Early detection of successful coronary reperfusion based on serum myoglobin concentration: comparison with serum creatine kinase isoenzyme MB activity

Skin blood flow and its oscillatory components in patients with acute myocardial infarction

BACKGROUND/AIMS

Laser Doppler flowmetry (LDF) was used to determine the influence of acute myocardial infarction (AMI) and of successful reperfusion treatment on basal skin blood flow and its oscillatory components.

METHODS

Skin LDF was performed on all extremities in 58 patients 4-9 days after AMI (Killip class I), and in 71 healthy age- and sex-matched controls. Wavelet analysis was applied to evaluate oscillatory components within the interval 0.005-2 Hz.

RESULTS

AMI patients had reduced mean flow (p < 0.01) and oscillatory components (p < 0.04) in all extremities. Reperfused (n = 40), compared to nonreperfused (n = 18), patients had higher mean flow and total spectral amplitude at all recording points. The difference was statistically significant only in legs (group median LDF in the left leg was 9.68 AU for reperfused and 5.71 AU for nonreperfused patients, p < 0.04, and 11.47 and 4.24 AU in the right leg, p < 0.01). Reperfused patients had significantly higher total spectral amplitude in both legs (p < 0.04).

CONCLUSIONS

In AMI patients, reduced skin blood flow and its oscillatory components may reflect ongoing neurohumoral activation despite absence of clinically apparent heart failure. The reduction of blood flow and its oscillatory components was larger in nonreperfused AMI patients, although they had a comparable left ventricular function.

Evaluation of coronary artery patency using cardiac markers

The availability of a reliable marker of infarct-related artery (IRA) patency status may permit early identification of patients with patent IRA, for whom repeat thrombolysis or rescue percutaneous coronary intervention (PCI) may not be necessary. We found that the ratio of serum myoglobin levels obtained before and 60-min after initiation of thrombolytic therapy provides a useful indication of the IRA patency status. When the 60-min myoglobin ratio was >4.0, the probability of a patent IRA was 90%, suggesting that emergency coronary angiography to determine their IRA status may be unnecessary when this pattern of release of myoglobin is observed. The low specificity of this marker could be addressed by its combined use with other noninvasive tests such as ST-segment resolution and the persistence of chest pain at the time of angiography.

Serum myoglobin/carbonic anhydrase III ratio as a marker of reperfusion after myocardial infarction

BACKGROUND

Coronary patency is important for short- and long-term outcome after myocardial infarction. Serum myoglobin concentration is a sensitive marker of myocardial damage and its specificity can be improved by simultaneous measurement of carbonic anhydrase III, a skeletal muscle marker. In the present study we evaluated the role of myoglobin/carbonic anhydrase III ratio as a non-invasive marker of reperfusion.

METHODS

We measured myoglobin, carbonic anhydrase III and creatine kinase MB-fraction release serially in 29 patients with acute myocardial infarction treated with thrombolysis and in 28 patients treated with primary coronary angioplasty.

RESULTS

Thrombolytic therapy was followed by a 9.1+/-2.2-fold increase in myoglobin and 10.8+/-3.3-fold increase in creatine kinase MB-fraction during the first hour of treatment, while carbonic anhydrase III remained unchanged. The peak value of myoglobin/carbonic anhydrase III ratio was found at 2 h and that of creatine kinase MB-fraction at 8 h after thrombolysis. Knowledge of the reperfusion time point during primary angioplasty and follow-up of cardiac markers revealed that cut-off points of 3 and 10 h for the peak values of myoglobin/carbonic anhydrase III ratio and creatine kinase MB-fraction can be used as indicators for reperfusion, respectively. Myoglobin/carbonic anhydrase III ratio measured before treatment and at 2 and 4 h after the onset of treatment screened 23 of those 25 patients with probable reperfusion after thrombolysis.

CONCLUSIONS

We conclude that measuring myoglobin/carbonic anhydrase III ratio during the first hours after initiation of thrombolysis may be useful in evaluating the success of reperfusion after acute 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.

