Risikostratifizierung des akuten Koronarsyndroms

BACKGROUND

The spectrum of symptoms of patients with active ischemic heart disease ranges from silent ischemia to acute myocardial infarction and the extent of myocardial damage from reversible myocardial injury to extensive necrosis. The term "acute coronary syndrome" comprises this continuum. In particular the evaluation of patients without ST-segment elevation is difficult, for clinical symptoms, ECG criteria and CK-MB measurements appear insufficient for appropriate risk stratification.

TROPONIN MEASUREMENT

Serial measurements of either troponin T or I reliably detect minor myocardial damage in those patients, who are known to be at a higher risk for adverse cardiac events comparable to the risk of patients with acute myocardial infarction. Hence determination of troponins allow superior risk stratification contributing to early triage and therapeutic decision making. Without elevation of troponins the cardiac risk for death or myocardial infarction will not exceed 1%.

CONCLUSION

Patients with elevated troponins should be early hospitalized and further evaluated in order to begin efficacious therapy as soon as possible. These patients represent a high-risk subgroup of patients clinically classified as unstable angina, who might benefit from potential antithrombotic treatment such as low-molecular weight heparin or glycoprotein IIb/IIIa antagonists without or with revascularization strategies.

Analytical and diagnostic performance of troponin assays in patients suspicious for acute coronary syndromes

BACKGROUND

The controversy whether there is a clinically significant difference between troponin T (cTnT) and troponin I (cTnI) in regard to predictive value and cardiac specificity is still ongoing.

METHODS

We evaluated enzyme-linked immunosorbent assay systems for cTnI and cTnT in patients with acute coronary syndromes and multiple control groups to define threshold values for risk stratification and compare their predictive value.

RESULTS

In 312 patients with noncardiac chest pain, cTnI levels were below the detection limit of 0.2 microg/L and cTnT levels were 0.011 [0.010-0. 013] microg/L. In patients with end-stage renal failure (n = 26) and acute (n = 38) or chronic (n = 16) skeletal muscle damage, median concentrations were 0.20 [0.20-0.35], below the detection limit, and 0.20 [0.20-0.25] for cTnI, and 0.04 [0.01-0.10], 0.011 [0.005-0.025], and 0.032 [0.009-0.054] microg/L for cTnT. In patients with acute coronary syndromes (n = 1130), maximized prognostic value for 30-day outcome (death, infarction) was observed at a threshold level of 1.0 microg/L for cTnI (29.0% positive) and at 0.06 microg/L for cTnT (35. 0% positive). Significant differences in the area-under-the-curve values were observed between cTnI and cTnT (0.685 vs. 0.802; p = 0. 005). For both markers, the area-under-the-curve values did not increase with the second (within 24 h after enrollment) or third (48 h) blood draw. CTnI showed a less strong association with 30-day outcome than cTnT. When cTnI was put in a logistic multiple-regression model first, cTnT did add significant information.

CONCLUSION

By using the defined threshold values and the employed test systems, single testing for cTnI and cTnT within 12 h after symptom onset was appropriate for risk stratification. Despite the lower cardiac specificity for cTnT, it appears to have a stronger association with the patients' outcome, whereas, as previously shown, the ability to identify patients who benefit from treatment with a GP IIb/IIIa receptor antagonist is similar.

Cardiovascular risk and therapeutic benefit of coronary interventions for patients with unstable angina according to the troponin T status

AIMS

Elevation of troponin T in patients with unstable angina is predictive of adverse outcomes. Since no advanced therapeutic concept for such high-risk patients has been established, we investigated cardiac risk prior to, during, and after coronary revascularization in patients with unstable angina stratified according to the troponin T status.

METHODS AND RESULTS

Out of 351 patients with unstable angina, troponin was elevated for 36% of the patients as determined by qualitative bedside tests. The patients were followed during hospitalization and 30 days after discharge for incidence of death and myocardial infarction. In troponin-positive patients, clinical symptoms were more refractory to medical treatment than in troponin-negative patients (78% vs 44%;P=0.002). Although these patients were catheterized earlier (1.6 vs 3.4 days;P=0.005) and more frequently (95% vs 69%;P<0.001), troponin-positive patients suffered a higher incidence of cardiac events prior to scheduled revascularization (death, myocardial infarction; 6.4% vs 0.4%;P<0.001). The angiogram for troponin-positive patients confirmed a more severe coronary artery disease requiring revascularization (69% vs 50%;P=0.001). Also the following coronary intervention was more complicated (death, myocardial infarction; 15.3% vs 4.8%;P=0.02). During the 30-day follow-up period, cardiac risk remained elevated for troponin-positive patients.

CONCLUSIONS

Troponin T rapid testing reliably identified high-risk patients with unstable angina. A higher event rate was observed prior to and particularly in association with the coronary intervention. Coronary revascularization did not abrogate the increased risk of troponin-positive patients during the 30-day follow-up.

Evaluation of a rapid whole blood ELISA for quantification of troponin I in patients with acute chest pain

BACKGROUND

Troponin I (cTnI) provides important prognostic information in patients with chest pain. We wished to evaluate a rapid, whole-blood analyzer for quantitative point-of-care testing.

METHODS

A quantitative point-of-care test system (Stratus CS((R)); Dade-Behring) for cTnI with an incorporated centrifuge was evaluated in 412 patients with chest pain less than 12 h.

