Mitigation of the clinical significance of spurious elevations of cardiac troponin I in settings of coronary ischemia using serial testing of multiple cardiac markers

Retrospective analysis of intra-patient laboratory variation demonstrates that the BD Vacutainer® Barricor™ blood collection tube reduces troponin variation

OBJECTIVE

The BD Vacutainer® Barricor™ plasma blood collection tube uses a mechanical separator during centrifugation to separate plasma from the cellular elements of blood. Compared to use of plasma separator tubes (PST™) with gel, Barricor™ produces a cleaner sample with less residual cellular content. We sought to determine if Barricor™ reduces pre-analytical error compared to PST™.

DESIGN & METHODS

We used a model previously published that utilizes serial differences between intra-patient measurements transformed into a Taylor series of variation vs time with the y-intercept equal to the sum of short-term analytic variation, preanalytic variation and biologic variation. The intra-patient variation of chloride, sodium, potassium, and troponin-T (hs-TnT) obtained from the Emergency Department of a large tertiary care center sampled with PST™ (May 2015-April 2018, n = 59,762 specimens) or Barricor™ (May 2018-May 2021, n = 61,512 specimens) was evaluated. All specimens were analyzed on either Roche Modular or Cobas® instruments. For each analyte, pairs of intra-patient results were tabulated and separated by 1 h intervals. The average between-pair variations were then regressed against time. We also determined the number of intra-patient outliers using the reference change value for each analyte.

RESULTS

The Barricor™ hs-TnT y-intercept (-0.0132) was significantly lower than the PST™ intercept (0.9109; p = 0.022). This was also true for chloride (y-intercept = 1.0067 in Barricor™ and 1.3431 in PST™, p = 0.037). The percentage of hs-TnT outliers was significantly lower in Barricor™ (8.32 %) vs PST™ (12.2 %; p < 0.001).

CONCLUSION

The analytical and biological variations are assumed to be steady over the study periods; we ascribe the difference in the y-intercept to the preanalytical effect of the Barricor™ tube reducing platelets and other cellular debris.

Outcomes associated with the high sensitivity cardiac troponin testing in patients presenting with non-cardiovascular disorders

There are limited data regarding the utility of troponin testing in patients presenting with non-cardiovascular (CV) symptoms as the primary manifestation. The study population comprised 2057 patients who presented to the emergency department (ED) of a US healthcare system with non-CV symptoms as the primary manifestation between January and September 2018. We compared the effect of high-sensitivity cardiac troponin T (hs-cTnT) (n = 901) after its introduction vs. 4th generation cTnT (n = 1156) on the following outcomes measures: ED length of stay (LOS), coronary tests/procedures (angiography or stress test), and long-term mortality. Mean age was 64 ± 17 yrs., and 47% were female. Primary non-CV manifestations included pneumonia, obstructive pulmonary disease, infection, abdominal-complaint, and renal failure. Mean follow up was 9 ± 4 months. Patients' demographics and medical history were clinically similar between the two troponin groups. A second cTn test was obtained more frequently in the hs-cTnT than cTnT (84% vs. 32%; p < 0.001), possibly leading to a longer ED stay (8.1 ± 8.2 h vs 5.6 ± 3.4 h, respectively; p < 0.001). Coronary tests/procedures were performed at a significantly higher rate in the hs-cTnT than cTnT following the introduction of the hs-cTnT test (28% vs. 22%, p < 0.001). Multivariate analysis showed that following the introduction of hs-cTnT testing, there was a significant 27% lower risk of long-term mortality from ED admission through follow-up (HR = 0.73, 95%CI 0.54-0.98; p = 0.035). In conclusion, we show that in patients presenting primarily with non-CV disorders, the implementation of the hs-cTnT was associated with a higher rate of diagnostic coronary procedures/interventions, possibly leading to improved long-term survival rates.

