Elevated CK-MB with normal total creatine kinase in suspected myocardial infarction: associated clinical findings and early prognosis

Serum Creatine Kinase-MB Isoenzyme Activity among Subjects with Uncomplicated Essential Hypertension: Any Sex Differences

Hypertension (high blood pressure) is a major health challenge and more women than men are affected by the condition. Complications as a result of this condition often lead to disabilities and premature death. The objective of this study was to evaluate creatine kinase-MB (CK-MB) activity in uncomplicated hypertension and to know whether sex differences exist in the activity of the enzyme. Serum creatine kinase-MB isoenzyme activity, troponin I, and lipid profile were evaluated in 140 male and 100 female Nigerians with hypertension. The control group was comprised of 100 (50 males and 50 females) normotensive subjects. Measured parameters were assayed using Selectra Pros chemistry analyzer. The means were compared between males and females using Students't-test. The mean CK-MB activity of the female hypertensive subjects was significantly higher (p < 0.001) than the males. Similarly, the mean cardiac troponin I (cTnI) of the female hypertensive subjects was significantly higher (p < 0.001) than the males. Conversely, the mean CK-MB activity of the female normotensive subjects was significantly lower (p < 0.001) than the male counterparts. There was no difference in the levels of cTnI between male and female normotensive subjects. Serum CK-MB activity was higher in female than male hypertensive subjects. In the light of these results, cardiac markers should be routinely done in the evaluation of hypertensive subjects and sex-specific consideration may be recognized in the management of these patients.

Discordant Cardiac Biomarkers: Frequency and Outcomes in Emergency Department Patients With Chest Pain

STUDY OBJECTIVE

We evaluate associations between pairs of discordant cardiac biomarkers (positive MB band of creatine kinase [CKMB] with negative creatine kinase, positive CKMB with negative cardiac troponin, and positive troponin with negative CKMB) and the presence of acute coronary syndromes in emergency department (ED) chest pain patients.

METHODS

This was a secondary analysis of a prospective registry. Data were obtained from the multicenter Internet Tracking Registry of Acute Coronary Syndromes, which included 17,713 ED visits for possible acute coronary syndrome between June 1999 and August 2001. First visits and first ED cardiac biomarker results from the 9 sites, 8 in the United States and 1 in Singapore, were included. Subjects were excluded for incomplete information or an initial ECG consistent with ST-segment elevation myocardial infarction. Acute coronary syndrome was defined by diagnosis-related group code indicating myocardial infarction, positive invasive or noninvasive diagnostic testing, revascularization, or death during hospitalization or within 30 days.

RESULTS

Of 8,769 eligible patients, 1,614 (18.4%) had acute coronary syndrome. The CKMB and cardiac troponin results were discordant in 7% of patients (CKMB+/cardiac troponin-, 4.9%, CKMB-/cardiac troponin+ 2.1%), whereas increased CKMB with normal creatine kinase levels occurred in 239 (3.1%) patients. The unadjusted odds ratios with 95% confidence intervals for acute coronary syndrome in patients with and without discordant markers were: CKMB+/CK- 5.7 (4.4-7.4), CKMB+/CK+ 4.4 (3.6-5.2), CKMB-/cTn+ 4.8 (3.4-6.8), CKMB+/cTn- 2.2 (1.7-2.8), CKMB+/cTn+ 26.6 (18.0-39.3). For the group with cardiac troponin, the reference category was negative troponin and negative CKMB; for the group with creatine kinase, the reference category was negative CKMB but either a positive or negative creatine kinase.

CONCLUSION

Among the spectrum of ED patients with chest pain, an increased CKMB level with a normal creatine kinase level identifies patients at increased risk for acute coronary syndrome. Similarly, an increased troponin level regardless of CKMB level and an increased CKMB level regardless of troponin level identify patients at higher risk for acute coronary syndrome than those with uniformly normal cardiac biomarker levels. Our data suggest that discordant cardiac biomarkers may identify patients at increased risk for acute coronary syndrome.

Elevated creatine kinase-MB with normal creatine kinase predicts worse outcomes in patients with acute coronary syndromes: results from 4 large clinical trials

BACKGROUND

The degree to which elevated creatine kinase (CK)-MB in the presence of normal CK is predictive of outcome is not well understood despite having been studied for decades. This analysis examined whether normal CK with elevated CK-MB in patients with non-ST-segment elevation acute coronary syndrome (NSTE ACS) is an independent predictor of worse outcomes. A concomitant goal was to contribute insight to the debate over how patients with NSTE ACS should be managed.

METHODS

Data for 25,960 patients from the GUSTO IIb, PARAGON A and B, and PURSUIT trials were analyzed. Of these patients, 6402 were excluded from primary analysis because of missing (unmeasured) biomarkers. Patients with complete laboratory data (n = 19,558) were grouped by CK and CK-MB results. To confirm the primary analysis results, data from patients with missing biomarkers were used in an imputation model.

RESULTS

Patients were categorized in 1 of 4 groups: normal CK + normal CK-MB; normal CK + elevated CK-MB; elevated CK + normal CK-MB; or elevated CK + elevated CK-MB. For the primary outcome, 180-day death, or myocardial infarction, Kaplan-Meier estimates were 14.9%, 20.8%, 14.5%, and 18.2%, respectively. Regardless of total CK, elevated CK-MB was associated with a 25% to 49% increased relative risk of worse outcomes. Findings from the analyses were verified by the multivariable model.

