Myoglobin, creatine kinase MB, and cardiac troponin-I to assess reperfusion after thrombolysis for acute myocardial infarction: results from TIMI 10A

Cardiac Troponin Biosensor Designs: Current Developments and Remaining Challenges

Acute myocardial infarction (AMI) is considered as one of the main causes of death, threating human lives for decades. Currently, its diagnosis relies on electrocardiography (ECG), which has been proven to be insufficient. In this context, the efficient detection of cardiac biomarkers was proposed to overcome the limitations of ECG. In particular, the measurement of troponins, specifically cardiac troponin I (cTnI) and cardiac troponin T (cTnT), has proven to be superior in terms of sensitivity and specificity in the diagnosis of myocardial damage. As one of the most life-threatening conditions, specific and sensitive investigation methods that are fast, universally available, and cost-efficient to allow for early initiation of evidence-based, living-saving treatment are desired. In this review, we aim to present and discuss the major breakthroughs made in the development of cTnI and cTnT specific biosensor designs and analytical tools, highlighting the achieved progress as well as the remaining challenges to reach the technological goal of simple, specific, cheap, and portable testing chips for the rapid and efficient on-site detection of cardiac cTnI/cTnT biomarkers in order to diagnose and treat cardiovascular diseases at an incipient stage.

Atherosclerosis Risk Factors in Patients with Reactive Hypoglycemia

PURPOSE

Glucose metabolism disorders are an established risk factor for atherosclerosis. Although reactive hypoglycemia (RH) can be classified as one of these disorders, its role as a potential atherosclerosis risk factor remains unclear. The aim of the study was to assess whether patients with RH have a higher risk of atherosclerosis.

PATIENTS AND METHODS

We recruited 178 patients (N=178) with suspected RH who were hospitalized after 2014 and underwent a prolonged 5-hour oral glucose tolerance test. The study cohort was divided into 2 groups depending on the results of the oral glucose tolerance test: Group 1 - subjects without RH (n=44), Group 2 -subjects with RH (n=134).

RESULTS

The analyzed groups differed significantly in terms of the following risk factors for atherosclerosis: high-density lipoprotein (HDL) cholesterol levels (54.3±18.8 mg/dL vs 63±18.5 mg/dL, p=0.003) and atherogenic indices (Castelli I: 3.7±1.2 vs 3.1±1.3, p=0.004; Castelli II: 2.1±0.9 vs 1.7±0.9, p=0.007; the atherogenic index of plasma: 0.34±0.33 vs 0.18±0.3, p=0.006; and the atherogenic coefficient: 2.7±1.2 vs 2.1±1.3, p=0.004). Univariate logistic regression showed that RH should not be considered to be a predictor of an increased atherogenic index of plasma (odds ratio [OR]=0.3 [95% confidence interval [CI] [0.16-0.7], p=0.002). Multivariate logistic regression revealed triglyceride levels (OR 1.14 [1.07-1.2], p=0.001) and body weight (OR 1.07 [1.03-1.12], p=0.002) to be independent risk factors for atherosclerosis.

CONCLUSION

Atherosclerosis risk factors are no more prevalent in patients with RH. RH does not increase the risk of an abnormal atherogenic index of plasma.

A graphene oxide/gold nanoparticle-based amplification method for SERS immunoassay of cardiac troponin I

A multiple signal amplification of a SERS biosensor was developed for sensitive detection of cTnI with the aid of GO/AuNP complexes.

Integrative volumetric bar-chart chip for rapid and quantitative point-of-care detection of myocardial infarction biomarkers

Here we developed an integrated volumetric bar-chart chip (IV-Chip) technology by integration of our previous V-Chip with a fluid handling design to generate an instrument-free POC device and greatly reduce the detection time and effort. The IV-Chip test requires only 1 μL of serum separated from finger-prick blood. The serum sample and ELISA reagents are directly loaded into the device using a pipette, and a shift of the two layers of the device generates homogeneous liquid segments in the microfluidic channel. Under vacuum pressure generated by a regular syringe, the segments flow into the ELISA wells in sequence and a sandwich ELISA reaction takes place. As a result of the automated washing and reacting strategy, the IV-Chip allows rapid tests for myocardial infarction biomarkers, and turnaround time is greatly reduced to 15 min. The specificity and accuracy of quantitative multiplex detection of MI biomarkers CK-MB, troponin I and myoglobin, are 87.5% and 95.8%, respectively.

