Diagnostic performance and prognostic value of serum troponin T in suspected acute myocardial infarction

Biomarker Development in Cardiology: Reviewing the Past to Inform the Future

Cardiac biomarkers have become pivotal to the clinical practice of cardiology, but there remains much to discover that could benefit cardiology patients. We review the discovery of key protein biomarkers in the fields of acute coronary syndrome, heart failure, and atherosclerosis, giving an overview of the populations they were studied in and the statistics that were used to validate them. We review statistical approaches that are currently in use to assess new biomarkers and overview a framework for biomarker discovery and evaluation that could be incorporated into clinical trials to evaluate cardiovascular outcomes in the future.

Atrial fibrillation-induced cardiac troponin I release

BACKGROUND

Cardiac troponin I (cTnI) is highly specific for myocardial damage and for the diagnosis of acute coronary syndrome. We investigated cTnI utility and predictive value in patients with atrial fibrillation (AF) in the acute setting.

METHOD

We studied 354 consecutive patients with the primary diagnosis of AF and clinical symptoms suggestive of myocardial ischemia presenting to our emergency department. cTnI was obtained on presentation. Patients with ST-segment elevation myocardial infarction were excluded. Coronary angiography was performed in 100 patients.

RESULTS

cTnI was elevated (>0.09 μg/L) in 51 of 354 (15%) patients. The mean cTnI in these patients was 0.37 μg/L (0.09-3.14). In 23 of 100 patients undergoing coronary angiography, cTnI was elevated. Only 6 of these 23 patients (26%) had significant stenosis. In 77 of 100 patients undergoing coronary angiography, cTnI was normal, revealing significant stenosis in 25 patients (33%). The positive predictive value of elevated cTnI for a coronary intervention was 26% and the negative predictive value was 68%. Using multivariate logistic regression, we found that heart rate on presentation, the presence of angina pectoris, left ventricular ejection fraction, serum creatinine, and hemoglobin independently predicted elevated cTnI level.

CONCLUSION

These data are the first to show that AF in the acute setting is frequently associated with cTnI elevations. AF patients with high heart rate and/or angina pectoris often show false elevated cTnI levels. These findings are relevant for clinicians evaluating patients with acute AF and myocardial ischemia symptoms. Appropriate clinical guidelines must be established that also consider AF-related elevations in cTnI.

Cardiac biomarkers in acute myocardial infarction

Each year, a large number of patients are seen in the Emergency Department with presentations necessitating investigation for possible acute myocardial infarction. Patients can be stratified by symptoms, risk factors and electrocardiogram results but cardiac biomarkers also have a prime role both diagnostically and prognostically. This review summarizes both the history of cardiac biomarkers as well as currently available (established and novel) assays. Cardiac troponin, our current "gold standard" biomarker criterion for the diagnosis of myocardial infarction has high sensitivity and specificity for this diagnosis and therapies instituted in patients with elevated troponin have been shown to influence outcomes. Other markers of myocardial necrosis, inflammation and neurohormonal activity have also been shown to have either diagnostic or prognostic utility, but none have been shown to be superior to troponin. The measurement of multiple biomarkers and the use of point of care markers may accelerate current diagnostic protocols for the assessment of such patients.

Biochemical markers in acute coronary syndrome

Owing to their higher risk for cardiac death or ischemic complications, patients with acute coronary syndrome (ACS) must be identified from other causes of chest pain. Patients with acute coronary syndrome are divided into categories based on their electrocardiogram; those with new ST-segment elevation and those who present with ST-segment depression. The subgroups of patients with ST-segment elevation are candidates for immediate reperfusion, while fibrinolysis appears harmful for those with non-ST elevation myocardial infarction. There is increasing evidence to encourage appropriate risk stratification before deciding on a management strategy (invasive or conservative) for each patient. The TIMI, GRACE or PURSUIT risk models are recommended as useful for decisions regarding therapeutic options. Cardiac biomarkers are useful additions to these clinical tools to correctly risk stratify ACS patients. Cardiac troponin is the biomarker of choice to detect myocardial necrosis and is central to the universal definition of myocardial infarction. The introduction of troponin assays with a lower limit of detection will allow for earlier diagnosis of patients who present with chest pain. Analytical and clinical validations of these new assays are currently in progress. The question is whether the lower detection limit of the troponin assays will be able to indicate myocardial ischemia in the absence of myocardial necrosis. Previous to the development of ultrasensitive cardiac troponin assays free fatty acids unbound to albumin and ischemia modified albumin were proposed as biochemical markers of ischemia. Advances in our knowledge of the pathogenesis of acute coronary thrombosis have stimulated the development of new biomarkers. Markers of left ventricular performance (N-terminal pro-brain natriuretic peptide) and inflammation (e.g. C-reactive protein) are generally recognized as risk indicators. Studies suggest that using a number of biomarkers clinicians can risk stratify patients over a broad range of short and long term cardiac events. Nevertheless, it is still under debate as to which biomarker combination is best preferred for risk prediction. This review will focus on recent practice guidelines for the management of patients with ACS as well as current advances in cardiac biomarkers, their integration into clinical care and their diagnostic, prognostic and therapeutic utility.

Evaluation of myocardial metabolism with microdialysis after protection with cold blood- or cold crystalloid cardioplegia. A porcine model

OBJECTIVES

There has been a considerable change in the patient population referred for cardiac surgery in the last decade. More complex and marginal patients require optimized myocardial protection. An insufficient cardioplegic procedure results in anaerobic metabolism during cardiac arrest with subsequent lactate accumulation. Increased lactate level is regarded as a predictor for low cardiac output syndrome. In an acute porcine model we examined two standard cardioplegic methods. Myocardial microdialysis was used to investigate the metabolism during cardioplegic arrest and in the reperfusion period.

METHODS

Twelve domestic pigs were randomly chosen to receive either cold blood-or cold crystalloid cardioplegia. After midline sternotomy two microdialysis probes were implanted in two different regions of the heart. Cardiopulmonary bypass was initiated, aorta was clamped, and antegrade cardioplegia was delivered. These conditions were maintained for 90 min. Subsequent to myocardial reperfusion the animals were observed for 180 min. Microdialysis and plasma markers to characterize myocardial metabolism, and plasma markers for myocardial failure and necrosis were obtained every 30 min.

RESULTS

Lactate concentrations were significantly increased in the cold crystalloid cardioplegia group compared to the cold blood cardioplegia group, in tissue dialysate (p < 0.001) as well as in serum (p = 0.018). Pyruvate concentrations in the dialysate were significantly increased in the cold crystalloid cardioplegia group compared to the cold blood cardioplegia group (p = 0.008). There were no significant differences in dialysate concentrations of glycerol. Plasma markers for myocardial failure (Brain Natriuretic Peptide) and for myocardial necrosis (Cardiac Troponin T) showed no differences between the groups.

CONCLUSION

The results indicate that cold blood cardioplegia offers superior protection of the heart, in terms of more rapid normalization of myocardial metabolism. The microdialysis technique seems to have a high sensitivity and ability to detect even minor metabolic changes. This enhances the possibility of designing a myocardial protection, which might lower morbidity and mortality risk.

The role of cardiac troponin T and other new biochemical markers in evaluation and risk stratification of patients with acute chest pain syndromes

BACKGROUND AND HYPOTHESIS

Increased serum creatinine kinase (CK) and CK-MB enzyme levels have been used for years to detect myocardial infarction (MI). However, serum myoglobin and CK-MB mass or protein levels may indicate MI earlier; cardiac troponin T is the most specific marker of myocardial injury and it can detect even minor myocardial necrosis. The diagnostic and prognostic utility of the traditional and new markers of cardiac injury in the emergency evaluation of patients with acute chest pain syndromes were therefore compared.