CONCLUSIONS

CK-MB remains a reliable marker for myocardial necrosis and a strong predictor of worse prognosis. All patients with ACS should have CK-MB measurement to search for cardiac ischemia. Patients with elevated CK-MB should receive aggressive management commensurate with their increased risks.

Biochemical and clinicopathological changes induced by Bungarus coeruleus venom in a rat model

Bungarus coeruleus, a common venomous snake allied to the cobra, is responsible for most envenomations in India. This study examines the pathological effects of B. caeruleus venom and the associated biochemical changes in a rat model. Increased serum aspartate aminotransferase (48%), creatine kinase (30%), and lactate dehydrogenase (6%) were detected after a sublethal dose of 25 microg/kg of B. caeruleus venom was injected intramuscularly into rats observed for 180 min. The venom induced hyperglycemia and increased serum alkaline phosphatase (55%) and urea (90%) concentrations, whereas cholesterol and triglycerides remained normal. Histopathological changes in the heart-hemorrhage, multifocal areas of myocardial fiber necrosis-and constriction of blood vessels in the kidney, with congested vessels, hemorrhage and necrosis of proximal tubules, liver congestion, and hemorrhage were found.

Effect of elevated concentration of alkaline phosphatase on cardiac troponin I assays

Troponin I is the regulatory subunit of troponin complex associated with the actin thin filament within muscle cells. Cardiac troponin I (cTnI) is a good marker for diagnosis of myocardial damage. Several immunoassays are available for determination of cTnI in serum. The Stratus cTnI fluorometric enzyme immunoassay (Dade International) uses alkaline phosphatase (ALP) substrate. The microparticle enzyme immunoassay (MEIA) for cTnI (Abbott Laboratories) also uses ALP conjugate. On the other hand, the chemiluminescent assay (CLIA) for cTnI (Bayer Diagnostics) does not use ALP. ALP activity may frequently be elevated in serum of patients being evaluated for suspected myocardial infarction. Therefore, we studied the potential interference of ALP in cTnI assays. Serum pools were prepared from patients, and various concentrations of ALP solution were added to different aliquots. The cTnI concentrations were measured by the Stratus, MEIA, and CLIA assays. We observed no interference of ALP in the MEIA and CLIA assay for cTnI. On the other hand, we observed significant positive interference of ALP when cTnI concentrations were measured using the Stratus.

Normal CK, elevated MB predicts complications in acute coronary syndromes

The implications of an elevated Creatine kinase (CK)-MB isoenzyme (MB) in suspected acute coronary syndromes, with a normal total CK, is not well established. Despite many guidelines on managing patients with acute coronary ischemia, none indicates strategies for patients with elevated MB and with a normal CK. The outcome consequence of this result is not firmly established. Our objective was to prospectively evaluate outcomes in patients with suspected acute coronary syndromes, normal initial total CK, and increased MB. All Emergency Department patients with suspected acute coronary syndromes and creatinine < 2.0 mg/dL were eligible for study entry. Serial CK and MB fractions were measured on arrival in the Emergency Department, then 8 and 16 h postpresentation. A composite outcome of death, Q-wave myocardial infarction, or revascularization was defined at the index visit and 6 months later. Outcomes were determined by blinded record review and by telephone contact. In the 698 patients entered, the acute composite outcome rate was 25% (175) and 6.3% (44) at 6 months. Acute and 6 month adverse outcome rates were statistically the same for all patients with an elevated MB fraction, regardless of the total CK level. An elevated MB conferred a higher event rate than did a normal MB. We conclude that the adverse event rate for patients with suspected acute coronary syndromes and an elevated MB is the same whether or not the total CK is elevated. These patients should be considered as having had an acute coronary syndrome.

Negative interference of bilirubin and hemoglobin in the MEIA troponin I assay but not in the MEIA CK-MB assay

Troponin I is a sensitive and specific marker for the diagnosis of myocardial infarction. Several commercially available immunoassays measure the concentration of troponin I in serum. The microparticle enzyme immunoassay (MEIA) for troponin I (Abbott Laboratories, Abbott Park, IL) is widely used in clinical laboratories, including our hospital laboratory. We studied the effect of bilirubin and hemolysis on the MEIA for troponin I and compared our assay with a newly available chemiluminescent assay (CLIA) for troponin I (Bayer Diagnostics, Tarrytown, NY). We also measured CK-MB concentration using the MEIA CK-MB assay. One serum pool was prepared by combining several specimens of one patient with elevated troponin I and with a diagnosis of myocardial infarction. Other serum pools were prepared by combining sera with similar troponin I values. All serum pools showed normal bilirubin concentrations and had no hemolysis. Then we supplemented aliquots of serum pools with various concentrations of bilirubin (5.0, 10.0, 15.0, and 20.0 mg/dL). After supplementation, troponin I concentrations were measured again using the MEIA and CLIA. We observed a statistically significant decrease in troponin I concentration in the presence of bilirubin with the MEIA. For example, in serum pool 1, the troponin I concentration was 16.3 (bilirubin: 0.8 mg/dL). In the presence of 5.0, 10.0, 15.0 and 20.0 mg/dL of added bilirubin, the cardiac troponin I concentrations were 13.9, 13.4, 13.3 and 13.0 ng/ml respectively. We observed similar negative interference of bilirubin in troponin I measurement by the MEIA in other pools. The troponin I value decreased slightly (not statistically significant) in one pool and did not change in two other pools in the presence of bilirubin when we measured troponin I concentration using the CLIA. Interestingly, bilirubin did not interfere with the MEIA CK-MB assay. Moderate hemolysis did not have any effect on the troponin I assay using either the MEIA or CLIA. However, gross hemolysis (hemoglobin > 40 mg/dL) interfered with both assays for troponin I.

