CPK-MB Isoenzyme Research Articles

Preventive Effects of Egyptian Sweet Marjoram (Origanum majorana L.) Leaves on Haematological Changes and Cardiotoxicity in Isoproterenol-Treated Albino Rats

We made an attempt to evaluate/compare the cardioprotective activity of two different doses (50 and 100 mg/kg body weight, given orally for 30 consecutive days) of Egyptian sweet marjoram leaf powder (MLP) and marjoram leaf aqueous extract (MLE) against isoproterenol (ISO)-induced myocardial infarcted rats (150 mg/kg body weight, twice at an interval of 24 h on days 29 and 30). The present study showed (probably for the first time) that both MLP and MLE (especially the high dose) significantly alleviated (P < 0.05-0.001) erythrocytosis, granulocytosis, thrombocytosis, shortened clotting time, the increase in relative heart weight, myocardial oxidative stress and the leakage of heart enzymes (creatine phosphokinase (CPK), CPK-MB isoenzyme, lactate dehydrogenase and aminotransferase) in ISO-treated rats through reactivating non-enzymic (reduced glutathione) and enzymic (catalase, glutathione peroxidase, glutathione S-transferase, superoxide dismutase) antioxidant defence system and inhibiting the production of nitric oxide and lipid peroxidation in heart tissues. The modulatory effects of marjoram leaves shown in the present study were dose-dependent in most cases and much higher in MLE (4.3-20.3 % for all parameters taken together). In addition, the doses used in the present study were considered safe. In conclusion, this study may have a significant impact on myocardial infarcted patients.

Impacto de la obesidad central en la extensión del área de necrosis miocárdica

Metabolic syndrome consists of a group of factors that predict the risk of having an acute cardiovascular event. Some of these factors increase the risk of myocardial infarction and are also associated with the severity of cardiovascular events. The objective was to determine the influence of factors associated with metabolic syndrome, and especially abdominal obesity, on the size of coronary events, estimated by the concentration of total creatine phosphokinase (CPK) and CPK-MB isoenzyme (CPK-MB).We performed a cross-sectional study of 40 men diagnosed with acute coronary syndrome. We collected clinical data (age, history of diabetes, dyslipidemia and hypertension ) and anthropometric data [body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHR)]. CPK and CPK-MB concentrations were measured to determine the maximum concentration reached in order to estimate the size of the myocardial infarction area.The prevalence of metabolic syndrome was 30%. Approximately 84% of the patients were overweight and 42% had abdominal obesity. A positive association was found between myocardial enzymes and anthropometric parameters (BMI, WC, WHR). The variable showing the closest association with the size of myocardial infarction was central obesity [total CPK, r (Pearson) = 0.47; p<0.003] and (CPK-MB, r= 0.4; p<0.01). Metabolic syndrome was not a predictive factor for the size of myocardial necrosis (beta=-0.29; p<0.1). Multiple regression analysis showed that WC predicted maximal total CPK (beta=37.15; 95% CI, 9.16-65.15; p<0.01) and CPK-MB concentrations (beta=5.7; 95% CI, -0.4-11.9; p< 0.06) after an acute coronary event.The presence of abdominal obesity was associated with greater myocardial necrosis size after an acute coronary event.

