Troponin T to diagnose myocardial infarction in bypass surgery

Utility of cardiac biomarkers in sports medicine: Focusing on troponin, natriuretic peptides, and hypoxanthine

Evidence-based consensus suggests that physical activity and regular exercise training can reduce modifiable risk factors as well as rate of mortality and morbidity in patients with chronic diseases, such as cardiovascular disease (CVD), diabetes, obesity and cancer. Conversely, long-term exercise training and drastic increase in vigorous physical activity may also cause acute cardiovascular events (e.g. acute myocardial infarction) and deleterious cardiac remodeling, particularly when exercise is performed by unfit or susceptible individuals. There is a reversed J-shaped hormesis-like curve between the duration and intensity of exercise and level of CVD risks. Therefore, it is important for an early detection of cardiac injuries in professional and amateur athletes. Under this context, this article focuses on the use of biomarker testing, an indispensable component in the current clinical practices especially in Cardiology and Oncology. We attempt to justify the importance of using circulating biomarkers in routine practices of Sports Medicine for an objective assessment of CVD events following exercise. Special attentions are dedicated to three established or emerging cardiac biomarkers (i.e. cardiac troponins, natriuretic peptides, hypoxanthine) for myocardial tissue hypoxia/ischemia events, muscle stress, and the consequent cellular necrotic injury. Based on these focused analyses, we propose use of circulating biomarker testing in both laboratory and point-of-care settings with an increasingly broader involvement or participation of team physicians, trainers, coaches, primary care doctors, as well as educated athlete community. This diagnostic approach may improve the quality of medical surveillance and preventive measures on exercise-related CVD risks/outcomes.

High-sensitivity cardiac troponin release after conventional and minimally invasive cardiac surgery

After cardiac surgery, a certain degree of myocardial injury is common. The arbitrarily proposed biomarker cut-off point in the Third Universal Definition for diagnosing coronary artery bypass grafting (CABG)–related perioperative myocardial infarction (PMI) is controversial and unvalidated for non-CABG surgery. Minimally invasive cardiac surgery is often thought to be associated with less myocardial damage compared to conventional surgical approaches. We conducted a real-life prospective study with serial sampling of high-sensitivity cardiac troponin T (hs-cTnT) in patients undergoing conventional and minimally invasive cardiac surgery. Four different types of cardiac surgery were performed in 400 patients (February 2014–January 2015): CABG, aortic valve replacement, minimally invasive mitral/tricuspid valve surgery through the HeartPort (HP) technique and combined CABG/valve surgery. Each group was further subdivided for comparison between the different surgical techniques. Blood samples were collected consecutively at intensive care unit (ICU) admission and 3, 6, 9, 12, 18, 24 and 48 h thereafter. The hs-cTnT values by peak timepoint differed significantly depending on the surgical approach. The overall peak timepoint for hs-cTnT occurred 6 h after ICU admission. The combined surgery and multiple-valve HP groups had the highest values (medians of 1067.5 (744.9–1455) ng/L and 1166 (743.7–2470) ng/L, respectively). The peak hs-cTnT values for patients developing PMI showed high variability. Differentiation between cardiac surgery–related necrosis and PMI remains challenging. This study emphasizes the importance of a clinically reliable biomarker cut-off value in addition to electrocardiography and echocardiography to optimize PMI diagnosis.

Association of Troponin Trends and Cardiac Morbidity and Mortality After On-Pump Cardiac Surgery

BACKGROUND

Elevated, single-measure, postoperative troponin is associated with adverse events after cardiac surgery. We hypothesized that increases in troponin from the first to the second postoperative day are also associated with all-cause, 12-month mortality and major adverse cardiac events (MACE).

METHODS

This observational study included consecutive adults undergoing on-pump cardiac surgery with cardiac arrest. Troponin T was measured on the first and second postoperative day and was classified as "increasing" (>10%), "unchanged" (10% to -10%), or "decreasing" (<-10%). The primary endpoint was all-cause, 12-month mortality. Secondary endpoints were all-cause 12-month mortality or MACE and both outcomes at 30 days. The main analysis was by multivariable Cox regression.

RESULTS

Of 1,417 included patients, 99 (7.0%) died and 162 (11.4%) died or suffered MACE at 12 months. A significant interaction (p < 0.001) between first postoperative day troponin and the troponin trend from the first to the second postoperative day on 12-month, all-cause mortality precluded an analysis independent of first postoperative day troponin. Consequently, we stratified patients by their first postoperative day troponin (cutoff, 0.8 μg/L). Increasing troponin was associated with higher mortality in patients with first postoperative day troponin T ≥ 0.8 μg/L (hazard ratio, 1.98; 95% CI, 1.09 to 3.59; p = 0.025).

CONCLUSIONS

Troponin changes from the first to the second postoperative day should not be interpreted without consideration of the first postoperative day troponin concentration. For patients with a first postoperative day troponin ≥ 0.8 μg/L, an increase by more than 10% from the first to the second postoperative day was significantly associated with all-cause, 12-month mortality and other adverse events.

Postoperative High-Sensitivity Troponin and Its Association With 30-Day and 12-Month, All-Cause Mortality in Patients Undergoing On-Pump Cardiac Surgery

BACKGROUND

Troponin T is a predictor of cardiac morbidity and mortality after cardiac surgery with most data examining fourth generational troponin T assays. We hypothesize that postoperative high-sensitivity troponin T (hsTnT) measured in increments of the upper limit of the norm independently predicts 30-day all-cause mortality.