Cardiac troponins: 25 years on the stage and still improving their clinical value

Twenty-five years ago, non-isotopic immunoassays for measuring the cardiac specific isoforms of troponin I (cTnI) and T (cTnT) were developed. Both biomarkers radically changed the diagnosis, prognosis, and therapy indication of acute coronary syndromes (ACS) and, particularly, of myocardial infarction (MI). However, cardiac troponins (cTn) rapidly demonstrated their usefulness in other cardiac and non-cardiac conditions, a part of the ischemic coronary diseases. Consequently, the number of patients to be tested for cTn and the number of tests requested to clinical laboratories sharply increased. Though the manufacturers continuously improved the analytical characteristics of the first cTn assays and produced different cTn assay "generations", the universal definition of myocardial infarction required less-than-available analytical imprecision at the cTn concentration used to assess MI (i.e. the 99th reference percentile). To address the clinical requirements, manufacturers developed the high-sensitivity cTn (hs-cTn) assays that allow to measure the 99th reference percentile with adequate precision, to detect cTn in many healthy subjects and, hence, to calculate the hs-cTn biological variation and especially to observe in very short time intervals serial differences in hs-cTn attributable to cardiac ischemia. Since the number of patients attending the emergency departments (ED) for a suspected ACS or MI is increasing, the improved properties of hs-cTn assays, allowing faster and safer patient assessment, will help to alleviate the sometimes overcrowded EDs. However, there are many biological, analytical, and clinical factors that can influence the true hs-cTn values of a patient. Clinicians and laboratory professionals should know about them for the best interpretation of the otherwise largely useful hs-cTn measurements. In conclusion, 25 years after their introduction for clinical use, "cTn are still on the stage and improving their clinical value".

Relationship between high sensitivity troponins and estimated glomerular filtration rate

BACKGROUND

Diagnosis of acute coronary syndrome may be challenging because of high troponin concentrations in patients with chronic kidney disease.

OBJECTIVE

the aim of this study is to investigate the difference between high sensitivity troponin T and troponin I in four groups of patients separated according to eGFR values and the effect of renal function both on troponin T and troponin I.

METHODS

119 outpatients were divided into 4 groups according to their eGFR values as Group 1: eGFR<30, Group 2: eGFR between 30 and 60, Group 3: eGFR between 60 and 90 and Group 4: eGFR >90mL/min/1.73m(2). The cardiac troponin T and I concentrations were measured concurrently.

RESULTS

Troponin T values of all patients who have eGFR values lower than 30mL/min/1.73m(2) were above the decision point, but cTnI values of only 2 patients were above the decision limit (40ng/L) in this group. There was a strong and significant negative relationship between eGFR and hs-cTnT [log(y)=2.3-0.72log(x); R(2)=0.625] whereas there was no significant relationship between eGFR and hs-cTnI [log(y)=1.28-0.08log(x); R(2)=0.013] when eGFR was taken into consideration as a continuous variable.

CONCLUSION

In this study, we found that cTnT increases with decreasing eGFR values, but cTnI is not affected by the change in eGFR values.

A review of troponins in ischemic heart disease and other conditions

Measuring cardiac troponin (cTn) I and T levels is currently considered to be a cornerstone for making the diagnosis of acute coronary syndrome (ACS).Based on current literature, cTnI and cTnT are known to be very sensitive and specific for myocardial damage, regardless of the underlying cause. Lately, it has been found that cTns can be elevated and reflect worse prognoses in many situations where ACS is excluded. Such information can affect the validity of cTns as markers for ACS without classic symptoms. This may call for a revision of the troponin cutoff values to make a diagnosis of ACS. Furthermore, it opens a new field of study to determine appropriate management of patients with elevated cTn levels in whom ACS has been excluded.

Troponin utilization in patients presenting with atrial fibrillation/flutter to the emergency department: retrospective chart review

Background

There are few recommendations about the use of cardiac markers in the investigation and management of atrial fibrillation/flutter. Currently, it is unknown how many patients with atrial fibrillation/flutter undergo troponin testing, and how positive troponin results are managed in the emergency department. We sought to look at the emergency department troponin utilization patterns.

Methods

We performed a retrospective chart review of patients with atrial fibrillation/flutter presenting to the emergency department at three centers. Outcome measures included the rates of troponins ordered by emergency doctors, number of positive troponins, and those with positive troponins treated as acute coronary syndrome (ACS) by consulting services.

Results

Four hundred fifty-one charts were reviewed. A total of 388 (86%) of the patients had troponins ordered, 13.7% had positive results, and 4.9% were treated for ACS.

