The significance of the MB isoenzyme in patients with acute cardiovascular disease with a normal or borderline total CPK activity

Propofol anaesthesia and metabolic acidosis in children

BACKGROUND

We aimed to investigate the effect of propofol infusion anaesthesia on acid-base status and liver and myocardial enzyme levels of children during short-term anaesthesia.

METHODS

Thirty-six children, aged 3-12 years, were randomized into two groups. In group P (n = 18), induction and maintenance were performed with propofol, 3 mg x kg-1 and 20, 15 and 10 mg x kg-1 x h-1, respectively. In group H (n = 18) following induction with 5 mg x kg-1 thiopenthal, anaesthesia was maintained with 2-3% halothane. Blood samples were obtained following anaesthesia induction and 30, 60 and 120 min after discontinuation of anaesthesia.

RESULTS

There was no difference in lactate dehydrogenase, myocardial creatininephosphokinase, aspartate aminotransferase, alanine aminotransferase and cholesterol levels between and within the groups. All postoperative triglyceride levels were higher and pH levels were lower in group P than group H (P < 0.05) and there was no difference within the groups.

CONCLUSIONS

In these healthy patients, short-term use of propofol did not result in significant acidaemia, nor alterations in hepatic or myocardial enzyme levels.

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.

Myocardial infarction associated with phenylpropanolamine

Phenylpropanolamine is a sympathomimetic agent widely used in over-the-counter and prescription decongestant medications. We describe a young woman without cardiac risk factors who sustained myocardial infarction after unintentional overuse of a nasal decongestant containing phenylpropanolamine. The pathophysiology of myocardial injury and current management strategies as related to this agent are discussed. Although serious adverse reactions to phenylpropanolamine are uncommon, potentially serious harm may be caused by this widely available drug in healthy individuals.

Creatine kinase-MB elevation after coronary intervention correlates with diffuse atherosclerosis, and low-to-medium level elevation has a benign clinical course: implications for early discharge after coronary intervention

OBJECTIVES

The study evaluated the incidence and predictors of creatine kinase-MB isoenzyme (CK-MB) elevation after successful coronary intervention using current devices, and assessed the influence on in-hospital course and midterm survival.

BACKGROUND

The CK-MB elevation after coronary intervention predominantly using balloon angioplasty correlates with late cardiac events of myocardial infarction (MI) and death. Whether CK-MB elevation after nonballoon devices is associated with an adverse short and midterm prognosis is unknown.

METHODS

The incidence and predictors of CK-MB elevation after coronary intervention were prospectively studied in 1,675 consecutive patients and were followed for in-hospital events and survival.

RESULTS

CK-MB elevation was detected in 313 patients (18.7%), with 1-3x in 12.8%, 3-5x in 3.5% and >5x normal in 2.4% of patients. Procedural complications or electrocardiogram changes occurred in only 49% of the CK-MB-elevation cases; CK-MB elevation was more common after nonballoon devices (19.5% vs. 11.5% after percutaneous transluminal coronary angioplasty; p < 0.01). Predictors of CK-MB elevation on multivariate analysis were diffuse coronary disease (p = 0.02), systemic atherosclerosis (p = 0.002), stent use (p = 0.04) and absence of beta-blocker therapy (p = 0.001). Adverse in-hospital cardiac events were more frequent in patients with >5x CK-MB elevation, with no significant difference between 1-5x CK-MB elevation versus normal CK-MB group. During a mean follow-up of 13 +/- 3 months, the incidence of death in the CK-MB-elevation group was 1.6% versus 1.3% in the normal CK-MB group (p = NS).

CONCLUSIONS

The CK-MB elevation after coronary intervention was observed even in the absence of discernible procedural complications and was more common in patients with diffuse atherosclerosis. In-hospital clinical events requiring prolonged monitoring were higher in >5x CK-MB-elevation patients only. Midterm survival of CK-MB-elevation patients was similar to those with normal CK-MB. Our prospective analysis shows a lack of adverse in-hospital cardiac events and suggests that early discharge of stable 1-5x normal CK-MB-elevation patients after successful coronary intervention is safe.