ST segment resolution as a tool for assessing the efficacy of reperfusion therapy

Rapid, simple and inexpensive measures are needed to assess the efficacy of reperfusion therapy both in clinical practice and in clinical trials testing novel reperfusion regimens. In the last decade, several observations have led to a favorable reappraisal of the utility of ST segment monitoring as a simple means of assessing reperfusion in patients receiving fibrinolytic therapy for acute ST elevation myocardial infarction, and ST resolution is being used increasingly in clinical practice and in clinical research. This review focuses on four interrelated roles for ST segment monitoring: the assessment of epicardial reperfusion and the identification of candidates for rescue percutaneous coronary intervention; the evaluation of microvascular and tissue-level reperfusion; the determination of prognosis early after fibrinolytic therapy; and the use of ST segment resolution to compare different reperfusion regimens.

Early noninvasive detection of failed epicardial reperfusion after fibrinolytic therapy

Available noninvasive techniques for identifying patients with failed epicardial reperfusion after fibrinolytic therapy are limited by poor accuracy. It is unknown whether combining multiple noninvasive predictors would improve diagnostic accuracy and facilitate identification of candidates for rescue percutaneous coronary intervention. In the Thrombolysis In Myocardial Infarction (TIMI) 14 trial, we evaluated the ability of ST-segment resolution (n = 606), chest pain resolution (n = 859), and the ratio of 60-minute/baseline serum myoglobin (n = 308) to identify patients with angiographic evidence of failed reperfusion 90 minutes after fibrinolysis. Three criteria were prospectively defined: <50% ST resolution at 90 minutes, presence of chest pain at the time of angiography, and myoglobin ratio <4. Patients who met any individual criterion were more likely to have less than TIMI 3 flow and an occluded infarct-related artery (TIMI 0/1 flow) than those who did not meet the criterion (p <0.005 for each). When the 3 criteria were used together (n = 169), patients who satisfied 0 (n = 29), 1 (n = 68), 2 (n = 51), or 3 (n = 21) of the criteria had a 17%, 24%, 35%, and 76% probability of failing to achieve TIMI 3 flow (p <0.0001 for trend), a 0%, 6%, 18%, and 57% probability of an occluded infarct-related artery (p <0.0001 for trend), and a 0%, 1.5%, 2.0%, and 9.5% rate of 30-day mortality (p = 0.05 for trend), respectively. Use of the criteria in combination increased positive predictive values without decreasing negative predictive values. In conclusion, ST-segment resolution, chest pain resolution, and early washout of serum myoglobin can be used in combination to aid in the early noninvasive identification of candidates for rescue percutaneous coronary intervention.

Development of a simple whole blood panel test for detection of human heart-type fatty acid-binding protein

OBJECTIVE

For the diagnosis of acute myocardial infarction (AMI), we have developed a rapid and simple whole blood panel test for the detection of human heart-type fatty acid-binding protein (H-FABP) using one-step immunochromatography.

METHODS AND RESULTS

We have developed a whole blood panel test for rapid detection of human H-FABP using a one-step immunochromatography technique. The result of this panel test was not affected by the other contents of the blood such as bilirubin, hemoglobin and others. Furthermore, no cross-reactivity of the antibodies was found with other cardiac markers or other tissue-type FABPs. The result of this panel test was similar to the diagnostic cut-off value, 6.2 ng of H-FABP per mL of serum which was evaluated by the enzyme-linked immunosorbent assay (ELISA).

CONCLUSION

We have developed a simple one-step immunochromatography technique to detect H-FABP in whole blood sample. Further studies are required to identify the value of this point-of-care testing (POCT) as a diagnostic marker for AMI.

Assessment of coronary reperfusion in patients with myocardial infarction using fatty acid binding protein concentrations in plasma

OBJECTIVE

To examine whether successful coronary reperfusion after thrombolytic treatment in patients with confirmed acute myocardial infarction can be diagnosed from the plasma marker fatty acid binding protein (FABP), for either acute clinical decision making or retrospective purposes.