Conclusions

Troponin tests are ordered in a high percentage of patients with atrial fibrillation/flutter presenting to emergency departments. Five percent of our total patient cohort was diagnosed as having acute coronary syndrome by consulting services.

Troponin-positive, MB-negative patients with non-ST-elevation myocardial infarction: An undertreated but high-risk patient group: Results from the National Cardiovascular Data Registry Acute Coronary Treatment and Intervention Outcomes Network-Get With The Guidelines (NCDR ACTION-GWTG) Registry

BACKGROUND

Despite the 2000 and 2007 redefinition of myocardial infarction (MI), patients who are troponin (Tn) positive ([+]) but MB negative ([-]) may not be considered to have MI, particularly in the absence of known coronary disease (prior MI or revascularization; coronary artery disease [CAD]). How this affects treatment and outcomes has not been well described.

METHODS

Direct arrival patients with non-ST elevation MI (NSTEMI) enrolled in the American College of Cardiology NCDR ACTION-GWTG Registry were included. Patients missing marker data who were Tn (-) and had CAD were excluded. Troponin (+) patients were categorized as MB (+) (n = 11,563) or MB (-) (n = 4,501). Treatments and in-hospital outcomes were compared between the 2 groups using logistic regression.

RESULTS

Of the 16,064 NSTEMI patients, 28% were MB (-). The MB (-) patients were older (median age 68 vs 65 years) and had more comorbidities (hypertension 71% vs 66%, diabetes 31% vs 27%, heart failure 22% vs 19%; all Ps < .01). After adjusting for baseline characteristics, MB (-) patients were significantly less likely to receive clopidogrel, antithrombins, glycoprotein IIb/IIIa antagonists, or angiography (all Ps < .001). In-hospital mortality was lower in MB (-) patients (3.8% vs 4.9%, P < .01), which remained significant after adjusting for baseline variables (odds ratio 0, 69, 95% CI 0.6-0.9, P = .002).

CONCLUSIONS

Patients without known CAD who have NSTEMI and are MB (-) have a higher risk profile but are less likely to receive guideline-recommended acute pharmacologic treatment than those who are MB (+). Given the relatively high mortality in this group, increased emphasis on improving quality of care in Tn (+)/MB (-) patients is warranted.

Gender differences in correlates of troponin assay in diagnosis of myocardial infarction

Cardiac troponins are the most sensitive and specific biomarker for myocardial infarction (MI) diagnosis. If there is a gender bias in MI diagnosis, it could be reduced by more consistently applying objective diagnostic criteria to improve women's outcomes. This study set out to assess the accuracy and correlates of the cardiac troponin I (cTnI) assay in the diagnosis of non-ST-segment elevation MI, to determine how the assay accuracy and correlates vary by gender, and to explore the interaction between factors that may influence cTnI accuracy and affect gender differences in diagnosis. The data were obtained from the CHECKMATE study. It included 924 patients with possible myocardial ischemia excluding subjects with ST-segment elevation. The Dade-Behring Stratus CS STAT near-patient instrument (Dade Behring, Inc, Newark, Del) was used to measure cTnI. We assessed baseline troponin accuracy using a standard MI definition. There were 125 subjects with a definite MI diagnosis. Baseline troponin was 44% sensitive and 97% specific in predicting MI, with no significant gender differences. In contrast, other positive cardiac markers, namely rising or falling creatine-kinase MB fraction and positive electrocardiogram, occurred more frequently in men. Sensitivity (SE) of baseline troponin was higher in subjects where baseline troponin was obtained longer than 2 hours after the chest pain onset. The study did not observe a significant difference in the assay SE or specificity by gender. This observation, plus the fact that other positive cardiac markers occurred more frequently in men, suggest the troponin test may help to improve the diagnosis of MI in women.

