Sensitivity and long-term prognostic value of cardiac troponin-I increase shortly after percutaneous transluminal coronary angioplasty

Cardiac Troponin I Increase After Successful Percutaneous Coronary Angioplasty: Predictors and Long-Term Prognostic Value

After successful percutaneous coronary interventions (PCI), elevations of cardiac enzymes are not rare, but it is still not clear whether those elevations are associated with adverse late outcome. The purpose of the study was to investigate the relation between cardiac troponin I (cTn-I) increase after successful percutaneous intervention and late outcome. The study consisted of 100 consecutive patients (mean age 56 ±9.8, 84% male) who had successful elective coronary balloon angioplasty with or without stent implantation. Patients with stable angina (n=54) and unstable angina (n=46) were included in the study. Blood samples for measurement of cTn-I were taken before and immediately after the procedure, and every 6 hours for the first 24 hours. Patients with preprocedural cTn-I elevation were excluded from the study. Postprocedural cTn-I elevation was detected in 34 patients (34%, troponin (+) group) and cTn-I levels were normal in 66 patients (66%, troponin (-) group). Logistic regression analysis showed that intervention in patients with unstable angina, stent implantation following balloon dilation, and maximal inflation pressure were the predictors of cTn-I elevation (p=0.035, p=0.038, and p=0.014, respectively). During the prospective follow-up period for 21 ±7.5 months, the incidence of major cardiac events including recurrent angina, acute myocardial infarction, death, and revascularization were not different in patients with and without cTn-I elevation. Overall, major cardiac events occurred in 9 patients (26%) in the troponin (+) group and in 13 patients (20%) in the troponin (-) group. Kaplan-Meier survival analysis showed that cTn-I elevation was not an important correlate of overall cardiac events (log-rank: 1.66, p=0.19). The authors conclude that postprocedural cTn-I elevation is related to unstable angina, stent implantation following predilation, and inflation pressure, and there is no association with minor myocardial injury occurring after successful percutaneous coronary intervention and late adverse cardiac events.

Diagnostic and prognostic value of minor elevated cardiac troponin levels for percutaneous coronary intervention-related myocardial injury: a prospective, single-center and double-blind study

Cardiac troponin-I (cTnI) and -T (cTnT) are sensitive and specific markers of myocardial injury. However, the role of increased cTnI and cTnT in percutaneous coronary intervention (PCI)-related myocardial injury remains controversial. In this prospective, single-center and double-blind study, we aimed to determine the diagnostic and prognostic value of cTnI as well as cTnT (cTns) in PCI-related myocardial injury in a Chinese population. A total of 1,008 patients with stable angina pectoris and non-ST-segment elevation acute coronary syndrome were recruited. The levels of cTnI and cTnT were examined before and after PCI. All patients were followed up for 26±9 months to observe the incidence of major adverse cardiac events (MACEs). Our results showed that post-PCI cTnI and/or cTnT levels were increased to more than the 99^th percentile upper reference limit (URL) in 133 (13.2%) patients, among which 22 (2.2%) were more than 5 × 99^th percentile URL. By univariate analysis, an elevation in cTns after PCI was not an independent predictor of increased MACEs, HR 1.35 (P  =  0.33, 95%CI: 0.74–2.46). In conclusion, our data demonstrate that the incidence of PCI-related myocardial injury is not common in a Chinese population and minor elevated cTns levels may not be a sensitive prognostic marker for MACEs.

Prognostic value of cardiac troponin-I or troponin-T elevation following nonemergent percutaneous coronary intervention: a meta-analysis

OBJECTIVES

The aim of this meta-analysis was to assess the prevalence and prognostic value regarding mortality of cTnT or cTnI elevations after nonemergent percutaneous coronary intervention (PCI) in a large number of cohort/registry studies.

BACKGROUND

Routine cardiac troponin measurement after elective PCI has been controversial among interventionalists. Recent studies have provided conflicting data in regard to predictive value of cardiac troponin-T (cTnT) and troponin-I (cTnI) elevation after non-emergent PCI.

