The diagnostic and prognostic value of the 12-lead electrocardiogram in assessing the severity of coronary disease in the acute phase of an acute myocardial infarct

The conventional twelve-lead electrocardiogram (ECG) still is the cheapest, most used and absolutely essential diagnostic method for the acute phase of myocardial infarction (MI) allowing risk stratification and coronary prognostic evaluation in this phase mainly by the localization of the ST segment depression and/or T wave inversion (ST/T changes) not related to the infarct area in Q-Wave MI or at any localization in case of non-Q wave MI. The etiology and pathophysiology of these ST/T changes in the setting of MI has been controversial. With the objective of determining ECG prognostic and diagnostic value, 70 patients (Pts) (59 men and 11 women, mean age 58 + 13) admitted in the acute phase of MI were studied with revision of acute phase ECG ST/T changes. All patients underwent coronary angiography and ventriculography at the moment of hospital discharge. Patients were divided into two classifications: A) MI localization: A1--Q-wave MI (anterior--20 pts, inferior--29 pts, lateral--1 pt); A2--non-Q wave--20 pts. B) Evidence of ST/T changes outside the infarct area in Q wave MI or at any localization in non-Q wave MI (group B1--with ST/T changes, group B2--without ST/T changes). We correlated the angiographically documented coronary artery disease in groups with ST/T changes and their localization. RESULTS: A1) Anterior MI group: in the 6 pts (30%) with "opposite" (inferior) ST/T changes, right coronary artery (RCA) disease was documented in 5 and in the other 14 patients the RCA did not show significant lesions. Inferior MI group: in the 24 Pts (83%) with "opposite" (precordial) ST/T changes. 23 of them had angiographic correlation (left anterior descending (LAD) and/or circumflex (CX) artery disease). Lateral MI group: one Pt with anterior wall ST/T changes and LAD and CX disease. A2) Non-Q wave group: in 13 pts (87%) the diseased vessels were correlated with the site of ST/T changes. B1) Q-Wave AMI: left main and 3-vessel disease in 2 pts, 3-vessel disease in 17 pts, 2-vessel disease in 9 pts, 1-vessel disease in 2 pts and non-significant disease in one pt. Non-Q wave MI: left main and 3-vessel disease in 1 pt, 3-vessel disease in 7 patients, 2-vessel disease in 3 pts and 1-vessel disease in 4 pts. B2) non-Q Wave MI: 3-vessel disease in 5 pts, 2-vessel disease in 7 pts, 1-vessel disease in 6 pts and non-significant disease in 1 pt. Non-Q wave MI: 2-vessel disease in 2 pts and non-significant disease in 1 pt. IN CONCLUSION: When pts were divided according to MI localization, a correlation was found between the ST/T changes outside the infarct area with CAD in 91% of Pts in the Q-Wave infarction group, with more significance in inferior and lateral MI. In the non-Q wave group, we found correlation between the a coronary lesions and the localization of ST/T changes in 87% of the pts. The pt group with ST/T changes presented, when compared with the pt group without these changes, evidence of more severe coronary artery disease (CAD): 3 vessels or left main with 3 vessel disease. However, only in the Q-Wave infarction group was a statistically significant difference found between the group with ST/T changes compared to the group without these changes, concerning to the existence of more severe coronary disease.     

Potential proischemic effect of early enalapril in hypotension-prone patients with acute myocardial infarction. The CONSENSUS II Holter Substudy Group