Frequency of elevated troponin I and diagnosis of acute myocardial infarction

This study evaluated the incidence and type of acute myocardial infarction (AMI) in a consecutive population with increased troponin I (TnI). AMI has recently been redefined and subclassified. Incidence, demographic data, angiographic findings, and hospital mortality of patients with various AMI subtypes or an increased TnI in the absence of AMI have not been previously reported in a prospective study. Over a 3-month period, all patients admitted from an emergency room or from in-patient services with >1 TnI level >0.04 ng/ml were evaluated and subclassified in AMI subgroups. In-hospital or recent coronary angiograms were reviewed. In-hospital mortality was noted. Of 2,944 patients with serial TnI measurements, 728 had an increased TnI and 701 (23.8%) were evaluated. Two hundred sixteen (30.8% with increased TnI and 42.7% with "rule-out MI" on admission) met criteria for AMI. One hundred forty-three (20.4%) had type 1, 64 (9.1%) had type 2, whereas 461 (65.8%) did not meet criteria for AMI. On multivariate analysis, use of angiography, peak TnI level, hyperlipidemia, and illicit drug use were independently associated with the diagnosis of AMI. TnI of 0.28 ng/ml had a 70% sensitivity and specificity for AMI diagnosis. In conclusion, a minority admitted with increased TnI have AMI by the universal definition. Type 1 is the most common AMI and is associated with higher TnI values and these patients are more likely to undergo angiography. Type 2 AMI is often associated with illicit drug use.

Role of monitoring changes in sensitive cardiac troponin I assay results for early diagnosis of myocardial infarction and prediction of risk of adverse events

BACKGROUND

We sought to determine the diagnostic accuracy of the cardiac troponin I (cTnI) VITROS(R) Troponin I-ES assay for early detection of acute myocardial infarction (AMI) and for risk prediction of adverse events in patients with symptoms of acute coronary syndrome (ACS).

METHODS

cTnI was measured on admission and approximately 6 h postadmission in 381 patients. The 99th percentile cTnI concentration (0.034 microg/L) and change [delta (delta)] between admission and follow-up concentrations were evaluated in diagnostic sensitivity and specificity calculations. Risk of cardiac event or death within 60 days was evaluated by Cox proportional hazards regression.

RESULTS

AMI occurred in 52 patients. Diagnostic sensitivities (95% CI) of admission and follow-up cTnIs for AMI were 69% (55%-81%) and 94% (84%-99%), respectively. The corresponding specificities (95% CI) were 78% (73%-82%) and 81% (77%-85%), and ROC curve areas were 0.82 vs 0.96 (P < 0.001). Deltas between admission and follow-up cTnI >30% had a sensitivity of 75% (95% CI 61%-86%) and a specificity of 91% (95% CI 87%-94%). During follow-up, 1 cardiac death, 2 noncardiac deaths, 52 AMIs, 6 coronary artery bypass grafts, and 43 percutanous coronary interventions occurred in 62 patients. A delta cTnI >30%, when added to either initial cTnI >0.034 microg/L or follow-up cTnI >0.034 microg/L, improved risk stratification for cardiac event or death (P < 0.001).

CONCLUSIONS

Admission cTnI measured by the VITROS ES assay is a sensitive biomarker for detection of AMI. Utilizing >30% cTnI delta in addition to either the baseline or follow-up concentration improved both specificity and risk assessment in patients presenting with symptoms of ACS.

Epidemiology of myocardial infarction

Myocardial infarction is a key component of the burden of cardiovascular disease. The assessment of the incidence and case fatality of myocardial infarction are important determinants of the decline in coronary disease mortality. The change in biomarkers used to diagnose myocardial infarction raises several methodologic, clinical, and public health challenges, which are discussed herein.

Repeated Thoracic Discharges From a Stun Device

BACKGROUND

Little objective laboratory data are available describing the physiologic effects of stun guns or electromuscular incapacitation (EMI) devices, but increasing morbidity and even deaths are associated with their use. We hypothesized that exposure to EMI discharges in a model animal system would induce clinically significant acidosis and cardiac arrhythmia.

METHODS

Ten Yucatan mini-pigs, six experimental and four sham controls, were anesthetized with ketamine, xylazine, and glycopyrrolate. Experimental pigs were exposed to two 40-second discharges from an EMI device over the left thorax. Electrocardiograms, troponin I, blood gases, and lactate levels were obtained pre-exposure, at 5, 15, 30, 60 minutes, and at 24, 48, and 72 hours postdischarge.