METHODS

We included consecutive patients undergoing on-pump cardiac surgery from February 2010 to March 2012 in a prospective cohort that measured hsTnT at 0600 of the first and second postoperative day. Our primary end point was 30-day, all-cause mortality. The secondary end point was 12-month, all-cause mortality in patients surviving the first 30 days. We divided hsTnT into 5 predetermined categorizes based on the upper limit of the norm (ULN). We used Cox regression to examine an association of hsTnT independent of the EuroSCORE II at both 30 days as well as at 12 months in patients surviving the first 30 days. We assessed the area under the receiver operating characteristics curve and the net reassignment improvement for examining the benefit of adding of hsTnT to the EuroSCORE II for prognostication and restratification of 30-day, all-cause mortality.

RESULTS

We included 1122 of 1155 eligible patients (75% male; mean age 66 ± 11 years). We observed 58 (5.2%) deaths at 30 days and another 35 (3.4%) deaths at 12 months in patients surviving 30 days. HsTnT categorized by ULN exhibited a graded response for the mortality. Furthermore, hsTnT remained an independent predictor of all-cause mortality at 30 days (adjusted hazard ratio 1.019 [1.014-1.024] per 10-fold increase in ULN) as well as at 12 months (adjusted hazard ratio 1.019 [1.007-1.032]) in patients surviving the first 30 days. The addition of hsTnT to the EuroSCORE II significantly increased the area under the receiver operating characteristics curve (area under curve: 0.816 [95% confidence interval, 0.754-0.878] versus area under curve: 0.870 [95% confidence interval, 0.822-0.917], respectively; P = .012). Finally, adding hsTnT to the EuroSCORE II improved restratification by the net reassignment improvement, primarily by improving rule-out of events.

CONCLUSIONS

This analysis suggests that, similar to previous assays, higher postoperative concentrations of hsTnT are independently associated with all-cause mortality in patients undergoing on-pump cardiac surgery.

Biomonitors of cardiac injury and performance: B-type natriuretic peptide and troponin as monitors of hemodynamics and oxygen transport balance

Serum biomarkers, such as B-type natriuretic peptide and troponin, are frequently measured in the cardiac intensive care unit. A review of the evidence supporting monitoring of these biomarkers is presented.

DESIGN

A search of MEDLINE, PubMed, and the Cochrane Database was conducted to find literature regarding the use of B-type natriuretic peptide and troponin in the cardiac intensive care setting. Adult and pediatric data were considered.

RESULTS AND CONCLUSION

Both B-type natriuretic peptide and troponin have demonstrated utility in the intensive care setting but there is no conclusive evidence at this time that either biomarker can be used to guide inpatient management of children with cardiac disease. Although B-type natriuretic peptide and troponin concentrations can alert clinicians to myocardial stress, injury, or hemodynamic alterations, the levels can also be elevated in a variety of clinical scenarios, including sepsis. Observational studies have demonstrated that perioperative measurement of these biomarkers can predict postoperative mortality and complications.

RECOMMENDATION AND LEVEL OF EVIDENCE

(class IIb, level of evidence B): The use of B-type natriuretic peptide and/or troponin measurements in the evaluation of hemodynamics and postoperative outcome in pediatric cardiac patients may be beneficial.

Markers for perioperative myocardial ischemia: what both interventional cardiologists and cardiac surgeons need to know

All novel markers of myocardial ischemia (ischemia-modified albumin, choline, unbound free fatty acids) lack cardiac specificity. Therefore, for the specific detection of myocardial ischemia selective blood sampling from an inserted coronary sinus catheter is needed, which limits the applicability of these markers in most clinical routine settings. In addition, the superiority of these novel markers over the calculation of myocardial lactate production, the current criterion standard for the laboratory diagnosis of myocardial ischemia, has not been demonstrated so far, and even comparative data is frequently lacking. Further the superiority of these new candidate markers over lactate determination for the diagnosis of myocardial ischemia in peripherally drawn blood samples has not been demonstrated either, and these novel parameters appear not to be a breakthrough for laboratory diagnosis of myocardial ischemia during or after percutaneous coronary interventions or coronary artery bypass grafting. The determination of cardiac troponin I or troponin T is the current criterion standard for the laboratory diagnosis of myocardial damage due to their higher sensitivities and specificities compared to creatine kinase isoenzyme MB. According to current knowledge, troponin increases in peripherally drawn blood samples must be regarded as an indicator of myocardial necrosis which, however, may be limited, only detectable by troponin and may be missed by creatine kinase isoenzyme MB determination. After on-pump coronary artery bypass grafting the generally applied troponin discriminator limits are not valid as there is limited, inevitable cardiac tissue damage occurring during the surgical procedure. Therefore, troponins are significantly increased after reperfusion of the arrested heart over values seen before bypass and also in patients without complications. Perioperative myocardial infarctions can be reliably identified by their characteristic troponin time courses, and both peak concentrations and time of peak values are diagnostic criteria. Troponin release is lower in off-pump compared to on-pump bypass surgery. Despite the controversy over the significance of troponin elevations after clinically uncomplicated and successful procedures, it is tempting to postulate that less myocardial damage as detected by troponin release is beneficial for the patient. After elective percutaneous coronary interventions, only troponin increases >8-fold the upper reference limit were associated with increased mortality in long-term follow-up.