METHODS

One hundred and fifteen consecutive patients with an acute coronary syndrome, and 64 controls recruited during the same period, were examined. The time elapsed from onset of symptoms to blood collection was recorded. Cardiac markers were measured in specimens collected upon arrival (0 h), and 2 and 5-9 h, and later in cases of longer observation. The major cardiac events occurring up to 40 months after the index examination were recorded.

RESULTS

cTnT levels provided unique information: they were the most specific indicators of myocardial damage and identified unstable angina patients at high risk of future major events. Up to 6 h after the onset of chest pain, the new markers were elevated more frequently than the traditional ones and permitted earlier MI recognition. The worst prognosis (nonfatal myocardial infarction or death) was noted in subjects with chest pain at rest within 48 h before the index examination and elevated cTnT levels.

CONCLUSIONS

The new markers, particularly cardiac troponin T, offer considerable advantages and they should be more widely used in the diagnosis and risk stratification of acute coronary syndromes.

A prospective study of an algorithm using cardiac troponin I and myoglobin as adjuncts in the diagnosis of acute myocardial infarction and intermediate coronary syndromes in a veteran's hospital

BACKGROUND

Accurate and cost-effective evaluation of acute chest pain has been problematic for years. The high prevalence of missed myocardial infarctions (MI) has led to conservative triage behavior on the part of physicians, leading to expensive admissions to coronary care units. New algorithms are sorely needed for more rapid and accurate triage of patients with chest pain to appropriate treatment settings.

HYPOTHESIS

We sought to test an algorithm for rapid diagnosis of MI and acute coronary syndromes using cardiac troponin I (cTnI) and myoglobin as adjuncts to creatine kinase (CK)-MB. We hypothesized our algorithm would be both sensitive and specific at early time points, and would allow safe stratification of patients not ruling in by conventional CK-MB criteria.

METHODS

This was a 6-month prospective study of 505 consecutive patients who presented with chest pain at a university-affiliated veteran's hospital. The percentage of MIs at various time points was identified using combinations of markers. Safety outcomes were assessed by follow-up of patients discharged home. Cost savings analysis was assessed by surveying the physicians as to whether the use of the algorithm affected their disposition of patients. Forty-nine patients ruled in for MI. Using the combination of cTnI, 2-h doubling of myoglobin, and CK-MB, 37 (76%) ruled in at the time of presentation, 43 (88%) at 2 h, and 100% by 6 h.

RESULTS

Cardiac troponin I plus a 2-h myoglobin was as accurate as the combination of all three markers and performed better than CK-MB in detecting patients presenting late and as a predictor for complications when CK-MB was normal. Of the 456 patients with normal markers after 6 h, only 140 were sent to the coronary care unit (CCU), and 176 were sent home. A 3-month follow-up showed minimal adverse events. One-half of physicians completing a survey stated the use of markers changed their disposition of patients, leading to an estimated 6-month cost savings of a half-million dollars.

CONCLUSIONS

We developed an algorithm using troponin I and myoglobin as adjuncts to usual CK-MB levels that allowed for rapid and accurate assessment of patients with acute MI. It also afforded physicians important input into their decision making as to how best to triage patients presenting with chest pain. Their comfort in sending home certain subgroups of patients who otherwise would have been admitted to the CCU was rewarded with a good short-term prognosis and a large cost savings to the hospital.

Differences between early, intermediate, and late angioplasty after coronary artery bypass grafting

The aim of the present study was to identify patients with recurrent ischemia after coronary artery bypass surgery (CABG) treated by percutaneous coronary intervention (PCI). Graft failure after CABG may be managed conservatively or treated by surgery or PCI. We thought to investigate clinical, angiographic, and procedural characteristics in relation to clinical outcome. This was a retrospective single-center study. Patients who underwent revascularization by PCI with a previous CABG were analyzed. Patients were divided in 3 groups, depending on interval between CABG and index PCI: group 1, interval <72 hours; group 2, interval between 72 hours and 1 year; group 3, interval >1 year. Two hundred twenty-one patients were studied. Clinical characteristics and survival curves were comparable in groups 2 and 3. Postoperative creatine kinase MB and troponin values were significantly higher in group 1 (P = 0.000). From group 1, significantly more patients (10.5%) required emergency CABG after the index PCI than compared with group 2 (2.1%) and group 3 (0%), (P = 0.003). There were more off-pump CABGs in group 1 than in the other 2 groups. Group 1 received less PCIs in native ungrafted vessels compared with the other 2 groups. Mortality in group 1 (18.4%) was higher than in the other 2 groups (7.4 and 4.5%, respectively; P < 0.05). Mortality in group 1 was higher in the acute phase of follow-up. PCI performed less than 72 hours after CABG is feasible but accompanied by a higher mortality and redo CABG. This outcome is probably related to the high-risk patient category.

A serial follow up study of cardiac marker enzymes during the week after acute myocardial infarction

Laboratory infarction diagnostics are based on the detection of elevated serum activities of creatine kinase (CK) Creatine kinase Isoenzyme MB (CKMB) and Transaminases. Determination of these cardiac marker enzymes permits the diagnosis of transmural myocardial infarction. However in such patients the diagnosis of acute myocardial infarction can be confirmed by the clinical symptoms and changes in the ECG, in addition to the enzyme assays. The 50 AMI patients selected in the present study were those admitted to the ICCU of Shri Krishna Hospital, Karamsad. The blood samples were taken at Zero hours (i.e. at the time of admission of the patient). Within 6 hrs of the starting of chest pain, 1.5 million units of streptokinase were mixed with 100 to 150ml of normal saline and administered by infusion over a period of one hour. The blood samples were further collected at intervals of 6 hrs, 14hrs, 32hrs, 48hrs, 5(th) day and 7(th) day. The blood samples were analyzed for CK, CKMB, SGOT, α HBDH and Cardiac specific Troponin T. By 6hrs the CK and CKMB values had started rising, the rise continuing at 14hrs with peak values at 32hrs. The CK showed a slight decrease by 48 hrs. The cardiac Troponin T showed wide time window from 4 hrs to 7(th) day for detecting myocardial damage. The maximum cardiac Troponin T values were during the first 24hrs. Cardiac Troponin T in serum appears to be a more sensitive and early indicator of myocardial cell injury in comparison to CKMB.

Biochemical markers of myocardial injury

The serum markers of myocardial injury are used to help in establishing the diagnosis of myocardial infarction. The older markers like aspartate amino-transferase, creatine kinase, lactate dehydrogenase etc. lost their utility due to lack of specificity and limited sensitivities. Among the currently available markers cardiac troponins are the most widely used due to their improved sensitivity specificity, efficiency and low turn around time. Studies have shown that cardiac troponins should replace CKMB as the diagnostic 'gold standard' for the diagnosis of myocardial injury. The combination of myoglobin with cardiac troponins has further improved the accuracy in the diagnosis of acute coronary syndromes and thereby reducing the hospital stay and patients' money. Among the other new markers of early detection of myocardial damage, heart fatty acid binding protein, glycogen phosphorylase BB and myoglobin/carbonic anhydrase III ratio seem to be the most promising. But the search for the most ideal marker of myocardial injury is still on.

Plasma markers of activated hemostasis in the early diagnosis of acute coronary syndromes

BACKGROUND

Because acute coronary syndromes (ACS) are caused by intracoronary thrombosis, plasma markers of coagulation have relevance for early diagnosis.