METHODS

Electronic and manual searches were conducted of all published studies reporting on the prognostic impact of cTnT or cTnI elevation after elective PCI. A meta-analysis was performed with all-cause mortality at follow-up as the primary endpoint.

RESULTS

We identified 22 studies, involving 22,353 patients, published between 1998 and 2009. Postprocedural cTnT and cTnI were elevated in 25.9% and 34.3% of patients, respectively. Follow-up period ranged from 3 to 67 months (mean: 17.7 ± 14.9 months). The results showed no heterogeneity among the trials (Q-test: 25.39; I(2) : 17%; P = 0.23). No publication bias was detected (Egger's test: P = 0.16). The long-term all-cause mortality in patients with cTnI or cTnT elevation after PCI (5.8%) was significantly higher when compared to patients without cTnI or cTnT elevation (4.4%); OR 1.45 (95% CI: 1.22-1.72), P < 0.01. In addition, the postprocedural composite adverse clinical events of all-cause mortality or myocardial infarction (MI) in patients with cTnI or cTnT elevation after PCI (9.2%) was significantly higher when compared to patients without cTnI or cTnT elevation (5.3%); OR 1.77 (95% CI: 1.48-2.11), P < 0.01.

CONCLUSIONS

The current meta-analysis indicates that cTnI or cTnT elevation after nonemergent PCI is indicative of an increase in long-term all-cause mortality as well as the composite adverse events of all-cause mortality and MI. Efforts to routinely monitor periprocedural cTn levels along with more intensive outpatient monitoring/treatment of patients with cTn elevations may help to improve the long-term adverse outcomes in these patients following non-emergent PCI.

Coronary stent length predicts PCI-induced cardiac myonecrosis

BACKGROUND

Myocardial necrosis complicates one-third of percutaneous coronary intervention (PCI, MI4a) and may adversely affect the outcome. We assessed the angiographic variables associated with MI4a that may help to identify those at highest risk.

METHODS AND RESULTS

Cardiac troponin-I (cTnI) was measured after PCI in 243 patients undergoing elective PCI. Patients were grouped according to post-procedure cTnI result: minor or no elevation (<0.1 ng/ml), PCI-related MI4a (0.1 to <0.78 ng/ml) and WHO defined MI by the Troponin-I Ultra method (>or=0.78 ng/ml). Angiographic variables were analyzed in blinded manner and correlated with cTnI rise. Minor or no cTnI elevation after PCI occurred in 116 of 243 (48%) patients, MI4a in 65 of 243 (27%) and WHO defined MI in 62 of 243 (25%). Independent predictors of MI4a included stent length [odds ratio (OR) 1.04 per mm; P=0.0015], X-ray screening time (OR 1.05 per minute; P=0.016) and procedural chest pain requiring opiates (OR 7.92; P=0.00066). The stenting of proximal vessel segments with fewer collaterals (large myocardial area at risk), diminished myocardial perfusion (P=0.0065) and side branch compromise were associated with cTnI elevation. Clinical events were more frequent following MI4a (9.4 vs. 3.4%, P=0.07).

CONCLUSION

These data show that cTnI release after elective PCI is predominantly related to stent length. Minimizing the stent length deployed may reduce the cTnI release and improve prognosis.

Relation of troponin I levels following nonemergent percutaneous coronary intervention to short- and long-term outcomes

