Serum enzyme determinations in the diagnosis and assessment of myocardial infarction

Cardiac dysfunction in a patient with familial hypokalemic periodic paralysis

A 19-year-old white man with familial hypokalemic periodic paralysis developed evidence of cardiac dysfunction during a episode of flaccid paralysis. This consisted of elevated total creatine phosphokinase (CPK), an increased myocardial fraction of CPK (myocardial band), alteration in the lactic dehydrogenase isoenzyme pattern, severe bradycardia, and evidence of left ventricular dysfunction. These findings, in conjunction with selected cases from the literature, suggest the possibility that cardiomyopathy may be a heretofore unrecognized complication of this disorder.

Creatine phosphokinase isoenzymes and Trypanosoma cruzi infections

1. Substantial increases in total creatine phosphokinase (CPK) and in isoenzymes from heart (CPK-MB) and skeletal muscle (CPK-MM) were observed during acute infections with the House 510 and House 11 strains of Trypanosoma cruzi. 2. In infections with the reticulotropic Tulahuen strain total CPK levels were lower and the isoenzyme pattern was essentially normal. 3. Gamma-glutamyl transpeptidase was considerably increased in the Tulahuen but not in the House 510 and House 11 infections. 4. These findings are useful in assessing tissue damage during T. cruzi infections and they also demonstrate differences between myotropic and reticulotropic strains which may aid in their taxonomic classification.

99mTc-imidodiphosphonate: a superior radio-pharmaceutical for in vivo positive myocardial infarct imaging. II: Clinical data

99mTc-Imidodiphosphonate was investigated as a new myocardial infarct imaging agent. In the acute phase, 50 patients admitted to the coronary care unit were serially scanned over a period of 7 days. A mobile gamma camera linked on line to a remote data processor was used. Because of higher uptake in infarcted myocardium and faster blood clearance, superior images than those recorded with 99mTc-pyrophosphate were obtained. Its ease of preparation, low cost, and favourable dosimetry (because of its label with conventional 99mTc) transforms this agent into the present radiopharmaceutical of choice for acute infarct imaging in particular if sizing and follow-up is intended versus time and type of treatment. In this series, no false positive cases were seen. The sensitivity of the method in the detection of full thickness myocardial infarction was 95%. It dropped to 70% in the detection of subendocardial infarction. However, some of these apparent false negative cases may reflect severe ischaemia without infarction. It is postulated that this discrimination may not always be realistic.

Control of the acute phase response. Serum C-reactive protein kinetics after acute myocardial infarction

In order to investigate the magnitude and kinetics of the C-reactive protein (CRP) response after differing degrees of tissue injury, we studied changes in serum concentration of this acute phase protein in 19 patients after mild or extensive acute myocardial infarction. An increase in serum CRP concentration was seen in all patients. The rate of increase in concentration was found to be exponential, with a mean hourly rate constant for the entire group of patients of 0.085 (doubling time, 8.2 h). Patients with extensive infarction attained mean serum CRP levels about 4 times as great as did patients with mild infarction. No difference could be shown in the mean rate constant between these groups, the greater CRP response in the former group resulting principally from a more protracted period of rise in serum CRP concentration. A lag period before serum CRP levels began to rise was noted in only 4 of the 13 patients in whom this could be assessed. 7 of 10 patients with presumed unstable angina (coronary insufficiency) showed no rise in CRP concentration, while a small increase as noted in 3 patients. The data suggest that acute tissue injury, such as myocardial infarction, rapidly leads to acceleration in synthesis of CRP, and that the duration of this period of acceleration is related to the extent of tissue injury.