RESULTS

Results were available within 15 min. CVs were 4.5% at 0.1 microgram/L, 4.2% at 0.25 microgram/L, and 6.5% at 0.82 microgram/L. The detection limit was 0. 01 microgram/L. The 97.5% percentile in a healthy population was 0.08 microgram/L. Based on ROC curve analysis, a threshold of 0.15 microgram/L was calculated for the detection of acute myocardial infarction (AMI). With it, sensitivity for the detection of patients with AMI (n = 62) was 63% at arrival and 98% after 4 h (Stratus II((R)), 48% and 85%, respectively; P <0.01). In 42% of patients with unstable angina (n = 121), cTnI was >/=0.08 microgram/L (Stratus II, 28%; P <0. 01). During 30 days, death or AMI occurred in 25.5% of these cTnI-positive vs 2.9% of cTnI-negative patients (Stratus II, 29.4% vs 5.8%).

CONCLUSION

The Stratus CS provided better analytical performance and comparable or better prognostic information than the Stratus II.

[Cost-effectiveness of a rapid test for troponin in emergency admissions]

BACKGROUND AND OBJECTIVE

The assessment of patients with acute chest pain according to the risk of cardiac involvement takes time and expensive tests. This study was undertaken to evaluate whether the measurement of troponin 1 (Tnl) would reliably recognize those patients with an increased risk of cardiac disease so that unnecessary hospital stay could be avoided or at least reduced.

PATIENTS AND METHODS

A qualitative rapid test for Tnl was performed, at emergency admission and 4 hours later, on the blood of 812 consecutive patients with acute left-chest pain of < or = 12 hours' duration. Admission was decided on the basis of clinical symptoms, ECG findings and CK-MB results. All cardiac events (death, myocardial infarction) within the next 30 days were recorded for all patients.

RESULTS

Of the 812 patients (56% males; average age 62 +/- 12 years) 65% were admitted. At a daily cost of DM 635 and a mean duration of stay of 4.2 days, the total costs were DM 173,000 per 100 evaluated patients. None of the patients with a negative Tnl test and normal or ECGs that were not interpretable regarding ischaemic signs had cardiac events during the follow-up period of 30 days. By restricting hospitalization to patients with positive Tnl test and/or ST-T changes in the ECG a cost reduction of up to 14% could be achieved (P < 0.01). The cost of the Tnl test (DM 18) would be covered by reducing the number of admitted patients by about 2.1%.

CONCLUSION

Performance of two Tnl tests is a cost-effective way of assessing the risk of cardiac events in patients with acute left-chest pain.

Analytical performance and clinical application of a new rapid bedside assay for the detection of serum cardiac troponin I

Detection of cardiac troponin I (cTnI) in patients suspected of having an acute coronary syndrome is highly predictive for an adverse outcome. We evaluated a bedside test for cTnI that uses a polyclonal capture antibody and two monoclonal indicator antibodies. Clinical studies were performed in patients with acute coronary syndrome and patients with chest pain but no evidence of acute myocardial injury. The whole-blood, 15-minute assay had a concordance of 98.9% with an ELISA for cTnI and a detection limit of 0.14 microg/L, and the device tolerated temperatures between 4 degrees C and 37 degrees C. Diagnostic sensitivity for myocardial infarction at arrival (3.5 +/- 2.7 h after onset of symptoms) was 60% [creatine kinase isoenzyme MB (CK-MB) mass, 48%; CK activity, 36%; P < 0.01], and 4 h later, diagnostic sensitivity was 98% (CK-MB mass, 91%; CK activity, 61%; P < 0.01). In 38% of the patients with unstable angina, at least one positive cTnI test was found (CK-MB mass, 4%; CK activity, 2%). No false-positive test results were found in renal failure or injury of skeletal muscle. We conclude that the diagnostic efficacy of the cTnI rapid test was comparable with the cTnI ELISA and superior to CK-MB determination. Therefore, this device could facilitate decision-making in patients with chest pain at the point of care.

Emergency room triage of patients with acute chest pain by means of rapid testing for cardiac troponin T or troponin I

BACKGROUND

Evaluation of patients with acute chest pain in emergency rooms is time-consuming and expensive, and it often results in uncertain diagnoses. We prospectively investigated the usefulness of bedside tests for the detection of cardiac troponin T and troponin I in the evaluation of patients with acute chest pain.

METHODS

In 773 consecutive patients who had had acute chest pain for less than 12 hours without ST-segment elevation on their electrocardiograms, troponin T and troponin I status (positive or negative) was determined at least twice by sensitive, qualitative bedside tests based on the use of specific monoclonal antibodies. Testing was performed on arrival and four or more hours later so that one sample was taken at least six hours after the onset of pain. The troponin T results were made available to the treating physicians.

RESULTS

Troponin T tests were positive in 123 patients (16 percent), and troponin I tests were positive in 171 patients (22 percent). Among 47 patients with evolving myocardial infarction, troponin T tests were positive in 44 (94 percent) and troponin I tests were positive in all 47. Among 315 patients with unstable angina, troponin T tests were positive in 70 patients (22 percent), and troponin I tests were positive in 114 patients (36 percent). During 30 days of follow-up, there were 20 deaths and 14 nonfatal myocardial infarctions. Troponin T and troponin I proved to be strong, independent predictors of cardiac events. The event rates in patients with negative tests were only 1.1 percent for troponin T and 0.3 percent for troponin I.

CONCLUSIONS

Bedside tests for cardiac-specific troponins are highly sensitive for the early detection of myocardial-cell injury in acute coronary syndromes. Negative test results are associated with low risk and allow rapid and safe discharge of patients with an episode of acute chest pain from the emergency room.