Cardiac troponin elevation pattern in patients undergoing a primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: characterization and relationship with cardiovascular events during hospitalization

HYPOTHESIS

We aimed to describe the kinetics and associated prognostic implications of the cardiac troponin release curve after a primary percutaneous coronary intervention (PPCI) in patients presenting with ST-segment elevation myocardial infarction (STEMI).

PATIENTS AND METHODS

We prospectively determined, in a prespecified timely manner, serial cardiac troponin I levels and obtained clinical, ECG, and echocardiographic data from 175 consecutive patients hospitalized with STEMI who underwent PPCI. The median peak troponin levels and time until troponin peaking were determined.

RESULTS

The troponin elevation curve following PPCI was single peaked, with a median value measuring 715 times the upper normal limit and a median peaking time of 8 h. Later-peaking troponin levels were associated with a TIMI flow grade of 0/1 at the initiation of angiography and with lack of at least 70% regression in the ST-elevation on the first post-PPCI ECG. Higher peak values were similarly associated with these two parameters as well as with a lower blush score and with distal embolization during PPCI. Both higher peak values and later peaking of troponin were associated independently with higher occurrence of the combined adverse cardiovascular event outcomes consisting of death, congestive heart failure, and recurrent infarction.

CONCLUSION

The cardiac troponin elevation curve following PPCI for STEMI shows a single peak and is affected by the adequacy of myocardial reperfusion. This method can serve as a simple surrogate for risk stratification of patients with STEMI who undergo PPCI.

The cardioprotective effect of danshen and gegen decoction on rat hearts and cardiomyocytes with post-ischemia reperfusion injury

Background

Danshen (Salviae Miltiorrhizae Radix) and Gegen (Puerariae Lobatae Radix) have been used for treating heart disease for several thousand years in China. It has been found that a Danshen and Gegen decoction (DG) exhibiting an anti-atherosclerosis effect, which improves the patients’ heart function recovery. Pre-treatment with DG was reported to have protective effects on myocardium against ischemia/reperfusion injury. In the present study, we aim to investigate the post-treatment effect of DG on ischemic-reperfusion injuries ex vivo or in vitro and the underlying mechanisms involved.

Methods

The rat heart function in an ischemia and reperfusion (I/R) model was explored by examining three parameters including contractile force, coronary flow rate and the release of heart specific enzymes within the heart perfusate. In vitro model of hypoxia and reoxygenation (H/R), the protective effect of DG on damaged cardiomyocytes was investigated by examining the cell structure integrity, the apoptosis and the functionality of mitochondria.

Results

Our results showed that DG significantly improved rat heart function after I/R challenge and suppressed the release of enzymes by damaged heart muscles in a dose-dependent manner. DG also significantly inhibited the death of cardiomyocytes, H9c2 cells, with a H/R challenge. It obviously decreased cell apoptosis, protected the mitochondrial function and cell membrane skeleton integrity on H9c2 cells. The cardio-protection was also found to be related to a decrease in intracellular calcium accumulation within H9c2 cells after I/R challenge.

Conclusion

The potential application of DG in treating rat hearts with an I/R injury has been implied in this study. Our results suggested that DG decoction could act as an anti-apoptotic and anti-ion stunning agent to protect hearts against an I/R injury.

[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.