Coronary angiography and left ventriculography in survivors of transmural and nontransmural myocardial infarction

Recent studies have suggested a similar prognosis for patients with transmural myocardial infarction and nontransmural myocardial infarction despite a smaller infarct size in the latter patients estimated by creatine phosphokinase (CPK). Thirty-one patients with transmural myocardial infarction and 17 patients with nontransmural myocardial infarction as defined by electrocardiographic criteria underwent coronary angiography and left ventriculography from 10 to 24 days after they had an acute myocardial infarction. Forty-three of these 48 patients were asymptomatic following their myocardial infarction. When compared to patients with nontransmural myocardial infarction, those with transmural myocardial infarction had greater peak CPK levels, 1,090 +/- 210 versus 290 +/- 60 IU (p less than 0.01). There was no difference in prevalence of single, double or triple vessel coronary artery disease, mean number of coronary arteries 50 per cent narrowed (2.0 +/- 0.2 versus 2.0 +/- 0.2), near total or total occlusions, coronary score (Friesinger) (7.9 +/- 0.6 versus 8.2 +/- 0.7), left ventricular ejection fraction (48 +/- 2 versus 53 +/- 4), or per cent of akinetic-dyskinetic myocardial segments (66 of 242 [27 per cent] versus 32 of 132 [24 per cent]) between two groups. The similar extent of coronary artery narrowing and degree of left ventricular dysfunction may explain the similar prognosis for patients with transmural myocardial infarction and those with nontransmural myocardial infarction despite differences in enzymatically estimated acute infarct size.

Isoenzymes of creatine phosphokinase in acute myocardial infarction

Serial determinations of creatine phosphokinase (CPK) isoenzymes were performed in 400 patients with definite acute myocardial infarction (AMI). The findings were correlated with the clinical course and the findings in another 300 cases of increased CPK levels. MB-CPK, the cardiac fraction, was present in all 400 cases of AMI and in only 5 cases of the 300 patients with high CPK due to causes other than AMI. Based on the magnitude and time course of the total CPK in relation to the MB-CPK, five different patterns are described which correlate with the clinical course. Our findings thus suggest that the determination of CPK isoenzymes can be a most helpful diagnostic tool in the care of the cardiac patient.

Evaluation of electrocardiogram in emergency room as a decision-making tool

The contribution of the electrocardiogram to the clinical judgment used by the physician in the emergency room to determine the necessity for hospitalizing patients was evaluated. Thirty-five percent of all 1,578 patients with presumed myocardial infarction referred to the Chaim Sheba Medical Center, Tel Hashomer, Israel, for a one-year period had subsequently diagnosed myocardial infarctions. The ECG in the emergency room detected only 65 percent of these. The physician's clinical judgment was impressive in his decision to admit to the hospital almost all of the remaining 35 percent, while not admitting very many of the patients who did not have subsequently diagnosed myocardial infarctions. When the myocardial infarction was not evident on the ECG and the abnormalities on the tracings were identical for patients with subsequent myocardial infarctions and those without, again the physician made the right choice more often than the wrong. The follow-up ECG also attested to the good judgment of the physician in the emergency room. Of the emergency room ECGs of patients without subsequent myocardial infarctions who were admitted to the hospital, 17 percent showed myocardial infarction by follow-up, while this happened to only 2 percent of those denied admission.

Clinical evaluation of the enhancement of vagal tone in acute myocardial infarction by edrophonium hydrochloride: effects on ventricular arrhythmias, His bundle electrography, and left ventricular function

