommended guidelines for reviewing, reporting, and conducting research on post-resuscitation care: The Utstein style

The aim of this report is to establish recommendations for reviewing, reporting, and conducting research during the post-resuscitation period in hospital. It defines data that are needed for research and more specialised registries and therefore supplements the recently updated Utstein template for resuscitation registries. The updated Utstein template and the out-of-hospital "Chain of Survival" describe factors of importance for successful resuscitation up until return of spontaneous circulation (ROSC). Several factors in the in-hospital phase after ROSC are also likely to affect the ultimate outcome of the patient. Large differences in survival to hospital discharge for patients admitted alive are reported between hospitals. Therapeutic hypothermia has been demonstrated to improve the outcome, and other factors such as blood glucose, haemodynamics, ventilatory support, etc., might also influence the result. No generally accepted, scientifically based protocol exists for the post-resuscitation period in hospital, other than general brain-oriented intensive care. There is little published information on this in-hospital phase. This statement is the result of a scientific consensus development process started as a symposium by a task force at the Utstein Abbey, Norway, in September 2003. Suggested data are defined as core and supplementary and include the following categories: pre-arrest co-morbidity and functional status, cause of death, patients' quality of life, in-hospital system factors, investigations and treatment, and physiological data at various time points during the first three days after admission. It is hoped that the publication of these recommendations will encourage research into the in-hospital post-resuscitation phase, which we propose should be included in the chain-of-survival as a fifth ring. Following these recommendations should enable better understanding of the impact of different in-hospital treatment strategies on outcome.

Prevalence of troponin-T elevation during out-of-hospital cardiac arrest

To determine the prevalence of myocardial ischemia before out-of-hospital cardiac arrest (OOHCA), we determined the prevalence of elevated cardiac troponin-T levels in subjects at the time of OOHCA. Plasma was collected from 63 subjects during resuscitation. Troponin levels were elevated (> or =0.03 ng/ml) in 25 subjects (39.7%; 95% confidence intervals [CI] 29% to 52%). Increasing age was associated with elevated troponin (OR 1.10; 95% CI 1.04 to 1.17). Elevated troponin levels did not reliably predict short-term outcome. Because troponin increases hours after the onset of ischemia, these data reveal that about 40% of OOHCA cases can undergo intervention before collapse.

Do clinically relevant transthoracic defibrillation energies cause myocardial damage and dysfunction?

Sufficiently strong defibrillation shocks will cause temporary or permanent damage to the heart. Weak defibrillation shocks do not cause any damage to the heart but also do not defibrillate. A relevant and practical question is what range of shock energies is most likely to defibrillate while not causing damage to the heart. This question is most difficult to answer in the pre-hospital defibrillation setting where the patients' size and shape vary, placement of the defibrillation patches vary, and the etiology of their arrhythmia varies. Unlike internal defibrillators, which are tested at implantation, efficacy of an external defibrillator is determined only once, when it is most needed. This review discusses shock damage and dysfunction caused by monophasic waveforms as well as biphasic waveforms. Evidence is presented suggesting that for perfused hearts, the threshold for damage is well above any shock size delivered clinically. For non-perfused hearts, both in humans and animals, evidence is presented that monophasic shocks of up to 5 J/kg do not cause any more cardiac damage/dysfunction than that associated with smaller shocks and that much of this damage is caused by the ischemic period itself rather than the shock. Although many patients can be defibrillated with 150 J (2.2 J/kg) biphasic shocks, some patients may require biphasic shocks up to 360 J (5 J/kg) to be defibrillated. Studies still need to be performed comparing the efficacy and damaging effects of 360 J biphasic shocks to 150 J biphasic shocks. Until those studies are completed, it seems reasonable to use the same 360 J (5 J/kg) energy limit for biphasic shocks as for monophasic shocks.

