Evaluation of CK-MB isoform analysis for early diagnosis of myocardial infarction

Ellagic acid inhibits cardiac arrhythmias, hypertrophy and hyperlipidaemia during myocardial infarction in rats

OBJECTIVE

The objective was to evaluate the protective effect of ellagic acid against experimentally induced cardiac arrhythmias, hypertrophy and its association with altered lipid metabolism during myocardial infarction in rats.

METHODS

Rats were treated with ellagic acid (7.5 and 15 mg/kg) orally for a period of 10 days. After 10 days of pretreatment, isoproterenol (100 mg/kg) was injected subcutaneously at an interval of 24 h for 2 days to induce myocardial infarction. On the 12th day, the cardiac rhythm was observed. The rats were sacrificed and the heart was isolated from each rat. Ventricular hypertrophy and myocardial necrotic scores were analysed in the myocardium. Lipid peroxidation products in the plasma were analysed. Changes in the lipid profile were measured using the plasma and heart tissue homogenates of normal and experimental rats.

RESULTS

Isoproterenol-induced rats showed arrhythmias, hypertrophy and increased levels of myoglobin, creatine kinase-MB, lipid peroxidation products compared to the normal control rats. Ventricular hypertrophy and increased myocardial necrotic scores were observed in isoproterenol-induced rats. Oral pretreatment with ellagic acid restored pathological arrhythmias, ventricular hypertrophy, lipid peroxidation, altered lipid profile and myocardial necrosis in the isoproterenol-induced myocardial infarcted rats.

CONCLUSIONS

Oral pretreatment with ellagic acid was safe and effective in cardio protection against ISO-induced arrhythmias, hypertrophy and myocardial necrosis. Anti lipid peroxidation property and anti hyperlipidaemic activity through 3-hydroxy-3 methyl glutaryl CoA reductase inhibition by ellagic acid may be the reasons for the beneficial action of ellagic acid against experimentally induced myocardial infarction.

[Experiences with cardiac troponin assessments]

After the JESC/ACCC guideline (approved in year 2000), cardiac troponins became the first-line laboratory markers in the diagnosis of acute coronary syndrome. Since 2006, there is a hemodynamic laboratory in our Hospital and since July, 2007, there is a so called "one gate" Emergency Unit.

AIM

Since the amount of the cardiac troponin assessments has risen, we aimed to analyze the background of this elevation, the results and the cause of the false positivity, as well.

METHODS

We analyzed our cardiac troponin results assessed in the second half of year 2008.

RESULTS

In this time we have had 2656 cardiac troponin examination in 1787 patients. 280 positive results were examined in 203 patients, but acute coronary syndrome was proved only in 110 patients. The remaining cases were false positive but only for detecting acute coronary syndrome, because many other diseases were proved in the background of these patients, and only one result was really (literally) false positive.

CONCLUSIONS

Because of the very low rate of positive results we have to think about restriction of asking that examination. We emphasize that there are many non-acute coronary syndrome diseases with positive cardiac troponin results. This situation needs an urgent and close communication between the clinicians and the laboratory staff.

Brain (B-type) Natriuretic Peptide

Heart failure is the leading cause for hospitalization in the United States, resulting in over $8 billion in costs annually. Over 4.8 million Americans are afflicted with the disease and the number is increasing as the baby boomer generation continues to age. It is imperative that new and innovative modalities of therapy and diagnosis evolve as we continue to redefine the nature of heart failure and discover more about this debilitating disease. This article addresses the implications for endogenous brain (B-type) natriuretic peptide (BNP) testing in patients diagnosed with heart failure as well as the implications for the first available form of exogenous BNP, nesiritide. In addition, the pathophysiology of heart failure and traditional treatment modalities are discussed.

Prospective evaluation of emergency department patients with potential coronary syndromes using initial absolute CK-MB vs. CK-MB relative index