Delta CK-MB outperforms delta troponin I at 2 hours during the ED rule out of acute myocardial infarction

It has been shown that a rise in creatine kinase MB bank (CK-MB) of > or = + 1.6 ng/mL in 2 hours is more sensitive and equally specific for detection of acute myocardial infarction (AMI) as compared with a 2-hour CK-MB > or = 6 ng/mL during the emergency department (ED) evaluation of chest pain. Because cardiac specific troponin I (cTnI) is thought to have similar early release kinetics as compared with CK-MB mass, we undertook a retrospective cohort study in 578 chest pain patients whose baseline CK-MB and cTnI was less than two times the hospital's upper limits of normal and who underwent a 2-hour CK-MB and cTnI to compare sensitivities and specificities of the 2-hour delta CK-MB (deltaCK-MB) and delta cTnI (delta cTnI) for AMI and 30-day Adverse Outcome (AO). Thirty day AO was defined as AMI, life-threatening complication, death, or percutaneous transluminal coronary angioplasty (PTCA)/coronary artery bypass graft (CABG) within 30 days of ED presentation. Optimum delta values were determined by choosing the smallest cutoff value greater than the assay precision where the deltaCK-MB and delta cTnI had a positive likelihood ratio for 30-day AO of > or = 15. A deltaCK-MB > or = +1.5 ng/mL was more sensitive than a deltaTnI > or = +0.2 ng/mL for AMI (87.7% versus 61.4%; P < .0005) and 30-day AO (56.7% versus 42.3%; P < .005). There were no differences in specificities for AMI and 30-day AO. Combining the two tests (MBdelta > or = +1.5 ng/mL and/or a deltaTnI > or = +0.2 ng/mL) resulted in an incremental increase in sensitivity of 89.5% for AMI and 61.9% for AO (P < .005). Patients with either a rise in CK-MB of > or = +1.5 ng/mL or rise in cTnI of > or = +0.2 ng/mL in 2 hours should receive consideration for aggressive antiischemic therapy and further diagnostic testing before making an exclusionary diagnosis of nonischemic chest pain.

Characteristics and prognosis of patients with suspected acute myocardial infarction and elevated MB relative index but normal total creatine kinase

"MB Leak" patients who develop an elevated MB relative index with a normal total creatine kinase (CK) level are not as well characterized as those who have diagnostic enzyme elevations in the setting of ST elevation (elevation) or non-ST elevation acute myocardial infarction (AMI). During a 1-year period, we studied all patients hospitalized in an urban academic hospital with suspected AMI who developed an elevated MB relative index within 24 hours of presentation. Of 595 patients, 44% had MB Leak, 34% had non-ST elevation AMI and 22% had ST elevation AMI. Patients with MB Leak and non-ST elevation AMI were significantly older than those with ST elevation AMI (mean ages 69, 71, and 63 years, respectively; p <0.001), and were more likely to have previous AMI (55%, 46%, 12%; p <0.001) or past coronary revascularization (40%, 19%, 12%; p <0.001). The in-hospital death rate of patients with MB Leak was half that of patients with non-ST elevation AMI or ST elevation AMI (6%, 12%, 12%; p = 0.03). By 1 year after presentation, the death rate of patients with MB Leak (17%) was intermediate between that of non-ST elevation AMI (24%) and ST elevation AMI (14%). Within the MB Leak group, those with elevated absolute CK-MB levels were at highest risk. In a multivariable model using MB Leak as the referent, the relative risks for 1 year death were 1.4 (95% confidence interval, 0.9 to 2.2) for patients with non-ST elevation AMI and 1.7 (0.8 to 3.4) for patients with ST elevation AMI. Patients with MB Leak are at high risk for cardiovascular events in the hospital and for death by 1 year. Therefore, they may benefit from early aggressive therapy and risk stratification. These results suggest that CK-MB should be measured in all patients with suspected AMI, regardless of their total CK level.