Enhanced electrical stability of acutely ischemic myocardium with vagal stimulation and acetylcholinesterase inhibition has been demonstrated experimentally. To extend these findings clinically, within 24 hours of acute myocardial infarction, 11 patients underwent continuous 10 hour Holter monitoring: 2.5 hour control before and after 5 hour constant edrophonium infusion (0.25 to 2.00 mg./minute). Continuous infusion of the agent lowered heart rate 92 to 78 b.p.m. (p less than 0.01). Although mean total ventricular extrasystoles (PVC's) per 5 hours per patient (131) and PVC's per 1,000 beats (4.7) were unchanged (p greater than 0.05), potentially lethal tachyarrhythmias (malignant PVC's: multifocal, R on T, paried, greater than 5 per minute or ventricular tachycardia) were terminated in six of 10 patients by edrophonium. However, serious ventricular arrhythmias continued in three patients and appeared in four despite the agent. Ventricular fibrillation did not occur during the 10 hour period of study. In addition, the patients were evaluated hemodynamically and by His bundle electrograms before and after a 10 mg. bolus of edrophonium prior to the 10 hour constant infusion: heart rate declined (88 to 72 b.p.m., p less than 0.01), while mean arterial pressure (98 mm. Hg), left ventricular filling pressure (14 mm. Hg), cardiac index (2.4 L. per minute per square meter), and stroke work index (36 Gm.m./M.2) were unchanged (p greater than 0.05). The edrophonium bolus prolonged the A-H interval (117 to 135 msec., p less than 0.01) while the H-Q interval was unaltered (48 msec; p greater than 0.05). It is concluded that increased vagal tone with edrophonium did not reduce the over-all presence of premature ventricular contractions in the entire study group; however, the malignant nature of PVCs and ventricular tachycardia appeared to be lessened by the parasympathomimetic agent in certain patients. In addition, no adverse hemodynamic or intraventricular conduction effects were produced by edrophonium administration.

Excretion of myoglobin in urine after actue myocardial infarction

We studied myoglobin excretion in 33 patients admitted to the coronary care unit with a provisional diagnosis of acute myocardial infarction. Sixteen proved to have definite and uncomplicated acute myocardial infarction and 17 possible infarction, using WHO criteria. For 5 days after admission, aliquots of every urine specimen voided by each patient were analysed for myoglobin using an immunochemical method able to detect a minimum urinary myoglobin concentration of 0-02 mg/ml. Myoglobinuria was detected in 14 of the 16 patients with definite infarction but was not found in any of the 17 patients with possible infarction. There were 3 patterns of myoglobin excretion. In 8 of the 14 patients it was excreted in one episode starting 10 to 40 hours after the onset of chest pain and lasting for 5 to 45 hours. In 3 of the remaining patients it was excreted over a much longer period (mean 83 hours) and in the final 3 patients myoglobinuria occurred in 2 or 3 intermittent episodes with periods of between 10 and 20 hours during which it was not detected. Total myoglobin excretion, which varied between 2 and 100 mg (mean 51 mg), did not correlate with peak serum enzyme levels. We concluded that in the appropriate clinical setting, the finding of myoglobinuria provides additional evidence for a diagnosis of acute myocardial infarction. The variable myoglobin excretion pattern suggests that in seemingly uncomplicated myocardial infarction there is considerable variation between patients in the pattern of evolution of the infarction process. This may be relevant to the assessment of measures directed towards limiting infarct size.

LDH isoenzymes and myocardial infarction in patients undergoing coronary bypass surgery: an excellent correlation

To evaluate the efficacy of LDH isoenzymes in the detection of myocardial infarction in patients undergoing coronary bypass surgery, 73 patients were studied pre- and postoperatively by ECG, CPK, SGOT, total serum LDH, and LDH isoenzyme measurements. A reversal of the LDH1:LDH2 ratio was considered indicative of myocardial necrosis. Accordingly, the patients were separated into two groups: Group A (23 patients) who demonstrated an LDH1:LDH2 ratio exceeding 1.0 and Group B (50 patients) who failed to reveal an LDH1;LDH2 reversal. The two groups were similar in regard to preoperative evaluation and operative procedure performed. The postoperative ECG findings were significantly different. In Group A 18 of 23 patients (78 per cent) developed significant new Q waves. This occurred in only one patient in Group B. Significant arrhythmias occurred in 70 per cent of the patients in Group A as compared to 14 per cent of those patients in Group B. Severe congestive heart failure and/or clinical evidence of shock occurred in 39 per cent of Group A patients and in none in Group B. The results of our study indicate that the reversal of the LDH1:LDH2 ratio is a valuable tool for the evaluation of postoperative myocardial infarction.