Tissue Trauma in Abdominal and Laparoscopic-Assisted Vaginal Hysterectomy

Study Objective To compare the degree of tissue damage between abdominal and laparoscopic-assisted hysterectomy. Design Prospective, randomized, controlled study (Canadian Task Force classification I). Setting University hospital. Patients Forty-six women. Intervention Laparoscopic-assisted and abdominal hysterectomy. Measurements and Main Results The degree of tissue injury caused by surgical trauma was assessed by measuring plasma levels of creatine phosphokinase (CPK), C-reactive protein (CRP), lactic dehydrogenase (LDH), and CA 125 in patients undergoing laparoscopic-assisted (n = 23) and abdominal hysterectomy (n = 23). Plasma levels of CPK-MB isoenzyme were measured in order to exclude the possibility of myocardial injury. Blood samples were taken preoperatively, and on the first and second postoperative days. There was no difference in demographic characteristics between the groups. One patient in the laparotomy group and two patients in the laparoscopy group were excluded from analysis due to bladder injury, postoperative thrombophlebitis, and conversion to laparotomy because of severe adhesions. The mean operation time was longer (105.5 ± 23.1 minutes vs 77.3 ± 18.7 minutes, p <.001), but the duration of hospital stay was shorter (2.7 ± 0.8 days vs 4.3 ± 1.4 days, p <.001) and analgesic requirement was lower in the laparoscopy group compared with the abdominal group. We observed significant postoperative increases in CRP and CPK in both groups on postoperative days 1 and 2, whereas the increase in LDH was significant only in the laparotomy group on postoperative day 2. There were no significant changes in CPK-MB and CA 125. Moreover, mean plasma levels of CRP and CPK were significantly higher in the laparotomy group on postoperative days 1 and 2 than in the laparoscopy group (p <.05). Conclusion Surgery is a significant cause of tissue injury that can be assessed by specific enzymes and proteins. We suggest that laparoscopic surgery causes less tissue damage as assessed by lower postoperative CRP and CPK values, and that less tissue trauma related with laparoscopic surgery may account for early mobilization and reduced analgesic requirement in these patients.

Detection of Transitory Myocardial Ischemia Secondary to Perinatal Asphyxia

Background Transitory myocardial ischemia (TMI) is seen as a complication of severe asphyxia. Its presentation is variable, ranging from tachypnea to cardiogenic shock, and it is often masked by the predominant disease. The objective of this study was to detect TMI secondary to perinatal asphyxia in a population of asphyxiated newborns (NB) in comparison with asphyxiated NB with no evidence of TMI. Methods From April 1996 to December 1997, 43 asphyxiated (stressed) NB were studied. Three were excluded. Patients were placed into two groups: Group A with TMI ( n = 33) and Group B without TMI ( n = 7). Results No significant differences were found in gestational age, birth weight, extrauterine age, Apgar score, or total creatine phosphokinase values between the two groups. Differences were found in CPK-MB levels and in ischemic electrocardiographic changes and blockages, especially for Group A. In this group, only 24 (72.7%) were cardiovascularly symptomatic. Conclusions We conclude that TMI secondary to perinatal asphyxia is more frequent than has been reported. Thus, it would be useful in all asphyxiated NB to measure CPK-MB isoenzyme activity and patients can then be submitted to an electrocardiogram for detection in order to offer opportune treatment when required.

Elevated Serum CPK-MB Isoenzyme after Cryoprostatectomy

Elevated Serum CPK-MB Isoenzyme after Cryoprostatectomy

Role of Xanthine Oxidase in the Potentiation of Doxorubicin-Induced Cardiotoxicity by Mitomycin C

Clinical evidence has suggested that mitomycin C (MMC) potentiates doxorubicin (DOX) induced cardiotoxicity. In this study a mouse model was used to examine the effect of DOX on the ability of cardiac tissue to bioactivate MMC to generate oxygen radicals. Cardiac damage was assessed by measuring serum CPK-MB isoenzyme levels and thiobarbituric acid reactive substances (TBARS) in the cardiac tissue. The exposure of animals to DOX or DOX and MMC over a three week period led to an increase in serum CPK-MB isoenzyme levels as well as TBARS. Treatment with DOX led to an increase in MMC-dependent, NADH-dependent, cyanide insensitive oxygen consumption, compared to control animals, thereby suggesting increased MMC-dependent oxygen radical generation. Levels of xanthine oxidase (XO; EC 1.1.3.22) and NADPH:cytochrome C reductase, two enzymes known to bioactivate MMC with subsequent oxygen radical generation, were measured in cardiac tissue with a 4.5 x increase in XO activity seen in DOX treated animals vs controls and no change in NADPH:cytochrome C reductase activity. Cardiac levels of xanthine dehydrogenase (XDH; EC 1.1.1.204) activity in DOX treated animals decreased while the XO/XDH ratio increased, suggesting a conversion of XDH to XO following DOX treatment.