Increases of creatine kinase (CK) and CK-MB cardiac enzymes after nonemergent percutaneous coronary intervention (PCI) have been associated with an increased risk of cardiovascular events during follow-up. However, there are limited data about the incidence and prognostic significance of an isolated increase of cardiac troponin I (cTnI) without an increase in CK-MB after PCI. The aim of this study was to evaluate the impact of an isolated cTnI increase on long-term survival in patients undergoing nonemergent PCI with normal CK-MB levels after PCI. Using the 2004/2005 Cornell Angioplasty Registry, we evaluated the clinical outcomes in 1,601 patients (undergoing elective or urgent PCI) with normal preprocedure cTnI and CK-MB and normal CK-MB levels after the procedure. Patients were divided into 2 groups based on the presence of cTnI increase after PCI. The mean follow-up period was 24.6 +/- 7.6 months. An increase in cTnI was observed in 831 patients (51.9%). Drug-eluting stents were used in 87% of patients and glycoprotein IIb/IIIa inhibitors were administered in 48% of patients. Incidence of in-hospital major adverse cardiovascular events was low, 0.1% versus 0% (p = 1.000), in patients with versus without cTnI increases, respectively. By 2 years of follow-up, Kaplan-Meier survival rates were 94.1% versus 96.4% (log-rank p = 0.020) in those with versus without cTnI increases, respectively. By multivariate Cox regression analysis, an increase in cTnI after PCI (hazard ratio 1.62, 95% confidence interval 1.01 to 2.59, p = 0.047) was an independent predictor of increased long-term mortality. In conclusion, an isolated increase in cTnI after nonemergent PCI is common, not associated with more frequent adverse in-hospital outcomes compared to patients with normal cTnI, and provides long-term prognostic information regarding mortality.

Incidence and determinants of myocardial infarction following percutaneous coronary interventions according to the revised Joint Task Force definition of troponin T elevation

BACKGROUND

Elevations in troponin T (TnT) occur frequently following percutaneous coronary intervention (PCI) and are associated with an adverse prognosis. The Joint ESC/ACC/AHA/WHF Task Force have released a proposal for a universal definition of myocardial infarction (MI), including diagnostic criteria for PCI associated MI. This is based on a TnT cut-point of more than three times the 99th percentile (0.03 ng/ml), which better reflects the precision of the assay. Our study investigated the incidence and predictive factors of a PCI associated MI, using the revised definition.

METHODS

325 patients were studied following PCI with stenting. TnT was collected at both 8 and 18 h following PCI in patients with either stable or unstable angina and normal baseline TnT levels. Comparison was made of both clinical and procedural characteristics of patients with and without a rise in TnT following intervention, using cut points of 0.01 and 0.03 ng/ml.

RESULTS

TnT was elevated > or = 0.03 ng/ml in 27% and > or = 0.01 ng/ml in 39% of patients following PCI. Troponin elevation was significantly more likely in those patients who experienced peri-procedural ischemic symptoms or EKG changes, or in whom abciximab was used. The variables associated with a troponin rise showed a greater difference between TnT positive and negative patients when using 0.03 ng/ml compared to 0.01 ng/ml, suggesting that this may be a better definition of PCI-related MI.

CONCLUSIONS

Approximately one-quarter of low risk patients experience a procedural MI according to the revised definition. Rises in troponin were significantly associated with peri-procedural ischemic symptoms and EKG changes, and abciximab use, consistent with this level of TnT reflecting true myocardial necrosis.

Prognostic value of troponin after elective percutaneous coronary intervention: A meta-analysis

BACKGROUND

Although the prognostic importance of troponin in patients with anacute coronary syndrome is clear, the significance of troponin elevation after elective percutaneous coronary intervention (PCI) is a subject of debate. However, most studies up to now had a small sample size and insufficient events during follow-up.

METHODS

Electronic and manual searches were performed of studies reporting on prognosis of troponin after elective PCI. A meta-analysis was done of all suitable studies, with death in follow-up as primary endpoint and the combination of death or nonfatal myocardial infarction in follow-up as secondary endpoint.

RESULTS

20 studies involving 15,581 patients were included. These studies were published between 1998 and 2007. Overall, troponin was elevated after elective PCI in 32.9% of patients. The follow-up period varied between 3 and 67 months (mean 16.3). Increased mortality was significantly associated with troponin elevation after PCI (4.4% vs. 3.3%, P = 0.001; OR 1.35). Furthermore, the combined endpoint of mortality or nonfatal myocardial infarction also occurred more often in patients with post-procedural troponin elevation (8.1% vs. 5.2%, P < 0.001; OR 1.59).

CONCLUSIONS

According to this meta-analysis, troponin elevation after elective PCI provides important prognostic information.

Prognostic importance of troponin T and creatine kinase after elective angioplasty

BACKGROUND

The prognostic importance of elevated cardiac enzymes after elective percutaneous coronary intervention has been debated. Therefore, we performed a prospective observational study to evaluate the prognostic value of postprocedural rise of troponin T and creatine kinase.