The detection of myoglobin in urine and its application to the diagnosis of myocardial infarction

An indirect haemaglutination method was developed for the immunochemical detection of myoglobin in human urine. Myoglobin was found in the urine of 84% of 44 patients with acute myocardial infarction. In contrast, it was detected in the urine of 2.7% of 147 control subjects and in none of a control group of 15 patients who had received intramuscular injections. In patients with myocardial infarction, myoglobin was detected in most but not all urine specimens collected between 10 and 50 hours after the onset of chest pain. The results suggest that the detection of myoglobin in urine may be a valuable addition to present tests for the diagnosis of acute myocardial infarction.

Localization of cardiac myosin-specific antibody in myocardial infarction

Specific localization of purified antibody against cardiac myosin has been demonstrated in areas of altered myocardial membrane permeability after experimental myocardial infarction. Intravenously administered radioiodine-labeled antimyosin was selectively localized in infarcted myocardium of seven dogs 24 h after coronary occlusion. The mean ratio (+/-SE) of antimyosin antibody in infarcted to normal myocardium in the center of the infarct was 4.2+/-0.4 for endocardial and 2.9+/-0.3 for epicardial layers. By utilizing (Fab')2 fragments of antimyosin obtained by pepsin digestion of purified antibody, the ratio of uptake was increased in eight dogs to 6.1+/-0.6 in the endocardial and 3.3+/-0.4 in the epicardial layers at the infarct center 24 h after occlusion. These ratios were further increased in the infarct center to 13.8+/-1.2 in the endocardial and 7.3+/-0.8 in the epicardial layers when eight dogs were sacrificed 72 h after coronary occlusion. The specificity of antimyosin (Fab')2 localization in infarcted myocardium was demonstrated in four dogs by simultaneous intravenous administration of 125I-labeled antimyosin (Fab')2 and 131I-labeled normal rabbit gamma globulin (Fab')2. Nonspecific trapping of normal rabbit IgG (Fab')2 was observed to be about 38% of total antimyosin (Fab')2 uptake in the central zone of infarction. Regional blood flow was related to antimyosin (Fab')2 uptake in infarcted myocardium by utilizing simultaneous administration of 85Sr-labeled microspheres. An inverse exponential relationship between antimyosin (Fab')2 uptake and regional blood flow was observed (r=0.85). The specific localization of antimyosin antibody or its (Fab')2 components in infarcted myocardium suggests a conceptually new approach to myocardial infarct localization and sizing.

The clinical course, early prognosis and coronary anatomy of subendocardial infarction

The following prospective study was undertaken to observe the clinical course, early prognosis and coronary anatomy of patients with subendocardial infarction. Subendocardial infarction was defined as typical chest apin (greater than 15 minutes), serum enzyme elevation and persistent (greater than 48 hours) new T wave inversion and/or S-T segment depression in the absence of new pathologic Q waves. Fifty consecutive patients were defined, followed in a prospective manner and subjected to early coronary arteriography. A prior history of unstable angina was found in 33 patients (66 per cent); 22 patients (44 per cent) had significant dysrhythmias during the acute hospital phase, and seven patients (14 per cent) had evidence of mild left ventricular failure. Coronary arteriography demonstrated significant lesions (greater than 75 per cent narrowing in at least one vessel) in all 50 patients, with 30 patients (60 per cent) having either double- or triple-vessel disease. Follow-up (mean 10.6 months) revealed that 15 patients (30 per cent) had stable angina, 23 patients (46 per cent) unstable angina and only 12 patients (24 per cent) remained free of angina. Of 28 patients in a medically treated group, acute transmural infarctions developed in six (21 per cent) and one died (3 per cent). We conclude that subendocardial infarction is symptomatically an unstable entity, is associated with severe coronary artery disease and, in a medically treated group, is followed by a significant incidence of early transmural myocardial infarction (21 per cent). Therefore, these patients require in-hospital monitoring, careful follow-up and consideration for early coronary arteriography.

A diminution of enzyme release in the anoxic guinea-pig heart observed after cardoiplegic treatment

1. Under anaerobic conditions there was an increase in the release of malate dehydrogenase, lactate dehydrogenase and creatine phosphokinase from isolated perfused guinea-pig hearts. 2. The increased enzyme releases were significantly reduced by pretreatment with cardioplegic solution. 3. This finding suggests a relationship between myocardial energy metabolism and enzyme release or retention.