The effects of diagnostic criteria on trends in coronary heart disease morbidity: The Minnesota heart survey

The Minnesota Heart Survey assessed attack rates of MI in Twin Cities residents ages 30–74 years in 1970 and 1980. The age-adjusted attack rate per 100,000 of definite MI was similar in 1970 (174.2) and 1980 (179.9) p > 0.05, using ECG, chest pain, and blood enzyme concentrations of aspartate transaminase and/or lactic dehydrogenase as criteria. The attack rate of definite MI also remained constant when autopsy findings were included in the algorithm, 197.0 in 1970 and 191.4 in 1980 ( p > 0.05). Adding creatine phosphokinase (CPK) and CPK-MB isoenzyme to the algorithm increased the rate of definite MIs from 209.0 in 1970 to 277.0 in 1980 ( p < 0.001). Interpretation of long-term trends in coronary heart disease morbidity is highly dependent upon variables used to validate cases. Care must be taken to maintain consistent criteria to avoid bias due to improvements in diagnostic techniques over time which increase sensitivity for detection of cardiac ischemia.

Emergency surgery in patients with post-traumatic myocardial contusion

Little information concerning the prognostic and functional significance of post-traumatic myocardial contusion appears to exist. During a 10-month period, 19 patients with major blunt thoracic trauma were diagnosed as having myocardial contusion using clinical findings, serial ECG and CPK-MB isoenzyme determinations, and biventricular radionuclide angiocardiography (RA). All patients had associated thoracic and extrathoracic injuries. ECG and RA were useful and complementary tests, detecting abnormalities in 90% and 47% of patients, respectively. Only one patient had an abnormally elevated CPK-MB. All patients required operative treatment for associated injuries, 15 (79%) on the day of admission. Eleven patients required perioperative cardiac inotropic support and one needed IABP. No late complications were attributable to the cardiac contusions per se; no patients died. Emergency surgery for associated injuries in patients with myocardial contusion can be safely performed using hemodynamic monitoring to guide cardiac inotropic support measures. Myocardial contusion does not constitute an absolute contraindication to necessary operations in polytraumatized patients.

Emergency Surgery in Patients with Post-traumatic Myocardial Contusion

Little information concerning the prognostic and functional significance of post-traumatic myocardial contusion appears to exist. During a 10-month period, 19 patients with major blunt thoracic trauma were diagnosed as having myocardial contusion using clinical findings, serial ECG and CPK-MB isoenzyme determinations, and biventricular radionuclide angiocardiography (RA). All patients had associated thoracic and extrathoracic injuries. ECG and RA were useful and complementary tests, detecting abnormalities in 90% and 47% of patients, respectively. Only one patient had an abnormally elevated CPK-MB. All patients required operative treatment for associated injuries, 15 (79%) on the day of admission. Eleven patients required perioperative cardiac inotropic support and one needed IABP. No late complications were attributable to the cardiac contusions per se; no patients died. Emergency surgery for associated injuries in patients with myocardial contusion can be safely performed using hemodynamic monitoring to guide cardiac inotropic support measures. Myocardial contusion does not constitute an absolute contraindication to necessary operations in polytraumatized patients.

The use of gated radionuclide angiography in the diagnosis of cardiac contusion

No currently used diagnostic test is an accurate predictor of patients who will develop morbidity or mortality from cardiac contusion. In a prospective study we used gated cardiac radionuclide angiography to assess cardiac function in 30 patients with blunt chest trauma, and we compared the results of this test with those of other diagnostic studies for cardiac contusion to determine whether gated angiography is a more accurate predictor of serious cardiac injury. Diagnostic tests included the following: serial electrocardiograms (ECG), serial creatine phosphokinase muscle-brain isoenzyme (CPK-MB) and lactic dehydrogenase (LDH) isoenzymes, gated cardiac radionuclide angiography, and technetium-99m (Tc-99m) pyrophosphate scintigraphy. Abnormal studies were present in 26 patients; 22 showed abnormalities in CPK-MB, 19 on ECG, and five on gated scan. No patient demonstrated an abnormal Tc-99m pyrophosphate scan or abnormal elevation of LDH isoenzyme. Although no diagnostic test was predictive of morbidity and mortality, CPK-MB isoenzyme was the only test to correlate with morbidity and mortality. Morbidity and mortality correlated most closely with the number of associated major injuries and the presence of hypotension or hypoxia.