Evaluation of coronary artery patency using cardiac markers

The availability of a reliable marker of infarct-related artery (IRA) patency status may permit early identification of patients with patent IRA, for whom repeat thrombolysis or rescue percutaneous coronary intervention (PCI) may not be necessary. We found that the ratio of serum myoglobin levels obtained before and 60-min after initiation of thrombolytic therapy provides a useful indication of the IRA patency status. When the 60-min myoglobin ratio was >4.0, the probability of a patent IRA was 90%, suggesting that emergency coronary angiography to determine their IRA status may be unnecessary when this pattern of release of myoglobin is observed. The low specificity of this marker could be addressed by its combined use with other noninvasive tests such as ST-segment resolution and the persistence of chest pain at the time of angiography.

Usefulness of rapid quantitative measurement of myoglobin and troponin T in early diagnosis of acute myocardial infarction

BACKGROUND

New equipment, the Cardiac Reader(TM), which can measure blood concentrations of troponin T (T) and myoglobin (M) in only 15 min at the bedside was evaluated for early diagnosis of acute myocardial infarction (AMI).

METHODS AND RESULTS

A total of 34 consecutive patients with AMI who came to hospital within 24 h after onset were studied. Blood samples were collected from the patients at admission and 6, 12, 24, 48 h after onset to qualitatively and quantitatively measure T, M and creatine kinase-MB fraction. There were 20 patients with positive results by qualitative troponin T test and 29 with positive results by quantitative test. Of the patients who visited hospital within 3 h of onset, 17% were positive by the qualitative test and 67% cases had positive results in the quantitative test. The patients were divided into 2 groups according to the flow grade in the infarct-related coronary artery. In the TIMI 0-1 group (n=28), serum myoglobin concentrations were higher than in the TIMI 3-4 group (n=6) at admission and at their peak.

CONCLUSION

The rapid quantitative test of T and M is useful for early diagnosis of AMI and as an indicator of its severity, which can be evaluated from the myoglobin concentration in the hyper-acute phase.

Myoglobin--a marker of reperfusion and a prognostic indicator in patients with acute myocardial infarction

BACKGROUND

Early noninvasive identification of patients with occluded infarct-related arteries after thrombolysis has important prognostic and therapeutic implications. Recent reports indicate that plasma kinetics of cardiac marker proteins could be very useful in diagnosis of myocardial reperfusion. Although angiographic assessment remains the ideal procedure for determining patency, it is expensive, invasive, not within the reach of most patients in developing countries, and the long-term follow-up data are still sparse.

HYPOTHESIS

The present study was undertaken to investigate whether plasma kinetics of myoglobin in conjunction with clinical markers and another biochemical marker, creatine kinase, could be used to predict myocardial reperfusion more accurately and to investigate the correlation between myoglobin release after thrombolysis and mortality in patients with acute myocardial infarction (AMI) over a follow-up period of 18 months.

METHODS

Eighty-three consecutive patients with AMI receiving streptokinase treatment were studied for plasma kinetics of myoglobin in conjunction with clinical markers and creatine kinase to predict reperfusion and were followed for a period of 18 months.

RESULTS

Increased baseline mean +/- standard deviation levels of myoglobin were observed among "nonresponders" to streptokinase treatment compared with "responders" (469 +/- 386 microg/l vs. 270 +/- 211 microg/l). There was significantly more release of myoglobin following thrombolytic treatment among the responders than among the nonresponders (mean ratio of myoglobin levels at 90 min to 0 min 6.01 +/- 9.2 vs. 1.03 +/- 0.64). In a follow-up of 61 patients over a period of 18 months, 31% mortality was observed in the nonresponder group compared with 11.7% in the responder group. In responders, the mean ratio of myoglobin levels at 90 and 0 min was significantly less among those who died (p = 0.019) than among those who survived.

CONCLUSION

A myoglobin release profile in combination with other clinical markers offers inexpensive, noninvasive, and a reasonably reliable way of assessing coronary artery patency after thrombolytic treatment.