Effects of myocardial revascularization following acute coronary occlusion in pigs

In a comparative study in pigs the extent of myocardial infarction has been estimated following a temporary three hour coronary occlusion and following a permanent coronary ligation. For evaluation of the cellular injury the infarct size has been determined by a histochemical staining procedure and correlated with serum enzyme studies (creatine phosphokinase, alpha-hydroxybutyric dehydrogenase) in the surviving animal. No significant difference could be detected between the two experimental groups and the extent of cellular damage was similar. A strict linear correlation was found between the serum enzyme activity plotted logarithmically and the morphological infarct size. Likewise the incidence of ventricular fibrillation depended on the extent of cellular injury. Myocardial revascularization does not appear to benefit a pig heart subjected to an acute coronary occlusion lasting three hours or more. Revascularization may even be harmful by creating a haemorrhagic infarct, as found in all the animals submitted to a transient coronary occlusion.

Precordial ST-segment mapping. 4. Experience with mapping of ST-segment depression in anterior transmural myocardial infarction

In order to assess the relative significance of precordial ST-segment elevations and depressions, 32 patients with anterior transmural myocardial infarction were studied utilizing serial 49-lead precordial maps. Theoretically, zones of ST-segment depression adjacent to major zones of ST-segment elevation might represent border areas of mild ischemia, and hence could be more readily amenable to intervention therapy. As expected, an extensive zone of ST-segment elevation was observed precordially in each of these patients. However, zones of ST-segment depression in adjacent areas were noted to occur inconsistently, were limited in distribution and magnitude, and bore no fixed relationship to zones of ST-segment elevation. Thus, mapping of precordial ST-segment depression in anterior transmural infarction probably has a limited role in assessing evolution of ischemic injury or therapy in these patients. This finding does not, however, vitiate the significance of ST-segment depressions in angina, intermediate coronary syndrome, or non-transmural infarction, conditions which may deserve further study using mapping techniques.

Creatine phosphokinase following cardioversion

Serial estimations of total serum creatine phosphokinase (CPK) have been performed before and during 18-51 hours after cardioversion of supraventricular tachyarrhythmias in 12 patients without acute myocardial infarction (AMI). The maximal CPK rise was 78 mU/ml (110%) and the CPK did not exceed the upper normal limit (130 mU/ml) in more than two patients (149 respectively 156 mU/ml). The CPK rise we have observed in a series of AMI patients varied between 101 (133%) and 2 260 mU/ml (3 780%), mean 900 mU/ml (1 184%). Therefore, cardioversion performed as described seldom seems to interfere with diagnosing AMI by serial estimations of serum CPK during the next 24 hours.

Specificity of elevated serum MB creatine phosphokinase activity in the diagnosis of acute myocardial infarction

Creatine phosphokinase (CPK) isoenzyme determinations are useful in the diagnosis of myocardial infarction. However, until suitably sensitive and precise quantitative procedures became available, the diagnostic specificity of serum CPK isoenzyme elevations could not be thoroughly examined. In this study an assay procedure capable of accurately determining activity of individual CPK isoenzymes even in serum samples with normal total CPK activity was employed to obtain two types of information. First, CPK isoenzyme profiles were examined in extracts of a spectrum of human tissues obtained at operation to determine whether the isoenzyme associated with myocardium is presented in other human tissues in quantities sufficient to produce increased activity in serum. In addition, CPK isoenzymes were analyzed quantitatively in serial serum samples from 50 hospitalized control subjects, 100 patients with acute myocardial infarction, 100 patients undergoing non-cardiac surgery and 50 patients undergoing cardiac catheterization to determine whether insult to tissues other than the heart is associated with increased "myocardial" CPK isoenzyme activity in serum. Results from analyses of tissue extracts indicated that myocardium is the only tissue surveyed containing sufficient MB CPK to account for substantial increases in serum MB activity. Results from analyses of serial serum samples indicated that MB CPK activity levels are consistently elevated after myocardial infarction, averaging 0.089 IU/ml. However, after cardiac cathetrization or noncardiac surgery peak serum MB activity remains low, averaging only 0.004 IU/ml despite marked elevations in total serum CPK activity. Thus, elevated serum MB CPK activity is a highly specific as well as sensitive criterion of myocardial injury.