DESIGN

Retrospective substudy of the GUSTO trial.

SETTING

10 hospitals in four European countries.

PATIENTS

115 patients were treated with thrombolytic agents within six hours after the onset of acute myocardial infarction. Patency of the infarct related artery was determined by angiography within 120 minutes of the start of thrombolysis.

MAIN OUTCOME MEASURES

First hour rate of increase in plasma FABP concentration after thrombolytic treatment, compared with increase in plasma myoglobin concentration and creatine kinase isoenzyme MB (CK-MB) activity. Infarct size was estimated from the cumulative release of the enzyme alpha hydroxybutyrate dehydrogenase in plasma during 72 hours, or from the sum of ST segment elevations on admission. Logistic regression analyses were performed to construct predictive models for patency.

RESULTS

Complete reperfusion (TIMI 3) occurred in 50 patients, partial reperfusion (TIMI 2) in 36, and no reperfusion (TIMI 0+1) in 29. Receiver operating characteristic (ROC) curve analyses showed that the best performance of FABP was obtained when TIMI scores 2 and 3 were grouped and compared with TIMI score 0+1. The performance of FABP as a reperfusion marker was improved by combining it with alpha hydroxybutyrate dehydrogenase infarct size, but not with an early surrogate of infarct size (ST segment elevation on admission). In combination with infarct size FABP performed as well as myoglobin (areas under the ROC curve 0.868 and 0.857, respectively) and better than CK-MB (area = 0.796). At optimum cut off levels, positive predictive values were 97% for FABP, 95% for myoglobin, and 89% for CK-MB (without infarct size, 87%, 88%, and 87%, respectively), and negative predictive values were 55%, 52%, and 50%, respectively (without infarct size, 44%, 42%, and 34%).

CONCLUSIONS

FABP and myoglobin perform equally well as reperfusion markers, and successful reperfusion can be assessed, with positive predictive values of 87% and 88%, or even 97% and 95% when infarct size is also taken into account. However, identification of non-reperfused patients remains a problem, as negative predictive values will generally remain below 70%.

Failed thrombolysis in myocardial infarction

Prompt treatment with thrombolytic therapy in acute myocardial infarction has been proven to reduce infarct size and mortality. However, reperfusion fails to occur in 30-50% of patients, either due to impaired epicardial artery flow or microvascular occlusion, with these patients experiencing a higher morbidity and mortality. We review the diagnosis and management of failed thrombolysis in acute myocardial infarction.

Heart-type fatty acid binding protein as a marker of reperfusion after thrombolytic therapy

Accurate, rapid, and simple noninvasive measures of infarct-related artery (IRA) patency are needed to identify patients with failed coronary reperfusion for rescue percutaneous coronary intervention (PCI). Heart-type Fatty Acid Binding Protein (H-FABP) is a small, cytosolic protein found in high concentrations in the myocardium. We evaluated the efficacy of H-FABP as a marker for successful reperfusion after thrombolysis. Fifty-eight subjects from the TIMI 14 trial had H-FABP and myoglobin concentrations measured at baseline (immediately prior to thrombolysis) and 60, 90, and 180 min after thrombolysis. All patients underwent coronary angiography at 90 min. By 60 min after thrombolysis, median concentrations of H-FABP and myoglobin were significantly higher in patients with a patent IRA than in those with an occluded IRA (P<0.01 for each). Similarly, the 60 and 90 min/baseline H-FABP and myoglobin ratios were significantly higher among patients with a patent IRA (P<0.01 for each). There were no significant differences in marker concentrations or ratios between patients with TIMI grade 2 and TIMI grade 3 flow. The area under the ROC curve tended to be greater for the 60 and 90 min/baseline myoglobin ratios than for similar ratios of H-FABP (0.71 and 0.73 vs. 0.64 and 0.62; P=ns). In conclusion, successful reperfusion can be detected within the first 60 min after thrombolysis with either H-FABP or myoglobin. Despite a favorable kinetic profile, however, H-FABP does not appear to represent a significant advance over myoglobin in the noninvasive detection of reperfusion after thrombolysis.

