Non-invasive assessment of perioperative myocardial cell damage by circulating cardiac troponin T

Early myocardial injury and coagulation activation in thoracoscopic left atrial appendage clipping

BACKGROUND

Thoracoscopic left atrial appendage clipping as a new strategy for stroke prevention. This study was established to observe the changes in myocardial injury and coagulation during the perioperative to provide the basis for anticoagulation strategy.

METHODS

Fifty-two patients with nonvalvular atrial fibrillation who completed thoracoscopic left atrial appendage clipping alone and 52 matched controls with thoracoscopic lobectomy were included in the study. The changes in coagulation and myocardial enzyme during the perioperative period were compared by t-test or nonparametric test. Linear correlation analysis was performed on the trend changes of each indicator in the left atrial appendage clipping group.

RESULTS

Compared with the control group, the postoperative cardiac troponin I level in the thoracoscopic left atrial appendage clip group was significantly higher than that before the operation; there was no significant difference in the increase of myoglobin between the two groups. In the coagulation function, there was no significant difference in the increase of fibrinogen between the two groups. Postoperative D-dimer and fibrin degradation products were significantly increased, especially the left atrial appendage clip group was significantly higher than the control group, and even showed a trend of secondary increase. Cardiac troponin I was positively correlated with C-reactive protein, fibrinogen and von Willebrand Factor activity, and the Spearman nonparametric correlation coefficients were 1, 0.829, and 0.829, respectively (all p < .05).

CONCLUSION

Thoracoscopic left atrial appendage closure surgery presents early myocardial injury and activation of coagulation function. The secondary increase of coagulation index needs our attention.

Essential role of laboratory physicians in transformation of laboratory practice and management to a value-based patient-centric model

The laboratory is a vital part of the continuum of patient care. In fact, there are few programs in the healthcare system that do not rely on ready access and availability of complex diagnostic laboratory services. The existing transactional model of laboratory "medical practice" will not be able to meet the needs of the healthcare system as it rapidly shifts toward value-based care and precision medicine, which demands that practice be based on total system indicators, clinical effectiveness, and patient outcomes. Laboratory "value" will no longer be focused primarily on internal testing quality and efficiencies but rather on the relative cost of diagnostic testing compared to direct improvement in clinical and system outcomes. The medical laboratory as a "business" focused on operational efficiency and cost-controls must transform to become an essential clinical service that is a tightly integrated equal partner in direct patient care. We would argue that this paradigm shift would not be necessary if laboratory services had remained a "patient-centric" medical practice throughout the last few decades. This review is focused on the essential role of laboratory physicians in transforming laboratory practice and management to a value-based patient-centric model. Value-based practice is necessary not only to meet the challenges of the new precision medicine world order but also to bring about sustainable healthcare service delivery.

High-sensitivity troponin T release profile in off-pump coronary artery bypass grafting patients with normal postoperative course

BACKGROUND

The aim of the study was to investigate the high-sensitivity troponin T (hs-TnT) release profile in off-pump coronary artery bypass grafting (OPCABG) patients with normal postoperative course.

METHODS

From January 2015 to October 2016, 398 consecutive OPCABG patients who had normal postoperative courses were enrolled. Blood samples for hs-TnT were collected at several time points and the comparisons among different time points grouped by various factors were further analyzed.

RESULTS

There were 317 male and 81 female patients, with a median age of 64. For 66.1% of the patients, peak hs-TnT occurred at the 24th hour after OPCABG, regardless of the groups divided by different factors. In total, the hs-TnT values were much higher in male group (P = 0.035), in patients who need 5 or more bypass grafts (P = 0.035) and in patients with high-risk EuroSCORE II assessment (P = 0.013). However, we failed to find any significant differences between different age groups (P = 0.129) or among different coronary heart disease classifications (P = 0.191).

CONCLUSIONS

The hs-TnT values were affected by various factors and culminated around the first 24 h following OPCABG. It may provide some useful information for future clinical studies of myocardial biomarkers after OPCABG.

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.

The Effects of Exercise on Cardiovascular Biomarkers: New Insights, Recent Data, and Applications

The benefit of regular exercise or physical activity with appropriate intensity on improving cardiopulmonary function and endurance has long been accepted with less controversy. The challenge remains, however, quantitatively evaluate the effect of exercise on cardiovascular health due in part to the amount and intensity of exercise varies widely plus lack of effective, robust and efficient biomarker evaluation systems. Better evaluating the overall function of biomarker and validate biomarkers utility in cardiovascular health should improve the evidence regarding the benefit or the effect of exercise or physical activity on cardiovascular health, in turn increasing the efficiency of the biomarker on individuals with mild to moderate cardiovascular risk. In this review, beyond traditional cytokines, chemokines and inflammatory factors, we systemic reviewed the latest novel biomarkers in metabolomics, genomics, proteomics, and molecular imaging mainly focus on heart health, as well as cardiovascular diseases such as atherosclerosis and ischemic heart disease. Furthermore, we highlight the state-of-the-art biomarker developing techniques and its application in the field of heart health. Finally, we discuss the clinical relevance of physical activity and exercise on key biomarkers in molecular basis and practical considerations.

High-Sensitivity Troponin Release Profile After Cardiac Surgery

BACKGROUND

Postoperative serum troponin levels and perioperative myocardial infarction (MI) rates correlate with mortality and morbidity following cardiac surgery. The objective of this study was to document the release profile of high sensitivity troponin T (hsTnT) following different cardiac operations.

METHODS

Patients undergoing one of five different isolated cardiac surgical procedures (eligible preoperative hsTnT <29ng/L, serum creatinine < 0.2mmol/L) were recruited prospectively. Serum hsTnT was measured at 0, 4, 6, 8, 10, 12, 24 and 72hours after the first surgical insult to myocardium, together with daily electrocardiographs.

RESULTS

There were 10 patients in the on-pump coronary artery bypass group and 5 each in the remaining groups (off-pump coronary artery bypass, open aortic valve replacement, transcutaneous aortic valve implantation and mitral valve replacement). Five additional patients were excluded due to perioperative MI or renal failure. Median [range] of peak hsTnT was 241[99-566], 64[50-136], 353[307-902], 115[112-275], and 918[604-1166] ng/L, respectively. Operations with the lowest peak hsTnT values peaked earliest (four hours) while those with highest values peaked latest (eight hours).

CONCLUSION

After cardiac surgery, the hsTnT profile peaks four to eight hours after the initial surgical insult. The magnitude and timing of the peak correlates to the expected degree of surgically-induced myocardial injury.

Angiography for Management of Perioperative Myocardial Ischemia: Does it Have Any Role?

Objective

Perioperative myocardial ischemia (PMI) is a relatively rare but potentially fatal complication after coronary artery bypass grafting and is due to graft-related problems in a significant proportion of cases. The usual indicators of MI in the postoperative setting are unreliable and therefore have uncertain diagnostic value. Angiography, the criterion standard for preoperative angina, remains underused for evaluation of PMI. The aim of this study was to evaluate the role of angiography in the management of PMI.