Terminal warm blood cardioplegia in mitral valve replacement: prospective study

Terminal warm blood cardioplegia has had a profound impact on cardiac surgery, especially in coronary artery bypass surgery, but there have been few studies on its use in mitral valve replacement. The purpose of this study was to determine whether terminal warm blood cardioplegia offers any advantages in mitral valve replacement. Forty patients with mitral valve disease were prospectively randomized to one of two groups of 20 with different techniques of myocardial protection: group A had cold blood cardioplegia, and group B had cold blood cardioplegia with terminal warm blood cardioplegia. Intraoperative and postoperative variables were used to assess primary outcomes. Postoperative troponin T release was measured as a secondary outcome. Improved spontaneous recovery of sinus rhythm was observed in group B, but the difference was not significant. The maximum doses of inotropics, duration of inotropic support, intensive care unit stay, and postoperative left ventricular ejection fraction were similar in both groups. Troponin T release at 0 and 6 h postoperatively was not different between the two groups. This study did not find any benefit of terminal warm blood cardioplegia in either clinical outcome or troponin T release after mitral valve replacement.

The comparison and validity of troponin I assay systems in diagnosing myocardial ischemic injury after surgical coronary revascularization

OBJECTIVE

A prospective observational study was conducted to test the agreement between 2 commercially available automated cardiac troponin-I immunoassay systems (Opus Plus, Behring Diagnostics UK Ltd, Hounslow, UK; AxSYM, Abbott Laboratories, Abbott Park, IL) and to determine a normal reference range and threshold value indicative of perioperative myocardial infarction (PMI) after elective coronary artery bypass graft (CABG) surgery for the Opus Plus system.

DESIGN

Prospective, observational study. Setting : Single institution, cardiothoracic specialty hospital.

PARTICIPANTS

Seventy patients undergoing elective CABG surgery.

INTERVENTIONS

After institutional review board approval, patients received standardized anesthetic, surgical, and myocardial preservation techniques. Serial electrocardiographs, creatine kinase-MB, troponin-I, and perioperative outcome data were collected. Correlation between the immunoassay systems was tested using 124 duplicate samples from the first 18 patients. The normal reference range and threshold value indicative of PMI were tested for the Opus Plus system using duplicate samples from all 70 patients.

MEASUREMENTS AND MAIN RESULTS

Peak troponin-I concentrations (median [interquartile range]) differed significantly when measured by the Opus Plus and AxSYM immunoassay systems (5.61 [3.20-22.35] microg/L v 46.50 [14.55-70.95] microg/L, respectively; p < 0.001). There was clear proportional bias that was corrected with log transformation of the raw data. By using confidence interval and receiver operating characteristic curve analysis, the authors showed that a value > or =15 mug/L was indicative of PMI (Opus Plus system) and accordingly report a 35.7% (2.9% Q-wave) overall incidence of PMI in this study population (n = 70).

CONCLUSIONS

These data highlight differences between commercially available troponin-I assay systems. The authors recommend that each institution establish a local reference range and threshold indicative of perioperative myocardial infarction for its specific patient population and assay system and provide sample methodology.

Prophylactic nitroglycerin did not reduce myocardial ischemia during accelerated recovery management of coronary artery bypass graft surgery patients

OBJECTIVE

To evaluate the use of a high dose of nitroglycerin (NTG) for prophylaxis against myocardial ischemia and infarction in patients undergoing coronary artery bypass graft (CABG) surgery with accelerated recovery.

DESIGN

Prospective, double-blind, placebo-controlled randomized study.

SETTING

A university-based medical center.

PARTICIPANTS

Forty adult patients presenting for elective CABG surgery.

INTERVENTIONS

Forty patients were divided into 2 blinded study groups. Twenty patients received 2 microg/kg/min of NTG starting before induction of anesthesia and continuing for 6 hours after extubation in the intensive care unit. The placebo group (n = 20) received normal saline during this same interval.

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, incidence and severity of myocardial ischemia, and myocardial infarction rates were determined. There were no differences in hemodynamic parameters between groups. The incidence of ischemia was approximately 35% in each group. Myocardial infarction (as determined by elevated creatine kinase-MB fraction, troponin I, and electrocardiogram criteria) was 10% in the placebo group and 5% in the NTG group (p = 0.234).

CONCLUSIONS

This study shows a high incidence of myocardial ischemia and infarction in patients presenting for CABG surgery with an accelerated recovery management scheme. NTG was well tolerated clinically; however, it was not found to be protective against myocardial ischemia or infarction in this setting.

Cardiac myofibrillar proteins: biochemical markers to estimate myocardial injury

Ischaemic heart disease represents the most common of the serious health problems in the contemporary society and acute myocardial infarction (AMI) is the major cause of cardiovascular morbidity and death. The accurate localization and determination of the infarct size and the volume of myocardium at risk at the time of insult is crucial and vital for the choice of treatment. Initially the ischaemic cells are reversibly injured. However, if these changes are not reverted at the earliest, it results in the death of the myocyte. This irreversible myocyte necrosis travels transmurally towards epicardium in the form of a wavefront. A timely intervention during evolving infarct could reduce and delimit the infarct and preserve the left ventricular function. Enzyme analysis and electrocardiography (ECG) along with the clinical history of the patient is still considered to constitute a reliable triad in the diagnosis of myocardial infarction (MI). Efforts have been made to relate infarct size with the serum enzyme level changes without much success. In addition, a number of specialist techniques such as planar radioisotope imaging, single photon emission computed tomography (SPECT), positron emission tomography (PET), Echocardiography, Ventriculography and nuclear magnetic resonance (NMR) imaging have been devised to support diagnosis in the patients who show ambiguous symptoms and ECG findings. However most of these procedures are unavailable to the patients due to economic reasons while others have suffered due to non-availability of ideal radiopharmaceuticals. Major advances have been made in the methods based on immunological techniques to improve the detection and estimation of infarct. These methods are exclusively based upon the production and availability of specific antibodies against intracellular, cardiac specific components.