RESULTS

No acute or delayed cardiac arrhythmias were seen. Heart rate was not affected significantly (p>0.05). A subclinical increase in troponin I was seen at 24 hours postdischarge (0.040+/-0.030 ng/mL, p>0.05). Central venous blood pH (7.432+/-0.014) and pCO2 (36.1+/-0.9 mm Hg) were not changed significantly (p>0.05) during the 60-minute postdischarge period. A moderate significant increase in lactate occurred in the 5-minute postdischarge group (4.9+/-0.3 mmol/L, p=0.0179). All blood chemistry and vital signs were normal at 24, 48, and 72 hours postdischarge.

CONCLUSIONS

Although significant changes in some parameters were seen, these changes were small and of little clinical significance. Lengthy EMI exposures did not cause extreme acidosis or cardiac arrhythmias. These findings may differ from those seen with other EMI devices because of the unique MK63 waveform characteristics or to specific characteristics of the model systems.

Falsely elevated cardiac troponin I levels

The measurement of cardiac troponins (cTn) is of considerable usefulness in the diagnosis of acute coronary syndrome. Abnormal levels of serum cTn are occasionally found in patients who are not suffering a myocardial infarction. This may be observed in several well-known situations including pulmonary embolism, pericarditis, myocarditis, coronary vasospasm, sepsis, congestive heart failure, supraventricular tachycardia with hemodynamic compromise, re-nal insufficiency, and prolonged strenuous endurance exercise. Endogenous antibodies such as heterophile antibodies, rheumatoid factor, and other autoantibodies are known to interfere with the immunoassay measurements of many different analytes, including the widely used Abbot AxSYM cTnI analyzer. Other sources of circulating antibodies include immunotherapies, vaccinations, or blood transfusions that may interfere with these immunoassays as well. We examine the case of a 48-year-old man with a history of hypercholesterolemia and obesity who presented with chest pain and was found to have elevated Tn I levels on two separate occasions. Further work-up revealed that the Tn I levels were spuriously elevated because the patient's blood revealed a normal cTnI level when mixed with polyethylene glycol to inactivate any antibodies interfering with the cTnI assay.

Prevalence and determinants of troponin T elevation in the general population

BACKGROUND

The prevalence and determinants of cardiac troponin T (cTnT) elevation in the general population are unknown, and the significance of minimally increased cTnT remains controversial. Our objective was to determine the prevalence and determinants of cTnT elevation in a large, representative sample of the general population.

METHODS AND RESULTS

cTnT was measured from stored plasma samples in 3557 subjects of the Dallas Heart Study, a population-based sample. cTnT elevation (> or =0.01 microg/L) was correlated with clinical variables and cardiac MRI findings. The sample weight-adjusted prevalence of cTnT elevation in the general population was 0.7%. In univariable analyses, cTnT elevation was associated with older age, black race, male sex, coronary artery calcium by electron beam CT, a composite marker of congestive heart failure (CHF), left ventricular hypertrophy (LVH), diabetes mellitus (DM), and chronic kidney disease (CKD) (P<0.001 for each). Subjects with minimally increased (0.01 to 0.029 microg/L) and increased (> or =0.03 microg/L) cTnT had a similar prevalence of these characteristics. In multivariable logistic regression analysis, LVH, CHF, DM, and CKD were independently associated with cTnT elevation.

CONCLUSIONS

In the general population, cTnT elevation is rare in subjects without CHF, LVH, CKD, or DM, suggesting that the upper limit of normal for the immunoassay should be <0.01 microg/L. Even minimally increased cTnT may represent subclinical cardiac injury and have important clinical implications, a hypothesis that should be tested in longitudinal outcome studies.

Diagnostic Accuracy and Prognostic Value of Dobutamine Stress Myocardial Contrast Echocardiography in Patients with Suspected Acute Coronary Syndromes

BACKGROUND

Both early stress testing and cardiac troponin I (cTnI) measurements are useful in assessing the prognosis of patients with acute coronary syndrome (ACS). We sought to determine the accuracy and prognostic value of wall motion analysis (WMA) and myocardial perfusion analysis (MPA) with real-time myocardial contrast echocardiography (RTMCE) during dobutamine stress in this patient population.

METHODS

We performed dobutamine stress RTMCE to assess perfusion in 158 consecutive patients (mean age: 61 +/- 13 years) with chest pain and possible ACS. Of these, 119 had normal cTnI, while 39 had isolated elevations of cTnI (range: 0.5-9.0 ng/ml). Quantitative angiography was performed within 1 month of RTMCE in 61 patients. Patients were followed for 16 months (range: 6-46 months). Cardiac events included death, nonfatal myocardial infarction, recurrent unstable angina, or need for urgent revascularization.