Methods

Between January 2011 and September 2012, a total of 2312 isolated primary consecutive coronary artery bypass graft surgeries were performed, of which 2057 (89%) were carried out on the beating heart. Twenty-six (1.12%) of these patients needed perioperative angiography. The patients needing angiography were selected on the basis of a number of clinical, biochemical, and other diagnostic parameters

Results

Twenty-six patients with PMI required angiography, of which 18 (69 %) were found to have graft-related issues. The mean (SD) time between operation and angiography was 24.58 (6.71) hours. Of the 18 patients, 17 (94.44%) required surgical intervention and 1 patient was treated with angioplasty. There were 2 deaths (11.1%) in the group undergoing intervention. Angiographic findings included occluded vein graft (n = 7), narrowing of the left internal mammary artery (n = 3), and kinking or stretching of grafts (n = 8).

Conclusions

Angiography is useful in diagnosing graft-related problems in the perioperative period. In presence of signs of graft compromise, we suggest that having a low threshold for angiographic graft evaluation may be beneficial in a carefully selected subset of patients after coronary artery bypass.

Qualification of cardiac troponins for nonclinical use: a regulatory perspective

The US Food and Drug Administration (FDA) Biomarker Qualification Review Team presents its perspective on the recent qualification of cardiac troponins for use in nonclinical safety assessment studies. The goal of this manuscript is to provide greater transparency into the qualification process and factors that were considered in reaching a regulatory decision. This manuscript includes an overview of the data that were submitted and a discussion of the strengths and shortcomings of these data supporting the qualification decision. The cardiac troponin submission is the first literature-based biomarker application to be reviewed by the FDA and insights gained from this experience may aid future submissions and help streamline the characterization and qualification of future biomarkers.

Does dexmedetomidine provide cardioprotection in coronary artery bypass grafting with cardiopulmonary bypass? A pilot study

OBJECTIVE

The purpose of this pilot study was to evaluate whether dexmedetomidine has a cardioprotective effect during coronary artery bypass graft surgery with cardiopulmonary bypass (CPB).

DESIGN

A prospective, double-blind, randomized controlled trial.

SETTING

A university hospital.

PARTICIPANTS

Thirty-eight patients undergoing coronary artery bypass graft surgery.

INTERVENTIONS

Patients were randomized into 2 groups: dexmedetomidine and placebo groups. In the dexmedetomidine group, dexmedetomidine infusion was started by a loading dose of 0.5 μg/kg/10 min, followed by a continuous infusion of 0.5 μg/kg/h. The placebo group received the same volume of saline. Measurements of central venous pressure, mean pulmonary artery pressure (MPAP) and cardiac index were performed before and after dexmedetomidine loading dose and 2, 24 and 48 hours after CPB. Simultaneously, arterial blood was sampled for CK-MB, cardiac troponin T, and N-terminal probrain natriuretic peptide.

MEASUREMENTS AND MAIN RESULTS

CK-MB, cardiac troponin T and N-terminal probrain natriuretic peptide values were elevated in the periods after CPB in both groups (p<0.05) and there were no statistically significant differences between groups. MPAP was decreased in the dexmedetomidine group at the 2nd, 24th and 48th hour after CPB (p<0.001, p<0.001, p = 0.002, respectively). Higher cardiac index values were seen earlier in the dexmedetomidine group than in the placebo group (p< 0.05).

CONCLUSIONS

Myocardial damage was not reduced by administration of 0.5 μg/kg loading dose and 0.5 μg/kg/h infusion of dexmedetomidine. However MPAP tended to be lower in the dexmedetomidine group. Large-scale clinical outcome studies are indicated to confirm the effect of dexmedetomidine.

The clinical significance of cardiac troponins in medical practice

Troponins are regulatory proteins that form the cornerstone of muscle contraction. The amino acid sequences of cardiac troponins differentiate them from that of skeletal muscles, allowing for the development of monoclonal antibody-based assay of troponin I (TnI) and troponin T (TnT). Along with the patient history, physical examination and electrocardiography, the measurement of highly sensitive and specific cardiac troponin has supplanted the former gold standard biomarker (creatine kinase-MB) to detect myocardial damage and estimate the prognosis of patients with ischemic heart disease. The current guidelines for the diagnosis of non-ST segment elevation myocardial infarction are largely based on an elevated troponin level. The implementation of these new guidelines in clinical practice has led to a substantial increase in the frequency of myocardial infarction diagnosis. Automated assays using cardiac-specific monoclonal antibodies to cardiac TnI and TnT are commercially available. They play a major role in the evaluation of myocardial injury and prediction of cardiovascular outcome in cardiac and non-cardiac causes. In this review we discuss the clinical applications of cardiac troponins and the interpretation of elevated levels in the context of various clinical settings.

[Cardiac biomarkers for diagnosis of myocardial infarction]

Diagnosis of postoperative myocardial infarction is often difficult, based on tools with a low sensitivity (clinical symptoms, EKG), or with a low specifity (old biomarkers, echocardiographic abnormalities) or inadequate for clinical practice (scintigraphy). Since 1995, clinicians may use more cardiospecific markers (troponin) allowing to modify strategy for postoperative myocardial infarction diagnosis. The aim of this review is to resume such an attitude.

Plasma Troponins as Markers of Myocardial Damage during Cardiac Surgery with Extracorporeal Circulation

All types of cardiac surgery involve considerable injury to the myocardium. However, it is difficult to differentiate, in the immediate post-operative state, between ischemic alterations associated with the cardiac surgery itself and the pathological alterations of a peri-operative myocardial infarction. The diagnosis of damaged myocardium, classically performed with the enzymatic markers creatine kinase (CK) and its muscle fraction (CK-MB), has become more precise with the option of measuring cardiac troponins T and I. We measured these markers in 58 patients undergoing elective cardiac surgery with extra-corporeal circulation (ECC). The patients included 37 cases undergoing valve surgery, 14 for coronary revascularization, 6 for mixed procedures, and 1 for closure of an inter-atrial communication. The markers were measured in plasma at baseline (at anesthesia initiation), 5 min post-ECC commencement, following aorta de-clamping, during the surgical closure, and 6, 18 and 42 hrs after surgery. All the markers were increased significantly relative to the baseline values. Troponin I, CK and CK-MB values peaked between 6 and 18 hrs after surgery, troponin T between 18 and 42 hrs, and myoglobin at the surgical closure. The values of all markers were higher in patients undergoing coronary surgery compared to those in patients undergoing valve surgery. In the evaluation of myocardial damage after surgery, the measurement of classical markers such as CK and myoglobin remain valid, but other markers such as troponins provide significant additional diagnostic benefit and, thus, need to be included in the routine biochemical measurements for monitoring myocardial damage associated with the surgical procedure.

Detected troponin elevation is associated with high early mortality after lung resection for cancer

Background

Myocardial infarction can be difficult to diagnose after lung surgery. As recent diagnostic criteria emphasize serum cardiac markers (in particular serum troponin) we set out to evaluate its clinical utility and to establish the long term prognostic impact of detected abnormal postoperative troponin levels after lung resection.

Methods

We studied a historic cohort of patients with primary lung cancer who underwent intended surgical resection. Patients were grouped according to known postoperative troponin status and survival calculated by Kaplan Meier method and compared using log rank. Parametric survival analysis was used to ascertain independent predictors of mortality.

Results

From 2001 to 2004, a total of 207 patients underwent lung resection for primary lung cancer of which 14 (7%) were identified with elevated serum troponin levels within 30 days of surgery, with 9 (64%) having classical features of myocardial infarction.