Biochemical and immunological changes in chickens experiencing pulmonary hypertension syndrome caused by Enterococcus faecalis

Recent studies have proven that Enterococcus faecalis (1.5 x 10(7) live bacteria from a tryptic broth culture given s.c. or intra-abdominally (IA) to 5-wk-old broilers) caused pulmonary hypertension syndrome (PHS) in 97% of the birds within 48 h. Definitive diagnosis of PHS was made at necropsy by observing a cavity on the surface of the right ventricular wall and by increased ratio of left ventricular weight to total ventricular weight. A nonlethal method of diagnosing PHS would enhance the study of PHS and alert production poultrymen to the onset of ascites (waterbelly), which is the cuLminating event of PHS. In the present study, serum hemoglobin, glucose, protein, cholesterol, aspartate amino transferase (AST) and creatine kinase-MB (myocardial in origin) enzymes, differential leukocyte numbers, and specific antibody levels against Ent. faecalis were evaluated as nonlethal diagnostic indicators of PHS. Decreases in serum protein and cholesterol of 3 and 10%, respectively, plus increases in percentages of basophils and monocytes of 18 and 40%, respectively, appear to indicate that PHS has been initiated. An agglutinating antibody, specific against Ent. faecalis, but not against other closely related bacteria, has been developed. Presence of this antibody in a bird means that the bird has previously encountered Ent. faecalis. Thus, this antibody may become a diagnostic for PHS in fast-growing chickens.

Myoglobin levels at 12 hours identify patients at low risk for 30-day mortality after thrombolysis in acute myocardial infarction: a Thrombolysis in Myocardial Infarction 10B substudy

OBJECTIVE

We sought to identify, by use of serum cardiac markers, patients at low risk for 30-day mortality after ST-segment elevation myocardial infarction.

BACKGROUND

Baseline cardiac markers are currently used to identify patients at increased risk for short-term events. We hypothesized that serum markers measured after treatment could identify patients at low risk for 30-day mortality.

METHODS

A total of 839 patients from the Thrombolysis in Myocardial Infarction (TIMI) 10B study had myoglobin, cardiac-specific troponin-I, creatine kinase (CK)-MB measurements at the following time points; baseline, 90 minutes, and 3 and 12 hours after thrombolysis. By use of receiver operating characteristic analysis, thresholds were derived to predict 30-day mortality with at least 95% negative predictive value.

RESULTS

Ninety minutes after thrombolysis myoglobin was superior to troponin-I or CK-MB in identifying patients at low risk for mortality. The 30-day mortality for 12-hour myoglobin < or = 239 ng/mL was 1.4% compared with 9.1% for levels > 239 ng/mL (P < .001). For 12-hour troponin-I (threshold 81.5 ng/mL), mortality was 1.9% versus 6.6% (P = .001) if above threshold; similarly for CK-MB at 12 hours (threshold 191 ng/mL) it was 3.3% versus 7.9% (P = .02). Multivariate analysis of baseline and posttreatment cardiac markers, age, sex, infarct artery location, and 90-minute TIMI flow grade identified only 12-hour myoglobin among the cardiac markers as independently predicting a low 30-day mortality (odds ratio 0.11, 95% confidence interval 0.02-0.50, P < .004).

CONCLUSION

Serum cardiac markers can identify greater than two thirds of patients at low risk for 30-day mortality. A low 12-hour myoglobin level (< or = 239 ng/mL in this substudy) identifies such patients at low risk and could potentially assist in early risk stratification and triage after ST-segment elevation myocardial infarction.

Assessment of coronary reperfusion in patients with myocardial infarction using fatty acid binding protein concentrations in plasma

OBJECTIVE

To examine whether successful coronary reperfusion after thrombolytic treatment in patients with confirmed acute myocardial infarction can be diagnosed from the plasma marker fatty acid binding protein (FABP), for either acute clinical decision making or retrospective purposes.

DESIGN

Retrospective substudy of the GUSTO trial.

SETTING

10 hospitals in four European countries.

PATIENTS

115 patients were treated with thrombolytic agents within six hours after the onset of acute myocardial infarction. Patency of the infarct related artery was determined by angiography within 120 minutes of the start of thrombolysis.