Influence of mammary artery as a bypass vessel on the results of seven biochemical assays after coronary artery bypass surgery

We compared the changes in troponin T, creatine MB isoenzyme mass concentration (CK-MB mass), creatine kinase MB isoenzyme activity (CK-MB activity), creatine kinase (CK), alpha-hydroxybutyrate dehydrogenase (HBD), lactate dehydrogenase (LD) and aspartate aminotransferase (AST) concentrations after coronary artery grafting with saphenous vein grafts, without or in combination with uni- or bilateral internal mammary artery(ies) as bypass vessels in 73 patients. An increase in CK concentration after surgery was highest for the bilateral internal mammary artery bypass patient group and lowest for the group who received only saphenous vein grafts. We present 90th percentile values for the seven tests.

Serum cardiac troponin-T concentrations predict development of coronary artery disease in heart transplant patients

BACKGROUND

Development of coronary artery disease in cardiac allograft recipients is the major cause of graft failure after the first year of transplantation. Unfortunately, there is no noninvasive method of identifying patients at greatest risk of developing this disease. We have asked whether serum concentrations of cardiac troponin-T predict development of coronary artery disease.

METHODS

Annual coronary angiograms, serial endomyocardial biopsies, and serum cardiac troponin-T concentrations were obtained from 68 cardiac transplant patients who were followed for 68.8+/-11.9 months after surgery. Troponin-T concentrations were measured by using an enzyme-linked immunosorbent assay, and biopsies were assessed histologically for rejection grades and immunohistochemically for cellular infiltrates, arteriolar endothelial activation, fibrin deposits, and vascular fibrinolytic and anticoagulant components.

RESULTS

Troponin-T values did not associate with demographic, clinical, or laboratory findings, but they significantly associated with arteriolar endothelial activation (P<0.001), fibrin deposition (P<0.001), depletion of vascular fibrinolytic (P=0.007) and anticoagulant components (P=0.02), and infiltration of macrophages (P <0.001) but not T lymphocytes (P=0.36). Troponin-T concentrations also significantly associated with future development of coronary artery disease (P<0.001). Patients with persistent troponin-T values of 0.10 ng/ml or greater were found to develop the disease within 8.7+/-2.1 months, whereas patients who had initial troponin-T values of 0.10 ng/ml or greater and subsequently fell and remained below 0.10 ng/ml did not develop coronary artery disease in 40 months.

CONCLUSIONS

Troponin-T concentrations significantly associated with macrophage infiltrates, microvascular fibrin deposits, arteriolar endothelial activation, depletion of vascular fibrinolytic and anticoagulant components, and the future development of coronary artery disease. The troponin-T assay is an outpatient procedure performed on small amounts of blood at little cost, risk, or inconvenience, and it appears to be the first biochemical predictor of transplant-induced coronary artery disease.

Cardiac troponin T and troponin I release during coronary artery surgery using cold crystalloid and cold blood cardioplegia

OBJECTIVE

To evaluate and compare myocardial protection using cold crystalloid and blood cardioplegia by measuring release of cardiac Troponin T and Troponin I during coronary artery surgery.

METHODS

Forty two patients undergoing myocardial revascularization were prospectively randomised into two groups in whom myocardial protection was achieved with either antegrade cold (4 degrees C) crystalloid (CCP) (n = 21) St. Thomas' I cardioplegic solution. Serial venous blood samples were collected for measurement of cardiac Troponin T and Troponin I, prior to induction of anesthesia and at 4, 12, 24 and 48 h after removal of the aortic cross clamp.

RESULTS

There were no hospital deaths in the two groups and one patient in each group suffered a perioperative myocardial infarction. Rising levels of Troponin T and Troponin I were found in all patients. Serum concentrations increased as early as 4 h after removal of the aortic cross clamp, and reached a peak at 12 h postoperatively in both groups. These levels subsequently declined, but remained higher than preoperative values at 48 h. There were no differences between the two groups with respect to serum Troponin T and I release at 4, 12, 24 and 48 h, area under the respective curves, and peak Troponin T and I release. Serum Troponin levels were significantly higher in patients with unstable angina and in two patients who suffered a perioperative myocardial infarction.

CONCLUSION

Serum release of cardiac Troponin T and Troponin I is significantly raised in low risk patients undergoing myocardial revascularization. This release is similar when either cold crystalloid or cold blood cardioplegia are used. This may imply that both methods offer identical protection to the myocardium in a low risk group of patients.

Ischaemic preconditioning reduces troponin T release in patients undergoing coronary artery bypass surgery

OBJECTIVE

To investigate whether ischaemic preconditioning could reduce myocardial injury, as manifest by troponin T release, in patients undergoing elective coronary artery bypass surgery.

DESIGN

Randomised controlled trial.

SETTING

Cardiothoracic unit of a tertiary care centre.

PATIENTS

Patients with three vessel coronary artery disease and stable angina admitted for first time elective coronary artery bypass surgery were invited to take part in the study; 33 patients were randomised into control or preconditioning groups.

INTERVENTION

Patients in the preconditioning group were exposed to two additional three minute periods of myocardial ischaemia at the beginning of the revascularisation operation, before the ischaemic period used for the first coronary artery bypass graft distal anastomosis.