The median time to follow up (interquartile range) was 22 (1 to 52) months, and the one and five year survival probabilities (95% CI) for patients without and with postoperative troponin elevation were 92% (85 to 96) versus 60% (31 to 80) and 61% (51 to 71) versus 18% (3 to 43) respectively (p < 0.001).

T stage and postoperative troponin elevation remained independent predictors of mortality in the final multivariable model. The acceleration factor for death of elevated serum troponin after adjusting for tumour stage was 9.19 (95% CI 3.75 to 22.54).

Conclusion

Patients with detected serum troponin elevation are at high risk of early mortality with or without symptoms of myocardial infarction after lung resection.

Relationship between postoperative cardiac troponin I levels and outcome of cardiac surgery

BACKGROUND

Cardiac surgery may be associated with significant perioperative and postoperative morbidity and mortality. Underlying pathology, surgical technique, and postoperative complications may all influence outcome. These factors may be reflected as a rise in postoperative troponin levels. Interpretation of troponin levels in this setting may therefore be complex. This study assessed the prognostic significance of such measurements, taking into account potential confounding variables.

METHODS AND RESULTS

One-thousand three hundred sixty-five patients undergoing cardiac surgery underwent measurement of cardiac troponin I (cTnI) at 2 and 24 hours after surgery. The relationship of these measurements to subsequent mortality was established. After taking into account all other variables, cTnI levels measured at 24 hours were independently predictive of mortality at 30 days (odds ratio [OR] 1.14 per 10 microg/L, 95% confidence interval [CI] 1.05 to 1.24, P=0.002), 1 year (OR 1.10 per 10 microg/L, 95% CI 1.03 to 1.18, P=0.006), and 3 years (OR 1.07 per 10 microg/L, 95% CI 1.00 to 1.15, P=0.04). Cardiac TnI levels in the highest quartile at 24 hours were associated with a particularly poor outcome.

CONCLUSIONS

cTnI levels measured 24 hours after cardiac surgery predict short-, medium-, and long-term mortality and remain independently predictive when adjusted for all other potentially confounding variables, including operation complexity.

Reduced cytokines release and myocardial damage in coronary artery bypass patients due to L-arginine cardioplegia supplementation

BACKGROUND

Recently, L-arginine has been added to cardioplegia to limit myocardial ischemic damage. The mechanism of action is related to the production of nitric oxide, with vasodilatation and reduction of endothelial dysfunction. Our prospective randomized study on coronary artery bypass patients investigates the effect of L-arginine on myocardial stress as expressed by myocardial cytokines release and myocardial ischemia in terms of troponin T concentration.

METHODS

Coronary artery surgery patients were randomly assigned to receive 7.5 g L-arginine in 500 mL of cardioplegic solution (group A). Group B was used as control. Cold blood 4:1 anterograde and retrograde cardioplegia with warm induction was administered. Blood samples were collected from the retrograde coronary sinus catheter to determine interleukin-2 receptor, interleukin-6, and tumor necrosis factor levels. Serum samples at different time points were also analyzed to measure myocardial ischemia markers. Hemodynamic and echocardiographic evaluations were obtained perioperatively.

RESULTS

Sixty-five patients were enrolled (group A, treated with L-arginine, n = 33; group B, control, n = 32). Wedge pressure and intensive care unit stay were significantly reduced in group A (p = 0.023 and p = 0.03, respectively). Cytokines levels were lower in group A, with a significance for interleukin-6 (p = 0.026); troponin T was reduced in treated patients (0.33 versus 0.57 ng/mL at 18 hours: p = 0.009).

CONCLUSIONS

Coronary artery surgery patients benefit from L-arginine cardioplegia supplementation in terms of reduced inflammatory reaction, limitation of myocardial ischemia, and better hemodynamic performance. Moreover, a clinical advantage is evident in terms of a shorter intensive care unit stay in patients treated with L-arginine.

Heart fatty acid binding protein in the rapid evaluation of myocardial damage following valve replacement surgery

BACKGROUND

Myocardial damage occurs following valve replacement surgery. We estimated the value of heart fatty acid binding protein (H-FABP) in these patients.

METHODS

Sixty elected patients were enrolled and distributed into single (group A) and double (group B) valve replacement groups. The clinical data were outlined and blood samples were collected perioperatively for determination of plasma levels of H-FABP, cardiac troponin-I (cTn-I), and CK-MB in both groups.

RESULTS

56 patients completed the study and no significant difference of clinical data was observed except CPB time and ACC time between groups. H-FABP level elevated quickly after reperfusion and peaked significantly earlier than cTn-I and CK-MB, it also declined rapidly but did not return to baseline at 24 h after reperfusion. Three markers' levels were all higher in group B than in group A after reperfusion with significant differences at their peaks and thereafter. Patients with postoperative complications had significantly higher H-FABP levels than usual. H-FABP peak level associated well with the length of CPB and ACC as well as with other 2 markers' peak levels in both groups.

CONCLUSION

Compared with cTn-I and CK-MB, H-FABP is an earlier and potentially useful marker in the rapid evaluation of myocardial damage following valve replacement surgery with CPB.

Cardiac Biomarkers for Detection of Myocardial Infarction: Perspectives from Past to Present

Editor’s Note: With great pleasure and anticipation in recognition of Clinical Chemistry’s 50th anniversary, I have been able to arm-twist four talented scientists to document their impressive marks on the science of diagnostics in the field of cardiac biomarkers and detection of myocardial infarction. Their exciting discoveries and applications have dramatically influenced the fields of laboratory medicine and cardiology and have greatly influenced the care and management of thousands of patients suffering from coronary artery disease leading to acute myocardial infarction. As a matter of historical record, I owe a great deal of thanks to each one of the coauthors of this special report because each one has personally influenced my scientific career. I met Dr. Rosalki, during my postdoctoral training, at a national AACC meeting, where he kindly answered my numerous queries regarding creatine kinase enzymology and muscle physiology. Dr. Roberts, while serving as Director of the Coronary Care Unit at Washington University in St. Louis, generously allowed this fledgling fellow into his laboratory and shared many of his clinical and experimental findings with me. Dr. Katus, whom I first met at a scientific meeting sponsored by Boehringer Mannheim in 1986 in Bavaria, where I first became fascinated with cardiac troponin T, has remained a friend and colleague. Lastly, Dr. Ladenson, who as mentor, scientific colleague, and close friend remains ultimately responsible for both my professional growth as a clinical chemist (he was my postdoctoral fellowship advisor) and for stimulating and encouraging my goals and aspirations in the field of cardiac biomarkers. With the descriptions of the ground-breaking science described below, I am extremely excited and optimistic that the future of cardiac biomarkers is secure and open to new discoveries by the Rosalkis, Robertses, Katuses, and Ladensons of the future.

—Fred Apple

Temporal pattern of cardiac troponin I after thoracotomy and lung surgery

BACKGROUND

Several studies have shown that patients with perioperative myocardial infarction (MI) are at higher risk for subsequent cardiac events and the identification of these patients is important. However, the diagnosis of perioperative MI can be difficult in many cases. The cardiac troponins are biomarkers with high cardiospecificity, and the aim of this study was to assess cTnI and cTnT among other cardiac biomarkers after thoracotomy and lung surgery.