MAIN OUTCOME MEASURES

First hour rate of increase in plasma FABP concentration after thrombolytic treatment, compared with increase in plasma myoglobin concentration and creatine kinase isoenzyme MB (CK-MB) activity. Infarct size was estimated from the cumulative release of the enzyme alpha hydroxybutyrate dehydrogenase in plasma during 72 hours, or from the sum of ST segment elevations on admission. Logistic regression analyses were performed to construct predictive models for patency.

RESULTS

Complete reperfusion (TIMI 3) occurred in 50 patients, partial reperfusion (TIMI 2) in 36, and no reperfusion (TIMI 0+1) in 29. Receiver operating characteristic (ROC) curve analyses showed that the best performance of FABP was obtained when TIMI scores 2 and 3 were grouped and compared with TIMI score 0+1. The performance of FABP as a reperfusion marker was improved by combining it with alpha hydroxybutyrate dehydrogenase infarct size, but not with an early surrogate of infarct size (ST segment elevation on admission). In combination with infarct size FABP performed as well as myoglobin (areas under the ROC curve 0.868 and 0.857, respectively) and better than CK-MB (area = 0.796). At optimum cut off levels, positive predictive values were 97% for FABP, 95% for myoglobin, and 89% for CK-MB (without infarct size, 87%, 88%, and 87%, respectively), and negative predictive values were 55%, 52%, and 50%, respectively (without infarct size, 44%, 42%, and 34%).

CONCLUSIONS

FABP and myoglobin perform equally well as reperfusion markers, and successful reperfusion can be assessed, with positive predictive values of 87% and 88%, or even 97% and 95% when infarct size is also taken into account. However, identification of non-reperfused patients remains a problem, as negative predictive values will generally remain below 70%.

Tenecteplase

Each month, subscribers to The Formulary® Monograph Service receive five to six researched monographs on drugs that are newly released or are in late Phase III trials. The monographs are targeted to your Pharmacy and Therapeutics Committee. Subscribers also receive monthly one-page summary monographs on the agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation (DUE) is also provided each month. The monographs are published in printed form and on diskettes that allow customization. Subscribers to the The Formulary Monograph Service also receive access to a pharmacy bulletin board called The Formulary Information Exchange (The F.I.X). All topics pertinent to clinical pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The October 2000 Formulary monographs are argatroban, tinzaparin sodium, balsalazide, methylphenidate extended-release tablets, and eflornithine hydrochloride cream. The DUE is on argatroban.

Tenecteplase

Each month, subscribers to The Formulary® Monograph Service receive five to six researched monographs on drugs that are newly released or are in late Phase III trials. The monographs are targeted to your Pharmacy and Therapeutics Committee. Subscribers also receive monthly one-page summary monographs on the agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation (DUE) is also provided each month. The monographs are published in printed form and on diskettes that allow customization. Subscribers to the The Formulary Monograph Service also receive access to a pharmacy bulletin board called The Formulary Information Exchange (The F.I.X). All topics pertinent to clinical pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The October 2000 Formulary monographs are argatroban, tinzaparin sodium, balsalazide, methylphenidate extended-release tablets, and eflornithine hydrochloride cream. The DUE is on argatroban.

Heart-type fatty acid binding protein as a marker of reperfusion after thrombolytic therapy

Accurate, rapid, and simple noninvasive measures of infarct-related artery (IRA) patency are needed to identify patients with failed coronary reperfusion for rescue percutaneous coronary intervention (PCI). Heart-type Fatty Acid Binding Protein (H-FABP) is a small, cytosolic protein found in high concentrations in the myocardium. We evaluated the efficacy of H-FABP as a marker for successful reperfusion after thrombolysis. Fifty-eight subjects from the TIMI 14 trial had H-FABP and myoglobin concentrations measured at baseline (immediately prior to thrombolysis) and 60, 90, and 180 min after thrombolysis. All patients underwent coronary angiography at 90 min. By 60 min after thrombolysis, median concentrations of H-FABP and myoglobin were significantly higher in patients with a patent IRA than in those with an occluded IRA (P<0.01 for each). Similarly, the 60 and 90 min/baseline H-FABP and myoglobin ratios were significantly higher among patients with a patent IRA (P<0.01 for each). There were no significant differences in marker concentrations or ratios between patients with TIMI grade 2 and TIMI grade 3 flow. The area under the ROC curve tended to be greater for the 60 and 90 min/baseline myoglobin ratios than for similar ratios of H-FABP (0.71 and 0.73 vs. 0.64 and 0.62; P=ns). In conclusion, successful reperfusion can be detected within the first 60 min after thrombolysis with either H-FABP or myoglobin. Despite a favorable kinetic profile, however, H-FABP does not appear to represent a significant advance over myoglobin in the noninvasive detection of reperfusion after thrombolysis.