Significance of mild transient release of creatine kinase-MB fraction after percutaneous coronary interventions

BACKGROUND

The clinical significance of minor elevations in creatine kinase-myocardial band isoenzyme (CK-MB) after coronary interventions has not been systematically evaluated.

METHODS AND RESULTS

We examined 4484 patients who underwent successful percutaneous transluminal coronary angioplasty or directional coronary atherectomy and whose peak CK levels did not exceed twice the upper limit of laboratory normal. Group 1 (3776 patients) had no CK or MB elevation after the procedure (ie, CK < or = 180 IU/L, with MB fraction < or = 4%). Group 2 (450 patients) had a peak CK level between 100 and 180 IU/L, with MB fraction > 4%, and group 3 (258 patients) had a peak CK level between 181 and 360 IU/L, with MB fraction > 4%. The strongest correlate of postprocedure CK-MB elevation was the performance of directional coronary atherectomy (odds ratio, 4.1; P < .0001), followed by the development of > or = 1 in-1ab minor procedural complication (odds ratio, 2.6; P < .0001). Clinical follow-up was available in 4461 patients (99.5%), with a mean duration of 36 +/- 22 months. Survival analysis, adjusted with Cox proportional hazards regression model, showed that the groups with elevated CK-MB had a significantly higher incidence of cardiac death (risk ratio, 1.3; P = .04) and myocardial infarction (risk ratio, 1.3; P = .03). Major ischemic complications (death, myocardial infarction, and coronary revascularization) occurred more frequently in the groups with increased CK-MB (groups 1 versus 2 versus 3, 37.3% versus 43.3% versus 48.9%; P = .01).

CONCLUSIONS

This study shows that minor elevations of CK-MB after successful coronary interventions identify a population with a worse long-term prognosis compared with patients with no enzyme elevations and appear to have an adverse effect on long-term prognosis. Future studies of percutaneous coronary revascularization should include routine measurements of biochemical cardiac markers as important predictors of long-term prognosis.

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.

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?

The prognostic significance of immunoradiometric CK-MB assay (IRMA) diagnosis of myocardial infarction in patients with low total CK and elevated MB isoenzymes

Patients with suspected myocardial infarction present a diagnostic problem when they have normal total serum creatine kinase (CK) and an elevated myocardial fraction of this enzyme (CK-MB). We studied 40 patients with normal total serum CK and elevated CK-MB (by standard electrophoretic technique), using an immunoradiometric assay (IRMA) for CK-MB. Diagnosis based on IRMA results of serum samples collected prospectively was compared with diagnosis based on application of strict diagnostic criteria with and clinical diagnosis of the responsible physician(s) by chart review. Diagnostic agreement of all three methods and clinical outcome (mean follow-up 6 months after discharge) were analyzed and compared with two control groups: "rule in" group (17 patients) with elevated total CK, CK-MB, and abnormal electrocardiogram (ECG); and "rule out" group (18 patients) with normal total CK, CK-MB, and ECG. All three diagnostic methods (1) clinical discharge diagnosis, (2) chart review diagnosis by application of strict diagnostic criteria, and (3) IRMA diagnosis, agreed completely for both control groups. Follow-up control group outcomes were in concert with expected outcomes for these groups. Diagnostic differences between methods 1 and 2, and 1 and 3 were statistically significant for the study group. Furthermore, only diagnosis based on the IRMA showed a predictive capability for outcome in this study group when compared with the other methods. Follow-up revealed a similar incidence of cardiac events in the study group (56%) and in the "rule in" control group (60%), but not in the "rule out" group (7%).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Significance of elevated MB isoenzyme with normal creatine kinase in acute myocardial infarction