Evaluation of a point-of-care system for quantitative determination of troponin T and myoglobin

We present the results of a multicenter evaluation of a new point-of-care system (Cardiac Reader) for the quantitative determination of cardiac troponin T (CARDIAC T Quantitative test) and myoglobin (CARDIAC M test) in whole blood samples. The Cardiac Reader is a CCD camera that optically reads the immunochemical test strips. The measuring range is 0.1 to 3 microg/l for CARDIAC T Quantitative and 30 to 700 microg/l for CARDIAC M. Both tests are calibrated by the manufacturer. The reaction times of the tests are 12 or 8 minutes, respectively. Method comparisons were performed with 281 heparinized blood samples from patients with suspected acute coronary syndromes. The results obtained with CARDIAC T Quantitative showed a good agreement compared with cardiac troponin T ELISA (r = 0.89; y = 0.93x + 0.02). The method comparison between CARDIAC M and Tina-quant Myoglobin also showed a good agreement between both assays (r = 0.98; y = 0.92x + 1.6). Test lot-to-lot comparisons yielded differences of 2% and 6% for CARDIAC T Quantitative and of 0 to 11% for CARDIAC M. The within-run imprecision with blood samples and control materials was acceptable for CARDIAC T Quantitative (CV 10 to 15%) and good for CARDIAC M (CV 5 to 10%). The between-instrument CV was below 7% for CARDIACT Quantitative and below 5% for CARDIAC M. The cross-reactivity of CARDIAC T Quantitative with skeletal troponin T was approximately 0.003%. No significant analytical interference was detected for any of the assays in investigations with biotin (up to 100 microg/l), hemoglobin (up to 0.125 mmol/l), hematocrit (26 to 52%), bilirubin (up to 340 micromol/l), triglycerides (up to 5.0 mmol/l), and 18 standard drugs. With the Cardiac Reader reliable quantitative results can be easily obtained for both cardiac markers. The system is, therefore, particularly suitable for use in emergency rooms, coronary care units and small hospitals.

Myoglobin, creatine-kinase-MB and cardiac troponin-I 60-minute ratios predict infarct-related artery patency after thrombolysis for acute myocardial infarction: results from the Thrombolysis in Myocardial Infarction study (TIMI) 10B

OBJECTIVES

We examined the diagnostic performance of serum myoglobin, creatine-kinase-MB (CK-MB) and cardiac troponin-I (cTnI) for predicting the infarct-related artery (IRA) patency in patients receiving TNK-tissue plasminogen activator (TNK-tPA) therapy for acute myocardial infarction (AMI) in the Thrombolysis in Myocardial Infarction (TIMI) 10B trial.

BACKGROUND

A reliable noninvasive serum marker of IRA patency is desired to permit early identification of patients with a patent IRA after thrombolysis.

METHODS

We measured myoglobin, CK-MB and cTnI concentrations in sera obtained just before thrombolysis (T0) and 60 min later (T60) in 442 patients given TNK-tPA and who underwent coronary angiography at 60 min.

RESULTS

Angiography at 60 min showed a patent IRA (TIMI flow grade 2, 3) in 344 and occluded IRA (TIMI flow grade 0, 1) in 98 patients. The median serum T60 concentration, the ratio of the T60 and T0 serum concentration (60-min ratio) and the slope of increase over 60 min for each serum marker were significantly higher in patients with patent arteries compared with patients with occluded arteries. The area under the receiver-operating characteristic (ROC) curve for diagnosis of occlusion was 0.71, 0.70 and 0.71 for the 60-min ratio of myoglobin, cTnI and CKMB, respectively. The 60-min ratios of > or =4.0 for myoglobin, > or =3.3 for CK-MB and > or =2.0 for cTnI yielded a probability of patency of 90%, 88% and 87%, respectively.