Cardiac troponin I is reliable with immediate but not medium-term cardiac complications after abdominal aortic repair

BACKGROUND

The diagnosis of cardiac complications is particularly challenging in the postoperative course of non-cardiac surgery. Follow-up of patients suggests that silent or symptomatic postoperative myocardial infarction have similar short-term outcomes. Cardiac troponin I (cTnI) has been reported as being a sensitive and specific marker of these complications.

METHODS

We conducted a prospective study to determine the cut-off values of cTnI which may predict cardiac complications, i: in the postoperative period until discharge, and ii: during a 1-year period after aortic surgery. Three hundred and twenty-nine consecutive patients undergoing infrarenal aortic surgery were included over a 2-year period in a single center. cTnI was measured at recovery and on the 1st, 2nd and 3rd postoperative days. The presence or absence of cardiac complications was classified by reviewers who had no knowledge of cTnI. For evaluation of the ideal discrimination value of cTnI between the complicated and uncomplicated patient groups, we calculated receiver-operator characteristics for the mean values of the peak of cTnI.

RESULTS

Thirteen patients (4%) developed 19 postoperative cardiac complications. Thirteen patients (4%) died in the postoperative period. Nine patients (3%) developed 10 cardiac complications during the 1-year follow-up in 316 patients. In 280 patients, cTnI was below 0.5 ng/ml, in 22 patients between 0.5 and 1.5 ng/ml and the 27 remaining patients had a cTnI higher than 1.5 ng/ml. The area under the curve for postoperative cardiac complications was 0.84 (SD=0.21). A limit value of 0.54 ng/ml yielded a sensitivity of 75% and a specificity of 89%. The area under the curve for late cardiac complications was 0.45 (SD= 0.13).

CONCLUSION

A cTnI level greater than 0.54 ng/ml appears to be correlated with the occurrence of cardiac complications in the period until discharge, but no value of cTnI is predictive of late cardiac complications occurring in the 1st year after aortic surgery.

Resolution of ST-segment elevation in acute myocardial infarction--early prognostic significance after thrombolytic therapy. Results from the COBALT trial

In acute myocardial infarction, early identification of patients at a high mortality risk is important for planning further therapeutic strategies. Previous studies have demonstrated that the extent of early resolution of ST-segment elevation may represent a simple, quick and noninvasive assessment to identify high risk groups of patients. In a subgroup of the COBALT Study population (Continuous Infusion vs Double Bolus Administration of Alteplase), ST-segment elevation was measured before and 90 to 120 minutes after treatment with alteplase. The subgroup of n = 1,760 patients was not different from the total COBALT population of n = 7169 patients regarding most clinical parameters except Killip Class before treatment. However, the overall 30-day mortality differed significantly between the main study and the substudy (7.76% vs 3.52%; p < 0.001). Three groups of ST-segment resolution were defined: 1. complete resolution (resolution > or = 70%; 762 patients), 2. partial resolution (< 70% and > 30%; 491 patients), 3. no resolution (< 30%; 507 patients). Mortality rate at 30 days for complete, partial and no resolution of ST-segment elevation was 1.31%, 4.28% and 6.11%, respectively (p < 0.001). While this significant correlation between the extent of ST-segment resolution and mortality could be observed for inferior acute myocardial infarction, it could not be found in patients with anterior acute myocardial infarction. This in part may be due to a selection bias that leads to an extremely divergent mortality rate of anterior acute myocardial infarction in the main study and the substudy (10.1% vs 3.94%; p < 0.0001). Despite this limitation, resolution of ST-segment elevation in acute myocardial infarction after thrombolytic therapy allows to identify patients at a high mortality risk and may help to select patients for early invasive procedures such as PTCA. Patients with complete ST-segment resolution showed a particularly low mortality rate, irrespective of the alteplase regimen used (front-loaded alteplase vs double bolus alteplase).