The significance of elevated levels of the MB isomer of creatine kinase (CK-MB) when creatine kinase (CK) level is normal was studied in 400 patients with suspected acute myocardial infarction (AMI). In 350 patients both CK and CK-MB were elevated (group 1), in 21 only CK-MB was elevated (group 2), in 24 neither enzyme was elevated (group 3) and in 5 only CK was elevated (group 4). In 57% of patients in group 2 the CK level was doubled, with a characteristic enzyme curve, within the normal range, suggesting that an increase in CK had been missed because arbitrary definitions of "normal" were used. The median CK increase (60 IU/liter) in group 2 was greater than that in group 3 (23 IU/liter) (p less than 0.001). Patients in group 1 with small AMIs had a relative increase in CK similar to that in group 2. However, patients in group 2 had a lower baseline CK level so that peak CK did not become abnormally high despite a 5-fold increase in some patients. In patients in group 1 with small AMIs, CK was elevated in fewer samples than CK-MB. If only 2 samples were obtained in all patients, elevation of CK levels would have been missed in 63 group 1 patients, erroneously increasing the number of patients in group 2 fourfold (to 84 of 400, or 21%, instead of 21 of 400, or only 5%). Conversely, if patients in group 2 with a doubling of CK are excluded, the prevalence of elevated CK-MB with normal CK would be only 9 of 400 (2%).(ABSTRACT TRUNCATED AT 250 WORDS)

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

To test the hypothesis that patients with normal serum levels of creatine kinase (CK) but elevated percentages of MB isoenzyme fractions in suspected myocardial infarction may have sustained clinically significant events, we studied the hospital course of 347 consecutive patients admitted with suspected myocardial infarction. Two hundred twenty-three patients had normal CK levels (182 +/- 44 IU) and normal MB percentages (normal group), 68 had elevated levels of both CK (1395 +/- 178 IU) and MB percentage (10.5 +/- 0.6) (macroinfarction group), and 40 had normal CK levels (96 +/- 7 IU) but elevated MB percentages (9.6 +/- 0.5) with typical enzyme curves (microinfarction group). Compared to the normal group, microinfarction patients were older, had more congestive heart failure, required more intensive monitoring and therapy during longer stays, and sustained a higher in-hospital mortality rate. Thus, these microinfarction patients are at increased risk and therefore warrant aggressive treatment and further evaluation.

Diagnostic and prognostic significance of minimally elevated creatine kinase-MB in suspected acute myocardial infarction

CK-MB changes were studied using agarose gel electrophoresis in 244 patients admitted to a coronary care unit for suspected acute myocardial infarction (AMI). A range of minimally elevated CK-MB levels, from 1 to 24 IU/liter, was identified as representing uncertain AMI events. Positive AMI events were defined by elevations of 25 IU/liter or more documented in patients with new Q waves or abnormalities in all enzyme and isoenzyme levels. Negative AMI events were defined by elevation of 0 IU/liter, observed in all control subjects. The 1-year cardiac mortality rates in the "positive"-AMI (n = 91) and "uncertain"-AMI (n = 22) groups were identical (22%), and significantly higher than that in the "negative"-AMI group (n = 93) (6%) (p less than 0.05). However, when a larger uncertain-AMI group of 115 patients was compiled by 2 collaborating centers, the 1-year cardiac mortality rate in the 39 patients with chest pain alone was 0%, vs 33% in the 76 patients with accompanying severe medical problems such as cardiac or respiratory failure. Whether minimal CK-MB elevations represent AMI of limited extent is not clear. These elevations occur most often in association with severe medical problems, and in patients without such problems, they may not indicate a poor prognosis.

An evaluation of the immunochemical LD-1 method in routine clinical practice

We report our extended clinical experience with the use of an immunochemical method for LD-1 assay in 260 unselected, consecutive patients admitted with the clinical suspicion of recent myocardial infarction (M.I.). We determined on every patient total creatine kinase (CK) and total lactate dehydrogenase (LD) enzyme activity, and performed electrophoresis for LD isoenzymes as well as the heart-specific band of creatine kinase (CK-MB). An immunochemical assay for the heart-specific isoenzyme of LD (LD-1) was also performed. The timing of the samples was determined by the clinicians according to routine clinical protocols in the coronary care units. The diagnosis was based on the usual combination of clinical, electrocardiographic (EKG) and laboratory findings, and was arrived at independently by the clinician. In this extended series, the overall efficiency of the immunochemical LD-1 assay for the proper classification of the patients according with the discharge diagnosis was 92%. For CK-MB it was 90%, for EKG 77% and for LD electrophoresis 76%. The immunochemical LD-1 assay required no special instruments or highly skilled technicians and is probably the method of choice for the stat evaluation of recent M.I.