We compared the predictive properties of an initial absolute creatine kinase-MB (CK-MB) to creatine kinase-MB relative index (CK-MB RI) for detecting acute myocardial infarction (AMI), acute coronary syndromes (ACS), and serious cardiac events (SCE). Consecutive patients > 24 years of age with chest pain who received an electrocardiogram (EKG) as part of their Emergency Department (ED) evaluation had CK and CK-MB drawn at presentation. Patients were followed prospectively during their hospital course. The main outcome was AMI, ACS or SCE (death, AMI, dysrhythmias, CHF, PTCA/stent, CABG) within 30 days. The sensitivity, specificity, PPV and NPV of CK-MB and CK-MB RI to predict AMI, ACS, and SCE were calculated with 95% CIs. We enrolled 2028 patients. There were 105 patients (5.2%) with AMI, 266 (13.1%) with ACS, and 150 with SCE (7.4%). Absolute CK-MB had a higher sensitivity than CK-MB RI for AMI (52.0 vs. 46.9, respectively), ACS (23.5 vs. 20.8, respectively), and SCE (39.6 vs. 36.0, respectively), but a lower specificity than CK-MB RI for AMI (93.2 vs. 96.1, respectively), ACS (93.1 vs. 96.1, respectively) and SCE (93.3 vs. 96.3, respectively); and lower PPV for AMI (35.7 vs. 46.5, respectively), ACS (42.0 vs. 53.4, respectively) and SCE (38.5 vs. 50.5, respectively). The negative predictive values were similar for all outcomes. We conclude that the risk stratification of ED chest pain patients by absolute CK-MB has higher sensitivity, similar NPV, but a lower specificity and PPV than CK-MB relative index for detection of AMI, ACS, and SCE. The optimal test depends upon the relative importance of the sensitivity or specificity for clinical decision-making in an individual patient.

Myoglobin, creatine kinase MB isoforms and creatine kinase MB mass in early diagnosis of myocardial infarction in patients with acute chest pain

OBJECTIVES

Measurements of myoglobin and creatine kinase (CK)-MB isoforms have been suggested to be sensitive tests for the early diagnosis of myocardial infarction (MI). We have investigated the utility of myoglobin, creatine kinase (CK)-MB isoforms and creatine kinase MB mass (CK-MBm) in early diagnosis of MI using cardiac troponin T (cTnT) positivity as a reference.

DESIGN AND METHODS

The study population comprised 440 patients who had had chest pain for less than 12 h. Patients were divided into cTnT negative (cTnT-) or cTnT positive (cTnT+) patients (concentration of cTnT >0.1 microg/L at two different time points during 72 h).

RESULTS

At the time of admission to the emergency department receiver operating characteristics (ROC) curves of CK-MB isoforms and CK-MBm were not better than that of myoglobin. Six hours after admission CK-MB isoforms and CK-MBm provided statistically significantly larger areas under the curve (AUC) than myoglobin (p < 0.01). When ROC curves were related to the onset of chest pain (< 3 h, 3-6 h, and > 6 h) there were no significant differences between the cardiac markers studied.

CONCLUSIONS

According to the present findings, CK-MB isoforms or myoglobin offer no advantage over CK-MBm as early markers of myocardial infarction.

Test strategies for the detection of myocardial damage

In the space of half a century, cardiac marker testing has advanced incrementally from enzymes present in nearly all tissues to proteins having remarkable specificity for myocardium. Markers with other desirable properties, such as earlier release, have also been introduced and others may be anticipated, although a single perfect marker is not on the horizon. Optimum application of these new markers still requires improved robustness and harmonization of commercial assays, and continuing insights in the pathophysiology of acute coronary syndromes. As these advances occur, future testing will likely focus more on therapeutic decisions than on arbitrary diagnostic classifications.

Serum markers in the emergency department diagnosis of acute myocardial infarction

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

CK-MB isoforms for early risk stratification of emergency department patients

The potential clinical utility of single sample CK-MB isoforms measurement for early risk stratification of Emergency Department (ED) patients with possible myocardial ischemia was evaluated among 405 patients presenting to two urban EDs. Clinical and serologic data were prospectively collected and the occurrence of adverse events (AEs) and myocardial infarction (MI) during the 14-day outcome period was recorded and utilized to calculate and compare relative risks (RR) and predictive values of isoforms and CK-MB alone. Among the 405 patients, 67 accrued 105 AEs. Both isoforms and CK-MB alone were predictive of AEs with RR of 3.32 (2.09, 5.27) and 6.28 (4.64, 8.52), respectively. Isoforms had higher sensitivity for AEs compared to CK-MB (65.7% [54.3, 77.0] vs. 14.9% [6.4, 23.5]; p<0. 01) but lower specificity (69.2% [64.3, 74.2] vs. 99.7% [99.1,100. 0]; p<0.01). Isoforms' superior sensitivity allowed identification of many high risk patients missed by CK-MB alone. Further, for the prediction of MI, isoforms had superior diagnostic sensitivity and equivalent specificity. This investigation supports the emergency department use of early, single sample CK-MB isoform testing.