METHODS

24 consecutive patients were included in the final analysis. Venous blood samples were drawn prior to the procedure, 1-3, 4-6, 16-18 and 30-32 h after surgery. Thoracotomy was performed as a standard posterolateral incision on the left or right side under general anesthesia.

RESULTS

Both cTnI and cTnT were completely unaffected by the thoracotomy and the lung surgery. Furthermore, no single value of the troponins was above the 99th percentile at any time. In contrast, CK-MB was elevated in nearly half the patients, although the mean values complied well with the reference limit. CK and myoglobin were both considerably elevated and did not discriminate between acute myocardial infarction and release of the markers due to extracardiac injury.

CONCLUSIONS

Only the troponins were unaffected by extracardiac surgery and were, thus, reliable markers of myocardial injury in patients who underwent thoracotomy and lung surgery. If the troponins are unavailable, CK-MB mass combined with the CK-MB/CK percentage should be preferred.

Cardiac troponin T for prediction of short- and long-term morbidity and mortality after elective open heart surgery

BACKGROUND

Increased cardiac troponins in blood are observed after virtually every open heart surgery, indicating perioperative myocardial cell injury. We sought to determine the optimum time point for blood sampling and the respective cutoff value of cardiac troponin T (cTnT) for risk assessment in patients undergoing cardiac surgery.

METHODS

In a series of 204 patients undergoing scheduled open heart surgery, mainly for coronary artery bypass grafting (n = 132) or valve repair (n = 27), cTnT concentrations were measured before and 4 and 8 h after cross-clamping and then daily for 7 days. Individual risk was assessed by use of the Cleveland Clinic Foundation Risk score and intraoperative risk indicators such as duration of cardiopulmonary bypass, cross-clamping, and perioperative release of cardiac markers. Patients were followed for 28 months.

RESULTS

Cardiac mortality, all-cause mortality rates, and rates of nonfatal acute myocardial infarction (AMI) at 28 months were 6.9%, 8.8%, and 6.8%, respectively. cTnT was higher in patients with Q-wave AMI or postoperative heart failure requiring inotropic support, and in nonsurvivors. The ROC curve revealed a cTnT > or = 0.46 microg/L at 48 h as the optimum discriminator for long-term cardiac mortality. Stepwise logistic regression identified higher Cleveland Clinic Risk Score [odds ratio (OR) = 2.6 per point], cross-clamp time >65 min (OR = 6.6), and cTnT (OR = 4.9) as significant and independent predictors of long-term cardiac mortality.

CONCLUSIONS

A single postoperative cTnT measurement can be used to estimate myocardial cell injury that impacts long-term survival after open heart surgery. It adds independently to established risk indicators.

Unspecific elevation of plasma troponin-T and CK-MB after coronary surgery

OBJECTIVE

Biochemical markers of myocardial injury are frequently elevated after cardiac surgery. It is generally accepted that release unrelated to permanent myocardial damage explains a proportion of these elevations. However, little is known about the magnitude and temporal characteristics of this diagnostic noise. One way to address this issue would be to study a group without permanent myocardial injury.

DESIGN

The unique release kinetics of troponin-T (permanent myocardial injury causes a sustained release of structurally bound troponin) were used to identify patients with no or minimal permanent myocardial injury. Blood was sampled from patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) before surgery, 3 and 8 h after unclamping the aorta, and each morning until postoperative day 4, for analysis of enzymes and troponin-T. From 302 consecutive patients a subgroup was identified that fulfilled the following criteria: (a) normalized troponin-T levels < or = postoperative day 4; (b) no ECG changes indicating myocardial injury.

RESULTS

Seventy-seven patients fulfilled the criteria above and in this subgroup troponin-T (2.08 +/- 1.42 microg/l; range 0.35-8.99 microg/l) peaked at the 3 h recording and creatine kinase monobasic (CK-MB) (28.6 +/- 11.3 microg/l; range 11.9-86.0 microg/l) peaked at the 8 h recording after unclamping the aorta.

CONCLUSION

Substantial early elevations of plasma CK-MB and troponin-T occurred in patients with no or minimal permanent myocardial injury after CABG. Unspecific release was most pronounced during the timeframe that is usually studied to evaluate myocardial protective strategies or to compare revascularization procedures.

Diagnostic efficiency of rejection monitoring after heart transplantation with cardiac troponin T is improved in specific patient subgroups

Cardiac troponin T (cTnT) is a cardio-specific myofibrillar protein known to be elevated early after heart transplantation and during cardiac allograft rejection. cTnT determination in heart allograft recipients showed elevated levels in patients with higher degrees of graft rejection (International Society for Heart and Lung Transplantation grades >/=3A-4). Subgroup analyses revealed demographic patient characteristics markedly improving the diagnostic efficiency of cTnT measurement for rejection monitoring, including male recipient gender, recipient age <60 yr, female donor gender and donor age >/= 33 yr. The clinical utility of these parameters was confirmed by longitudinal patient data and may help to select recipients most likely to benefit from cTnT rejection surveillance.

Cardiac troponin I is increased after interventional closure of atrial septal defects

This study was designed to assess possible myocardial injury caused by interventional closure of atrial septal defects (ASDs) compared to diagnostic catheterization by measuring cardiac troponin I (cTn-I). Forty patients were enrolled; in 33 ASDs were successfully closed, while in 7 a diagnostic balloon sizing of the defect was performed only. Total cTn-I increased significantly from 0.1 to 1.9 microg/l at the end of the intervention and 2.23 at 4 hr and decreased to 1.35 at 15 hr. No significant increase could be detected in patients with diagnostic balloon sizing only or of CK/CK-MB levels either. Following interventional closure of ASDs with Amplatzer septum/PFO occluders, increased cTn-I levels for several hours indicate some transient, reversible myocardial membrane instability due to the device. Discrimination of ventricular myocardial infarction might be possible by estimating less sensitive CK and CK-MB levels only.

European Society of Cardiology and American College of Cardiology guidelines for redefinition of myocardial infarction: how to use existing assays clinically and for clinical trials

BACKGROUND

The European Society of Cardiology and American College of Cardiology guidelines for redefinition of myocardial infarction suggest that the cutoff value for diagnosis of acute myocardial infarction (AMI) be the 99th percentile of the reference population at a level measured with imprecision (coefficient of variation) > or =10%. No current commercially available troponin assay meets this requirement. Accordingly, questions have been raised about how to implement cutoff values from the guidelines. The Clinical Outcomes Utilizing Revascularization and Aggressive druG Evaluation (COURAGE) trial asked for recommendations concerning the use of troponin assays for the trial.

METHODS

Cutoff values for the various assays were obtained from package inserts or from direct communication with manufacturers.

RESULTS

The cutoff value with > or =10% imprecision was above the 99th percentile of the reference range for all assays. For the present, we suggest that this value be used for clinical and clinical trial purposes. It will account for analytic variability and individual biological changes. We provide recommendations for clinical practice and clinical trials concerning how to make the diagnosis of AMI in patients with ischemic symptoms and patients who undergo percutaneous coronary intervention and coronary artery bypass surgery.