Serum creatine kinase and creatine kinase MB isoenzyme responses of post-infarction patients after a graded exercise test

The response of total creatine kinase (CK) and the creatine kinase isoenzyme (CK MB) was studied in 22 male post-infarction patients (three to six months after myocardial infarction) after a functional graded exercise test, before entering a rehabilitation programme. Eleven subjects (group A) completed the test without developing significant electrocardiographic abnormalities. Eleven subjects (group B) showed changes that necessitated premature termination of the test. No significant differences were observed before the functional graded exercise test between the groups in serum concentration of CK, CK MB, and the percentage of CK MB to CK (MB/ CK%). The two groups were significantly different (p less than 0.01) 24 hours after the graded exercise test in CK MB and MB/CK%, but not in CK. In group B, CK and CK MB rose significantly after the graded exercise test (p less than 0.05) as did MB/CK% (p less than 0.01). In group A only CK showed a significant rise (p less than 0.05). It is probable that increases in CK MB after exercise arise from myocardial tissue efflux, reflecting reversible ischaemia. It is concluded from this study that CK MB appears to be a specific indicator of myocardial ischaemia and could, therefore, be of significant assistance in the clinical and functional assessment of the post-infarction patient.

Implications of increased myocardial isoenzyme level in the presence of normal serum creatine kinase activity

Although increased serum creatine kinase (CK) activity in the presence of an increased level of myocardial-specific isoenzymes (CKMB) has been strongly associated with acute myocardial infarction, the significance of an increased serum CKMB level in the presence of a normal total CK level is uncertain. In 335 consecutive patients suspected of having an acute myocardial infarction and 71 control subjects, peak serum CKMB and CK levels were correlated with the presence of other clinical criteria for acute myocardial infarction: (1) typical chest pain, (2) increased myocardial lactate dehydrogenase (LDH1/LDH2), (3) acute electrocardiographic changes (new or ST-T wave changes with evolution), and (4) an elevated CKMB level on 2 or more determinations or a typical CK curve. No control subject had an increase in CK or CKMB or any of the 4 criteria for myocardial infarction. Of the 176 subjects with normal CK and normal CKMB (Group 1), only 11% had more than a single criterion, and none had more than 2 criteria consistent with myocardial injury. In contrast, of the 83 with elevated CK and CKMB levels (Group 2), 93% had 2 or more and 81% had 3 or more of the 4 criteria. Of the 63 patients with elevated CKMB but a persistently normal CK (Group 3), 65% had 2 or more criteria for acute myocardial infarction and 77% had subendocardial electrocardiographic changes; these patients resembled those with both elevated CK and MB. The phenomenon of elevated CKMB with normal CK occurred in 20% of the patients aged greater than or equal to 70 years but in only 10% of the younger group (p less than 0.01). These findings suggest that elevated CKMB with normal CK likely represents definite myocardial injury, is more likely represents definite myocardial injury, is more common in the elderly, and should be considered part of the spectrum of nontransmural myocardial infarction.

Detection of ischemic myocardial injury in patients with normal, or moderately elevated, serum CK and AST activities

It is still undecided in clinical medicine if an increased serum CK-MB level indicates irreversible myocardial damage. We measured CK and AST activities on three serum samples obtained during the first 24 hours following admission of patients with a clinical history suggesting myocardial ischemia. Isoenzymes were not separated when CK and AST activities were less than 300 U/L and 35 U/L respectively, but were fractionated when the enzyme activities doubled during the first 24 hours even within their normal ranges. Over a three-year period this doubling occurred in 30 patients, one of whom was admitted twice to the hospital. The serum CK-MB fractions of these patients were 6% or greater in 26 and less than 6% in 5 admissions. The final clinical diagnosis given to the patients on 20 of these 26 admissions was acute subendocardial infarction. None of the five patients with a CK-MB fraction less than 6% had a clinical diagnosis of acute myocardial infarction. A comparative study of 102 patients with higher average enzyme activities but without doubling of both enzymes during a 24-hour period, did not yield a CK-MB of 6% or greater. None of this group of patients was diagnosed clinically as having had acute myocardial infarction.