Reflex testing II: evaluation of an algorithm for use of cardiac markers in the assessment of emergency department patients with chest pain

A reflex algorithm was developed and evaluated for the use of serum cardiac markers for the diagnosis and rule out of acute myocardial infarction (AMI), and risk stratification of unstable angina patients for those who present to emergency departments (ED) with chest pain. The process begins with testing of total CK and myoglobin at admission. Based on these results, the algorithm determines the need for subsequent testing for the CK-MB isoenzyme and cardiac troponin I (cTnI). The algorithm also directs the need for further blood collection and cardiac marker testing at 4, 8, and 12 h after presentation. A total of eleven stopping points were identified. For some of these stopping points, the algorithm concluded that further blood collections and testing was unnecessary and redundant. The algorithm was retrospectively evaluated on 101 non-consecutive chest pain patients who presented to the EDs at three hospitals. For the AMI group (n=34), six of nine possible different stopping points were reached: 64.7% of cases were diagnosed with the first sample at admission, an additional 32.3% after 4 h, and 2.9% at 8 h. The 12-h sample was not necessary for any of the AMI patients. For the non-AMI group (n=67), most reached the stopping point of no cardiac injury or risk. There were five unstable angina patients who had minor myocardial damage on the basis of a marginally increased cTnI. Of these, one patient subsequently suffered AMI, and three others required angioplasty or bypass surgery. Compared to performing four tests on all patient samples, the reflex algorithm would have reduced the number of necessary tests from 442 to 130 (71% reduction) for AMI patients, and 871 to 469 (46% reduction) for non-AMI patients, if prospectively implemented.

Creatine kinase and its CK-MB isoenzyme: the conventional marker for the diagnosis of acute myocardial infarction

Biochemical markers are commonly used for detection, diagnosis, and management of various diseases. Creatine kinase (CK) is an enzyme found in most tissues, and is the best known marker for the identification of acute myocardial infarction (AMI). We review the most common techniques used to quantify creatine kinase and its cardiac specific fraction, CK-MB. Electrophoresis, immunoinhibition, monoclonal immunoassay, and CK-MB isoform assays are considered for efficacy, sensitivity and specificity, and timeliness in the setting of acute non-traumatic chest pain. Limitations of the various techniques for identifying AMI are identified. Current recommendations for CK-MB panels, including combinations with other cardiac markers, are included.

Serial creatinine kinase (CK) MB testing during the emergency department evaluation of chest pain: utility of a 2-hour deltaCK-MB of +1.6ng/ml

BACKGROUND

Traditional methods of using creatinine kinase (CK)-MB to diagnose acute myocardial necrosis rely on the total CK-MB exceeding a threshold of normalcy before being considered diagnostic. Because the CK-MB rapid immunoassay is both sensitive and precise, a small difference between two serial samples over an appropriate time interval may result in an increased sensitivity for acute myocardial infarction (AMI) compared with traditional methods if an appropriate cutoff value is chosen.

METHODS AND RESULTS

Baseline and 2-hour CK-MB immunoassay measurements were performed in 710 patients with chest pain whose baseline CK-MB was less than two times upper limits of normal (<12 ng/ml) to determine whether a rise in CK-MB > or =+1.6 ng/ml is more sensitive and specific than an abnormal 2-hour CK-MB in the detection of patients with AMI during the initial emergency department evaluation of chest pain. The baseline (MBO) or 2-hour (MB2) CK-MB was considered positive if the CK-MB level was > or =6 ng/ml. MBdelta was defined as the difference of MB2 and MBO and was considered positive if the value was > or =+1.6 ng/ml. A positive MB2 was more sensitive for the detection of AMI (75.2% vs 17.7%; p < 0.0001) than a positive MBO. A positive MBdelta was more sensitive for the detection of AMI (93.8% vs 75.2%; p < 0.0001 ) than a positive MB2. There were no statistically significant differences in specificities for AMI for any test modality.

CONCLUSIONS

A rise in CK-MB of > or =+ 1.6 ng/ml in 2 hours is a useful marker of AMI during the initial emergency department evaluation of patients with chest pain.

Use of troponin T and creatine kinase-MB subunit levels for risk stratification of emergency department patients with possible myocardial ischemia

STUDY OBJECTIVES

To evaluate and compare the utility of measurement of troponin T and the creatine kinase MB subunit (CK-MB) for risk stratification of ED patients with possible myocardial ischemia.

METHODS

Prospective observational study of ED patients with symptoms of possible myocardial ischemia with early, single sample serologic testing for cardiac troponin T and CK-MB using an identity-unlinked process. Chart review (ED, inpatient, outpatient), and telephone and mail surveys identified adverse events (AEs) during the 14 days following enrollment. AEs recorded included death, respiratory or cardiac arrest, myocardial infarction (MI), atrial and ventricular arrhythmias, pulmonary edema, conduction disturbances, and recurrent angina. Measures of the predictive ability for AEs were calculated for troponin T, CK-MB, and a combined troponin T/CK-MB index (defined as positive if either troponin T or CK-MB levels exceeded threshold values).

RESULTS

Among 292 study patients, 45 (15.4%) experienced at least one AE, including seven deaths and 12 MIs. The troponin T result was positive in 34 patients, and the CK-MB result was positive in 15 patients; 6 patients had positive results for both markers and 43 patients had a positive combined troponin T/CK-MB index. Odds ratios (ORs) for occurrence of AEs among all patients were 4.4 (1.8 to 10.2), 10.0 (3.0 to 36.0), and 4.5 (2.0 to 9.8) for troponin T, CK-MB and the troponin T/CK-MB index, respectively. Both markers were individually predictive of AEs (troponin T = 4.3; CK-MB = 7.5) among all those with chest pain. Only the CK-MB level was significantly predictive of AEs among those presenting with symptoms other than chest pain (OR = 24.3 [1.1, 1448]), whereas only the troponin T level was significantly predictive among patients representing a disposition dilemma for the emergency physician (OR = 5.7 [1.4, 20.7]). When compared, the ORs for troponin T and CK-MB were not significantly different for any patient subgroup. The troponin T/CK-MB index did not have a higher prognostic value than either troponin T or CK-MB alone in any subgroup studied.