CONCLUSIONS

This is a first attempt to define cutoff values on the basis of the European Society of Cardiology and American College of Cardiology guidelines. These criteria will provide increased consistency until assays improve to allow full implementation of the guidelines.

Sialic acid or troponin T to detect perioperative myocardial damage in patients undergoing elective coronary artery bypass grafting

Sialic acid (SA), a family of acetylated derivatives of neuraminic acid, is elevated in patients with coronary heart disease. Cardiac troponin T (cTnT), myoglobin (Mb), and creatine kinase-MB (CK-MB) are specific markers of myocardial injury and are, at present, widely used to detect perioperative myocardial damage during coronary artery bypass grafting (CABG) surgery. The present study investigated the net myocardial release of SA and the cardiac markers (cTnT, Mb, CK-MB) during reperfusion after hypothermic cardioplegic cardiac arrest in 25 patients undergoing elective CABG. Additional paired arterial, central venous, and coronary sinus blood samples were obtained after atrial cannulation before aortic cross-clamping (preischemic sample) and at 1 and 10 min after aortic declamping (reperfusion samples). There were no increase in the SA, cTnT, Mb and CK-MB concentrations before aortic cross-clamping, but there was considerable release of these markers within 10 min after aortic declamping: cTnT release was significantly higher compared with baseline values before aortic cross-clamping. In contrast to SA, Mb, and CK-MB, the difference between baseline and release values for cTnT at 1 min after aortic declamping was not significant. The rate of increase for SA was significantly higher than for Mb, CK-MB and cTnT. SA is a unique and novel marker that could be particularly useful in assessing myocardial cell damage in patients undergoing cardiac surgery.

Variation of perioperative blood cTnT levels in patients undergoing cardiopulmonary bypass and its clinical implication

The clinical value of cardiac Troponin T (cTnT) as a marker in assessing myocardial cell damage in the patients undergoing open heart surgery was studied. Serum cTnT and CK-MB levels were measured in serial blood samples from 20 patients undergoing open heart surgery before operation, at aorta clamping, aorta opening, the end of CPB and the operation, and subsequently one h, one day, 3 days and one week after operation respectively. Ten patients receiving thoracic surgery were also subjected to the measurement of cTnT and CK-MB before and 24 h after operation. The results showed that peak concentrations were reached earlier in cTnT than in CK-MB, and the circulation cTnT remained high when CK-MB had already decreased to normal. In 10 patients receiving thoracic surgery, cTnT level was normal and CK-MB was increased in 4 patients after surgery. It was concluded that the sensitivity and specificity of cTnT was more than those of CK-MB and cTnT could be used as a routine indicator for myocardiac protection.

Intramyocardial troponin-T monitoring with microdialysis in coronary artery bypass surgery

OBJECTIVE

To investigate the time course of troponin-T release into the extracellular fluid of the myocardium and to distinguish between a rise in troponin-T due to implantation trauma and an increase due to cardiac arrest during coronary surgery.

DESIGN

Microdialysis probes were implanted in the heart of seven patients soon after sternotomy. Troponin-T was measured in the microdialysates and in peripheral blood from 3 h before to 24 h after heart arrest.

RESULTS

The troponin-T concentration in the microdialysates increased immediately after probe implantation and decreased to baseline within 70 min. This early peak is interpreted to reflect a local trauma. Three hours after cross-clamp release, a second peak of microdialysate troponin-T was recorded; 50 times higher than in serum. Eight to 24 h later a third peak occurred in five patients. Serum troponin-T was below the detection level at the beginning of the operation but increased linearly during the first 3 h of reperfusion and remained at that level thereafter.

CONCLUSION

Microdialysis is a safe technique providing more information on myocardial metabolism during and after bypass surgery than can be obtained from peripheral blood. The release of troponin-T in response to cardiac arrest can be distinguished in time from the local tissue response to probe implantation.

Cardiac marker responses to coronary artery bypass graft surgery with cardiopulmonary bypass and aortic cross-clamping

OBJECTIVE

To study several markers of myocardial injury in relation to aortic cross-clamping and cardiopulmonary bypass (CPB) after coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective observational study.

SETTING

University hospital.

PARTICIPANTS

Thirty adult patients who underwent elective CABG surgery with aortic cross-clamping and CPB.

MEASUREMENTS AND MAIN RESULTS

Serum levels of interleukin-6 (IL-6), interleukin-8 (IL-8), troponin-T (TnT), myosin light chain I (MLCI), and MB isoenzyme of creatine kinase (CK-MB), as markers of myocardial injury, were measured after induction of anesthesia for baseline values, then again at the end of surgery and on postoperative days 1, 3, and 5. IL-6, IL-8, and CK-MB levels were significantly elevated in the early postoperative stage. TnT significantly increased from the end of surgery to postoperative day 5. MLCI increased also but later than TnT. Aortic cross-clamping time correlated positively with peak TnT (r = 0.51, p < 0.05), TnT level on postoperative day 1 (r = 0.69, p < 0.01), and MLCI level on postoperative day 5 (r = 0.45, p < 0.05). CPB time was correlated only with peak TnT (r = 0.47, p < 0.05).

CONCLUSIONS

The increase in TnT level is strongly related to aortic cross-clamping.

Coronary revascularization: a procedure in transition from on-pump to off-pump? The role of glucose-insulin-potassium revisited in a randomized, placebo-controlled study

OBJECTIVE

To investigate an optimized glucose-insulin-potassium (GIK) solution regimen as an alternate myocardial protective strategy in off-pump coronary artery bypass graft (OP-CAB) surgery and as a supplement to conventional coronary artery bypass graft (CABG) surgery using cardiopulmonary bypass (CPB).

DESIGN

Prospective, randomized, placebo-controlled.

SETTING

Single institution, cardiothoracic specialty hospital.

PARTICIPANTS

Forty-four patients scheduled for elective multivessel coronary artery surgery using either conventional CPB (n = 22) or OP-CAB techniques (n = 22).

INTERVENTIONS

Preischemic, ischemic, and postischemic administration of GIK solution was carried out, optimally dosed to ensure nonesterified fatty acid (NEFA) suppression, and supplemented with magnesium, a glycolytic enzymatic cofactor.

MEASUREMENTS AND MAIN RESULTS

GIK solution therapy reduced plasma NEFA levels (p < 0.001) in OP-CAB surgery and CPB groups but failed to affect the incidence of non-Q wave perioperative myocardial infarction, incidence of postoperative atrial fibrillation, incidence of postoperative infection, reduction in creatinine clearance, or duration of postoperative intensive care unit or hospital length of stay. After adjusting for GIK solution therapy, OP-CAB surgery resulted in significantly less ischemic injury (troponin I >15 microg/L, 19.0% v 91.3%; p = 0.0001) and reduced postoperative infections (14.3% v 43.5%; p = 0.049).

CONCLUSION

GIK solution therapy achieved NEFA suppression and an insignificant trend toward reduced biochemical parameters of ischemic injury in OP-CAB surgery and CPB groups, but no major clinical benefit (perioperative myocardial infarction, intensive care unit length of stay, or hospital length of stay) was shown after elective CABG surgery in low-risk patients. Compared with CPB, OP-CAB surgery significantly reduced ischemic injury and postoperative infections.