RESULTS

The sensitivity, specificity, and accuracy of MPA for detecting a >50% coronary stenosis were 92%, 77%, and 88%, respectively, while they were 62%, 85%, and 67% for WMA. Three-year event-free survival was 87% in patients with negative WMA and MPA, 49% in those with positive WMA and MPA, and 51% in patients with negative WMA but positive MPA. Age-adjusted multivariate analysis demonstrated that the only independent predictors of cardiac events were a positive MPA (hazard ratio = 3.23; 95% CI = 1.23-8.49) and male sex (hazard ratio = 3.29; 95% CI = 1.21-8.97).

CONCLUSIONS

In patients suspected of having an ACS, RTMCE improved the accuracy of dobutamine stress echocardiography for detecting coronary artery disease, and was an independent predictor of outcome.

Effects of transvenous pacing on cardiac troponin release

Cardiac troponins are invaluable tools for the detection of minimal myocardial injury. No study to date has analyzed the effect of permanent cardiac pacing on minimal myocardial injury detection by cardiac troponin I (cTnI) measurement. We investigated 76 clinically stable patients (mean age 75 years, range 31-93 years, 59% men) listed for elective endocardial permanent pacemaker insertion. Patients were required to have normal levels of cardiac cTnI, aspartate transaminase (AST) and creatinine kinase (CK) on a venous blood sample taken immediately prior to elective pacemaker implantation. Repeat measurements of AST, CK, and cTnI were performed at a mean of 19.2 post implantation. There was a detectable small rise in cTnI levels above normal in 21% of patients in a second blood sample taken 18-21 hours later (mean cTnI 0.39 +/- 0.37 microg/L, normal < 0.15 microg/L). The only factor that correlated with this rise was prolonged x ray screening time for lead implantation.

Troponin I as a specific marker of myocardial injury: from theory to clinical practice in the diagnosis of acute coronary syndrome

OBJECTIVE

To assess the diagnostic accuracy of troponin I (TnI) elevation in patients with acute coronary syndrome (ACS) in the emergency department (ED).

METHODS

We retrospectively studied 166 patients with elevated TnI and electrocardiographic (ECG) change consistent with non-ST-segment elevation myocardial infarction. They were transferred from the ED to our coronary care unit (CCU) to undergo coronary angiography.

RESULTS

Significant coronary stenosis were identified in 101 (61%) of patients. The other 65 patients were found to have different cardiac diseases (n=52) and in 13 patients diagnoses were not even related to the cardiovascular system. Wall motion abnormalities were assessed by echocardiographic wall motion score index (WMSI). Positive predictive value (PPV) of TnI varied from 53 to 65% for higher progressive values of the biomarker. The following PPVs were then calculated: PPV(TnI+CK-MB)=64%; PPV(TnI+WMSI)=72%, PPV(TnI+CK-MB+WMSI)=74%.

CONCLUSIONS

Abnormal values of TnI were detected in a variety of diseases not related to ACS. Even if troponin release indicates myocardial injury, it is not always synonymous with infarction or ischemia. A misinterpretation of TnI elevation may give rise to a diagnostic dilemma and cause unnecessary morbidity. An integration of biomarkers (TnI and CK-MB), ECG and WMSI will help identify false-positive ACS patients and avoid inappropriate admissions to CCU.

Implication of different cardiac troponin I levels for clinical outcomes and prognosis of acute chest pain patients

OBJECTIVES

We compared outcomes in patients with non-ST-segment elevation acute coronary syndromes (ACS) according to the degree of cardiac troponin I (cTnI) elevation.

BACKGROUND

Controlled trials of high-risk patients have found that troponin elevations identify an even higher risk subset. It is unclear whether outcomes are similar among a lower risk, heterogeneous patient group. Also, few studies have reported outcomes other than myocardial infarction (MI) or death, based on the peak troponin value.