AIMS AND OBJECTIVES

To provide a critical review of these studies and specific attempts to close the diagnostic time gap left by traditional plasma markers of heart injury.

METHODS

Studies of ACS patients, with at least one control group, were included when blood samples were taken within 24 h after first symptoms prior to medication or intervention. Special attention was paid to studies reporting diagnostic performance, or combination of several markers into a single diagnostic index.

RESULTS

Markers with short plasma half-life (FPA, TAT, etc.) reflect ongoing thrombosis and may identify patients at increased risk. Markers with longer half-life (F1+2, D-Dimer, etc.) may be more useful to indicate a single acute thrombotic event. However, results are highly variable and depend on sampling time, clot property, degree of coronary obstruction and physiological condition. Early diagnostic performance of hemostatic markers was poor even when combined with heart injury markers.

CONCLUSIONS

Early measurement of hemostatic plasma markers in ACS patients provides pathophysiological information and may be helpful in risk stratification or to monitor anticoagulant therapy, but does not seem useful in routine clinical diagnosis of ACS.

Utility of admission cardiac troponin and "Ischemia Modified Albumin" measurements for rapid evaluation and rule out of suspected acute myocardial infarction in the emergency department

OBJECTIVE

To assess if the combination of cardiac troponin (cTn) and Ischemia Modified Albumin (IMA) can be used for early exclusion of acute myocardial infarction (AMI).

METHODS

Prospective consecutive admissions to the emergency department (ED) with undifferentiated chest pain were assessed clinically and by electrocardiography. A total of 539 patients (335 men, 204 women; median age 51.9 years) considered at low risk of AMI had blood drawn on admission. If the first sample was less than 12 hours from onset of chest pain, a second sample was drawn two hours later, at least six hours from onset of chest pain. Creatine kinase MB isoenzyme (CKMB) mass was measured on the first sample and CKMB mass and cTnT on the second sample. An aliquot from the first available sample was frozen and subsequently analysed for IMA. If cTnT had not been measured on the original sample cTnI was measured (n = 189).

RESULTS

Complete data were available for 538/539 patients. IMA or cTn was elevated in the admission sample of all patients with a final diagnosis of AMI (n = 37) with IMA alone elevated in 2/37, cTn alone in 19/37, and both in 16/37. In 173/501 patients in whom AMI was excluded both tests were negative. In the non-AMI group 22 patients had elevation of both IMA and cTn in the initial sample, suggesting ischaemic disease.

CONCLUSION

Admission measurement of cardiac troponin plus IMA can be used for early classification of patients presenting to the ED to assist in patient triage.

Biomarkers in acute coronary syndromes and their role in diabetic patients

Diabetic patients with acute coronary syndromes are at high risk for cardiovascular complications but risk stratification in these patients remains challenging. Regularly, diabetic patients have a less typical clinical presentation, which could lead to delayed diagnosis and subsequent delayed initiation of treatment. Since diabetic patients derive particular benefit from aggressive anti-platelet therapy, early diagnostic and therapeutic risk stratification of these patients is of critical importance to improve their adverse outcome. Although the electrocardiogram remains a pivotal diagnostic tool in the evaluation of patients suspected of having an acute coronary syndrome, only significant ST-segment changes provide reasonable prognostic information. Therefore, repeated assessment of circulating protein biomarkers represents a valuable diagnostic tool for improving efficacy and safety of decision-making in these patients. The combined use of biomarkers reflecting distinct pathophysiological aspects, such as myocardial necrosis, vascular inflammation, oxidative stress and neurohumoral activation, may significantly improve triage of patients with chest pain. These tools may identify those patients that are at particularly high risk for short-term and/or long-term cardiovascular events. Eventually, tailored medical and interventional treatment of diabetic patients should help to prevent these cardiac events in a cost-effective manner.

Use of a quantitative point-of-care test for the detection of serum cardiac troponin T in patients with suspected acute coronary syndromes

We compared a third generation quantitative cardiac troponin T (cTnT) point-of-care testing (POCT) from Roche Diagnostics with the laboratory assay (Roche Elecsys 2010 immunoassay analyser). Heparin-treated blood and serum were collected simultaneously in 133 unselected patients (mean age 62 +/- 14 years, 38% females) presenting to our hospital with possible cardiac chest pain. Results of the POCT were measured against the laboratory-based assay considered as the gold standard. There were 18 POCT positive versus 24 laboratory assay positive (> or = 0.03 ng/mL) patients. POCT was falsely negative in six patients, with values between 0.03 and 0.1 ng/mL. The POCT had a sensitivity of 75%, specificity of 100%, positive predictive value of 100%, negative predictive value of 95% and a total accuracy of 95%; kappa = 0.831 (P < 0.001). There was good correlation between the values of POCT and the laboratory assay: Y = 1.195X + 0.002, r2 = 0.94 (P < 0.0001). Whereas cTnT levels > 0.1 mg/mL were reliably detected with this current generation of POCT, cTnT levels between 0.03 and 0.10 ng/mL were not. Future generations of devices will need to improve sensitivity to reliably risk stratify patients with suspected acute coronary syndromes.

Cardiovascular outcome in hospitalized patients with minimal troponin I elevation and normal creatine phosphokinase

BACKGROUND

Among patients with acute coronary syndrome, elevated cardiac troponin and creatine phosphokinase MB fraction levels have both prognostic and diagnostic values. However, in hospitalized patients, cardiac biomarkers are measured in a variety of clinical situations including but not limited to acute coronary syndrome. Moreover, these patients may have elevated troponin levels with no increase in creatine phosphokinase MB fraction levels.

OBJECTIVE

To evaluate the cardiovascular outcome of acutely ill, hospitalized patients with minimal troponin I increase with normal creatine phosphokinase MB fraction.

METHODS

We identified 64 patients retrospectively from our database with minimal troponin I increase and normal creatine phosphokinase MB fraction hospitalized between November 1998 and April 2000. Discharged patients were questioned about re-hospitalization for myocardial infarction, unstable coronary syndrome, congestive heart failure and percutaneous coronary intervention by means of a structured questionnaire. For those patients who died during hospitalization, data were collected from hospital records. For patients who died at home or at a different institution, a surviving relative completed the questionnaire. Primary outcomes were death, myocardial infarction and the need for revascularization or re-hospitalization.

RESULTS

Composite endpoint of death, myocardial infarction, percutaneous coronary intervention or coronary artery bypass grafting and re-hospitalization for cardiac cause occurred in 35.95% of patients within 1 year.

CONCLUSIONS

There is a significant composite event rate of death, myocardial infarction or re-hospitalization for cardiac causes in acutely ill, hospitalized patients with normal creatine phosphokinase MB fraction and minimally elevated troponin I, regardless of the cause for hospitalization.

Does initial and delayed heart rate predict mortality in patients with acute coronary syndromes?

BACKGROUND

Lower admission heart rate (HR) is known to predict favorable outcome in ST-elevation acute myocardial infarction. However, there are limited short-term and no long-term data available regarding the prediction value of the initial HR in patients with the full spectrum of acute coronary syndromes (ACS). In addition, it is unknown whether the HR obtained later during hospitalization for ACS (i.e., Day 2 or 3) remains prognostically valuable.

HYPOTHESIS

The aim of this study was to investigate the utility of the initial and delayed HR in predicting outcome in patients with ACS.