OBJECTIVE: To examine effects of intracerebroventricular (ICV) administration of metformin on the responses to environmental stress and on arterial baroreflex function in conscious spontaneously hypertensive rats (SHR). METHODS: SHR were instrumented with an ICV cannula and prepared for measurements of the mean arterial pressure (MAP), heart rate, and renal sympathetic nerve activity (RSNA) during air-jet stress (AJS). After recovery from a pretreatment AJS period, rats were allocated randomly to ICV administration of either vehicle (saline; n = 9) or 1 mg metformin (which is inactive dose after intravenous administration; n = 8). After stabilization for 1 h, the AJS was repeated. The arterial baroreflex control of the heart rate and RSNA was examined at the end of the experiment. RESULTS: ICV metformin decreased the baseline heart rate (by 88+/-14 beats/min) and RSNA (by 19+/-8%) in the absence of changes in MAP. ICV vehicle did not affect responses to the AJS [change in MAP (deltaMAP) = +11+/-2 mmHg, change in heart rate (deltaHR) = +54+/-9 beats/min, change in RSNA (deltaRSNA) = +37+/-8%), but pressor, tachycardic, and renal sympathoexcitatory responses to the AJS were inhibited significantly by ICV metformin (deltaMAP = +4+/-3 mmHg, deltaHR = -5+/-5 beats/min; deltaRSNA = +11+/-3%). ICV metformin did not affect the arterial baroreflex range, but it did increase the maximal gain of the arterial baroreflex control of heart rate (-1.46+/-0.25 versus 0.67+/-0.13%/mmHg, P= 0.01) and RSNA (-5.04+/-1.10 versus -2.47+/-0.28%/mmHg, P = 0.053). CONCLUSIONS: Central metformin administration attenuated the renal sympathoexcitatory response to environmental stress and increased the gain of the arterial baroreflex control of heart rate and RSNA. These actions may contribute to the antihypertensive effect of metformin.     

Study of myocardial viability after myocardial infarction. Value and limits of magnetic resonance imaging compared with myocardial scintigraphy

The aim of this study was to compare myocardial thickness measured by magnetic resonance imaging and quantified fixation of thallium. Twenty-one patients 61.2 +/- 11 years were investigated after myocardial infarction of the anterior wall in 8 cases, inferior in 10 cases, lateral in 2 cases and apical in one case. The mean angiographic ejection fraction was 46.5 +/- 19%. Myocardial scintigraphy was performed after an exercise or pharmacological stress test and followed by a study of redistribution. The data was analysed by a quantitative method. Magnetic resonance imaging was performed with vertical and horizontal long axis views in systole and diastole with division of the left ventricle into the same 12 regions. Three groups were defined according to fixation during redistribution. Group I: regions with fixation > 80% (n = 155); group II: 60 to 80% (n = 78); group III: fixation < 60% (n = 19). All measurement of myocardial thickness were correlated (p < 0.01) with the fixation of thallium during redistribution. Systolic thickening, was significantly greater in group I (3.80 +/- 3.1 mm) than in groups II (2.20 +/- 3.8 mm) and III (1.56 +/- 2.4 mm) in which it was comparable. Regions in group III had systolic (8.61 +/- 3.53) and diastolic (6.89 +/- 3.3 mm) thicknesses significantly inferior to those in groups I (13.79 +/- 4.4 mm: 9.95 +/- 2.8 mm) and II (11.59 +/- 5.5 mm: 9.38 +/- 2.9 mm). Ninety per cent of regions with a systolic thickness of over 10 mm had fixation during redistribution of more than 60%. This study shows that myocardial thickness is correlated to scintigraphic data. The systolic thickness over 10 mm would confirm the viability of a given region.     

Comparison of serum myoglobin and creatine kinase MB isoenzyme in early diagnosis of acute myocardial infarction

We compared the clinical usefulness of serum myoglobin and creatine kinase MB (CK MB) isoenzyme determinations in the early diagnosis of acute myocardial infarction in 109 consecutive patients admitted to a coronary care unit. Of these, 37 patients were diagnosed as having definite infarction, three possible infarction, and 69 no infarction, using World Heath Organisation criteria. Blood samples were taken on admission and two to four hours later, Both CK MB and myoglobin were raised in the initial serum samples in 24 of the 37 patients with definite infarction. In an additional seven patients both CK MB and myoglobin were negative in the first specimen though both were detected in the second sample. In five patients CK MB preceded the appearance of myoglobin while in the remaining patient myoglobin appeared before CK MB. We conclude that the detection of serum myoglobin does not offer any clinical advantage over CK MG as an early indicator of myocardial infarction.     