CONCLUSIONS

The diagnostic performance of serum myoglobin, CK-MB and cardiac troponin-I (cTnI) 60-min ratios was similar. The probability of a patent IRA was very high (90%) in patients with 60-min myoglobin ratio > or =4.0, and early invasive interventions to establish IRA patency may not be necessary in this group. Serum marker determinations at baseline and 60-min after thrombolysis may permit rapid triage of patients receiving thrombolytic therapy by ruling out IRA occlusion.

Biochemical markers of the acute coronary syndromes

The acute coronary syndromes represent a continuum of myocardial ischemia ranging from angina, reversible tissue injury → unstable angina, frequently associated with minor myocardial damage → myocardial infarction and extensive tissue necrosis. Historically, coronary artery disease assessment has been mainly binary, using WHO criteria of symptoms, electrocardiography, and biochemical markers. The creatine kinase-MB isoenzyme (CK-MB) has been a benchmark for markers, but it is not specific for myocardium. Cardiac-specific isoforms of troponin T and I have emerged as sensitive myocardial infarction (MI) indicators and, importantly, for risk stratification of acute coronary syndrome patients. In addition to markers of myocardial cell necrosis, markers of plaque disruption (C-reactive protein and serum amyloid A), “angry” platelets (P-selectin), ischemia (glycogen phosphorylase-BB isoenzyme), and the procoagulant state and thrombosis (soluble fibrin) have potential use. Also, CK-MB and myoglobin have been combined with clinical indicators for monitoring reperfusion after thrombolytic therapy. Biochemical markers will continue to be an important clinical adjunct for MI diagnosis, risk assessment, and reperfusion monitoring in the future.

Myoglobin, creatine kinase MB, and cardiac troponin-I to assess reperfusion after thrombolysis for acute myocardial infarction: results from TIMI 10A

BACKGROUND

The availability of a reliable, noninvasive serum marker of reperfusion may permit early identification of patients with occlusion after thrombolysis who might benefit from further interventions.

METHODS

We measured myoglobin, creatine kinase MB (CK-MB), and cardiac troponin-I (cTnI) concentrations in sera obtained just before thrombolysis (T0) and 60 minutes later (T60) in 30 patients given TNK-tPA for acute myocardial infarction as part of the Thrombolysis in Myocardial Infarction (TIMI) 10A trial.

RESULTS

Angiography at T60 showed reperfusion (TIMI flow grade 2 to 3; n = 19) or occlusion (TIMI flow grade 0 to 1; n = 8). The median serum T60 concentration, the ratio of the T60 and T0 serum concentration, and the slope of increase over a 60-minute period for each serum marker were significantly higher in patients with patent arteries compared with patients with occluded arteries. The areas under the receiver operator characteristics curve for diagnosis of occlusion were 0.96, 0.91, and 0.87 for the T60 concentration of myoglobin, CK-MB and cTnI, respectively. Although the T60 levels of <469 ng/ml for myoglobin, <11.5 ng/ml for CK-MB, and < 1.1 ng/ml for cTnI identified all patients with occlusion, the specificity of myoglobin (94%) was higher than that of CK-MB (61%) and cTnI (67%). Similar results were obtained for the 60-minute ratios and 60-minute slopes for each marker, with indexes for myoglobin having the highest specificity.

CONCLUSIONS

In this pilot study, noninvasive diagnosis of occlusion 60 minutes after thrombolysis was achieved with a high degree of sensitivity and specificity with the myoglobin, CK-MB, and cTnI concentrations measured at that time point. These preliminary findings may permit a new strategy for assessment of the success of reperfusion, with triage to rescue angioplasty for patients in whom the 60-minute cardiac marker values or indexes are consistent with occlusion of the infarct-related artery.