METHODS

We examined mortality at 30 days and 10 months in 10,267 patients with ACS enrolled in the oral glycoprotein IIb/IIIa inhibition with Orofiban in Patients with Unstable coronary Syndromes-Thrombolysis In Myocardial Infarction (OPUS-TIMI) 16 trial. Patients were stratified by HR and day from onset of ACS into the following groups: (1) HR < 60 beats/min, (2) HR 60-80 beats/min, (3) HR 80-100 beats/min, (4) HR > 100 beats/min; and HR obtained on (1) Day 1, (2) Day 2, and (3) Day 3.

RESULTS

By univariate analysis, mortality at 30 days and at 10 months increased progressively with higher HR strata (1.4 vs. 1.6 vs. 2.3 vs. 5.6%, p < 0.001, and 2.6 vs. 4.2 vs. 6.5 vs. 11.8%, p < 0.001, respectively). Elevated HR remained associated with mortality irrespective of time from onset of ACS.

CONCLUSIONS

Higher initial and delayed HR is highly predictive of higher short- and long-term mortality in patients with ACS. This is a simple marker that could be easily used in risk assessment.

Review Article. Cardiac troponins and renal disease

Cardiovascular disease is the most common cause of death in patients with renal failure. Patients with renal failure are at greater risk of atypical presentations of myocardial ischaemia. Traditional markers of myocardial damage are often increased in renal failure in the absence of clinically suspect myocardial ischaemia. The cardiac troponins are specific markers of myocardial injury. Large-scale trials, excluding patients with renal disease, have shown the importance of the cardiac troponins in predicting adverse outcome and in guiding both therapy and intervention in acute coronary syndromes. Cardiac Troponin T and cardiac Troponin I are increased in patients with renal failure and this is likely to represent multifactorial pathology including cardiac dysfunction, left ventricular hypertrophy and cardiac microinfarctions. Increases in serum troponin from baseline, in patients with renal disease with acute coronary syndromes, may represent a poor prognosis. Small studies of patients with renal failure have suggested that elevation of the cardiac troponins is associated with an increased risk of cardiac death.

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.

Prognostic Importance of Predischarged Troponin T Levels in Acute Anterior Myocardial Infarction

The baseline cardiac troponin T (cTnT) level strongly predicts short-term mortality in acute coronary syndromes, but the added value of predischarged (7th day) measures to predict short-term outcome and left ventricular (LV) remodeling in patients with ST elevation myocardial infarction (MI) is controversial. Baseline, peak and predischarged cTnT results were evaluated in 52 patients (15 females, 37 males, mean age, 54.4 +/- 8.8 years) with first acute anterior MI. There were 4 deaths (all cardiac origin) during the 30 day follow up period. Kaplan-Meier analysis revealed patients with a predischarged serum cTnT level higher than the median level (1.2 ng/mL) had a higher mortality rate than those with submedian levels (P < 0.05). Additionally, the highest correlation rate was found between predischarged cTnT values and LV ejection fraction (LV-EF, r = -0.58, P < 0.002). There were no differences between the groups in the 7th day left ventricular diastolic parameters, but the 30th day isovolumetric relaxation time and mitral E wave deceleration time were shorter (146.9 +/- 30.1 vs 129 +/- 23.4 msec, P = 0.025 and, 185.8 +/- 51.8 vs 144.6 +/- 58.1 msec, P = 0.012) in patients with higher predischarged cTnT level. High levels of predischarged cTnT levels in patients admitted with first acute anterior MI defines a subgroup. These patients have poor systolic and diastolic functions and are at increased risk of short term mortality. This group of patients may have benefit from early intensive treatment strategies before discharge.

Sources of diagnostic inaccuracy of conventional versus new diagnostic criteria for myocardial infarction in an unselected UK population with suspected cardiac chest pain, and investigation of independent prognostic variables

OBJECTIVE

To assess the degree and sources of current diagnostic inaccuracy of serial conventional cardiac markers and ECGs compared with the new diagnostic criteria for myocardial infarction, with specific reference to physician specialty and the prognostic value of troponin T.

DESIGN

Prospective, blinded observational study.

SETTING

University hospital.

PATIENTS AND INTERVENTIONS

All suspected cardiac chest pain admissions for six months, with additional blinded measurement of CK-MB mass and troponin T. World Health Organization and new criteria myocardial infarction diagnoses were made by an expert panel.

MAIN OUTCOME MEASURES

Diagnostic adjustment by expert panel; completeness of serial measurements; six months prognosis.

RESULTS

A complete set of serial cardiac markers was not taken in 38.7% of patients, this being twice as likely when managed by non-cardiologists than by cardiologists (p < 0.0001). The WHO myocardial infarction diagnosis was adjusted by the expert panel in 4% of cases, this being 90% more likely in patients admitted under non-cardiologists (p = 0.026). The new criteria for myocardial infarction identified an additional 27.3% of infarcts, with a diagnostic alteration in 12.0% of the cohort; 45.2% of these cases had a potentially preventable cause for diagnostic adjustment. Only troponin T (p = 0.0004), ST depression (p = 0.003), and heart failure (p = 0.016) were independently predictive of prognosis.

CONCLUSIONS

Chest pain patients appear less likely to be fully and accurately assessed by non-cardiologists than by cardiologists. The new criteria for myocardial infarction identify approximately 25% of additional patients as MI, with potential additional advantages related to simplicity of diagnostic protocols. Troponin T was the most potent predictor of six month prognosis in an unselected cohort of chest pain admissions.

[Biological markers of myocardial necrosis]

New biological markers of myocardial injury have improved the management of patients with acute coronary syndromes. Among these markers, the most relevant are the cardiac troponins (troponin I and troponin T) because of their cardiospecificity, and myoglobin because of its combination of diagnostic sensitivity and usefulness for an early diagnosis. The serial analysis and combined use of both markers fulfill all diagnostic and prognostic requirements, and are helpful in indicating therapeutic strategies for acute coronary syndromes. However, these markers also have limitations, and their concentrations should always be interpreted in the light of the patient's clinical status.

Cardiac troponin T and myocardial injury during routine cardiac catheterisation in children

BACKGROUND

This study aims to investigate whether intracardiac catheterization produces myocardial damage on pediatric heart.

METHODS

Five blood samples were collected (basal, immediate post procedure, at 4, 12 and 24 h after the procedure) for troponin T and creatine kinase MB (CKMB) from 48 consecutive patients (age: 5.34+/-6.03 years). The effect of age, duration of procedure, pulmonary hypertension, cyanosis, and medication taken for congestive heart failure on the levels of troponin T and CKMB were sought.

RESULTS

The increase in CKMB (basal CKMB: 3.93+/-3.70 ng/ml; peak CKMB: 8.68+/-10.89 ng/ml; P<0.0001) and troponin levels (basal troponin: 0.002+/-0.003 ng/ml; peak troponin: 0.11+/-0.23 ng/ml; P<0.0001) over time was significant in the study group. Additionally younger patients (</=1 year), patients with pulmonary hypertension (mean pulmonary artery pressure >25 mmHg), longer procedure time (>30 min), and patients taking anti-congestive heart failure therapy had significantly higher levels of CKMB and troponin (P>0.05).

CONCLUSION

All patients undergoing cardiac catheterization are under risk of myocardial injury, and younger patients with pulmonary hypertension and especially with compensated cardiac failure have increased risk of myocardial damage, and need to be handled carefully.

[Prognostic value of troponin T in hospitalized patients with angina or non-ST-segment elevation myocardial infarction]

INTRODUCTION AND OBJECTIVES

Cardiac troponins are highly specific and sensitive for detecting minimal myocardial damage. The aim of our study was to determine the prognostic value of troponin T levels in patients hospitalized for suspected angina or myocardial infarction without ST-segment elevation.