MAIN OUTCOME MEASURE

Serum troponin T concentration at 72 hours after cardiopulmonary bypass.

RESULTS

The troponin T assays were performed by blinded observers at a different hospital. All patients had undetectable serum troponin T (< 0.1 microgram/l) before cardiopulmonary bypass, and troponin T was raised postoperatively in all patients. At 72 hours, serum troponin T was lower (P = 0.05) in the preconditioned group (median 0.3 microgram/l) than in the control group (median 1.4 micrograms/l).

CONCLUSIONS

The direct application of a preconditioning stimulus in clinical practice has been shown, for the first time, to protect patients against irreversible myocyte injury.

Effects of age and ischemic times on biochemical evidence of myocardial injury after pediatric cardiac operations

INTRODUCTION

The vulnerability of pediatric myocardium to ischemia is poorly documented in the clinical setting.

METHODS

Serial measurements of serum concentrations of myoglobin, the MB isoenzyme of creatine kinase, and cardiac troponins T and I and their respective areas under the curve were obtained, with particular reference to age and ischemic time, in 80 children undergoing cardiac operations. Sixteen (the control group) did not require cardiopulmonary bypass and 64 did.

RESULTS

In the control group there were increases (p < 0.01) in myoglobin and creatine kinase MB isoenzyme but no increase in cardiac troponin T or I; by contrast, the group treated with cardiopulmonary bypass had significant increases in all four markers but with differing temporal patterns. Younger age (especially < 12 months) was a highly significant explanatory variable only for the release of cardiac troponins T and I, and ischemic time was a significant explanatory variable for the release of creatine kinase MB isoenzyme, cardiac troponins T and I, but not myoglobin. In comparison with previous studies in adults, creatine kinase MB and cardiac troponin T concentrations were three times greater in children than in adults.

CONCLUSIONS

This study supports the specificity of cardiac troponins T and I as markers of myocardial injury after pediatric cardiac operations and defines the importance of age and ischemic time in determining their release. In comparison with previous data in adults, our results raise the possibility that the pediatric heart may be more vulnerable to the effects of ischemia and reperfusion. Cardiac troponins will permit comparison of new myocardial protective strategies or other potentially therapeutic myocardial interventions.

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

BACKGROUND

diagnosis of precipitating myocardial infarction is essential for management of victims of out-of-hospital cardiac arrest, since investigations and treatment are determined by the underlying cause. Skeletal muscle and myocardial damage from external cardiac massage and defibrillation may complicate biochemical diagnosis of myocardial infarction.

OBJECTIVES

(a) to examine the relationship between cumulative defibrillation energy and serum levels of cardiac troponin T and MB creatine kinase (MB-CK) mass in out-of-hospital cardiac arrest survivors without electrocardiographic evidence of myocardial infarction; (b) to reassess diagnostic thresholds for myocardial infarction using MB-CK mass and troponin T in this setting.

METHODS

77 victims of out-of-hospital cardiac arrest were studied. Serum was obtained for MB-CK mass, CK and troponin T estimation on the first 4 days of admission. Patients were divided into three groups using electrocardiographic criteria: group 1, myocardial infarction; group 2, no evidence of infarction; and group 3, equivocal electrocardiograms. Correlation coefficients were calculated for highest recorded levels of the biochemical markers versus defibrillation energy. Receiver-operating characteristic plots were used to determine optimum biochemical diagnostic thresholds for subjects in groups 1 and 2.

RESULTS

using predefined criteria, 27 patients had myocardial infarction, 34 did not have myocardial infarction and 16 had equivocal electrocardiograms. Significant correlations were found for defibrillation energy versus log troponin T (r = 0.42, P < 0.05), log MB-CK mass (r = 0.51, P < 0.01) and total CK (r = 0.68, P < 0.001) in group 2. Within groups 1 and 2, MB-CK mass and troponin T provided additional diagnostic value over MB-CK fraction (P < 0.001). Diagnostic accuracy was not improved by adjusting for shock energy. The optimum threshold value was 4 ng/ml for troponin T (sensitivity 88%, specificity 95%), 60 ng/ml for MB-CK mass (sensitivity 88%, specificity 88%) and 8% of total CK for MB-CK fraction (sensitivity 74%, specificity 82%). These values should be interpreted with caution, since this study is limited by the exclusion of patients with uncertain electrocardiographic diagnoses into group 3.

CONCLUSIONS

skeletal muscle and myocardial damage occurs in survivors of out-of-hospital cardiac arrest and is related to the duration of resuscitation. This complicates biochemical diagnosis of underlying myocardial infarction. Specific high diagnostic threshold values for MB-CK and troponin T are needed to optimise diagnostic accuracy. The use of MB-CK fraction leads to greater diagnostic error because of the variability of muscle CK release after resuscitation.

Factors associated with the release of cardiac troponin T following percutaneous transluminal coronary angioplasty

BACKGROUND

Recent studies have suggested that immunoassay of cardiac troponin T (cTnT) provides a more sensitive measurement of myocardial necrosis than creatine kinase MB (CK-MB) mass concentration.

HYPOTHESIS

The purpose of this study was to compare the release of cTnT and CK-MB isoenzyme in patients undergoing percutaneous coronary angioplasty, and to investigate the clinical, procedural, and angiographic correlates of abnormal elevations of both of these markers.