METHODS

Consecutively, admitted patients without ST-segment elevation on the initial electrocardiogram underwent serial marker sampling using creatine kinase (CK), CK-MB fraction, and cTnI. Patients were grouped according to peak cTnI: negative = no detectable cTnI; low = peak greater than the lower limit of detectability but less than the optimal diagnostic value; intermediate = peak greater than or equal to the optimal diagnostic value but less than the manufacturer's suggested upper reference limit (URL); and high = peak greater than or equal to the URL. Thirty-day outcomes included cardiac death, MI based on CK-MB, revascularization, significant disease, and a reversible defect on stress testing. Six-month mortality was also determined. Negative evaluations for ischemia included nonsignificant disease, no reversible stress defect, and negative rest perfusion imaging.

RESULTS

Of the 4,123 patients admitted, 893 (22%) had detectable cTnI values. Cardiac events and positive test results at 30 days and 6-month mortality increased significantly with increasing cTnI values. Negative evaluations for ischemia were significantly and inversely related to peak cTnI values. Although adverse events were significantly more common in patients with a low cTnI value than in those with negative cTnI, negative evaluations for ischemia were frequent.

CONCLUSIONS

Increased cTnI values are associated with worse outcomes. Although low cTnI values are associated with adverse events, they do not have the same implication as higher cTnI values, and nonischemic evaluations are frequent.

Impact of the troponin standard on the prevalence of acute myocardial infarction

BACKGROUND

Recent recommendations are that troponin should replace creatine kinase (CK)-MB as the diagnostic standard for myocardial infarction (MI). The impact of this change has not been well described. Our objective was to determine the impact of a troponin standard on the prevalence of acute non-ST-elevation MI.

METHODS

The current study was a retrospective analysis of consecutive patients without ST-segment elevation admitted for exclusion of myocardial ischemia to an inner city urban tertiary care center. All patients underwent serial marker sampling (CK, CK-MB, and cardiac troponin I [cTnI]). Patients with ST elevation consistent with acute MI (n = 130) or who did not have an 8 hour cTnI (n = 124) were excluded. The impact of 3 different cTnI diagnostic values were examined in 2181 patients: the lower limit of detectability (LLD); an optimal diagnostic value (OPT), chosen using receiver operator characteristic curve analysis; and the manufacturer's suggested upper reference level (URL), when compared to a gold standard CK-MB MI definition. In addition, MI prevalence was assessed using different CK-MB MI definitions and evaluated in patients with ischemic changes only.

RESULTS

The prevalence CK-MB MI was 7.8%. Using the various cTnI diagnostic values, the incidence of MI increased the prevalence by 28% to 195%. Using the optimal diagnostic value for cTnI, patients with cTnI elevations not meeting CK-MB MI criteria had an intermediate 30-day mortality (5.4%) compared to those with CK-MB MI (7.1%). Grouping the cTnI positive, CK-MB MI negative patients with the CK-MB MI patients rather than the non-CK-MB MI patients reduced mortality for both the MI (to 5.9%) and non-MI groups (from 1.9% to 1.6%).

CONCLUSIONS

Changing to a troponin standard will have a substantial impact on the number of patients diagnosed with MI. The revised definition for MI will have important clinical and health care implications.

Exercise-induced increases in cardiac troponins and prothrombotic markers

Cardiac troponin I and T are potent tools for risk stratification and clinical decision-making for patients in the appropriate clinical setting of an acute coronary syndrome. Although these findings are relevant to patients with a typical clinical presentation, caution should be exercised in generalizing the results to troponin-positive athletes with a low clinical suspicion of coronary artery disease. This review addresses the clinical relevance of increased troponin levels induced by strenuous exercise. The imprecision and lack of standardization of currently available troponin assays merit caution with the application of these findings. In addition, it may well be that if reparative processes are present and/or the release is not due to irreversible injury that increases in troponins after vigorous exercise are normal and should not be expected to be of pathophysiological significance. Due to this potential for misclassification, the crux of appropriate interpretation of troponin testing is careful consideration of the corresponding clinical scenario. Troponin-positive patients often have complex coronary lesion morphology with intracoronary thrombus and understandably derive particular benefit from platelet glycoprotein GpIIb/IIa inhibitors as well as low molecular weight heparins. Studies on exercise-induced activation of blood coagulation have produced conflicting results. At present, there is no clear evidence that a hemostatic imbalance may trigger acute cardiac events after strenuous exercise. In contrast to troponin-positive patients, it may thus be premature and even dangerous to recommend pharmacologic intervention (low molecular weight heparins) to (troponin-positive) endurance athletes even when exercising during high-altitude exposure.