Myocardial injury in children following resuscitation after cardiac arrest

BACKGROUND

Myocardial dysfunction occurs immediately after successful cardiac resuscitation. Our purpose was to determine whether measurement of cardiac troponin I in children with acute out-of-hospital cardiac arrest predicts the severity of myocardial injury.

METHODS AND RESULTS

This prospective, observational study was performed in the Pediatric Intensive Care Unit (PICU) on 24 patients following arrest, ranging in age from 8 months to 17 years. Troponin measurements were obtained on admission, and at 12, 24, and 48 h. Transthoracic echocardiograms were performed within 24 h after admission. Survival to hospital discharge was 29% (7/24). The mean age was 5.9+/-4.6 years for survivors and 4.2+/-5.3 years for non-survivors. The median (range) duration of cardiac arrest times for survivors was 6 min (3 to 63 min) versus 34 min (4 to 70 min) for nonsurvivors (P=0.02). Survivors received 1.3+/-2.2 doses of epinephrine (adrenaline) compared with 2.9+/-1.6 doses for non-survivors (P=0.02). Only one patient had ventricular fibrillation and defibrillation was unsuccessful. The ejection fraction for survivors averaged 73.2+/-11.2%, but for nonsurvivors only 55.4+/-19.8% (P=0.04). Ejection fraction correlated inversely with troponin at 12 h (r=-0.54, P=0.01) and at 24 h (r=-0.59, P=0.02). Circumferential fiber shortening for survivors was 37.5+/-7.8 and 25.5+/-10.7% for nonsurvivors (P=0.02). It also correlated inversely with troponin (r=-0.46, P=0.03 for survivors and r=-0.65, P=0.01, for nonsurvivors).

CONCLUSION

After cardiac arrest and resuscitation in pediatric patients, the severity of myocardial dysfunction was reflected in troponin I levels.

Successful resuscitation after cardiac arrest following massive brown snake envenomation

We report a 44-year-old Western Australian man who suffered a cardiac arrest several hours after a bite by a brown snake. He was successfully resuscitated after bolus administration of undiluted brown snake antivenom. We suggest that an initial bolus dose of at least five ampoules (5000 units) of undiluted brown snake antivenom should be given as primary therapy for cardiac arrest following brown snake envenomation in Western Australia.

Cardiac troponin T and cardiac enzymes after external transthoracic cardioversion of ventricular arrhythmias in patients with coronary artery disease

BACKGROUND

Serum levels of cardiac troponins after external cardioversion (ECV) for atrial fibrillation and atrial flutter are widely investigated, and no increases in cardiac troponin T (cTnT) levels have been reported. However, the effect of ECV on cardiac enzyme release may depend on the type of arrhythmias. Furthermore, ventricular tachycardia (VT) or ventricular fibrillation (VF) could cause release of cardiac enzymes after ECV due to underlying myocardial ischemia, myocardial dysfunction, or more pronounced hemodynamic deterioration during arrhythmia.

AIM

The purpose of this study was to determine whether direct current (DC) shock may increase cardiac enzyme levels in patients with coronary artery disease undergoing ECV for VT or VF, so that diagnosis of acute myocardial infarction, which initially presents with VT or VF, can be excluded.

METHOD AND RESULTS

We obtained measurement of cTnT, total creatine kinase (CK), and CK MB isoenzyme (CK-MB) activity before and after ECV in 27 patients (mean +/- SD age, 62 +/- 13 years) with induced VT or VF (22 patients) who required ECV during provocative electrophysiologic testing and who underwent ECV due to VT (5 patients) in the cardiology department. Blood samples were drawn before, and 4 h, 8 h, and 24 h after ECV. The total energy used was 630 +/- 375 J (range, 200 to 1,280 J). CK levels rose to the upper limit of reference range in seven patients (26%), and CK-MB activity was higher than the normal reference range in five patients (19%) after ECV. In contrast, cTnT concentrations remained within the normal range (< 0.1 micro g/L) in all patients. Peak CK and CK-MB activity levels strongly correlated with the total energy delivered.