METHODS

Total creatine kinase (total CK), CK-MB, and cTnT levels were measured immediately before and 12 h following intervention in 110 patients, including 100 consecutive patients undergoing coronary angioplasty and 10 control patients undergoing diagnostic cardiac catheterization. All patients had normal levels of all three markers at baseline. A postintervention total CK level > 225 U/l, an increase in CK-MB > 5.0 ng/ml, and/or an increase in cTnT > 0.04 ng/ml were considered indicative of myocardial injury.

RESULTS

Coronary angioplasty was successfully performed in all 100 patients without emergency bypass surgery or death, although six patients required emergent placement of an intracoronary stent for threatened closure. Eight patients demonstrated an abnormal increase in total CK, including six who were undergoing primary angioplasty for an acute myocardial infarction. One of these patients sustained a Q-wave infarction. Post angioplasty, 18 patients had elevations of both CK-MB and cTnT, 23 had elevations of only cTnT, and the remaining 59 patients had elevations of neither. All patients with CK-MB elevation also had cTnT elevation. Neither serologic marker increased in the diagnostic catheterization control patients. In comparison with patients without postintervention cTnT rise, patients with abnormal cTnT levels had a higher incidence of complex lesion morphology (p < 0.01) and intracoronary thrombus (p < or = 0.0001) prior to coronary angioplasty, and a higher incidence of coronary dissection (p < or = 0.01), abrupt closure (p < or = 0.05), and side-branch occlusion (p < or = 0.01) during angioplasty. In patients with elevation of both cTnT and CK-MB, postintervention CK-MB levels were 12-fold higher and cTnT levels were 21-fold higher than in patients with isolated elevation of only cTnT (p < 0.01).

CONCLUSIONS

These data indicate that > 40% of patients undergoing coronary angioplasty have evidence of minor degrees of myocardial damage, as evidenced by cTnT release. High-risk coronary lesions and both minor and major complications of angioplasty are associated with cTnT release. cTnT appears to be a more sensitive marker of myocardial injury than CK-MB under these circumstances. In comparison with isolated cTnT rise, elevation of both CK-MB and cTnT may be indicative of greater levels of myocardial injury.

Troponin T release with warm and cold cardioplegia

Cardiac troponin T (cTnT) levels were measured in 41 patients undergoing elective coronary artery surgery. Twenty-one patients received continuous warm antegrade blood cardioplegia to maintain asystole whilst 20 patients received antegrade cold blood cardioplegia intermittently. Serum levels of cTnT were determined preoperatively and at 0, 6, 12 and 18 h postbypass. Peak cTnT levels and total cTnT release (calculated from the area under the curve postoperatively) were found to be significantly higher (p < 0.05: Mann-Whitney) when cold cardioplegic solutions were used. Continuous warm cardioplegia results in lower cTnT release than intermittent cold blood cardioplegia suggesting that the former may provide better myocardial preservation.

Effects of myocardial ischemia on the release of cardiac troponin I in isolated rat hearts

BACKGROUND

The twofold aim of this experimental study was (1) to verify the correlation between the duration of ischemia and concentration of cardiac troponin I and (2) to compare the release of cardiac troponin I with histologic findings.

METHODS

Experiments were done on 18 rat hearts, which were perfused according to the Langendorff method, immediately after excision in group I (control group) and after immersion for 3 hours (group II) and 6 hours (group III) in St. Thomas' Hospital solution at 4 degrees C. During reperfusion, the release of cardiac troponin I, creatine kinase isoenzyme MB, and lactate dehydrogenase, the recovery of left ventricular pressure, and heart rates were compared among the three groups. After the experiment, three samples of myocardium (left ventricle, right ventricle, and septum) were taken for histologic examination.

RESULTS

Cardiac troponin I concentration was significantly higher in group III than in groups I and II and in group II compared with group I. Cardiac troponin I concentration increased as the ischemic period increased. The relation between cardiac troponin I release and ischemic duration tended to be linear. Creatine kinase MB and lactate dehydrogenase concentrations did not differ from one group to the other. Left ventricular pressure was not significantly different among the groups. In the control group, no heart had more than 10% of the myocytes affected. One of six hearts in group II and three of six in group III had more than 10% of myocytes affected.

CONCLUSION

This experimental study showed (1) that cardiac troponin I is an early marker of ischemic injury and (2) that cardiac troponin I concentration increases as the ischemic period increases. Early cardiac troponin I release appears to correlate with the extent of ischemic injury in rats undergoing buffer perfusion.

Cardiac troponin T release in multiply injured patients

Cardiac troponin T (cTnT), a new marker of myocardial tissue damage, was investigated in 32 consecutive multiply injured patients. cTnT, creatine kinase (CK) and CK isoenzyme MB (CK-MB) mass concentrations were measured immediately after admission, 12 and 24 h later and daily thereafter for 4 days. We found a moderate increase in cTnT in 22 patients (72 per cent; peaks: 0.6-5.1 micrograms/l). In only four of these 22 patients did the CK-MB mass/CK index indicate myocardial injury. ST-T alterations and arrhythmias did not occur significantly more frequently in patients with increased cTnT plasma concentrations or positive CK-MB mass/CK index. We found a moderate increase in cTnT in 72 per cent of all patients with multiple injuries, but we found no association between an increase in cTnT and the occurrence of electrocardiographic changes and arrhythmias.