Pressurized Rapid Cardioplegia versus Administration of Exogenous Substrate and Topical Hypothermia

Five hundred fifty-nine patients undergoing aortocoronary operation were analyzed retrospectively according to the type of myocardial protection implemented during the period of ischemia. In Group 1 (253 patients), a rapid method of hypothermic cardioplegia alone was utilized. In Group 2 (306 patients), slower infusion of the same solution with topical hypothermia was implemented. Cardiac isoenzymes (CPK-MB, LDH 1, LDH 2, serum glutamic oxaloacetic transaminase [SGOT]) and myocardial infarct index (MII) were measured postoperatively for 48 hours. Immediately after operation, a significant difference was found between Groups 1 and 2 in the CPK-MB isoenzyme mean value levels—12.1 versus 18.6 IU, p < 0.01—and MII mean values—5.2 versus 8.1, p < 0.01. CPK-MB variances between subgroups receiving two, three, and four grafts were significantly different in favor of Group 1. Differences were also found in LDH 1, LDH 2, total lactic dehydrogenase (LDH), and SGOT: Group 2 levels were significantly higher than in Group 1. There were ten intraoperative infarctions in Group 2 and none in Group 1. In 45% of the patients in Group 2, inotropic agents were necessary in the postoperative period versus none in Group 1. Spontaneous cardiac rhythm following ischemia occurred in 89.7% of the patients in Group 1 versus 29% in Group 2. A method of pressurized high-flow rapid cardioplegia with intermittent reperfusions alone, seems to provide adequate protection of the myocardium during ischemia over a slower low-flow method of infusion combined with topical hypothermia.

The effect of direct current countershock on the myocardium.

The effect of direct current countershock on the myocardium in 10 patients undergoing elective cardioversion was evaluated utilizing 99m Tc Pyrophosphate imaging and MB CPK isoenzyme estimations. No perfusion abnormality or elevation of MB CPK occurred. The cumulative energy required for cardioversion ranged from 200–800 w/sec. It is concluded that myocardial injury or necrosis does not develop within these energy settings.

CPK-MB isoenzyme determinations: Diagnostic and prognostic value in evaluation of blunt chest trauma

The incidence of myocardial contusion in patients with blunt chest trauma was examined. The criterion used for diagnosing contusion--actual cellular injury--was based on detection of the MB-isoenzyme of creatine phosphokinase, a sensitive and specific marker for cardiac cellular injury. Forty-nine patients with blunt chest trauma were evaluated using this diagnostic approach. Twenty-six demonstrated measurable serum levels of MB-CPK. Electrocardiographic (ECG) evaluation of this subgroup revealed that 85% exhibited anatomically localized ST-T wave abnormalities while 15% showed nonlocalized and nonspecific changes. Sixty-eight percent of those with localized abnormalities demonstrated ST segment changes depicting injury, most of which were localized to the anterior septal leads. The remaining 23 patients demonstrated non-detectable serum levels of MB-CPK and were classified as cardiac concussion on the basis of other clinical criteria. Twenty-six percent with concussion exhibited anatomically localized ECG changes. The remaining 74% had nonlocalized and nonspecific ECG changes.

A Comparison of Serum Isoenzyme Levels of Creatine Phosphokinase and Lactic Dehydrogenase in Patients Undergoing Thoracic Operations and Patients Admitted to a Coronary Care Unit

A prospective study comparing patients undergoing major thoracic surgical procedures with patients admitted to a coronary care unit was conducted. Surgical patients having bronchoscopy and mediastinoscopy (n = 12), anterior thoracotomy (n = 12), and posterolateral thoracotomy (n = 22) were compared with patients in the coronary care unit who had electrocardiographically proved myocardial infarctions (MI) (n = 11) and those with no electrocardiographic abnormalities (n = 12). Sera were studied by spectrophotometric analysis (creatine phosphokinase [CPK] and lactic dehydrogenase [LDH]), agarose gel electrophoresis (CPK and LDH), and antibody inhibition spectrophotometric analysis (CPK). The levels of total CPK did not rise above the upper limits of normal (100 IU/L) in patients who underwent bronchoscopy and mediastinoscopy. Total CPK elevations in patients undergoing thoracotomy (anterior thoracotomy, 428 ± 62 IU/L [mean ± standard error of the mean]; posterolateral thoracotomy, 652 ± 78 IU/L) were not significantly different from those sustaining acute MIs (463 ± 84 IU/L). Only transient minimal elevations of CPK-MB isoenzyme were noted, however, in the patients having posterolateral thoracotomy (25 ± 7 IU/L). These were significantly lower ( p < 0.001) than the elevations seen in patients sustaining acute MIs (80 ± 16 IU/L). In none of the surgical patients did LDH 1 exceed LDH 2 while all of the patients with MIs had such a shift ( p < 0.001). The data support the conclusion that the serum isoenzymes of CPK and LDH are capable of confirming the diagnosis of MI in patients recovering from major thoracic surgical procedures.