PATIENTS AND METHOD

We recorded the frequency of death, acute myocardial infarction, heart failure, or need for coronary revascularization in the three months after the onset of symptoms in 346 consecutive patients admitted for suspected acute coronary syndrome, excluding those who developed myocardial infarction with persistent ST-segment elevation.

RESULT

. Serum troponin T levels were > or = 0.1 ng/ml in 133 patients (troponin T positive group) and lower in 213 patients (troponin T negative group). The relative risk (RR) and 95 percent confidence intervals (95% CI) of individual and grouped events for the troponin T positive group were 3.2 (95% CI, 1.4-7.3; p = 0.006) for death; 2.8 (95% CI, 1.43-5.51; p = 0.003) for death or myocardial infarction; and 2.8 (95% CI, 1.6-5.0; p < 0.001) for death, myocardial infarction or heart failure. Diabetes mellitus and troponin T levels > or = 0.1 ng/ml had independent prognostic value after adjusting for age, sex, and electrocardiographic changes; with RR 2.5 (95% CI, 1.01-5.9) for death, myocardial infarction or heart failure.

CONCLUSIONS

The prognosis of patients hospitalized for chest pain who do not immediately develop transmural necrosis depends on serum troponin T levels at hospital admission. Troponin T levels > or = 0.1 ng/ml almost triple the risk of major events in the three months after the acute episode. The prognostic value of troponin T is independent of age, sex, presence of diabetes mellitus, and electrocardiographic changes.

Methods for detecting coronary disease: epidemiology and clinical management

The epidemic of atherosclerotic disease in wealthy countries had probably begun by 1900. Although a few physicians understood how atherosclerosis/thrombosis of the coronary arteries caused angina pectoris and myocardial infarction, the medical community did not accept that relationship until the 1920s. In wealthy countries, the epidemic peaked in mid-century, and it is now advancing in poor countries and in countries becoming affluent. Two recent developments in methods for disease detection, however, will profoundly affect not only our understanding of the epidemic of atherosclerotic disease, but also our management of patients. A redefinition of the clinical diagnosis of myocardial infarction, a well-used but imperfect measure of the epidemic, was published in September 2000. Criteria employed for about 50 years have now been replaced by criteria based on sensitive biochemical markers of necrosis of as little as 1 g of myocardium, accompanied by chest discomfort or electrocardiographic (ECG) changes, or following coronary artery intervention. The new criteria, adopted by the major societies of cardiology in Europe and the United States, is likely to increase the apparent incidence and prevalence of coronary heart disease (CHD). In the beginning of the twentieth century, diagnosis of CHD required an autopsy. In the end it was carried out by angiography as well, but it could not be applied to large proportions of the population. That has now been changed by new, non-invasive methods of computer tomography (CT) and magnetic resonance imaging (MRI), and patients, however, asymptomatic, will expect treatment for a disease that physicians have detected. Coronary artery disease (CAD) will be to CHD what occult cancer is to cancer.

Significant decline in case fatality after acute myocardial infarction in Denmark--a population-based study from 1994 to 2001

OBJECTIVE

We evaluated trends in in-hospital case fatality after acute myocardial infarction (AMI) in Denmark and analysed changes in the hospitalization rate for AMI.

DESIGN

National population-based registries were used to identify patients (> or =30 years) who were admitted for their first AMI from 1994 to 2001.

RESULTS

The annual relative decline in case-fatality rate was constant at 10.5% (95% confidence interval (CI) 9.5-11.5%). The decline was similar for both genders at all ages. The hospitalization rate decreased from 1994 to 1999 at an annual average of 4.3% (95% CI 3.4-5.1%). In 2000 and 2001 the average annual increase was 7-8%.

CONCLUSION

The case-fatality rate after AMI declined significantly in Denmark, similar to other Western countries, but the level is still higher than that of the USA. The increasing hospitalization rate coincided with changes in risk factors in the general population. However, the influence of introducing troponins in the diagnosis of AMI and diagnosis-related grouping may in particular account for the increased hospitalization rate.

Cardiac troponins

Cardiac troponins I and T are proteins integral to the function of cardiac muscle. They are very sensitive markers for the detection of myocardial damage, and the ability to assay their serum levels accurately and quickly have revolutionized the concepts of minor myocardial injury and infarction. They are also powerful prognostic indicators of future adverse cardiac events. Limitations, more of troponin T than I, include decreased specificity in renal failure and skeletal muscle disease. Rapid, whole blood assays are now available that can be done at the patient's bedside. This review discusses the cardiac troponins, their biochemistry, the assays for them currently available, and their roles in the evaluation of cardiac disease in the Emergency Department (ED).

The prognostic and therapeutic implications of increased troponin T levels and ST depression in unstable coronary artery disease: the FRISC II invasive troponin T electrocardiogram substudy

BACKGROUND

In unstable coronary artery disease, both increased troponin T level and occurrence of ST-segment depression are associated with a worse prognosis. In the Fast Revascularisation in InStability in Coronary disease trial II invasive study, we evaluated whether the troponin T level, alone and combined with ST depression, identified more severe coronary artery disease or a greater efficacy of an early invasive strategy.

METHODS

In the study, 2457 patients with unstable coronary artery disease were randomized to early invasive or noninvasive strategy. Troponin T value and admission electrocardiogram results were available in 2286 patients.

RESULTS

In the noninvasive cohort, death or myocardial infarction occurred in 16.6% with troponin T level > or =0.03 microg/L versus 8.5% with troponin T level < 0.03 microg/L (P <.001). In the invasive group, 49% of patients with both ST depression and troponin T level > or =0.03 microg/L had 3-vessel or left main disease compared with 17% if neither finding was present (P <.001). The invasive strategy reduced death/myocardial infarction at 12 months in the cohort with both ST depression and troponin T level > or =0.03 microg/L from 22.1% to 13.2% (risk ratio, 0.60; 95% confidence interval, 0.43 to 0.82; P =.001). In the cohort with either ST depression or troponin T level > or =0.03 microg/L or neither of these findings, the absolute gain of the invasive strategy was smaller and more uncertain.

CONCLUSION

Patients with unstable coronary artery disease with the combination of troponin T level > or =0.03 microg/L and ST depression have a poor prognosis and, in half of the cases, 3-vessel or left main disease. In these patients, an early invasive strategy will substantially reduce death/myocardial infarction.

Differences in the diagnosis of myocardial infarction by troponin T compared with clinical and epidemiologic criteria

We investigated the difference in the number of myocardial infarction (MI) diagnoses based on troponin T compared with clinical and epidemiologic (modified FINnish Multinational MONItoring of trends and determinants in CArdiovascular diseases) diagnoses, and the prognosis of patients with discordant diagnoses. Five hundred fifty-nine consecutive patients (315 men and 244 women, median age 69 years) were admitted to the hospital with a suspected acute coronary syndrome. Median follow-up time was 17 months. Of the 559 patients, 127 had a clinical and 137 an epidemiologic diagnosis of MI. When a diagnosis of MI was primarily based on troponin T (>0.10 microg/L), the number of MIs was 169, which increased by 33% compared with the number of MIs by clinical diagnosis, and by 23% compared with those by epidemiologic diagnosis. However, troponin T was not elevated in 13% of the 127 patients with the clinical diagnosis and in 14% of the 137 patients with the epidemiologic diagnosis of MI. Among patients in whom clinical diagnosis of MI was not made, the prognosis with regard to coronary death or nonfatal MI was not significantly worse in patients with troponin T >0.10 microg/L than < or =0.10 microg/L (hazard ratio 1.07; 95% confidence interval 0.62 to 1.84). In patients with a suspected acute coronary syndrome, troponin T-based diagnostics leads to an increase in the number of patients diagnosed with MI compared with clinical or epidemiologic diagnosis. The prognostic impact of troponin T in patients without clinical diagnosis of MI based on elevations in conventional enzyme activities needs further study in larger series of patients.