Lower cardiac troponin T levels in patients undergoing cardiopulmonary bypass and receiving high-dose aprotinin therapy indicate reduction of perioperative myocardial damage

Nowadays in many European heart centers the activation of the fibrinolytic system, always occurring during cardiopulmonary bypass, is routinely reduced by high-dose application of the proteinase inhibitor aprotinin (total of > 4 million KIU). In this study parameters of myocardial ischemic injury were investigated with the aim of identifying further benefits of aprotinin, particularly the protection of the myocardium during the ischemic period of aortic crossclamping. Forty patients with coronary artery disease who underwent aorta-coronary bypass grafting were randomly and in a double-blind fashion divided into two groups, one that received high-dose aprotinin therapy and one that received only saline solution. Markers such as troponin T, with high specificity for detection of myocardial ischemia and infarction, and markers with more general specificity such as creatine kinase, its isoenzyme, and lactate dehydrogenase showed significantly increased values after ischemia in both groups. In patients who received high-dose aprotinin therapy 3 days after cardiopulmonary bypass all parameters measured showed significantly lower levels compared with those in the control group. Therefore we can presume that the application of high-dose aprotinin provides myocardial protection from perioperative ischemic injury.

Use of cardiac troponin I as a marker of perioperative myocardial ischemia

Troponin I is a contractile protein comprising three isoforms, two related to the skeletal muscle and one to the cardiac fibers. Cardiac troponin I (CTn I) is specific, without any cross-reactivity with the other two. Several studies have demonstrated its release after acute myocardial infarction. In contrast, CTn I never has been found in a healthy population, marathon runners, people with skeletal disease, or patients undergoing non-cardiac operations. Thus, CTn I is a more specific marker of cardiac damage than common serum enzymes. It is also more sensitive, allowing diagnosis of perioperative microinfarction and detection of acute myocardial infarction much earlier after the onset of ischemia (4 hours). Using a rapid one-step assay, we measured the release of CTn I in two groups of patients after operation: 20 with calcified aortic stenosis and normal coronary arteries (aortic valve replacement group and control group) and 20 undergoing coronary artery bypass grafting. In the overall population CTn I peaked at hour 6 and practically disappeared after day 5. Mean values were higher in the coronary artery bypass grafting group. In the aortic valve replacement group, a positive correlation was found between aortic cross-clamping time and CTn I, which is a reliable marker of cardiac ischemia during heart operations and can be used to evaluate cardioprotective procedures.

Serum cardio-specific troponin T after open heart surgery in patients with and without perioperative myocardial infarction

One hundred and sixteen consecutive patients undergoing open heart surgery were studied to evaluate the diagnostic use of cardiac specific troponin T in serum (S-TnT) measured preoperatively, at day 1 and day 4 postoperatively. The results were related to perioperative myocardial infarction (POMI), diagnostically based on ECG-changes, as well as to other perioperative variables. Cardiac surgery resulted in increased levels of S-TnT day 1 in all patients, and the level of this increase was dependent on the type of surgical procedure performed and the duration of cardiac perioperative ischaemia. Similar results were observed for serum creatine kinase isoenzyme (mass determination) (S-CKMB), but differences were generally less well correlated with other perioperative variables. At day 1, patients with POMI had higher levels of S-TnT as well as S-CKMB when compared to patients without POMI. At day 4, most patients still had elevated levels of S-TnT, but the difference in S-TnT levels between patients with POMI and patients without POMI was more pronounced. In contrast, the levels of S-CKMB were essentially normalized in both groups. Measurements of S-TnT at day 4 appears to be of significant value in diagnosing POMI. However, most of the patients without POMI had increased levels of S-TnT at day 4, suggesting that some irreversible operatively induced myocardial damage had occurred. Thus, even at a late postoperative stage the perioperative duration of ischaemia and type and extent of the surgical procedure should be taken into consideration.

Lack of cardioprotective efficacy of allopurinol in coronary artery surgery

OBJECTIVE

To examine the cardioprotective efficacy of allopurinol in patients undergoing elective coronary artery surgery.

DESIGN

Prospective randomised trial.

SETTING

London teaching hospital.

PATIENTS

Twenty patients with at least moderately good left ventricular function undergoing elective coronary artery surgery and requiring at least two bypass grafts.

INTERVENTIONS

Patients were randomised to receive allopurinol (1200 mg in two divided doses) or to act as controls.

MAIN OUTCOME MEASURE

The primary determinant of the efficacy of myocardial protection was serial measurement (preoperatively and subsequently at one, six, 24, and 72 hours after the end of cardiopulmonary bypass) of cardiac troponin T (cTnT) a highly sensitive and specific marker of myocardial damage. Additional evidence was provided by serial measurement of the MB-isoenzyme of creatine kinase (CK-MB) and myoglobin, ECG changes, and clinical outcome.

RESULTS

There was no significant difference in age, ejection fraction, number of grafts, bypass times, or cross clamp times between the two groups. In both groups there was a highly significant (p < 0.01) rise in cTnT, CK-MB, and myoglobin. Peak concentrations were reached between one (CK-MB and myoglobin) and six hours (cTnT) after the end of cardiopulmonary bypass. At 72 hours cTnT concentrations were six times higher than baseline concentrations whereas CK-MB and myoglobin were approximately double baseline concentrations. There was no significant difference in cTnT, CK-MB, or myoglobin between the allopurinol and control groups at any time. There was no diagnostic ECG evidence of perioperative infarction in any patient.

CONCLUSION

Unlike previous reports this study did not show that allopurinol had a cardioprotective effect in patients with good left ventricular function undergoing elective coronary artery surgery.