CONCLUSION

Elevation of cTnT level after an urgent DC shock strongly indicates the diagnosis of acute myocardial infarction presented with life-threatening arrhythmias, rather than myocardial damage caused by ECV.

[External and internal electrical cardioversion: comparative, prospective evaluation of cell damage by means of troponin I]

INTRODUCTION AND OBJECTIVES

In this study we measured the concentrations of cardiac troponin I (cTnI) and several biochemical markers of myocardial damage after elective external cardioversion or internal cardioversion by specific catheters or automatic defibrillators.

MATERIAL AND METHODS

Biochemical markers were analyzed prospectively for 30 consecutive patients after electrical cardioversion. Concentrations of cTnI, myoglobin, creatine kinase (CK), CK-MB and the MB/CK ratio were determined in samples before cardioversion and 2, 8 and 24 h later. The shock energy ranged from 50 to 360 joules (235 106 joules) in external cardioversions and from 3 to 37 joules (15 8 joules) in internal cardioversions.

RESULTS

We detected abnormal concentrations of CK, myoglobin, CK-MB and MB/CK in 33% of the patients after external cardioversion. The concentrations of cTnI remained within normal limits at all times, with no elevations detected. Whereas no abnormal concentration of any biochemical marker was detected in any patient who required internal cardioversion for atrial fibrillation, two patients who underwent external cardioversion from an automatic defibrillator did have abnormal concentrations of CK-MB, myoglobin, and even of cTnI.

CONCLUSIONS

The concentration of cTnI remained below the detection limit after external cardioversion, even though the other more non-specific markers changed. No enzyme alteration was detected in patients who underwent internal cardioversion of atrial fibrillation.

Long-term mortality among patients discharged alive after out-of-hospital cardiac arrest does not differ markedly compared with that of myocardial infarct patients without out-of-hospital cardiac arrest

The aim of our research was to study the long-term prognosis among patients discharged alive after an out-of-hospital cardiac arrest (OHCA) in comparison with patients discharged alive after acute myocardial infarction (AMI) without OHCA, and also to study the long-term influence of AMI in connection with OHCA. Our research was conducted in the municipality of Göteborg. We retrospectively studied patients discharged from hospital 1990-91 after an OHCA of cardiac aetiology and patients discharged after an AMI without prehospital cardiac arrest. During 1980-98, we studied all patients discharged alive after OHCA of cardiac aetiology, divided into groups of precipitating AMI and no AMI. The study includes 48 patients discharged alive after an OHCA 1990-91, 30 (62%) of whom had a simultaneous AMI and 1425 patients with an AMI without OHCA. Compared with AMI survivors, survivors of an OHCA of cardiac origin were younger but had more frequently a history of congestive heart failure. Their mortality rate during the subsequent 5 years was 46%, compared with 40% among survivors of an AMI (NS). The 5-year mortality rate among patients with an OHCA precipitated by an AMI was 40%. When correcting for differences at baseline, the adjusted risk ratio for death among patients with an OHCA of cardiac origin was 1.2 (95% CI 0.8-1.8) compared with patients with an uncomplicated AMI. During 1980-98, 215 patients were judged as having an OHCA precipitated by an AMI and 115 patients had an OHCA of cardiac aetiology but no simultaneous AMI. Five-year mortality was 54% and 50% respectively (NS). It is concluded that survivors of an OHCA of cardiac origin differed from survivors of an uncomplicated AMI in that they were younger and more frequently had a history of cardiovascular disease. Their 5-year mortality after discharge was similar to that of survivors of an AMI without a prehospital cardiac arrest, even after adjusting for differences at baseline.