Acute coronary syndromes. The diagnostic role of troponins

Acute coronary syndromes (ACSs) represent the acute life-threatening phases of coronary heart disease. Clinical symptoms, EKG, and CK-MB measurements are frequently insufficient to evaluate patients without persisting ST elevations. Serial determinations of troponin T or troponin I after arrival in hospital disclose minor myocardial injury in patients presenting as unstable angina. This finding allows the currently best risk stratification and may contribute to cost-effectiveness. Without elevated troponins the risk for death or myocardial infarction during 30 days follow-up is not more than 1%. The lack of elevated troponins does not implicate that these patients do not have coronary artery disease. Patients with positive evidence of troponins represent a high-risk group who should be hospitalized and further evaluated, because the risk for myocardial infarction and death in 30 days is approximately 20%. Current studies indicate that early revascularization under glycoprotein IIb/IIIa antagonists represent the optimal treatment.

Clinical evaluation of the ACS:180 cardiac troponin I assay

All patients admitted to the coronary care unit with suspected acute coronary syndromes were evaluated by serial electrocardiography and blood draws on admission and at 4 and 12h from admission. Diagnosis was based on conventional WHO criteria. Samples were measured for creatine kinase (CK), cardiac troponin T (cTnT), myoglobin, CK isoenzyme MB (CK-MB) and cardiac troponin I (cTnI). A set of samples from individuals undergoing extreme endurance training was also examined. Analytical imprecision was consistent with published quality goals. Samples were stable for cTnI under a range of storage conditions, including multiple freeze thaw cycles. CK-MB, cTnI and cTnT were equally efficient for the diagnosis of acute myocardial infarction, irrespective of the final diagnostic criteria used. Both cTnI and cTnT were of equal efficiency in the identification of a high-risk subgroup of patients with unstable angina. Significant elevations of cTnI were not seen in an e ndurance-training group.

Measurement of cardiac troponins

The cardiac troponins form part of the regulatory mechanism for muscle contraction. Specific cardiac isoforms of cardiac troponin T and cardiac troponin I exist and commercially available immunoassay systems have been developed for their measurement. A large number of clinical and analytical studies have been performed and the measurement of cardiac troponins is now considered the 'gold standard' biochemical test for diagnosis of myocardial damage. There have been advances in understanding the development and structure of troponins and their degradation following myocardial cell necrosis. This has contributed to the understanding of the problems with current assays. Greater clinical use has also highlighted areas of analytical and clinical confusion. The assays are reviewed based on manufacturers' information, current published material as well as the authors' in-house experience.

The prognostic value of troponin in patients with non-ST elevation acute coronary syndromes: a meta-analysis

OBJECTIVES

This study was designed to compare the prognostic value of an abnormal troponin level derived from studies of patients with non-ST elevation acute coronary syndromes (ACS).

BACKGROUND

Risk stratification for patients with suspected ACS is important for determining need for hospitalization and intensity of treatment.

METHODS

We identified clinical trials and cohort studies of consecutive patients with suspected ACS without ST-elevation from 1966 through 1999. We excluded studies limited to patients with acute myocardial infarction and studies not reporting mortality or troponin results.

RESULTS

Seven clinical trials and 19 cohort studies reported data for 5,360 patients with a troponin T test and 6,603 with a troponin I test. Patients with positive troponin (I or T) had significantly higher mortality than those with a negative test (5.2% vs. 1.6%, odds ratio [OR] 3.1). Cohort studies demonstrated a greater difference in mortality between patients with a positive versus negative troponin I (8.4% vs. 0.7%, OR 8.5) than clinical trials (4.8% if positive, 2.1% if negative, OR 2.6, p = 0.01). Prognostic value of a positive troponin T was also slightly greater for cohort studies (11.6% mortality if positive, 1.7% if negative, OR 5.1) than for clinical trials (3.8% if positive, 1.3% if negative, OR 3.0, p = 0.2)

CONCLUSIONS

In patients with non-ST elevation ACS, the short-term odds of death are increased three- to eightfold for patients with an abnormal troponin test. Data from clinical trials suggest a lower prognostic value for troponin than do data from cohort studies.

The atherosclerosis epidemic: methodology, nosology, and clinical practice

An electronic search shows that there is a small but respectable amount of research on psychiatric and neurologic nosology. There is a also a small body of literature on endocrinologic nosology, but cardiologists almost never write about the nosology of heart disease. It does not keep them awake at night. Our understanding of the 20th-century epidemic of coronary artery disease (CAD), which dominates cardiology, has nevertheless been frustrated by problems of nosology. One of the purposes of this article is to discuss how our understanding of the epidemic has depended on classification of disease events and on the methods used to detect them. The other purpose is to show how current reclassifications of CAD and the major metabolic condition conducive to CAD, type 2 diabetes, each affect the practice of cardiology and medicine.

Results of a new rapid d-dimer assay (cardiac d-dimer) in the diagnosis of deep vein thrombosis

The objective was to evaluate the accuracy of a new full blood rapid D-dimer assay in the diagnosis of suspected deep vein thrombosis (DVT). In 100 consecutive patients with suspected DVT, clinical probability was staged according to a pretest score proposed by Wells. For the determination of plasma D-dimer, heparin and citrate blood samples were drawn, and Cardiac D-dimer, STA-LIA, and Tina-quant tests were performed. Final diagnosis was confirmed either by duplex sonography or ascending venography. DVT was diagnosed in 37%, thrombophlebitis in 10%, and no venous thromboembolism was diagnosed in 52%. In 2% pulmonary embolism was detected and one patient was dismissed before final diagnosis. Cardiac D-dimer assay from citrate tubes showed a sensitivity of 88.6%, a specificity of 54%, a positive predictive value of 57.4%, and a negative predictive value of 87.1%. Nearly identical results were observed with heparin tubes. Corresponding results were 88.6%, 48%, 52.5%, and 85.7% for STA-LIA and 88.6%, 46%, 53.4%, and 85.2% for Tina-quant, respectively. In conclusion, we can say that Cardiac D-dimer is a rapid, whole blood assay with a great potential for clinical use. It can help in diagnosing DVT from citrate as well as heparin tubes with comparable sensitivity, specificity, positive and negative predictive values as STA-LIA and Tina-quant tests.