Troponin T as a marker of perioperative myocardial cell damage

Unstable angina in patients undergoing CABG surgery is associated with a higher morbidity and mortality compared to patients with stable angina. Mortality ranges between 2 and 10% (20, 21). The importance of the preoperative status is only clear and well documented for patients with unstable angina who are unresponsive to medical treatment, patients who undergo emergency revascularization, and for patients with failed angioplasty. The adverse outcome in elective patients with unstable angina was statistically not significantly different from those with stable angina. Therefore, we may assume that in stabilized patients with unstable angina and minor myocardial cell damage intraoperative determinants like the duration of the aortic clamping period or the degree of revascularization are more relevant than the preoperative ones. These determinants may also be reflected by a marked and significant increase of troponin T in both groups during and after surgery. As for other cardiac enzymes, this increase of troponin T beginning immediately after reperfusion of the cardioplegic heart may limit its diagnostic value after cardiac surgery (6,22). On the other hand, troponin T may serve as a marker in assessing the effectiveness of different cardioprotective measures. Nevertheless, preoperatively elevated troponin T levels may indicate a jeopardized myocardium with an ongoing process of myocardial cell damage and may be of prognostic value. Antianginal and antiischemic therapy, therefore, has to be continued and completed until the day of surgery in these high-risk patients.

Myocardial release of troponin T after coronary bypass surgery

The temporal changes in cardiac S-troponin T, S-creatine kinase-MB(S-CK-MB)mass and S-myoglobin were studied for 5 days after coronary bypass grafting in 70 patients. Perioperative infarction occurred in ten patients (2 Q wave, 8 non-Q wave). All three markers showed significant increase even in patients without signs of perioperative infarction. Within 8-12 hours their levels rose significantly (p < 0.001) more in the infarction than in the non-infarction cases. Troponin T and CK-MBmass both showed early (< 8-12 h) peaks in patients with perioperative infarction. CK-MBmass returned to near normal levels within 48-72 hours, whereas troponin T remained markedly increased throughout the observation. Myoglobin concentrations varied widely among the infarction cases. In the non-infarction group, troponin T and CK-MBmass (but not myoglobin) were related to the aortic cross-clamp time. Troponin T (but not CK-MBmass) remained elevated throughout the study period in patients with longer cross-clamp times. These findings may indicate continuous release from damaged myocardium in cases of perioperative infarction. Troponin T and CK-MBmass can serve as markers of perioperative infarction and troponin T may also be useful as a marker in studies on myocardial protection.

Cardiac troponin T: a new marker of myocardial tissue damage in bypass surgery

The purpose of this study was to evaluate cardiac troponin T (TnT) in the diagnosis of minor perioperative myocardial tissue damage and small myocardial infarctions during aortocoronary bypass surgery. In 15 patients without enzymatic or electrocardiographic signs of perioperative myocardial ischemia (group 1, uncomplicated bypass surgery), TnT did not exceed 3.55 micrograms/L. In 3 patients with perioperative non-Q-wave infarctions (group 2), TnT was significantly higher than in group 1 patients. In all 3 patients, TnT peak concentrations exceeded 3.5 micrograms/L. Thirteen patients (group 3, borderline cases) showed either signs of perioperative myocardial ischemia by creatine kinase isoenzyme MB (CKMB) activity levels (CKMB > 20 U/L on the first postoperative day, 3 patients) or by electrocardiography (new ST-T segment alterations, 10 patients). TnT concentrations were comparable to group 1 patients and indicated uncomplicated bypass surgery in all 3 patients with solely elevated CKMB activities. On the other hand, TnT concentrations in 3 patients with electrocardiographic signs of perioperative myocardial ischemia were significantly higher than in uncomplicated patients (group 1) with peak values exceeding 3.5 micrograms/L. Thus, TnT indicated perioperative non-Q-wave infarctions not detected by CKMB activity in these 3 patients. These results are in accordance with findings in nonsurgical patients. They suggest a higher sensitivity and specificity of cardiac TnT compared to CKMB activity in the diagnosis of small perioperative myocardial infarctions after bypass surgery.

Cardiac troponin T in the diagnosis of myocardial injury

In the last several decades serum levels of cardiac enzymes and isoenzymes have become the final arbiters by which myocardial damage is diagnosed or excluded. Because conventionally used enzymes are neither perfectly sensitive nor specific, there is need for a new sensitive and cardiospecific marker of myocardial damage. Cardiac troponin T (TnT) is a contractile protein unique to cardiac muscle and can be differentiated by immunologic methods from its skeletal-muscle isoform. An enzyme immunoassay specific for cardiac TnT is now available in a commercial kit for routine use. The biggest advantage of this assay is its cardiospecificity. TnT measurements, however, are also highly sensitive in diagnosis of myocardial injury and accurately discern even small amounts of myocardial necrosis. TnT measurements are, therefore, particularly useful in patients with borderline CK-MB and in clinical settings in which traditional enzymes fail to diagnose myocardial damage efficiently because of lack of specificity--for example, perioperative myocardial infarction or blunt heart trauma. TnT release kinetics reveal characteristics of both soluble, cytoplasmic, and structurally bound molecules. It starts to increase a few hours after the onset of myocardial damage and remains increased for several days. TnT allows late diagnosis of myocardial infarction. The diagnostic efficiency remains at 98% until 6 d after the onset of infarct-related symptoms. TnT is also useful in monitoring the effectiveness of thrombolytic therapy in myocardial infarction patients. The ratio of peak TnT concentration on day 1 to TnT concentration at day 4 discriminates between patients with successful (greater than 1) and failed (less than or equal to 1) reperfusion. TnT measurements are very sensitive and specific for the early and late diagnosis of myocardial damage and could, therefore, provide a new criterion in laboratory diagnosis of the occurrence of myocardial damage.