The influence of chest compressions and external defibrillation on the release of creatine kinase-MB and cardiac troponin T in patients resuscitated from out-of-hospital cardiac arrest

OBJECTIVES

This study sought to determine the influence of resuscitative procedures, such as chest compressions and external defibrillation, on the release of creatine kinase (CK)-MB and cardiac troponin T (cTnT).

METHODS

In 87 patients with out-of-hospital cardiac arrest and successful cardiopulmonary resuscitation (CPR), the initial ECG rhythm, the duration of cardiac arrest and CPR, and the number of defibrillations were assessed on arrival in the hospital. The serum CK-MB and cTnT were measured 12 h after the event. We also assessed whether the patient developed cardiogenic shock within 12 h, and if the patient had acute myocardial infarction (AMI), which was confirmed or eliminated by of typical ECG findings, thallium-201 myocardial scintigraphy, or autopsy within the hospital stay. A backward stepwise linear regression model was applied to assess the association between the markers of myocardial injury (CK-MB and cTnT) and the above clinical variables.

RESULTS

CK-MB concentrations were independently associated with the presence of AMI [B 68.5 (SE 28.5, P = 0.018)], the duration of CPR (as a measure of trauma to the chest by means of chest compressions) [B 2.07 (SE 1.01, P = 0.045)] and cardiogenic shock [B 52.3 (SE 23.4, P = 0.03)]. The remaining clinical variables listed were excluded by the model. Cardiac troponin T concentrations were only associated with the presence of AMI [B 4.86 (SE 1.34, P = 0.0005)]. There was a non-significant association between increasing serum cTnT concentrations and the presence of cardiogenic shock [B 2.51 (SE 1.46, P = 0.09)]. The remaining clinical variables were excluded by the model.

CONCLUSION

The release of CK-MB appears to be influenced by the duration of resuscitation and the presence of cardiogenic shock. This has to be considered when interpreting serum CK-MB concentrations after CPR. The release of cTnT seems to be only associated with acute myocardial infarction, but not with the duration of chest compressions, or with the number of defibrillations administered.

Effect of DC shock on serum levels of total creatine kinase, MB-creatine kinase mass and troponin T

After successful resuscitation from cardiac arrest, it is important to identify whether the event has been triggered by a myocardial infarction, since this determines subsequent investigations and management. Previous studies have shown that biochemical indices of infarction become elevated after resuscitation in patients without myocardial infarction. This can lead to overdiagnosis of myocardial infarction in the post-arrest setting. The cause of the elevated enzyme levels is not known, but may involve electrical or mechanical injury to the heart during resuscitation. In this study we aimed to identify the effects of isolated direct current shock on serum levels of creatine kinase (CK), MB creatine kinase mass (MB-CK), and troponin T, and examined the relationships between enzyme levels and the dose of electrical energy used. Thirteen patients were studied who underwent DC cardioversion for atrial fibrillation. Serum was obtained for CK, MB-CK and troponin T estimation before and 10 min after cardioversion, at hourly intervals for 8 h, and 18 h after cardioversion. Total serum CK became significantly elevated after only 3 h and rose to a peak of 1294.4 IU l(-1) (P < 0.02) at 18 h. Post-shock CK levels were strongly correlated with total shock energy (r = 0.8, P < 0.01). Serum MB-CK was significantly elevated at 18 h among patients receiving total shock energies greater than 1000 J than in those receiving lower doses, reflecting a positive correlation (r = 0.64, P < 0.05) between shock energy and peak MB-CK level. Troponin T levels were not significantly elevated after cardioversion. In conclusion, total serum CK levels become significantly elevated early after cardioversion, suggesting rapid wash-out from injured skeletal muscle. MB-CK levels become significantly elevated in individuals receiving high energy shocks, probably due to release of small quantities of the CK-MB isoform from skeletal muscle. The negligible troponin T levels seen after high energy cardioversion indicate that significant myocardial injury does not occur. Electrical injury is not likely to account for the elevated troponin T levels seen after out-of-hospital resuscitation in patients without myocardial infarction.