METHODS

Troponin T (cut-off value 0.05 ng/ml) and creatine kinase (cut-off value 180 IU/l with muscle-brain fraction >4%) were measured 12 h after elective percutaneous coronary intervention in 713 consecutive patients without elevated troponin before the procedure. Primary endpoint was the combined incidence of death, myocardial infarction, stroke, repeat angiography or re-admission because of anginal symptoms during the follow-up period.

RESULTS

Troponin was elevated after the procedure in 150 patients (21%) and creatine kinase in 66 pts (9%), with a strong association between increased troponin and creatine kinase. After a mean follow-up of 10.9 months, mortality was low (1%) and not associated with increased troponin or creatine kinase. There was, however, a strong relation between postprocedural troponin and re-admission for angina (p=0.001) or myocardial infarction (p=0.001). Furthermore, troponin rise was significantly associated with an increased risk of the primary endpoint (relative risk 1.55 95% confidence interval 1.01-2.38). After multivariate analysis, troponin elevation but not increased creatine kinase was associated with an increased risk of the primary endpoint (relative risk 1.59 95% confidence interval 1.02-2.47 for troponin elevation versus 1.16 95% confidence interval 0.62-2.15 for increased creatine kinase).

CONCLUSION

Increase of troponin T after elective percutaneous coronary intervention has stronger prognostic implication when compared to increased creatine kinase.

Peri-procedural myocardial injury: 2005 update

During the past three decades, percutaneous coronary intervention has become one of the cardinal treatment strategies for stenotic coronary artery disease. Technical advances, including the introduction of new devices such as stents, have expanded the interventional capabilities of balloon angioplasty. At the same time, there has been a decline in the rate of major adverse cardiac events, including Q-wave acute myocardial infarction, emergency coronary artery bypass grafting, and cardiac death. Despite these advances, the incidence of post-procedural cardiac marker elevation has not substantially decreased since the first serial assessment 20 years ago. As of now, these post-procedural cardiac marker elevations are considered to represent peri-procedural myocardial injury (PMI) with worse long-term outcome potential. Recent progress has been made for the identification of two main PMI patterns, one near the intervention site (proximal type, PMI type I) and one in the distal perfusion territory of the treated coronary artery (distal type, PMI type II) as well as for preventive strategies. Integrating these new developments into the wealth of clinical information on this topic, this review aims at giving a current perspective on the entity of PMI.

Elevated troponin-I after percutaneous coronary interventions: Incidence and risk factors

BACKGROUND

Percutaneous coronary interventions (PCIs) are often complicated by postprocedural myocardial necrosis as manifested by elevated cardiac markers.

PURPOSE

To assess the incidence and risk factors of elevated troponin-I (TnI) after PCI.

METHODS AND RESULTS

We performed a retrospective analysis on 522 PCI cases over a 1-year period at a single center. An elevated postprocedural TnI (>1.0 ng/ml) occurred in 213 patients (40.8%). Overall, glycoprotein (GP) IIb/IIIa inhibitors were used in 52% of cases. Baseline clinical characteristics were similar between the positive and the negative TnI groups. A univariate analysis revealed that patients with elevated TnI post-PCI had significantly more multivessel (28% vs. 15%, P = .001) and multilesion interventions (44% vs. 27%, P<.0001). The lesions were longer, more often angulated and involving bifurcations, and more complex in the TnI-positive group. Stent use and number of stents was higher in the TnI-positive group, and longer inflation times (>30 s) or higher inflation pressures (>14 atm) were used more often in the TnI-positive group. GP IIb/IIIa inhibitor use was higher in the TnI-positive group (61% vs. 45%, P = .0007). After multivariable analysis, independent predictors of elevated TnI after PCI included multilesion intervention, lesion length, lesion angulation, and GP IIb/IIIa inhibitor use.

CONCLUSION

TnI is elevated in approximately 40% of cases after PCI. TnI is more likely to be elevated after intervention on multiple lesions, angulated or long lesions.