Serum markers in the emergency department diagnosis of acute myocardial infarction

No currently used cardiac-specific serum marker meets all the criteria for an "ideal" marker of AMI. No test is both highly sensitive and highly specific for acute infarction within 6 hours following the onset of chest pain, the timeframe of interest to most emergency physicians in making diagnostic and therapeutic decisions. Patients presenting to the ED with chest pain or other symptoms suggestive of acute cardiac ischemia therefore cannot make a diagnosis of AMI excluded on the basis of a single cardiac marker value obtained within a few hours after symptom onset. The total CK level is far too insensitive and nonspecific a test to be used to diagnose AMI. It retains its value, however, as a screening test, and serum of patients with abnormal total CK values should undergo a CK-MBmass assay. Elevation in CK-MB is a vital component of ultimate diagnosis of AMI, but levels of this marker are normal in one fourth to one half of patients with AMI at the time of ED presentation. The test is highly specific, however, and an abnormal value (particularly when it exceeds 5% of the total CK value) at any time in a patient with chest pain is highly suggestive of an AMI. There have been several improvements of CK-MB assay timing and subform quantification that appear highly useful for emergency physicians. Rapid serial CK-MB assessment greatly increases the diagnostic value of the assay in a timeframe suitable for ED purposes but unfortunately still misses about 10% of patients ultimately diagnosed with acute MI. Assays of CK-MB subforms have very high sensitivity, and, although unreliable within 4 hours of symptom onset, have excellent diagnostic value at 6 or more hours after chest pain begins. Automated test assays recently have become available and could prove applicable to ED settings. The cardiac troponins are highly useful as markers of acute coronary syndromes, rather than specifically of AMI, and abnormal values at any time following chest pain onset are highly predictive of an adverse cardiac event. The ED applicability of the troponins is severely limited, however, because values remain normal in most patients with acute cardiac events as long as 6 hours following symptom onset. Myoglobin appeared promising as a marker of early cardiac ischemia but appears to be only marginally more sensitive than CK-MB assays early after symptom onset and less sensitive than CK-MB at 8 hours or more after chest pain starts. Rapid serial myoglobin assessment, however, appears highly useful as an early marker of AMI. The marker has a very narrow diagnostic window. The clinician is left with several tests that are highly effective in correctly identifying patients with AMI (or at high risk for AMI), but none that can dependably exclude patients with acute coronary syndromes soon after chest pain onset. A prudent strategy when assessing ED patients with chest pain and nondiagnostic ECGs is to order CK-MB and troponin values on presentation in the hope of making an early diagnosis of AMI or unstable coronary syndrome. Although it is recognized that normal values obtained within 6 hours of symptom onset do not exclude an acute coronary syndrome, patients at low clinical risk and having normal cardiac marker tests could be provisionally admitted to low-acuity hospital settings or ED observation. After 6 to 8 hours of symptom duration has elapsed, the cardiac-specific markers are highly effective in diagnosing AMI, and such values obtained can be used more appropriately to make final disposition decisions. At no time should results of serum marker tests outweigh ECG findings or clinical assessment of the patient's risk and stability.

Possible reasons for the prognostic value of troponin-T on admission in patients with ST-elevation myocardial infarction

BACKGROUND

In patients with acute myocardial infarction and ST-segment elevation, increased troponin-T (TnT) on admission implies an increased mortality.

OBJECTIVE

To elucidate the underlying mechanisms of the prognostic value of TnT.

METHODS AND RESULTS

One hundred and one patients were included and all received thrombolytic treatment. The patients were compared according to TnT level on admission (cut-off 0.1 microg/l). Elevation of TnT was associated with long-term mortality and also with longer delay, more episodes of chest pain during the last 24 h and fewer noninvasive signs of reperfusion at 90 min. In the group with elevated TnT, the coronary angiography at 24 h showed a strong trend towards lower patency in the infarct-related artery. TnT was also associated with increased infarct size if a higher cut-off level (0.43 microg/l) was used. In univariate analysis, elevated TnT, longer delay, repeated chest pain, Q-waves on admission and reduced left ventricular (LV) function were significantly associated with long-term mortality. In multivariate models, only reduced LV function and less than TIMI (thrombolysis in myocardial infarction) grade 3 flow turned out to be significant independent risk factors.

CONCLUSIONS

The prognostic value of TnT level on admission regarding long-term mortality was confirmed and seems mainly to be explained by its association with longer delay and recent myocardial damage, but its association with reduced effect of thrombolytic treatment, larger infarct size and impaired LV function might also be of importance.

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.

Vectorcardiography is superior to conventional ECG for detection of myocardial injury after coronary surgery

OBJECTIVE

The reliability of conventional scalar ECG for diagnosis of perioperative myocardial infarction (PMI) in cardiac surgery has been questioned. For the diagnosis of myocardial infarction in general vectorcardiography (VCG) is superior to ECG. Therefore, the usefulness of conventional VCG and computerized analysis of spatial VCG changes for diagnosis of PMI were studied.

DESIGN

VCG registrations were obtained from 218 patients undergoing coronary surgery. The spatial QRS vector loop area of each VCG registration was calculated and the loop area before surgery compared with the loop area after surgery. Conventional VCG criteria for myocardial infarction and set values for loop area reduction were related to sustained elevation of plasma troponin-T and clinical course.

RESULTS

Both conventional VCG criteria and spatial changes translated better than Q-waves on scalar ECG into elevation of biochemical markers of myocardial injury and impaired clinical course.

CONCLUSION

VCG appears superior to conventional ECG as regards detection of myocardial injury in coronary surgery. Computerized programs have facilitated the registration and the interpretation of VCG and this methodology deserves further evaluation in cardiac surgery.

Unstable angina pectoris and non-Q-wave myocardial infarction

Unstable angina pectoris and non-Q-wave myocardial infarction are clinical syndromes that share many pathophysiologic and clinical features. In the spectrum of coronary artery disease, these syndromes lie between chronic stable angina and Q-wave myocardial infarction. Although both conditions are associated with significant morbidity and mortality, patients presenting with these syndromes can be further risk stratified into higher and lower risk based on a number of readily available clinical features and biochemical parameters. Such risk stratification can allow for more tailored treatment and better resource allocation. Although routine early coronary angiography and revascularization has not been shown to be superior to conservative management, certain high-risk patients may benefit from a more aggressive strategy. Medical therapy with the use of antiplatelet, anticoagulant, and antiischemic agents remains the cornerstone of emergent treatment for patients presenting with these syndromes. The recent demonstration of a reduction in both morbidity and mortality with the glycoprotein IIb/IIIa antagonists has further expanded the armamentarium of available agents. Following initial stabilization, risk stratification with stress testing can help identify patients with a large residual ischemic burden who may benefit from coronary angiography with revascularization if feasible.

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.

Time-dependent diagnostic performance of a rapid troponin T version 2 bedside test in patients with acute coronary syndromes

In a prospective trial, the diagnostic performance of the second version of the troponin T rapid assay (Trop T; cutoff 0.2 microg/L) was compared with the quantitative cardiac-specific troponin T assay (cTnT ELISA; cutoff 0.1 microg/L) and other established cardiac markers such as CK, CK-MB activity, CK-MB mass and myoglobin. Additionally, a 30-day follow-up was performed to determine the suitability of the Trop T assay and the reference markers for short-term risk stratification. Two-hundred-and-eighty-six consecutive patients with chest pain and suspected acute myocardial infarction (AMI) were enrolled in two CCU departments. Serial blood specimens were taken at admission and at 3, 6, 12, 24, 48, 72 and 96 h after admission. According to the biochemical criterion CK-MB mass, the patients were classified as having AMI in 154 patients (54%), unstable angina (UAP) in 72 patients (27%) and no evidence for acute cardiac ischemia in 55 patients (19%). Analytical method comparison of Trop T with cTnT ELISA (cutoff 0.1 microg/L) showed a good agreement, Trop T yielded only 4% false-negative and 3% false-positive results. The diagnostic performance of Trop T for the detection of AMI was only slightly inferior compared to cTnT ELISA. Beyond 12 h after admission, Trop T and cTnT ELISA maintained a sensitivity close to 100%, whereas the sensitivity of the other cardiac markers decreased sharply. The diagnostic sensitivity of Trop T for the detection of minor myocardial damage in UAP patients was the same as for cTnT ELISA. Death within 30 days' follow-up occurred only in AMI patients with a positive Trop T test result within the first 6 h after admission. The admission Trop T and cTnT ELISA were the only significant biochemical predictors of major cardiac events. In conclusion, these data show that Trop T has similar diagnostic sensitivity as cTnT ELISA and is a useful tool to confirm acute or subacute myocardial infarction. Trop T is an excellent marker in detecting minor myocardial damage in UAP patients and is suitable for short-term risk stratification.