[Applicability of a new definition of myocardial infarction and the opinion of Spanish cardiologists]

INTRODUCTION AND OBJECTIVES

The Working Group on Ischemic Heart Disease and Coronary Care Units of the Spanish Society of Cardiology evaluated the applicability of a new definition of infarction in Spanish hospitals, its current use, and the opinion of Spanish cardiologists.

METHODS

A telephone survey was made (from late 2001 to early 2002) in Spanish hospitals to evaluate the availability of troponin or creatine kinase MB mass determinations. A questionnaire was sent to all members of the Spanish Society of Cardiology to query about the availability of determinations of cardiac necrosis markers at their respective hospitals, use of the new definition, and whether they agreed with the new definition.

RESULTS

An important proportion of Spanish hospitals cannot determine myocardial necrosis markers (troponin or creatine kinase MB mass), mainly due to low-volume activity (fewer than 200 beds). The new definition of myocardial infarction was used by Spanish cardiologists always (24%), frequently (31%), sometimes (17%), seldom (14%), and never (11%). Agreement with the definition was complete in 21%, almost complete in 33%, half and half in 26%, rare in 10%, and absent in 7% of Spanish cardiologists.

CONCLUSIONS

A large percentage of Spanish hospitals cannot use the new definition of myocardial infarction because they cannot determine specific cardiac necrosis markers. Spanish cardiologists are not generally using the new definition and many do not agree with it.

Positive predictive value of a point-of-care testing strategy on first-draw specimens for the emergency department-based detection of acute coronary syndromes

CONTEXT

The rapid and accurate diagnosis of the etiology of chest pain is of central importance in the triage of patients presenting to emergency departments. The "first-draw" sensitivity of serum cardiac markers is known to be low on initial presentation; however, less is understood regarding the predictive value of a positive test in this situation.

OBJECTIVE

To determine the ability of a critical pathway combining medical history and physical examination, electrocardiographic findings, point-of-care testing, and central laboratory data to accurately predict the presence of acute coronary ischemia.

METHODS

We investigated the positive predictive value of a testing algorithm for first-draw specimens in clinical practice, combining a qualitative, point-of-care, triple-screen testing panel for cardiac markers, including myoglobin, creatine kinase-MB, and cardiac troponin I, with confirmation of the rapid assay in the central hospital laboratory by quantitative assays for creatine kinase-MB and cardiac troponin T.

RESULTS

While a positive result on any of the individual cardiac markers of the point-of-care test had a positive predictive value for the acute coronary syndrome of only 36% (creatine kinase-MB, 41%; myoglobin, 36%; and troponin I, 65%), the positive predictive value for the diagnosis of acute coronary syndrome increased to 76% if all 3 point-of-care markers were simultaneously positive. The positive predictive value for acute coronary syndrome for a positive confirmatory result in the hospital laboratory for either creatine kinase-MB or cardiac troponin T was 61%. Among those patients with a positive marker on both the point-of-care test and the laboratory test, a careful retrospective review of the clinical history (with exclusion of patients with nonischemic cardiac pathologies and renal insufficiency) increased the positive predictive value of this algorithm to 98%.

CONCLUSIONS

Our data suggest that qualitative, point-of-care, triple-screen cardiac marker testing of patients with chest pain at initial presentation may exhibit relatively low positive predictive values. Positive predictive value can be significantly improved by rapid confirmation in the hospital laboratory and careful review of clinical findings.

Perioperative myocardial infarction in noncardiac surgery: the diagnostic and prognostic role of cardiac troponins

Despite the number of technologies used, the diagnosis of perioperative myocardial infarction is still a challenge. Studies conducted in surgical series have demonstrated that cardiac troponins (cTns) have both a superior diagnostic sensitivity and specificity, compared with other traditional techniques, and an independent power to predict short- and long-term prognosis. Nevertheless, some points need to be clarified. They include the usefulness of cTns in patients with end-stage renal failure; the standardization of the cTns cut-off for the diagnosis of myocardial injury; the timing of postoperative blood samplings; the cost-effectiveness of a screening in asymptomatic patients; and the possible therapeutic strategies.