The clinical course of patients with acute myocardial infarction who are unsuitable for thrombolytic therapy because of the presenting electrocardiogram. UK Heart Attack Study Investigators

OBJECTIVE: To examine the clinical characteristics and 30-day fatality rate among patients with electrocardiograms (ECGs) ineligible for fibrinolysis in a consecutive series in four general hospitals in the UK. METHODS: We studied 2439 consecutive patients who were identified from regular ward visits, surveillance of results from hospital laboratories, and hospital discharge coding. RESULTS: Thirty percent (732) of patients did not have ECGs eligible for fibrinolysis therapy, while indications were uncertain in 55 (2%). Within the ineligible group, patients presenting with ST depression (n = 294) had a higher 30-day fatality rate than those with ST elevation or left bundle branch block (26% versus 17%; P < 0.001); they represented 40% of the group ineligible for fibrinolysis therapy, or 12% of the total cohort. Thirty-day fatality rates in patients presenting with pathological Q waves and no diagnostic ST segment changes (n = 130), those with T wave changes but no other abnormality (n = 168) and those with a normal ECG (n = 128) were 10%, 5% and 3%, respectively. Despite their high fatality rate, fewer patients with ST depression were admitted to coronary care units than those with ECGs eligible for fibrinolysis therapy (61% versus 85%; P < 0.001) and 23% did not receive heparin. The coronary anatomy in a subset of patients with ST depression showed two- or three-vessel disease in 79% and left main stenosis in 9%. The rates of coronary revascularisation were low in all groups (< 10%). CONCLUSION: Patients with ECGs ineligible for fibrinolysis therapy are a disparate group, with a high rate of fatality occurring in patients who present with ST depression. The high prevalence of multiple vessel coronary disease in patients with ST depression suggests that a more active management strategy is required.     

Physical exertion as a trigger of acute myocardial infarction. Triggers and Mechanisms of Myocardial Infarction Study Group

BACKGROUND: It is controversial whether the onset of myocardial infarction occurs randomly or is precipitated by identifiable stimuli. Previous studies have suggested a higher risk of cardiac events in association with exertion. METHODS: Consecutive patients with acute myocardial infarction were identified by recording all admissions to our hospital in Berlin and by monitoring a general population of 330,000 residents in Augsburg, Germany. Information on the circumstances of each infarction was obtained by means of standardized interviews. The data analysis included a comparison of patients with matched controls and a case-crossover comparison (one in which each patient serves as his or her own control) of the patient's usual frequency of exertion with the last episode of exertion before the onset of myocardial infarction. RESULTS: From January 1989 through December 1991, 1194 patients (74 percent of whom were men; mean age [+/- SD], 61 +/- 9 years) completed the interview 13 +/- 6 days after infarction. We found that 7.1 percent of the case patients had engaged in physical exertion (> or = 6 metabolic equivalents) at the onset of infarction, as compared with 3.9 percent of the controls at the onset of the control event. For the patients as compared with the matched controls, the adjusted relative risk of having engaged in strenuous physical activity at the onset of infarction or the control event was 2.1 (95 percent confidence interval, 1.1 to 3.6). The case-crossover comparison yielded a similar relative risk of 2.1 (95 percent confidence interval, 1.6 to 3.1) for having engaged in strenuous physical activity within one hour before myocardial infarction. Patients whose frequency of regular exercise was less than four and four or more times per week had relative risks of 6.9 and 1.3, respectively (P < 0.01). CONCLUSIONS: A period of strenuous physical activity is associated with a temporary increase in the risk of having a myocardial infarction, particularly among patients who exercise infrequently. These findings should aid in the identification of the triggering mechanisms for myocardial infarction and improve prevention of this common and serious disorder.     