Assessment of coronary reperfusion after thrombolysis with a model combining myoglobin, creatine kinase-MB, and clinical variables. TAMI-7 Study Group. Thrombolysis and Angioplasty in Myocardial Infarction-7

BACKGROUND

Several biochemical markers have been investigated for the noninvasive assessment of reperfusion after myocardial infarction. Because myoglobin is released very soon after myocardial injury and clears rapidly after reperfusion, it may prove to be an excellent marker of occlusion and reperfusion.

METHODS AND RESULTS

We examined the relation between various myoglobin measures and Thrombolysis In Myocardial Infarction (TIMI) flow grade in 96 patients enrolled in a study of front-loaded thrombolysis who underwent 90-minute angiography. We also combined myoglobin measures with models that include clinical and creatine kinase-MB variables. The myoglobin level measured within 10 minutes of acute angiography showed the best overall performance and was used for later analyses. Of the clinical variables examined, only time from symptom onset to thrombolysis and chest pain grade at angiography discriminated among TIMI flow grades. Combining the 90-minute myoglobin level and these clinical variables showed a significant difference (P<.0001) between both TIMI 3 versus TIMI 0 through 2 and TIMI 2 or 3 versus TIMI 0 or 1 flow. When the 90-minute myoglobin level was added to an established predictive model containing clinical variables and creatine kinase-MB measures, its contribution remained significant (P=.044). The area under the receiver operator characteristic curve for this combined model was .88.

CONCLUSIONS

A single myoglobin measurement obtained 90 minutes after the start of thrombolysis, combined with select clinical variables and creatine kinase-MB levels, enhances the noninvasive prediction of reperfusion after myocardial infarction.

Serum concentrations of myoglobin vs human heart-type cytoplasmic fatty acid-binding protein in early detection of acute myocardial infarction

We compared the diagnostic utility of serum concentrations of human heart-type cytoplasmic fatty acid-binding protein (H-FABPc), myoglobin, and their ratio for the early diagnosis of acute myocardial infarction (AMI) in 104 healthy volunteers and 165 patients at admission within 6 h of the onset of chest pain. The ROC curves of the H-FABPc [0.946, 95% confidence interval (CI) = 0.913–0.979] and myoglobin (0.895, 95% CI = 0.846–0.944) between patients with AMI and healthy volunteers were significantly greater than the area under the ratio of myoglobin to H-FABPc (0.823, 95% CI = 0.765–0.881). In 165 patients, the sensitivity (81.8%, 95% CI = 74.2–89.4%), specificity (86.4%, 95% CI = 78.1–94.6%), and predictive accuracy (83.6%, 95% CI = 78.0–89.3%) of H-FABPc &gt;12 μg/L in diagnosing AMI were significantly higher than those of myoglobin, and were similar to those of the combination of H-FABPc &gt;12 μg/L and the ratio ≤14. We conclude that H-FABPc is a more sensitive and specific marker than myoglobin for the early diagnosis of AMI, and that their ratio cannot give a clear advantage over the measurement of H-FABPc alone.

Early detection of successful coronary reperfusion based on serum concentration of human heart-type cytoplasmic fatty acid-binding protein