Early identification of permanent myocardial damage after coronary surgery is aided by repeated measurements of CK-MB

OBJECTIVE

ECG diagnosis of myocardial infarction after cardiac surgery is associated with major pitfalls and enzyme diagnosis is interfered by unspecific elevation unrelated to permanent myocardial injury. Sustained release of troponin-T is a marker of permanent myocardial injury if renal function is maintained. However, early identification of perioperative myocardial infarction is desirable and therefore the usefulness of creatine kinase monobasic (CK-MB) kinetics to detect myocardial injury early after coronary surgery was investigated.

DESIGN

Two hundred and eighty-six patients undergoing coronary surgery were studied with respect to release of enzymes and troponin-T preoperatively and postoperatively 3 and 8 h after unclamping the aorta, and every morning postoperative days 1-4.

RESULTS

CK-MB peak was found at 3 h (n = 145), 8 h (n = 103) and 16-20 h after unclamping (n = 38). Depending on when the CK-MB peak was recorded different demographic and perioperative characteristics were found. A sustained release of troponin-T was characteristic for the group with the CK-MB peak at 16-20 h after unclamping.

CONCLUSION

If CK-MB is measured only once it may be advisable to do it on the first postoperative morning as these measurements provided the best discrimination between patients with and without sustained elevation of troponin-T. However, repeated sampling provides additional information that aids in the early identification of permanent myocardial injury particularly in patients with borderline elevations of CK-MB.

Assessment of myocardial injury by troponin T in off-pump coronary artery grafting and conventional coronary artery graft surgery

PURPOSE

The present study was undertaken to assess the degree of myocardial injury, using troponin T (TnT), in off-pump coronary artery surgery (OPCAB) and in a comparable patient group undergoing conventional coronary artery graft surgery (CABG).

METHODS

Twenty-seven OPCAB and 27 CABG patients were investigated. Blood samples for TnT were taken at intubation and at 12, 24 and 72 h. Nine patients (five OPCAB, four CABG) underwent 2 h sampling for 12 h for the assessment of the TnT release profile. All patients had an electrocardiogram performed preoperatively and on the mornings of days 1 and 5 postoperatively.

RESULTS

The OPCAB group had significantly greater Canadian Heart Classification 3 patients (P = 0.003); however, other demographic data were similar between the two groups. All patients had normal TnT at initial sampling. The mean number of grafts in each group was 1.8 +/- 0.6 for OPCAB and 1.9 +/- 0.3 for CABG (P = NS). There were two new Q wave myocardial infarctions in the CABG group and none in the OPCAB group. These cases were excluded from biochemical analyses. Troponin T release was significantly less in the OPCAB group at 12 and 24 h (P < 0.001 and P = 0.03, respectively). Peak TnT release occurred at 6-8 h in both groups. Troponin T release was significantly lower in the OPCAB group at 2, 4, 6, 8, 10 and 12 h (P = 0.01, P = 0.03, P = 0.02, P = 0.02, P = 0.03 and P = 0.04, respectively). Postoperatively, the OPCAB group required less blood transfusion (P = 0.02).

CONCLUSIONS

The OPCAB group demonstrated a significantly reduced TnT release profile compared with the CABG group.

Serum markers for early diagnosis of non-'Q' wave and 'Q' wave myocardial infarction

The present study conducted on twenty-five uncomplicated cases of acute myocardial infarction diagnosed by clinical and electrocardiographic findings indicated significantly increased level of cardiac Troponin-T and increased activities of the enzymes total creatine kinase, creatine kinase-MB, aspartate transaminase and lactate dehydrogenase as compared to the twenty-five healthy control subjects. The level of cardiac Troponin-T and the activities of the enzymes total creatine kinase, creatine kinase-MB, aspartate transaminase and lactate dehydrogenase was found to be higher in "Q" wave myocardial infarction patients as compared to the non-"Q" wave and the controls. Since cardiac Troponin-T has been shown to increase in unstable angina and renal failure without cardiac disease and creatine kinase-MB activity has been found to be normal in patients with unstable angina and increase very slightly in patients with renal failure, it was concluded that a combination of cardiac Troponin-T and creatine kinase-MB activity was sufficient for the early diagnosis of acute myocardial infarction.

Heart-type fatty acid binding protein (hFABP) in the diagnosis of myocardial damage in coronary artery bypass grafting

OBJECTIVES

Heart-type fatty acid binding protein (hFABP) is an intracellular molecule engaged in the transport of fatty acids through myocardial cytoplasm and has been used as a rapid marker of myocardial infarction. However, its value in the evaluation of perioperative myocardial injury has not yet been assessed.

METHODS

32 consecutive patients undergoing coronary artery bypass grafting were included in a prospective, randomized study using standardized operative procedures and myocardial protection. Three patients with perioperative myocardial infarction were added. Serial blood samples were taken preoperatively, before ischemia, 5 and 60 min after declamping, 1 and 6 h postoperatively and on postoperative days 1, 2 and 10 and were tested for hFABP, creatine kinase isoenzyme MB (CKMB) and troponin I (TnI).

RESULTS

Hospital mortality was zero. The kinetics of the biochemical parameters revealed a typical pattern for each marker. In routine patients, hFABP levels peaked as early as 1 h after declamping, whereas CKMB and TnI peaked only 1 h after arrival in the intensive care unit. Patients with perioperative infarction displayed peak levels some hours later in all marker proteins. Peak serum levels of hFABP correlated significantly with peak levels of CKMB (r=0.436, P=0.011) and TnI (r=0.548, P=0.001), indicating the degree of myocardial damage.

CONCLUSIONS

hFABP is a rapid marker of perioperative myocardial damage and peaks earlier than CKMB or TnI. The kinetics of marker proteins in serial samples immediately after reperfusion is more suitable for the detection of perioperative myocardial infarction than a fixed cut-off level.

Ranolazine, a partial fatty acid oxidation inhibitor, reduces myocardial infarct size and cardiac troponin T release in the rat

Ranolazine reduces cellular acetyl-CoA content via inhibition of fatty acid beta-oxidation and activates pyruvate dehydrogenase. This metabolic switch increases ATP production per mole of oxygen consumed, reduces the rise in lactic acid and acidosis, and maintains myocardial function under conditions of reduced myocardial oxygen delivery. It is still unclear whether ranolazine causes a reduction of (i) infarct size and (ii) cardiac troponin T release, in a male Wistar rat model of left anterior descending coronary artery occlusion (25 min) and reperfusion (2 h). Rats were subjected to saline infusion (n=12) or ranolazine (bolus injection: 10 mg/kg plus infusion: 9.6 mg/kg/h, n=12), 30 min prior to left anterior descending coronary artery occlusion-reperfusion, respectively. Ranolazine caused a significant reduction in myocardial infarct size of approximately 33% compared to saline control (P<0.05). In addition, infusion of ranolazine significantly attenuated the release of cardiac troponin T into the plasma from 65+/-14 (controls) to 12+/-2 ng/ml. This study demonstrates for the first time that ranolazine significantly reduces (i) infarct size and (ii) cardiac troponin T release in rats subjected to left anterior descending coronary artery occlusion-reperfusion.

Persistently increased serum concentrations of cardiac troponin t in patients with idiopathic dilated cardiomyopathy are predictive of adverse outcomes

BACKGROUND

The measurement of serum concentrations of cardiac troponin T (TnT) is a simple, useful method to detect myocyte injury that may be repeated multiple times to follow patients without interobserver variability.