CONCLUSION

A positive test result for either troponin T or CK-MB in the ED successfully identified patients at significantly higher risk of adverse events during the 2 weeks following their ED visit. The two markers may complement each other in that each appears to have prognostic ability among a unique patient subgroup. ED marker measurement can provide useful prognostic information for patients with a broad spectrum of presentations consistent with possible myocardial ischemia.

Biochemical and histopathological alterations induced in rats by Tityus serrulatus scorpion venom and its major neurotoxin tityustoxin-I

Intravenous injection into the rat of sublethal doses of Tityus serrulatus scorpion venom (100 micrograms protein/kg) or its major neurotoxin tityustoxin-I (TsTX-I, 20 micrograms/kg) caused, 30-180 min after injection, statistically significant increases in the serum levels of aspartate aminotransferase, amylase, creatine kinase and lactate dehydrogenase, as well as hyperglycemia, a high level of plasma free fatty acids and a low level of liver glycogen. The in vitro serum levels of the above enzymes did not change. For alanine aminotransferase, gamma-glutamyl transferase and alkaline phosphatase, neither in vitro nor in vivo alterations were observed. The whole venom and TsTX-I caused hepatic congestion with hemolysis and hydropic degeneration. Other histological lesions included edema and congestion with subpleural hemorrhage in the lungs, hypertrophy of fibers with degeneration areas in the heart, and congestion and hemorrhage in the kidneys. In the salivary glands, alterations to the acini and ductules were visible. In the adrenal glands no morphological alterations could be detected at the studied doses. The results suggest that the in vivo enzymatic and histopathological alterations are due to tissue lesions evoked by the whole venom and TsTX-I. An indirect effect, however, induced by stimulation of acetylcholine and catecholamine release in the postganglionic nerve terminals, cannot be excluded.

Clinical and angiographic correlates of normal creatine kinase with increased MB isoenzymes in possible acute myocardial infarction

A retrospective study of patients with possible acute myocardial infarction was conducted over a 2-year period to evaluate the clinical characteristics, angiographic findings, and in-hospital prognosis in patients with normal total creatine kinase (CK) activity and increased MB isoenzyme activity (CK-MB). Thirty-nine cases were identified (study group) and compared with cases of Q-wave (n = 77) and non-Q-wave (n = 60) infarctions. Compared with the Q-wave group, study group patients were older (67.5 +/- 9.0 vs 60.8 +/- 11.5 years; p < 0.01) and more often had previous diagnoses of coronary disease (52.6% vs 18.2%; p < 0.01) and peripheral vascular disease (28.9% vs 10.4%; p = 0.02). Angina (92.2% vs 65.8%; p < 0.01) and ST elevation (81.8% vs 13.2%; p < 0.01) were more common in the Q-wave group. Nearly identical clinical profiles and electrocardiographic findings were observed in the study and non-Q-wave groups. Angiographic analysis revealed a higher frequency of multivessel disease in the study group (89.6%) than in the Q-wave group (48.6%, p < 0.01) but no difference between the study group and the non-Q-wave group (79.6%; p not statistically significant). Left ventricular function and in-hospital complications were similar among groups. It is concluded that patients with normal total CK activity and increased CK-MB concentration represent a subgroup of patients with non-Q-wave infarction with a high prevalence of multivessel coronary disease.

Age-related differences in the utilization of therapies post acute myocardial infarction

OBJECTIVE

To describe the effect of age on the care of patients hospitalized with acute myocardial infarction (MI).

DESIGN

Retrospective chart review of all cases with a primary or secondary discharge diagnosis of acute MI.

SETTING

Two large community hospitals in Milwaukee, Wisconsin, from July 1, 1990 to June 30, 1991.

PATIENTS

There were 771 charts reviewed, of which, 149 cases were aged 54 years or younger, 203 were 55 to 64 years, 224 were 65 to 74 years, and 195 were aged 75 years or older.

MEASUREMENTS

Hospital charts were examined for use of diagnostic and therapeutic interventions, including medications and procedures, as well as length of stay and in-hospital mortality.

RESULTS

Older patients were more likely to be female (18%, 20%, 38%, and 56% for the four age groups, respectively, P < .001 chi-square for linear trend), more likely to present with congestive heart failure (31%, 39%, 51%, and 72%, P < .001), and had a higher in-hospital mortality rate (5%, 7%, 10%, and 18%, P < .001). Older patients had a longer length of stay in the hospital. The use of cardiac catheterization in these post-MI patients was high and did not decrease until after age 75 (85%, 88%, 88%, and 47%, P < .001). The percentage of patients receiving balloon angioplasty decreased with age (51%, 51%, 43%, and 20%, P < .001), whereas the percentage of patients receiving myocardial revascularization did not significantly differ with age (15%, 22%, 25%, and 19%, P = .46). Aspirin was less likely to be prescribed to older patients at discharge (79%, 82%, 70%, and 62%, P < .001).

CONCLUSION

A surprisingly high percentage of those older than age 65 received invasive tests and interventions. This high utilization rate coexists with our continued ignorance about the efficacy of these tests and interventions in older adults.