Incidence, predictors, and clinical significance of troponin-I elevation without creatine kinase elevation following percutaneous coronary interventions

The objectives of this study were to investigate the incidence, predictors, and clinical significance of isolated postprocedural troponin-I elevations in a consecutive series of patients who underwent percutaneous coronary intervention. We observed, in a series of 1,128 patients, that isolated troponin-I elevations without concomitant creatine kinase elevations occurred in 17% of patients after percutaneous coronary intervention, and that even troponin-I elevations 5 times above the upper limit of normal did not predict events after hospital discharge.

Prognostic implication of cardiac troponin T increase following stent implantation

OBJECTIVE

To identify the incidence and clinical significance of myocardial injury following elective stent implantation.

DESIGN

Prospective clinical study with 278 consecutive patients undergoing stenting of de novo coronary or saphenous vein graft lesions. Incidence of periprocedural myocardial injury was assessed by analysis of 12 lead ECG, creatine kinase (CK; upper limit of normal (ULN) 70 IU/l for women, 80 IU/l for men), and cardiac troponin T (cTnT; point of care test; threshold 0.1 ng/ml) before and 6, 12, and 24 hours after the intervention. Major adverse cardiac events (MACE: acute myocardial infarction, bypass surgery, and cardiac death) were recorded during clinical follow up (mean (SD) 7.8 (5.3) months).

RESULTS

Following elective stenting, the rate of a positive cTnT status was 17.3%, the rate of CK increase of 1-3x ULN 14.7%, the rate of CK increase of > 3x ULN 1.4%, and the rate of Q wave myocardial infarction 0.4%. Cardiac mortality during follow up was higher in patients with postprocedurally increased CK (7.1% v 1.3%, p = 0.01, log rank) and cTnT (9.1% v 0.9%, p < 0.001, log rank). In addition, postprocedurally increased cTnT was associated with a higher overall incidence of MACE (13.1% v 4.0%, p < 0.01, log rank) and was identified as an independent factor for MACE during follow up (hazard ratio 3.27, 95% confidence interval 1.14 to 9.41, p = 0.028).

CONCLUSIONS

Following elective stent implantation, a positive cTnT status identified patients at risk of a worse long term outcome. Treatment strategies have to be developed that lead to prognostic improvement by reducing periprocedural myocardial injury.

Prognostic value of cardiac troponin I elevation after percutaneous coronary intervention in patients with chronic renal insufficiency: a 12-month outcome analysis

Serum cardiac troponin I (cTnI) is a highly specific marker for myocardial damage in patients with chronic renal insufficiency (CRI), unlike creatine kinase myocardial band fraction (CK-MB), which may be elevated in the absence of myocardial injury in patients with CRI. We studied 116 consecutive CRI patients (serum creatinine +/- 1.8 mg/dL, not on dialysis) with normal baseline cTnI levels who underwent successful percutaneous coronary intervention (PCI). Patients were divided into two groups: group 1, elevated postprocedural cTnI (n = 50), and group 2, normal cTnI (n = 66). Patients with elevated cTnI were older and had a higher incidence of postinfarction angina and lower creatinine clearance compared to patients who did not have cTnI elevation. Atheroablative devices (rotational and directional atherectomy and excimer laser coronary angioplasty) were more frequently used in group 1 patients (27.1% vs. 18.5%; P = 0.04). In-hospital mortality, cardiac mortality, and Q-wave myocardial infarction rates did not differ between the two groups. At 12-month follow-up, total mortality rates were significantly higher in group 1 (28.0% vs. 9.9%; P = 0.002). Multivariate analysis showed that cTnI was an independent predictor of late mortality (OR = 2.26; CI = 1.07-4.77; P = 0.03). Thus, in patients with CRI, elevated cTnI levels after successful PCI is an important predictor of poor long-term outcome. Our data suggest that patients with cTnI elevation > 3 times above normal values are particularly at higher risk.