Using serum markers in the early diagnosis of myocardial infarction

Because thrombolytic therapy can save lives and salvage left ventricular function after acute myocardial infarction, rapid and precise diagnosis is essential. Electrocardiographic changes, and the patient's history and physical examination may not confirm the diagnosis of myocardial infarction. Serum markers have specific advantages and disadvantages in confirming this diagnosis. An understanding of the advantages and disadvantages of using serum markers can enhance the clinician's ability to efficiently and accurately triage patients to appropriate care.     

A decision tree for the early diagnosis of acute myocardial infarction in nontraumatic chest pain patients at hospital admission

STUDY OBJECTIVE: To find an accurate algorithm for the diagnosis of acute myocardial infarction in nontraumatic chest pain patients on presentation to the emergency department. DESIGN: In a prospective clinical study, we compared the diagnostic performances of clinical symptoms, presenting ECG, creatinine kinase, creatine kinase MB activity and mass concentration, myoglobin, and cardiac troponin T test results of hospital admission blood samples. By classification and regression trees, a decision tree for the diagnosis of acute myocardial infarction was developed. SETTING: Emergency room of a Department of Internal Medicine (University Hospital). PATIENTS: One hundred fourteen nontraumatic chest pain patients (median delay from onset of chest pain to hospital admission, 3 h; range, 0.33 to 22): 26 Q-wave and 19 non-Q-wave myocardial infarctions, 49 patients with unstable angina pectoris, and 20 patients with chest pain caused by other diseases. MEASUREMENTS AND RESULTS: Of each parameter taken by itself, the ECG was tendentiously most informative (areas under receiver operating characteristic plots: 0.87 +/- 0.04 [ECG], 0.80 +/- 0.08 [myoglobin], 0.80 +/- 0.04 [creatine kinase MB mass], 0.77 +/- 0.04 [creatine kinase activity], 0.69 +/- 0.06 [clinical symptoms] 0.67 +/- 0.06 [creatine kinase MB activity], 0.67 +/- 0.05 [troponin T]). In patients presenting 3 h or less after the onset of chest pain, ECG signs of acute transmural myocardial ischemia were the best discriminator between patients with and without myocardial infarction. In patients presenting more than 3 h, however, creatine kinase MB mass concentrations (discriminator value, 6.7 micrograms/L) were superior to the ECG, clinical symptoms, and all other biochemical markers tested. This algorithm for diagnosing acute myocardial infarction was superior to each parameter by itself and was characterized by 0.91 sensitivity, a 0.90 specificity, a 0.90 positive and negative predictive value, and a 0.90 efficiency. CONCLUSIONS: We found an algorithm that could accurately separate the myocardial infarction patients from the others on admission to the emergency department. Therefore, this classifier could be a valuable diagnostic aid for rapid confirmation of a suspected myocardial infarction.     

Beneficial effects of captopril on prognosis in patients with acute myocardial infarction. Shanghai Secondary Prevention of Acute Myocardial Infarction Study Group

OBJECTIVES: To assess the effects of early and long-term angiotensin-converting enzyme inhibitor treatment with captopril on clinical outcome in patients with acute myocardial infarction (AMI). METHODS: Eight hundred and twenty-two patients with AMI who were hospitalised within 72 hours of symptoms and had no cardiogenic shock were randomly allocated to captopril (n = 478, Group I) and conventional treatment (n = 344, Group II). Cardiac events including congestive heart failure, reinfarction, severe arrhythmias and cardiac death during hospitalization and follow-up period (average 20 months) were determined. RESULTS: The overall mortality rate during hospitalization was lower in group I than in group II (P = 0.0001), this was true for patients with anterior (P = 0.0003), inferior (P = 0.0411) and anterior inferior AMI (P = 0.0232). During follow-up, despite similar occurrence rate of reinfarction and severe arrhythmias in the two groups, the mortality rate (P = 0.0324) and total cardiac event rate (P = 0.055) were lower in group I than in group II. CONCLUSIONS: After AMI, early and long-term treatment with captopril exerts a beneficial effect on the prognosis of patients.     