Effect of the Kallikrein Inhibitor Aprotinin on Myocardial Ischemia and Necrosis in Man.

The effect of administration of aprotinin, a serine esterase inhibitor capable of inactivating kallikrein, on the extent and severity of acute myocardial ischemic injury and subsequent necrosis, was studied in 25 patients. Another group of 25 patients who did not receive aprotinin served as a control group.We administered 100,000 kallikrein inhibitor units (KIU) of aprotinin as a bolus dose, followed by a continuous infusion (4 ml/min) that contained 10,000 KIU/kg in 240 ml of dextrose/water solution, to all 25 patients admitted to the hospital within 30 to 60 minutes after the onset of acute myocardial ischemia.To measure the effect of aprotinin, three parameters were studied; the sum of S-T segment elevations (ΣST), the development of Q waves, and the prediction of infarct size by measuring the disappearance rate of creatine phosphokinase(MB CPK isoenzyme).The average ΣST in the treated group decreased from 40.5 ± 7.00 mv to 12.95 ±4.60 mv (P < 0.01); in contrast the control group's ΣST did not change significantly, from 54.25 ± 8.02 to 51.7 ± 6.8. Deeper Q waves evolved in the control group compared to the treated group: ΔQ (6 hours) = 1.0 ST (15 min) +1.19 (25 patients, r = 0.78); and in the treated group ΔQ (6 hours) = 0.66 ST (15min) + 0.91 (25 patients, r = 0.65) (P < 0.025).In the control group the estimated infarct size was 57.4 ± 4 CPK-gram equivalents(CPK-g-Eq). There was significantly less damage in the treated group: 19 ± 2 CPK-g-Eq (P < 0.01). Thus we conclude that aprotinin diminishes myocardial damage.

Electrocardiographic and serum enzymic alterations associated with cardiac alterations induced in dogs by single transthoracic damped sinusoidal defibrillator shocks of various strengths

The safety margin between the strength of shock needed to defibrillate the ventricle and shocks which produce cardiac damage has not previously been reported. This study quantitates the shock intensity required to produce ECG alterations, serum α-ILDH and MB CPK isoenzyme elevation and myocardial damage using single transchest damped sinusoidal defibrillator shocks. Shocks of 1 to 20 amperes per Kg. of body weight were applied. Fifty-six dog weighing 2.4 to 15 kilograms were shocked with defibrillator pulses via 10 centimeter diameter electrodes applied to the thorax. Electrocardiograms were taken to be analyzed for arrhythmias, S-T segment changes, and T wave changes. Serum enzyme levels were determined in 25 dogs. Macroscopic and histopathologic studies were conducted on the hearts. Transchest single damped sine wave shocks did not produce microscopically detectable cardiac damage until at least a threefold current overdose was applied. No macroscopic morphologic alterations were observed until at least a sixfold current overdose was applied and no deaths occurred until a twelvefold or greater current overdose was delivered. Incidence and severity of ECG changes, increase in serum enzyme activity, incidence and severity of cardiac damage, and incidence of mortality all correlated positively with shock strength. However, these four adverse effects did not correlate well with each other. Transient ECG changes were very frequent following shock application regardless of the morphologic damage produced, and hence the transient changes have little value as indicators or predictors of damage. Persistent ECG changes were predictive of morphologic changes but were not sensitive enough to detect damage in mildly injured hearts. Likewise, elevated serum cardiac isoenzyme activity was a reliable but insensitive indicator of damage.