Raised serum creatine phosphokinase activity in ankylosing spondylitis

Serum enzyme studies were made on 43 (37 male, 6 female) consecutive patients with ankylosing spondylitis. Serum creatine phosphokinase (CPK) activity was raised above 55 IU/l in 24 (65%) of 37 male patients (range 29-165 IU/l, mean 68) as compared with 2 (4%) out of 47 male controls (range 14-85 IU/l, mean 33: P less than 0-001); levels were greater than 35 IU/l in six (100%) out of six female patients (range 39-100 IU/l, mean 56) as against one (3%) of 35 female controls (range 3-106 IU/l, mean 16; P less than 0-001). The recognized pitfalls in interpreting CPK activity were avoided. In all of sixteen randomly selected patients isoenzyme studies confirmed that muscle is the source of the enzyme. There was a significant correlation between CPK activity and both spinal flexion and the reciprocal of finger-to-floor distance (P less than 0-5 in each case).

Creatine phosphokinase after submaximal physical exercise in untrained individuals

Serial estimations of total serum creatine phosphokinase (CPK) have been performed before and during 18-49 hours after submaximal physical exercise in 17 untrained individuals, mean age 50 years. The maximal CPK increase after exercise was 32 mU/ml (73%). The serum CPK did not exceed the upper normal limit (130 mU/ml) except in one individual (150 mU/ml). The maximal CPK increase in patients with acute myocardial infarction (AMI) varied between 101 mU/ml (133%) and 2 260mU/ml(3 790%), mean 900 mU/ml (1 184%). As the maximal CPK elevation in AMI occurs within the same period, it seems that heavy physical work of short duration just before the onset of symptoms will very seldom impair the diagnosis of AMI with the CPK technique used.

The assay of glycogen phosphorylase in human blood serum and its application to the diagnosis of myocardial infarction

Methods are described (a) for the estimation of glycogen phosphorylase activity (EC 2.4.1.1) in human blood serum based on the chemical determination of liberated orthophosphate or on the enzymic determination of glucose 1-phosphate in a coupled assay system and (b) for the electrophoretic separation of isophosphorylases I, II, and III in human. Glycogen phosphorylase activities ranging from 1.5 to 18 mU/ml were found in the serum of patients with acute myocardial infarction. In contrast, no glycogen phosphorylase activity was detected in the serum of healthy persons. The enzyme appears in the serum 4 hours after the onset of the infarction and reaches a maximum after 20 to 30 hours. Acrylamide gel electrophoresis of serum after a myocardial infarction revealed only muscle isophosphorylase I, the isoenzyme characteristic of the heart. No phosphorylase activity was detected in serum of patients with angina pectoris, endocarditis, and uncomplicative congestive heart failure. From these findings it appears that the new serum enzyme test may prove to be a valuable addition to presently existing methods for the early differential diagnosis of acute myocardial infarction.

Effects of reserpine and propranolol on anoxia-induced enzyme release from the isolated perfused guinea-pig-heart

The possibility of a protective effect by reserpine or propranolol on anoxia-induced released of malate and lactate dehydrogenase was investigated in isolated perfused hearts of guinea-pigs. After allowing 30 min of aerobic perfusion for the development of a steady state, the hearts from the nontreated group as well as the reserpine-pretreated or propranolol-treated group were subjected to a prolonged anoxia of 5 hrs. A marked enzyme release which occurred from the anoxic nontreated hearts was significantly inhibited by reserpine or propranolol. These findings suggest that the enzyme release from the anoxic myocardium is partly related to the liberation of endogenous catecholamines.