Risk stratification in unstable coronary artery disease--exercise test and troponin T from a gender perspective. FRISC-Study Group. Fragmin during InStability in Coronary artery disease

OBJECTIVES

The study was done to determine the prognostic yield of an early symptom-limited exercise test (ET) and measurement of troponin T (TnT) in men and women with unstable coronary artery disease (CAD), with special reference to gender differences.

BACKGROUND

Early risk assessment is essential for the application of appropriate treatment and further management in patients with unstable CAD. The early symptom-limited ET together with specific biochemical marker determination is an inexpensive, widely applicable method for early risk stratification. In women, however, the ET is considered less reliable, and there are few data on biochemical markers for risk stratification in women.

METHODS

In a substudy of the Fragmin during InStability in Coronary artery disease (FRISC I) trial, 395 women and 778 men with unstable CAD who performed an early ET were followed for six months. Blood samples for TnT determination were taken in 342 women and 621 men at inclusion.

RESULTS

Based on the ET results, low-, intermediate-, and high-risk response groups were identified with event rates of cardiac death or myocardial infarction (MI) of 1%, 9%, and 19%, respectively, among women and 8%, 14%, and 20%, respectively, among men. Patients who could not perform the ET had an event rate similar to the high-risk group. The TnT levels were divided into three groups: <0.06, 0.06-0.19, and > or = 0.20 microg/liter with event rates of 1%, 10%, and 18%, respectively, among women and 9%, 14%, and 18%, respectively, among men. Combining the ET results with TnT levels identified a low-risk group with an event rate of 3% in the male population and no events in the female population.

CONCLUSIONS

Direct comparison between men and women from the same population with a high pretest likelihood of disease suggests that both TnT and the early symptom-limited ET are at least as useful as prognostic risk indicators in women as they are in men.

Analytical and clinical performance of an improved qualitative troponin T rapid test in laboratories and critical care units

OBJECTIVE

To evaluate the performance of a visual troponin T rapid test in the hands of nontraditionally trained personnel of 2 critical care units in comparison to 3 laboratories.

METHODS

Method comparisons of the troponin T rapid test versus cardiac troponin T enzyme-linked immunosorbent assay were performed with 804 samples from 510 patients with suspected acute coronary syndromes. Cross-reactivity with skeletal troponin T was studied up to 5000 microg/L.

RESULTS

Laboratories and critical care units obtained comparable results in the analytical cutoff of the test (0.11 and 0. 10 microg/L) and in the diagnostic sensitivities in the detection of acute myocardial infarction (96% and 93% after 8 hours) and of high-risk patients with unstable angina pectoris (100% and 100%). Different percentages of false-positive results (0.2% and 3%) were found, which may reflect different objectives and strategies in these hospital units. The cross-reactivity with skeletal troponin T was less than 0.01%.

CONCLUSIONS

The troponin T rapid test gives reliable results not only when used by laboratory personnel experienced in the execution of analytical methods, but also in the hands of nurses and physicians working in clinical units outside the laboratory.

Laboratory diagnosis of patients with acute chest pain

The enzyme activities of creatine kinase (CK), its isoenzyme MB (CK-MB) and of lactate dehydrogenase isoenzyme 1 (LD-1) have been used for years in diagnosing patients with chest pain in order to differentiate patients with acute myocardial infarction (AMI) from non-AMI patients. These methods are easy to perform as automated analyses, but they are not specific for cardiac muscle damage. During the early 90's the situation changed. First creatine kinase MB mass (CK-MB mass) replaced the measurement of CK-MB activity. Subsequently cardiac-specific proteins troponin T (cTnT) and troponin I (cTnI) appeared on the scene, displacing LD-1 analysis. However, troponin concentrations in blood increase only from four to six hours after onset of chest pain. Therefore a rapid marker such as myoglobin, fatty acid binding protein or glycogen phosphorylase BB could be used in early diagnosis of AMI. On the other hand, CK-MB isoforms alone may also be useful in rapid diagnosis of cardiac muscle damage. Myoglobin, CK-MB mass, cTnT and cTnI are nowadays widely used in diagnosing patients with acute chest pain. Myoglobin is not cardiac-specific and therefore requires supplementation with some other analyses such as troponins to support the myoglobin value. Troponins are very highly cardiac-specific. Only the sera of some patients with severe renal failure, which requires hemodialysis, have elevated cTnT and/or cTnI without there being any evidence of cardiac damage. On the other hand, the latest studies have shown that elevated troponin levels in sera of hemodialysis patients point to an increased risk of future cardiac events in a similar manner to the elevated troponin values in sera of patients with unstable angina pectoris. In addition, the bedside tests for cTnT and cTnI alone or together with myoglobin and CK-MB mass can be used instead of quantitative analyses in the diagnosis of patients with chest pain. These rapid tests are easy to perform and they do not require expensive instrumentation. For routine clinical laboratory practice we suggest that in diagnosis of patients with chest pain, myoglobin and CK-MB mass measurements should be performed whenever they are requested (24 h/day) and cTnT or cTnI on admission to the hospital and then 4-6 and 12 hours later.

Comparison of troponin T versus creatine kinase-MB in suspected acute coronary syndromes

Limitations of creatine kinase-MB (CK-MB) have led to alternative biochemical markers, including troponin T (TnT), to detect myocardial necrosis. Limited data are available regarding the predictive value of this new marker in patients with chest pain of uncertain etiology. Therefore, we prospectively compared CK-MB and TnT in a broad population with suspected acute coronary syndromes, including those admitted to a short-stay chest pain unit. CK-MB, quantitative TnT levels, and a rapid bedside assay were performed at 0, 4, 8, and 16 hours. Adverse events, including infarction, recurrent ischemia, coronary surgery, need for catheterization and/or intervention, stroke, congestive heart failure, or death, were identified by chart review and by follow-up phone call at 6 months. Of 707 patients, 104 were excluded for creatinine >2 mg/dl or incomplete data, leaving a total cohort of 603 patients. Coronary Care Unit admissions were 18%, intermediate care admissions were 14%, telemetry admissions is 21%, and admissions to 24-hour short-stay area were 47%. TnT (at 0.1 ng/ml) and CK-MB were positive in a similar proportion of patients (20.4% and 19.7%, respectively); however, the patients identified by TnT and CK-MB were not identical. In-hospital adverse events occurred in 37.1% with no differences in positive predictive value for the markers (p = NS). If CK-MB and TnT were negative, the early adverse event rate was 27%. No cardiac marker was positive by 16 hours in 54.9% of patients with an adverse event. Six-month follow-up was obtained in 576 of the 603 patients (95.5%). One hundred fifty-five late adverse events occurred in 134 patients (23.3%) at an average of 3.3+/-2.5 months after discharge. If both markers were negative, the late event rate was 20.2% and did not increase in patients with positive CK-MB or TnT >0.2 ng/ml. However, the late event rate was substantially higher (52.9%) in those with intermediate TnT levels of 0.1 to 0.2 ng/ml (p = 0.002). Thus, TnT is a suitable alternative to CK-MB in patients with suspected acute coronary syndromes. The rapid bedside assay is comparable to quantitative TnT and may enable early diagnosis and triage. A negative cardiac marker value (TnT or CK-MB) does not necessarily confer a low risk of complication in patients presenting with acute chest pain to an emergency department.