Biochemical markers of myocardial damage

OBJECTIVE

To assess various biochemical markers of myocardial damage.

METHODS AND RESULTS

Before routinely using any test as a biochemical marker of myocardial damage, the published evidence for its diagnostic utility must be critically assessed. Such assessment includes receiver operator curve (ROC) curve analyses, confidence interval estimates of claimed sensitivity and specificity values, and the effects of testing in serial and parallel modes. It is also necessary to establish the test's rule-in (high specificity) and rule-out (high sensitivity) decision thresholds that may vary with time after the onset of symptoms. The spectrum of ischemic heart disease includes acute (sudden death, non-Q- and Q-wave infarctions) and chronic (stable, unstable, and variant angina) conditions. Biochemical markers of myocardial damage are of most value in the diagnosis of acute ischemic heart disease, although increasingly some of these markers are being found to possess a prognostic value in chronic ischemic heart disease. The markers of enzymatic activity include aspartate aminotransferase, creatine kinase (together with isoenzymes and isoforms), and lactate dehydrogenase and isoenzymes. Creatine kinase isoenzyme-2 may also be measured immunologically, and this type of assay is in increasing use both because of its speed and because its blood levels rise earlier than the corresponding activities. The commercially available nonenzymatic markers are myoglobin and troponin T; troponin I is expected to become available in late 1995. While myoglobin is a nonspecific indicator of myocardial damage, its diagnostic value is due to its early appearance in blood. Troponin T is more cardiac specific, but the published data appears to suggest that the cardiac specificity of troponin I is superior. Troponin levels become abnormal at about the same time after the onset of symptoms as mass assays of creatine kinase isoenzyme-2; therefore, they are not useful as early markers of myocardial damage.

CONCLUSION

The availability of these nonenzymatic markers of myocardial damage must force a reassessment of the continued use of the enzymatic markers. Are they necessary, and if so, which ones should be retained?

Creatine kinase-MB mass concentration versus creatine kinase-B activity for the detection of acute myocardial infarction in patients with slightly elevated total creatine kinase activity in serum

OBJECTIVE

The diagnostic value of creatine kinase-MB mass concentration (CK-MB mass) was compared with that of creatine kinase-B (CK-B) activity in patients with suspected acute myocardial infarction (AMI) but with total serum CK activity only slightly above the reference range.

DESIGN

One hundred consecutive blood samples with total CK activity between 120 and 360 U l-1 and CK-B activity > or = 9 U l-1 were analysed. Electrophoresis of CK isoenzymes was also performed.

SETTING

Patients from all departments of the hospital were included. About half of the patients originated from the coronary care unit.

SUBJECTS

The blood samples derived from 49 patients. Thirteen patients had at least one serum sample with total CK activity above 360 U l-1. These and another three patients were omitted from the study.

RESULTS

Acute myocardial infarction had been diagnosed clinically (with CK and CK-B methods) in 12 of 33 patients. However, using the CK-MB mass concentration of the reference method, five of these 12 patients did not have myocardial infarction whereas nine patients with small infarctions were undetected. A good correlation was seen between the results from CK-MB mass concentration and CK isoenzyme electrophoresis, but there was a poor correlation between these methods and CK-B activity including the CK-B/CK ratio. A relatively high proportion (24%) of the selected patients had increased levels of macro CK.

CONCLUSION

CK-B activity was inaccurate for the detection of probably myocardial infarction in patients with slightly elevated total CK activity. Increased levels of macro CK interfering with the CK-B assay was one explanation for this observation.

Diagnostic performance and prognostic value of serum troponin T in suspected acute myocardial infarction

Cardiac troponin T (TnT) is a new serological marker for use as a diagnostic tool for myocardial damage. A blinded prospective multicentre study representing 298 patients suspected of having acute myocardial infarction (AMI), and admitted to the coronary care units of six Scandinavian Hospitals was undertaken to assess the diagnostic performance and prognostic efficacy of a new cardiospecific TnT immunoassay. We used a discriminator TnT value of 0.20 microgram l-1. One hundred and fifty five patients (52%) had definite AMI, based on WHO criteria (all had peak S-TnT values of > or = 0.20 micrograms l-1); 127 patients (43%) had ischaemic heart disease (IHD) without AMI; and 16 patients (5%) had non-IHD (all had peak S-TnT values of < 0.20 microgram l-1). The 127 IHD-patients without definite AMI could be subdivided into a group of 44 patients with S-TnT peak values of > or = 0.20 microgram l-1, and a group of 83 patients with TnT below this level. An equal identification of these patients among the centres was seen (mean +/- SD 35 +/- 13%; range 20-55%). A follow-up study was able to define the clinical significance of these findings. The cumulative 6 months probability of suffering cardiac death or AMI was significantly higher in the subgroup with increased TnT values (14% (6/44)) as compared to the other subgroup (4% (3/83)) (Log-rank test, p = 0.025). The probability of cardiac events was 15% for the patients with definite AMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute myocardial infarction in chest pain patients with nondiagnostic ECGs: serial CK-MB sampling in the emergency department. The Emergency Medicine Cardiac Research Group

STUDY OBJECTIVES

This study tested the hypothesis that serial creatine phosphokinase (CK)-MB sampling in the emergency department can identify acute myocardial infarction (AMI) in patients presenting to the ED with chest pain and nondiagnostic ECGs.