Myoglobin, creatine-kinase-MB and cardiac troponin-I 60-minute ratios predict infarct-related artery patency after thrombolysis for acute myocardial infarction: results from the Thrombolysis in Myocardial Infarction study (TIMI) 10B

OBJECTIVES

We examined the diagnostic performance of serum myoglobin, creatine-kinase-MB (CK-MB) and cardiac troponin-I (cTnI) for predicting the infarct-related artery (IRA) patency in patients receiving TNK-tissue plasminogen activator (TNK-tPA) therapy for acute myocardial infarction (AMI) in the Thrombolysis in Myocardial Infarction (TIMI) 10B trial.

BACKGROUND

A reliable noninvasive serum marker of IRA patency is desired to permit early identification of patients with a patent IRA after thrombolysis.

METHODS

We measured myoglobin, CK-MB and cTnI concentrations in sera obtained just before thrombolysis (T0) and 60 min later (T60) in 442 patients given TNK-tPA and who underwent coronary angiography at 60 min.

RESULTS

Angiography at 60 min showed a patent IRA (TIMI flow grade 2, 3) in 344 and occluded IRA (TIMI flow grade 0, 1) in 98 patients. The median serum T60 concentration, the ratio of the T60 and T0 serum concentration (60-min ratio) and the slope of increase over 60 min for each serum marker were significantly higher in patients with patent arteries compared with patients with occluded arteries. The area under the receiver-operating characteristic (ROC) curve for diagnosis of occlusion was 0.71, 0.70 and 0.71 for the 60-min ratio of myoglobin, cTnI and CKMB, respectively. The 60-min ratios of > or =4.0 for myoglobin, > or =3.3 for CK-MB and > or =2.0 for cTnI yielded a probability of patency of 90%, 88% and 87%, respectively.

CONCLUSIONS

The diagnostic performance of serum myoglobin, CK-MB and cardiac troponin-I (cTnI) 60-min ratios was similar. The probability of a patent IRA was very high (90%) in patients with 60-min myoglobin ratio > or =4.0, and early invasive interventions to establish IRA patency may not be necessary in this group. Serum marker determinations at baseline and 60-min after thrombolysis may permit rapid triage of patients receiving thrombolytic therapy by ruling out IRA occlusion.

Cardiac troponin I and troponin T: recent players in the field of myocardial markers

The troponin (Tn) complex consists of three subunits referred to as TnT, TnI and TnC. Myocardium contains TnT and TnI isoforms which are not present in skeletal muscles and which can be separated from the muscular isoforms by immunological techniques. Using commercially available immunoassays, clinical laboratories are able to determine cardiac TnT and TnI (cTnT and cTnI) quickly and reliably as classical cardiac markers. After acute myocardial infarction, cTnT and cTnI concentrations start to increase in serum in a rather similar way than CK-MB, but return to normal after longer periods of time (approximately one week). Because of their excellent cardiac specificity, Tn subunits appear ideally suited for the differential diagnosis of myocardial and muscular damage, for example in noncardiac surgery patients, in patients with muscular trauma or with chronic muscular diseases, or after intense physical exercise. cTnT and cTnI may also be used for detecting evidence of minor myocardial damage: therefore they have found new clinical applications, in particular risk stratification in patients with unstable angina. In spite of the possible reexpression of cTnT in human skeletal muscles, and of the lack of standardization of cTnI assays, Tn subunits are not far to meet the criteria of ideal markers for acute myocardial injury. Only an insufficient sensitivity in the first hours following the acute coronary syndroms requiries to maintain an early myocardial marker in the cardiac panel for routine laboratory testing.