METHODS AND RESULTS

Multiple measurements of TnT with a second-generation assay were performed in 60 patients with dilated cardiomyopathy confirmed by coronary angiography and endomyocardial biopsy between April 1996 and December 1999. Three evolutionary patterns of TnT concentrations were identified. Thirty-three patients had concentrations of TnT <0.02 ng/mL throughout the follow-up period (group 1). The remaining 27 patients had high initial serum concentrations of TnT (>/=0.02 ng/mL). In 10 of these 27 patients, TnT decreased to <0.02 ng/mL during follow-up (group 2), whereas 17 had persistently high serum TnT concentrations despite being conventionally treated for chronic congestive heart failure (group 3). Although the initial echocardiographic left ventricular diastolic dimension (LVDd) and left ventricular ejection fraction (LVEF) were not significantly different among the 3 groups, follow-up echocardiography showed significantly decreased LVDd and increased LVEF in group 1 (each P:<0.01) and group 2 (each P:<0.05) compared with increased LVDd and decreased LVEF in group 3 (each P:<0.05). The cardiac event-free rate was significantly lower in group 3 than in groups 1 and 2 (each P:<0.001), and the survival rate was lower in group 3 than in group 1 (P:<0.05).

CONCLUSIONS

Persistently increased TnT concentrations in dilated cardiomyopathy suggest ongoing subclinical myocyte degeneration associated with deterioration of the patients' clinical status.

Implications of troponin testing in clinical medicine

During the past decade considerable research has been conducted into the use of cardiac troponins, their diagnostic capability and their potential to allow risk stratification in patients with acute chest pain. Determination of risk in patients with suspected myocardial ischaemia is known to be as important as retrospective confirmation of a diagnosis of myocardial infarction (MI). Therefore, creatine kinase (CK)-MB - the former 'gold standard' in detecting myocardial necrosis - has been supplanted by new, more accurate biomarkers.Measurement of cardiac troponin levels constitute a substantial determinant in assessment of ischaemic heart disease, the presentations of which range from silent ischaemia to acute MI. Under these conditions, troponin release is regarded as surrogate marker of thrombus formation and peripheral embolization, and therefore new therapeutic strategies are focusing on potent antithrombotic regimens to improve long-term outcomes. Although elevated troponin levels are highly sensitive and specific indicators of myocardial damage, they are not always reflective of acute ischaemic coronary artery disease; other processes have been identified that cause elevations in these biomarkers. However, because prognosis appears to be related to the presence of troponins regardless of the mechanism of myocardial damage, clinicians increasingly rely on troponin assays when formulating individual therapeutic plans.

Validation of NACB and IFCC guidelines for the use of cardiac markers for early diagnosis and risk assessment in patients with acute coronary syndromes

BACKGROUND

International guidelines have been established for the use of cardiac markers in the early diagnosis and risk assessment of patients with acute coronary syndromes.

METHODS

A single center, prospective observational study was conducted in a tertiary care university hospital on 200 consecutive patients with suspected acute myocardial infarction (AMI). Blood was drawn on admission and after 2, 4, 8, 12 and 24 h for the measurement of CK-MB/CK activity, myoglobin, CK-MB mass and troponin I. A 6-week follow-up was undertaken for the combined end point of acute coronary syndrome and death.

RESULTS

Myoglobin showed an early diagnostic sensitivity of 0.65 on admission, 0.90 after 2 h and 0.92 after 4 h compared with 0.46, 0.74 and 0.88 for CK-MB/CK activity. The combination of myoglobin and cTnI increased the diagnostic value compared with myoglobin alone on admission, 2 and 4 h later. In multivariate analysis, cTnI and CK-MB/CK mass, but not myoglobin and CK-MB/CK activity, were shown to be independent predictors on the 6-week follow-up.

CONCLUSIONS

Repetitive myoglobin measurements within 4 h of admission, combined with at least one early troponin test, was shown to be the strategy of choice in early AMI diagnosis and prognosis assessment.

Biochemical assessment of myocardial injury after cardiac surgery: effects of a platelet activating factor antagonist, bilateral internal thoracic artery grafts, and coronary endarterectomy

OBJECTIVE

Platelet activating factor antagonists reduce ischemia-reperfusion injury in experiments, but there is no supportive clinical evidence.

METHODS

A single-center, double-blind, minimized, placebo-controlled, randomized trial of low-dose (10 mg) or high-dose (100 mg) platelet activating factor antagonist was conducted in 150 patients undergoing coronary artery bypass grafting. Myocardial injury was determined by serial measurements of the MB isoenzyme of creatine kinase and cardiac troponin T. The effects of single or bilateral internal thoracic artery grafting and coronary endarterectomy on myocardial injury were also assessed.

RESULTS

The placebo and platelet activating factor antagonist groups were similar with respect to preoperative, intraoperative, and postoperative factors. Four patients (2.7%) died before discharge, 3 from cardiac events. Thirteen patients (9%) had biochemical evidence of myocardial infarction, of whom 3 died. Stepwise multiple regression analysis demonstrated that duration of cardiopulmonary bypass was the most important determinant of elevations in creatine kinase MB isoenzyme and cardiac troponin T up to 6 hours after the operation and that the use of a platelet activating factor antagonist and the number of internal thoracic artery grafts did not influence myocardial injury at any time. Endarterectomy was performed in 11 patients (7%), of whom 6 (55%) had biochemically defined myocardial infarction and of whom 1 died (9%). Endarterectomy was the most important determinant of elevated levels of creatine kinase MB isoenzyme and cardiac troponin T 24 and 48 hours after the operation.

CONCLUSION

Platelet activating factor antagonists do not reduce perioperative myocardial injury. Bilateral and single internal thoracic artery grafting results in similar levels of myocardial injury, whereas endarterectomy is frequently associated with biochemical evidence of myocardial injury.

Aortocoronary bypass grafting: a comparison of HTK cardioplegia vs. intermittent aortic cross-clamping

OBJECTIVE

Intermittend, hypothermic aortic cross-clamping (IAC) with myocardial fibrillation and cardioplegic arrest (CA) have been established both as effective methods for coronary artery bypass surgery (CABG). Nevertheless, there exists controversy about the more beneficial cardioprotective effect of one of these procedures in CABG-patients.

METHODS

In this prospective study we compared the clinical outcome, ischemic serum-markers (CK, CK-MB, Troponin I), electrocardiogram (ECG)-changes, and hemodynamic data of 103 patients. Randomization in group I (IAC; n=52) or group II (CA; n=51) was done consecutively, all data were compared by Student's t-test or chi(2)-test and P<0.05 was regarded as significant. The Bretschneider-HTK solution was used for cardioplegic arrest. Data were collected before operation, before ischemic arrest, after 5 and 60 min of reperfusion, 1 and 6 h after operation, 1, 2 and 10 days postoperatively.