DESIGN

Patients more than 30 years old who were evaluated initially in the ED and hospitalized for chest pain were studied. Serial CK-MB levels were analyzed prospectively using a rapid serum immunochemical assay for identification of AMI patients in the ED. Presenting ECGs showing new, greater than 1-mm ST elevation in two or more contiguous leads were considered diagnostic for AMI. All other ECGs were considered nondiagnostic ECGs. CK-MB levels were determined at ED presentation and hourly for three hours (total of four levels). Patients with at least one level of more than 7 ng/mL were considered to have a positive enzyme study. The in-hospital diagnosis of AMI was determined by the development of typical serial ECG changes or separate standard cardiac enzyme changes after admission.

SETTING

Eight tertiary-care medical center hospitals.

METHODS AND MAIN RESULTS

Of the 616 study patients, 108 (17.5%) were diagnosed in the hospital as AMI; 69 of these AMI patients (63.9%) had nondiagnostic ECGs in the ED. Of the patients with nondiagnostic ECGs, 55 (sensitivity, 79.7%) had a positive ED serial CK-MB enzyme study within three hours after presentation. Combining serial ED CK-MB assay results with diagnostic ECGs yielded an 88.4% sensitivity for AMI detection within three hours of ED presentation. The predictive value of a negative serial ED enzyme study for no AMI was 96.2% (specificity, 93.7%).

CONCLUSION

Serial CK-MB determination in the ED can help identify AMI patients with initial nondiagnostic ECGs. Use of serial CK-MB analysis may facilitate optimal in-hospital disposition and help guide therapeutic interventions in patients with suspected AMI despite a nondiagnostic ECG.

The predictive value of CKMB mass concentration in unstable angina pectoris: preliminary report

Unstable angina pectoris is a common clinical problem, and the diagnosis is based on clinical symptoms. However, these symptoms cannot identify high-risk patients. Holter monitoring can identify patients at high risk, but analysis of a large number of patients is time- and resource-consuming, as is angiographic examination. We determined whether creatine kinase MB isoenzyme mass concentration could predict the prognosis for patients with unstable angina pectoris. A total of 101 consecutive patients were studied, and blood samples were collected three times a day for 48 h after admission. Patients with unstable angina and elevated CKMB (but still within the normal range) had a significantly higher risk of developing acute myocardial infarction or requiring revascularization during 6 months of follow-up than patients without elevated CKMB. We conclude that CKMB analysis is a valuable tool that may be of use in selecting high-risk patients with unstable angina pectoris. This finding needs to be confirmed by more extensive studies.

Myocardial injury without heart failure following envenomation by the scorpion Leiurus quinquestriatus in children

The enzymatic activity of creatine kinase-MB isoenzyme (CK-MB), a sensitive and specific marker of myocardial damage, was measured in 32 children following scorpion envenomation. CK-MB activity, total creatine phosphokinase (CPK) and serum glutamine oxalacetic transaminase (SGOT) levels were examined for relationship with electrocardiographic (ECG) results and the clinical state of the children. Twenty-seven out of the 32 children had signs of systemic intoxication ("symptomatic" cases), while the other five children had only local signs ("asymptomatic" cases). Thirteen out of the 27 symptomatic children had enzymatic myocardial involvement characterized by high total CPK level, elevated CK-MB level and a CK-MB/CK ratio exceeding 6%. Six of these 13 children had ECG changes consistent with myocardial damage, and only one child had clinical signs of myocardial injury. None of the asymptomatic children, nor five healthy control children, had any evidence of myocardial damage as judged by CK-MB levels, clinical signs and ECG. Our study suggests that CK-MB activity is specific and highly sensitive in detecting myocardial damage in children following scorpion envenomation, and appears superior to ECG and clinical parameters. We speculate that the myocardial lesions are too small to cause heart failure in most cases, but they may account for the cardiovascular changes frequently seen in scorpion envenomation.

Prevention of creatine kinase-MB release in coronary artery disease and pacing-induced myocardial ischemia by isosorbide dinitrate spray

The effect of isosorbide dinitrate (ISDN) spray on release of the isoenzyme creatine kinase-MB (CK-MB) after myocardial ischemia induced by atrial pacing was evaluated in 8 patients with coronary artery disease. Atrial pacing to ischemia (ST-segment depression of greater than or equal to 1.5 mm for greater than or equal to 80 ms) resulted in elevation of CK-MB levels in plasma drawn from the coronary sinus, from 1.8 +/- 1.5 to 6.8 +/- 7.0 ng/ml (p less than 0.001) at 30 minutes after onset of ischemia. When atrial pacing was repeated at the same rate after 1 squirt of ISDN spray, 1.25 mg, the CK-MB levels were not altered despite significant ischemic ST-segment depression. It is concluded that ISDN prevents the process responsible for myocardial release of CK-MB, being either micronecroses or a reversible consequence of ischemia.

At what level of serum total creatine kinase activity can measurement of serum creatine kinase MB isoenzyme activity be omitted in suspected myocardial infarction?