Prognostic value of cardiac troponin I re-elevation following percutaneous coronary intervention in high-risk patients with acute coronary syndromes

Troponin I is a predictive marker of short- and intermediate-term adverse cardiac events in patients with acute coronary syndromes (ACS). These high-risk patients may benefit from early percutaneous coronary intervention. However, whether additional myocardial injury, defined as postprocedural troponin I elevation, may be associated with adverse short- and intermediate-term outcomes has not been fully explored. Accordingly, we studied 132 consecutive patients with non-ST-elevation ACS (62% with non-Q-wave myocardial infarction) and elevated troponin I levels at admission (>0.15 ng/ml) who underwent percutaneous coronary intervention > or =48 hours after admission. Troponin I levels were routinely measured at 6 and 18 to 24 hours after intervention and patients were stratified according to the presence or absence of troponin I re-elevation, defined as postprocedural troponin I levels >1 times the admission levels. In-hospital and cumulative 6-month clinical outcomes were compared between groups. Patients with troponin I re-elevation (n = 51) were older (68 +/- 13 vs 64 +/- 12 years, p = 0.05) and had experienced prior myocardial infarction more frequently (92.5 vs 82.1, p = 0.09), but otherwise had similar baseline clinical characteristics. Patients with troponin I re-elevation had significantly higher in-hospital mortality (9.8% vs 0%, p = 0.016) and a higher 6-month cumulative death rate (24% vs 3.7%, p = 0.001). There was a trend for an increased 6-month myocardial infarction rate in patients with troponin I re-elevation (13.7% vs 3.7%, p = 0.11) and target vessel revascularization was similar between groups (16.7% vs 17.4%, p = 0.92). By multivariate analysis, troponin I re-elevation (odds ratio [OR] 6.2, p = 0.011) and diabetes mellitus (OR 5.7, p = 0.014) were the strongest independent predictors for increased 6-month cumulative mortality, whereas creatine kinase MB-fraction re-elevation had no prognostic value. We conclude that troponin I re-elevation after percutaneous coronary intervention in high-risk patients with ACS is associated with a substantial increase in mortality and reduced event-free survival at 6-month follow-up.

Minor myocardial injury after elective uncomplicated successful PTCA with or without stenting: detection by cardiac troponins

Cardiac troponins are sensitive and specific markers for the detection of minor myocardial injury. However, they have been rarely used to monitor myocardial injury after coronary stenting. The purpose of the study was to measure cardiac troponin I (cTnI) and cardiac troponin T (cTnT) levels after elective uncomplicated successful percutaneous transluminal coronary angioplasty (PTCA) with or without coronary stenting and to compare their results with serum creatinine kinase MB isoenzyme (CKMB). CTnI and cTnT levels were compared with those of CK or CKMB in 98 consecutive patients with stable angina undergoing elective uncomplicated successful PTCA with stenting (n = 71) or without stenting (n = 27). Markers were measured before and 6, 12, 24, and 48 hr after the procedure. Peak postprocedural levels for each marker were compared and related to angiographic and procedural characteristics as well as to the occurrence of side-branch occlusion. None of the patients had abnormal markers before the procedure. Abnormal postprocedural values of one or more markers were observed in 28 patients (29%), 23 after stenting and 5 after PTCA alone. The frequencies of abnormal cTnI and cTnT levels were significantly higher than that of CKMB after coronary intervention (26% and 18% vs. 7%; P = 0.00016 and 0.015, respectively), with cTnI being the most significant. When compared with troponin-negative patients, abnormal cardiac troponin values were significantly related to total time of inflation (223 +/- 128 vs. 170 +/- 105 sec; P = 0.008) and inflation maximal pressure (12.9 +/- 2.3 vs. 12.0 +/- 2.7 atm; P = 0.04). Small side-branch occlusion was noticed in 36% of the troponin-positive patients and in 6% of the troponin-negative group (P = 0.00047). In conclusion, minor myocardial injury is not uncommon after elective uncomplicated successful PTCA with or without stenting. Cardiac troponins, especially cTnI, are more sensitive than CKMB for the detection of this minor myocardial injury. Total time of inflation and inflation maximal pressure are predictors of postprocedural elevation of cardiac troponins. Side-branch occlusion may account for some, but not all, periprocedural minor myocardial injury.

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.