RESULTS

There were no significant differences between both groups regarding general patient data: age (IAC: 64. 8+/-9.2 vs. CA: 63.8+/-9.0 years), left ventricular function (ejection fraction: IAC: 62+/-14 vs. CA: 64+/-13%), the amount of bypassed vessels (IAC: 3.4+/-0.5 vs. CA: 3.6+/-0.5), total bypass time (IAC: 113+/-31 vs. CA 108+/-20 min). The total time of ischemia was significantly less in the IAC group with 37+/-10 vs. 48+/-10 min in the CA group. In the IAC-group, a higher mortality was noticed (7. 7 vs. 3.9%; N.S.). This was combined with a significantly higher amount of patients with peak serum-values of CK-MB (>40 U/l) and troponin I (>50 ng/ml), 17 in the IAC-group (33%) vs. eight in CA-group (16%). Cerebral strokes were seen in two IAC-patients and none in CA-patients (NS). ECG-changes occurred in 22 IAC patients (42%) vs. 16 CA patients (31%); persistent ischemia related ECG-changes in six IAC (11.5%) vs. five CA-patients (9.8%).

CONCLUSIONS

Both cardioprotective methods, IAC and HTK-cardioplegia, seem to offer sufficient myocardial protection in normal CABG-procedures. Although neurologic disorders and mortality rates were higher in patients with intermittent aortic cross-clamping, the differences to the cardioplegia group were not significant. According to the analysis of increased ECG-changes, higher CK-MB and troponin I values, which occurred especially in patients with myocardial ischemia time longer than 40 min, we conclude that cardioplegic arrest with HTK seems to offer more beneficial effects in procedures with prolonged ischemia.

Perioperative myocardial cell injury: the relationship between troponin T and cortisol

STUDY OBJECTIVE

To investigate whether there is an association between Troponin T (TnT), reflecting myocardial cell injury, and cortisol, reflecting the degree of surgical trauma and associated stress, in light of our recent evaluation of TnT as a marker of perioperative myocardial cell injury.

DESIGN

Prospective, cohort study.

PATIENTS

70 patients (67.4 +/- 8.7 yrs) with definite or at-risk coronary artery disease (CAD) undergoing elective noncardiac surgery (vascular n = 38, abdominal n = 21, orthopedic n = 8) with general (n = 63) or regional (n = 4) anesthesia with postoperative on-demand analgesia.

MEASUREMENTS AND MAIN RESULTS

Morning blood samples for TnT (upper limit of normal: <0.2 ng/mL), CK-MB (reference range </=12 U/L), and cortisol (normal morning range 7-25 mcg/dL) were taken on the day before surgery, on the morning of surgery before induction of anesthesia, and on the first 5 postoperative days. Data were compared by analysis of variance. Three patients were excluded from the study because of incomplete blood samples of TnT or cortisol. Preoperative mean cortisol levels (mcg/dL +/- SD) were within the normal range and equal in TnT positive (n = 13) and negative (n = 54) patients (16.1 +/- 4.5 vs. 15.6 +/- 5.8). On the 1st postoperative day, there was a substantial increase of cortisol in the TnT positive group (35.7 +/- 26.9). Cortisol remained high until the 5th postoperative day (24.7 +/- 9. 4). There was a significant difference in the cortisol concentration in TnT-positive compared to TnT-negative patients (p < 0.001), a significant difference in the perioperative cortisol concentration over time (p < 0.05), and a significant interaction (p < 0.001). But there was no consistent temporal relationship between the increase of TnT and the increase of cortisol.

CONCLUSIONS

The significant relationship between a highly sensitive and specific marker of myocardial cell injury and a marker of stress suggests that cardiac-risk patients undergoing stressful surgical procedures might benefit from close perioperative TnT monitoring with early recognition of myocardial cell injury.

Evaluation of incidence, clinical significance, and prognostic value of circulating cardiac troponin I and T elevation in hemodynamically stable patients with suspected myocardial contusion after blunt chest trauma

BACKGROUND

The frequency and prognostic influence of myocardial injury in patients with blunt chest trauma is controversial. We investigated the value of cardiac troponin I (cTn-I) and cardiac troponin T (cTn-T), highly specific markers of myocardial injury, to determine whether their measurement would improve the ability to detect myocardial contusion in stable patients with blunt chest trauma in comparison with conventional markers and whether they were associated with significantly worse late clinical outcome.

METHODS AND RESULTS

Over an 18-month period, myocardial contusion was diagnosed in 26 of 94 patients (27.6%) with acute blunt chest trauma (motor vehicle crash; 81%), because of echocardiographic abnormalities (n = 12), electrocardiographic abnormalities (n = 29), or both. Patients with myocardial contusion had a significantly higher Injury Severity Score at the time of admission (p = 0.001) and a significantly longer hospital stay (p = 0.0008). All patients survived admission to hospital and were hemodynamically stable. None of the patients died or had severe in-hospital cardiac complications. The percentage of patients with elevated CK, (CK-MB/total CK) ratio, or CK-MB mass concentration was not significantly different between patients with or without myocardial contusion. However, there were significant differences between the two groups when we applied the commonly used threshold levels of CK-MB activity and myoglobin. The percentage of patients with elevated circulating cTn-I and cTn-T (> or = 0.1 microg/L) was significantly higher in patients with myocardial contusion (23% vs. 3%; p = 0.01 and 12% vs. 0%; p = 0.03, respectively). Complete changes in cTn-I and cTn-T correlated well (r = 0.91, p = 0.0001). Sensitivity, specificity, and negative and positive predictive values of cTn-I and cTn-T in predicting a myocardial contusion in blunt trauma patients were 23%, 97%, and 77%, 75%, and 12%, 100%, and 74%, 100%, respectively. Clinical follow-up was available in 83 patients (88%) (mean, 16 +/- 7.5 months). There were no deaths in either group directly attributed to cardiac complications. None of the patients had any long-term cardiac complications or myocardial failure related to blunt chest trauma.

CONCLUSION

Although improved specificity of cTn-I and cTn-T compared with conventional markers, it should be emphasized that the main problem with cTn-I and cTn-T is low sensitivity as well as low predictive values in diagnosing myocardial contusion. cTn-I and cTn-T measurement is currently not an improved method in diagnosing blunt cardiac injury in hemodynamically stable patients. Moreover, there was no association of postmyocardial contusion cell injury and late outcome in these patients when cTn-I and cTn-T and other conventional markers were considered.

Troponin T as a Marker of Infarction during Coronary Bypass Surgery

To evaluate serum troponin T as a marker of perioperative myocardial infarction, 50 patients undergoing coronary artery bypass grafting were divided into 2 groups. Group A (14 patients) had serum creatine kinase MB-isoenzyme levels above 100 U·L−1and electrocardiographic changes indicative of infarction. Group B (36 patients) had creatine kinase MB levels below 100 U·L−1and no electrocardiographic changes. Blood samples were obtained preoperatively, 6 hours after aortic declamping, and on postoperative day 1, 2, and 3. Following surgery, all patients had increased levels of troponin T and creatine kinase MB. Troponin T was significantly higher in group A compared to group B at 6 hours, day 1, and day 2 postoperatively. Creatine kinase MB levels were significantly higher in group A compared to group B at 6 hours and day 1 postoperatively. The increased levels of troponin T in patients without myocardial infarction suggest that some operative myocardial damage occurred. Patients with perioperative myocardial infarction had significantly higher levels of troponin T up to postoperative day 2, whereas creatine kinase MB levels were almost normal by day 2. This suggests that troponin T may be used up to 2 days postoperatively for detection of myocardial infarction.