The purpose of this study was to establish a discriminatory limit for serum total creatine kinase activity (CK activity) below which CK isoenzyme fractionation is unnecessary. We looked at 2610 serum samples from 1077 consecutive patients with suspected acute myocardial infraction (AMI). The CK activity was determined according to the Scandinavian recommended method. Isoenzymes of CK were separated by agarose gel electrophoresis, followed by fluorometric scanning. When the threshold for CK activity was 150 U/l, none of the samples had a creatine kinase MB isoenzyme activity (CK-MB activity) equal to or higher than 30 U/l (the diagnostic level), which has been found to differentiate between patients with AMI and those without AMI. Only 14 patients (1.3% of all patients investigated) had CK-MB activity peaks between 10 U/l (detection limit) and 30 U/l. Of these, AMI was only diagnosed in one. We recommend that CK-MB activity should be measured only when CK activity is higher than 150 U/l. This would make about 50% of all CK-MB measurements unnecessary.

Rapid serial enzyme measurements in evaluation of patients with suspected myocardial infarction

Because clinical and laboratory criteria cannot accurately establish the presence or absence of acute myocardial infarction (AMI) at the time of initial presentation, this diagnosis is not confirmed in the majority of patients admitted to coronary care units. To study the effectiveness of serial changes in enzyme activity in specimens taken at presentation and 8 hours later in establishing the likelihood of AMI, the results in 1,214 patients with acute cardiac symptoms of less than 24 hours' duration were retrospectively evaluated. In 1,007 patients with initially normal creatine kinase (CK), an increase in CK (positive delta-CK) occurred in 98% of patients with AMI and 16% of patients without AMI. In 196 patients with elevated total CK, a low ratio of CK to aspartate aminotransferase was found in 98% of patients with AMI and 33% of patients without AMI. These 2 enzyme ratios had a sensitivity greater than 90% in patients with typical and atypical histories. The overall predictive value of serial enzyme measurements for AMI was 53%, compared with 18% in patients selected for admission. These results suggest that serial enzyme measurements could be used in the initial evaluation of patients with suspected AMI, and have the potential to reduce the number of patients admitted to coronary care units who do not have AMI.

Elevated CK-MB isoenzyme after exercise stress test and atrial pacing in patients with ischemic heart disease

Using a highly sensitive monoclonal antibody kit for CK-MB, significant release of small amounts of CK-MB isoenzyme after exercise stress test was detected 4 to 6 h after induction of ischemia. This occurred in ten out of 15 patients with ischemic heart disease (66 percent) and in only one of the 18 healthy subjects (5.6 percent) serving as a control group. In five patients with coronary artery disease in whom atrial pacing was performed with simultaneous blood sampling from coronary sinus, a drastic elevation in CK-MB isoenzyme (from 2.04 +/- 2.06 ng/L to 10.88 +/- 6.9 ng/L; p less than 0.001) was detected within 10 to 30 min after induction of acute ischemia. A small but significant increase in total CK also was detected (from 21 +/- 12 IU/L to 52 +/- 14IU/L; p less than 0.01). These preliminary observations have to be further investigated in a larger group of patients before a definitive conclusion can be reached about the clinical significance of CK-MB release during exercise.

Usefulness of lactate dehydrogenase and lactate dehydrogenase isoenzymes for diagnosis of acute myocardial infarction

The usefulness of lactate dehydrogenase (LD) and LD isoenzymes in the diagnosis of acute myocardial infarction (AMI) is controversial. The present study reviewed 507 consecutive patients in whom creatine kinase, creatine kinase isoenzymes, LD and LD isoenzymes were ordered over a 1-month period. Of these, 249 had an insufficient number of serial enzyme determinations to establish a laboratory diagnosis of AMI. After excluding an additional 11 patients for other reasons, 247 patients remained for analysis. Of these, only 2 (0.8%) had myocardial infarction by standard clinical criteria with normal creatine kinase and creatine kinase-MB but elevated LD and abnormal LD isoenzymes. Seven patients (7 of 247, 2.8%) had false-positive LD isoenzymes. Thus, the routine use of LD and LD isoenzymes was of no use in most patients (96%) and led to the incorrect diagnosis of AMI more than 3 times as often as it helped with a correct diagnosis. Total 1-month charges for all the LD and LD isoenzymes obtained equalled +42,450. Therefore, it appears that LD and LD isoenzymes are not routinely useful in the diagnosis of AMI and may result in considerable unnecessary expense. It is suggested that LD and LD isoenzymes be ordered only under suspicion of late presentation (greater than 48 hours) of AMI.

Cardiac myonecrosis in hypertensive crisis associated with monoamine oxidase inhibitor therapy

A young woman taking tranylcypromine for depression was hospitalized with severe chest pain and hypertension after eating cheese. Electrocardiography initially showed arrhythmias and precordial ST segment depression. Myocardial creatine kinase values were elevated, and echocardiography showed regional ventricular dysfunction, suggestive of focal cardiac myonecrosis. The cardiovascular pathophysiology of tyramine hypertensive crisis and related catecholamine excess states, including pheochromocytoma and clonidine withdrawal, is reviewed. Cardiac myonecrosis is a potential adverse effect of the hypertensive crisis associated with monoamine oxidase inhibitor use. Psychiatric indications for monoamine oxidase inhibitors may be expanding, but clinicians should continue to exercise caution in the use of these agents.