Prognostic significance of hypertension and albuminuria for early mortality after acute myocardial infarction

The motile enterococci with the vanC gene have intrinsic low-level resistance to vancomycin, but have not been implicated in a nosocomial outbreak. We determined the colonization rate of motile enterococci in hospitalized and nonhospitalized patients. Perianal or stool specimens were cultured in Enterococcosel broth supplemented with 6 micrograms of vancomycin per mL. Rapid motility and pigment tests were performed on all enterococci isolated. A total of 82 motile and/or pigmented enterococci were isolated from 679 patients for a colonization rate of 12.1%. There were 43 Enterococcus gallinarum, 32 Enterococcus casseliflavus, 4 Enterococcus flavescens, and 3 Enterococcus mundtii identified. The E. gallinarum vancomycin MIC90 was 32 micrograms/mL and the E. casseliflavus vancomycin MIC90 was 8 micrograms/mL.     

Etiopathogenesis of acute myocardial infarction: role of early leukocytosis]

Ultrasonic standing wave chambers with acoustic pathlengths of 1.1 and 0.62 mm have been constructed. The chambers were driven at frequencies over the range 0.66-12.2 MHz. The behaviour of 2 microns diameter latex microparticles and 5 microns diameter yeast in the chambers has been elucidated. One (flow) chamber had a downstream laminar flow expansion section to facilitate observation of concentrated particle bands formed in the ultrasonic field. A second (microscopy) chamber allowed direct observation of band formation in the field and their characterisation by confocal scanning laser microscopy. Clear band formation occurs when the chamber pathlength is a multiple of half wavelengths at the driving frequency, so that the chamber rather than the transducer resonance has the most influence on band formation in this system. Band formation occurred in half-wavelength steps from a position one quarter of a wavelength off the transducer to a band at a similar distance from the reflector. Ordered band formation was preserved by the laminar flow in the expansion chamber, although bands that formed very close to the wall were dissipated downstream. The microscopy chamber provided evidence of significant lateral particle concentration within bands in the pressure nodal planes. The approaches described will be applicable to the manipulation of smaller particles in narrower chambers at higher ultrasonic frequencies.     

Early diagnosis of subacute free wall rupture complicating acute myocardial infarction

Of 2608 consecutive patients with acute myocardial infarction, 24 developed subacute free wall rupture (= 0.92%; 95% C.I. = 0.6-1.4). Clinical manifestations varied widely (shock on admission; 25% of cases; severe arrhythmias followed by shock: 17%; shock during hospital stay: 42%; symptoms suggestive of infarct extension without shock: 17%). The electrocardiograms were confusing rather than revealing: 56% of patients showed new ST segment elevations of 0.2 to 1 mV in the infarct-related leads, while autopsy or creatinine phosphokinase evidence of infarct extension was missing. In the first 21 cases, therefore, no definitive diagnosis was made before autopsy. Using 197 infarct patients in cardiogenic shock or with infarct extension during the acute stage, i.e. a patient group with comparable clinical manifestations, as control group, a logistic regression model was generated in which the variables age, lateral wall involvement and history of hypertension were used for estimating the probability of subacute rupture. In fact, probability may rise to more than 40% in major subgroups. As death occurred after a median interval of 8 h (45 min-6.5 weeks) following the onset of rupture symptoms, echocardiography must be performed urgently in all cases presenting symptoms of shock or infarct extension. Pretest probability which can be roughly estimated from our model as well as sensitivity and specificity of individual echocardiographic or clinical parameters are indispensable for correct therapeutic decisions. The routine application of this algorithm in our department contributed to a timely diagnosis in the last three consecutive cases of whom one patient survived.     

Rapid MB CK subform assay and the early diagnosis of myocardial infarction

Seventy percent of patients admitted to coronary care units are ruled out for acute myocardial infarction. It has been estimated that 2-3 billion dollars each year could be saved if these non-AMI patients could be identified early, allowing the patient to be admitted to a less intensive setting. This study evaluated a new bedside device, the Cardiac STATus CK-MB/Myoglobin device for its utility in rapidly ruling out AMI. The device demonstrated a 99% negative predictive value within three hours of patient presentation.