Left ventricular performance during and after sickle cell crisis

Although microvascular occlusion has been considered a basis for pathophysiology of the myocardium during the crisis of sickle cell anemia, the status of the left ventricle in uncertain. To determine if left ventricular performance is affected by crisis, 11 patients were evaluated noninvasively by the systolic time interval method on the first day of crisis and serially until recovery. There were no significant differences in the time intervals over this period. In addition, since the serum CPK-MB isoenzyme was not elevated during crisis and evidence of acute injury was not present on ECG, myocardial necrosis appeared unlikely. Four patients on subsequent admission exhibited systolic time interval values similar to the earlier crisis. To determine if there were chronic changes in cardiac function, subjects with sickle cell hemoglobin were studied between crises. Those under 23 years of age were not dissimilar from a group of normals and a group of patients with chronic blood loss anemia A significant abnormality of the PEP/LVET ratio was observed in subjects over 23 years of age. Similar observations were made on echocardiography, with subjects over the age of 23 demonstrating an abnormal ejection fraction compared to the younger group, despite enhanced end-diastolic diameter. Thus, it is suggested that the chronic hemolytic process in subjects with sickle cell anemia may effect cumulative myocardial alterations, resulting in chronic cardiac malfunction in the apparent absence of acute ischemia during crises.

Perioperative Myocardial Infarction Associated with Coronary Artery Bypass Graft Surgery: Improved Sensitivity in the Diagnosis Within 6 Hours after Operation with 99mTc-Glucoheptonate Myocardial Imaging and Myocardial-Specific Isoenzymes

The present study was performed to evaluate scintigraphic imaging with technetium 99m-labeled glucoheptonate and serum enzyme levels of creatine phosphokinase isoenzyme (MB-CPK) in the early diagnosis of perioperative acute myocardial infarction associated with saphenous vein bypass graft operations. Myocardial imaging was done in 27 patients (50% of whom were considered high-risk) before operation and again 5 hours after operation. Four of these patients (15%) had both electrocardiographic and serum MB-CPK evidence of acute myocardial infarction, and all 4 had developed positive postoperative scintigrams. Four other patients had only elevated serum MB-CPK, and scintigrams became positive after operation in 3 of them. In addition, serum MB-CPK 6 hours after operation was 83 ± 21 mIU/ml (mean ± standard error of the mean) in patients with positive post-operative scans compared with 24 ± 5 mIU/ml in those patients with negative postoperative scintigrams ( p < 0.001). Myocardial imaging with 99mTc-glucoheptonate in the perioperative period is rapid, safe, and atraumatic. Furthermore, our results suggest that it is a sensitive method for the early diagnosis of perioperative acute myocardial infarction, and, when imaging is combined with serum MB-CPK isoenzyme analysis, the reliability of the diagnosis of acute myocardial infarction is enhanced even further. Only 1 of the patients who showed perioperative myocardial damage had acute hemodynamic compromise or obvious impairment of recovery in the immediate postoperative period, and the 30-day mortality of the total group was 4% (1 of 27).

Evaluation of myocardial damage during coronary artery grafting with serial determinations of serum CPK MB isoenzyme

Serial determinations of creatine phosphokinase isoenzymes (CPK) were made during the operative period and the first postoperative week in 60 patients undergoing coronary artery bypass surgery. Electrocardiograms (ECG) and serum levels of glutamic oxaloacetic transaminase (SGOT) and lactic dehydrogenase (LDH) were also evaluated. All patients had increased CPK MB activity which first became detectable during the operative period. The CPK MB curves usually showed a peak during the first postoperative hours and then a rapid decay. Some curves, however, showed a different profile with a prolonged liberation of CPK MB. This type of curve was more frequent in patients with electrical signs of necrosis or ischemic injury. In this group, the total amount of CPK MB released was greater than that in patients with unchanged ECG tracings (p less than 0.05). A mean curve of CPK MB activity was calculated for the patients without electric and/or enzymatic signs of myocardial injury. Serum CPK MB determination is a useful technique for identifying perioperative myocardial infarction (MI) and the time sequence of its occurrence. The appearance of this isoenzyme in every patient undergoing coronary surgery is an interesting finding, and it significance needs to be clarified.

Creatine phosphokinase MB isoenzyme in hypothermia: Case reports and experimental studies

Six patients with severe medical disorders and profound hypothermia are presented who had elevated total serum creatine phosphokinase (CPK) and CPK-MB isoenzyme activity without clinical 3 or postmortem 3 evidence of acute myocardial infarction. Experiments in dogs indicate that hypothermia reduces total CPK activity in both striated and myocardial muscle resulting in increased serum enzyme activity. These data suggest that profound hypothermia may result in diffuse striated and cardiac muscle cellular injury without evidence of discrete infarction with consequent release of CPK-MB isoenzyme into serum.