Both human heart-type cytoplasmic fatty acid-binding protein (H-FABPc) and myoglobin are low molecular weight proteins that are abundant in the cytoplasm of myocardial cells. Unlike myoglobin, H-FABPc content in the skeletal muscle is less than in cardiac muscle. To investigate the usefulness of the serum concentration of H-FABPc in the early detection of successful coronary reperfusion, we measured serum concentrations of H-FABPc and myoglobin in 45 patients with acute myocardial infarction treated with intracoronary thrombolysis or direct percutaneous transluminal coronary angioplasty. Coronary angiography was performed every 5 min for reperfusion therapy to identify the onset of reperfusion. Reperfusion, defined as a TIMI grade 2 or 3, was achieved within 60 min of the initiation of reperfusion therapy in 30 patients (the reperfused group), but was not achieved in 15 patients (the non-reperfused group). Blood samples were obtained before initiation of treatment and 15, 30 and 60 min after initiation of treatment in the non-reperfused group. In the reperfused group, samples were obtained before reperfusion and 15, 30 and 60 min after reperfusion. The H-FABPc ratio (the ratio of value after to value before the initiation of treatment or reperfusion) increased sharply after the onset of reperfusion, peaking at 41 +/- 18 min, and decreased rapidly thereafter. The predictive accuracy of an H-FABPc ratio of > 1.8 for the detection of reperfusion within 60 min of the initiation of treatment was 93% at 15 min after reperfusion, 98% at 30 min, and 100% at 60 min. Similar rates of predictive accuracy were observed for a myoglobin ratio > 2.4. The H-FABPc ratio detected successful reperfusion as early as 15 min after the onset of reperfusion and was highly accurate in detecting reperfusion within 60 min of the onset of reperfusion. The predictive accuracy of the H-FABPc ratio was similar to that of the myoglobin ratio for the early detection of successful coronary reperfusion.

Use of cardiac markers as assessed by outcomes analysis

OBJECTIVES

This article will describe the outcomes studies that have been performed or are needed in relation to biochemical markers in coronary artery diseases (CAD).

METHODS AND RESULTS

Studies in five major areas are reviewed: the need for emergency department (ED) chest pain centers and the role of cardiac markers; impact of cardiac marker testing frequency on length of stay (LOS); interpretation of cardiac troponins T and I for risk stratification of cardiac patients with unstable angina (UA); serum markers for determining the success of intravenous thrombolytic therapy following acute myocardial infarction (AMI), and its role in rescue percutaneous transluminal coronary angioplasty (PTCA); and need and criteria for implementation of new cardiac tests.

CONCLUSIONS

Chest pain centers reduce unnecessary admissions and costs for AMI rule outs. Laboratories must perform testing on a stat basis for rapid rule out of AMI. Stat testing will also result in a reduction in hospital LOS for patients who rule in for AMI. For UA patients, studies are needed to determine how results of cardiac markers can be used to improve cardiac outcomes. Serial measurements of myoglobin offer the earliest discrimination for successful reperfusion, and should be used if rescue PTCA becomes important therapeutically. New markers for early diagnosis are needed to complement tests such as myoglobin and CK-MB isoforms. Markers that assess early pathophysiologic events of AMI such as inflammation, thrombosis, and pre-necrosis ischemia have the most promise.

Superoxide dismutase activity as a predictor of myocardial reperfusion and salvage in acute myocardial infarction

We attempted to predict successful myocardial reperfusion and salvage in acute myocardial infarction (AMI) by using measurements of plasma superoxide dismutase (SOD), a plasma free-radical scavenger, activity. Forty-nine patients with AMI were studied within 6 hours of symptoms onset. In group 1 (n = 26), primary percutaneous transluminal coronary angioplasty (PTCA) was undertaken, and plasma SOD activity was measured for 8 hours by the nitrite method. Left ventricular (LV) angiography was assessed before and 3 months after PTCA by computer LV contraction analysis. In group 2 (n = 23), TPA was infused intravenously over a 60-minute period, and plasma SOD activity was measured before and immediately after TPA infusion. In group 1, occluded coronary arteries were successfully dilated in 24 of 26 patients, and plasma SOD activity increased from 3.20 +/- 0.17 microns/ml to 4.66 +/- 0.29 microns/ml at 1 hour after PTCA (p < 0.001), returning to the basal level by 8 hours after PTCA. Plasma SOD activity did not significantly change patients with unsuccessful PTCA or those with the no-reflow phenomenon. The maximal increase in plasma SOD activity was significantly correlated with the grade of improvement in LV contraction (r = 0.852, p < 0.001). In group 2, the sensitivity and specificity of predicting coronary recanalization was 86% and 89%, respectively. In conclusion, myocardial reperfusion and salvage in AMI can be predicted by changes in plasma SOD activity.