Nondiagnostic electrocardiogram in patients with acute myocardial infarction. Clinical and anatomic correlations

The Diagnostic Value and Cost-Effectiveness of Creatine Kinase-MB, Myoglobin and Cardiac Troponin-T for Patients with Chest Pain in Emergency Department Observation Ward

Aim

To evaluate the diagnostic value and cost-effectiveness of creatine kinase-MB isomer, myoglobin and cardiac troponin-T for patients with chest pain in emergency department observation ward.

Method

A prospective study was carried out to include all patients presenting with chest pain of suspected cardiac origin and admitted to the observation ward. Electrocardiogram and blood tests for the three cardiac markers were performed at the time of consultation and six to eight hours after admission to the observation ward. Progress of the patients was followed up for 30-day survival or the condition reviewed up to six months and the final diagnoses were documented.

Result

A total of 480 patients were recruited. The incidence of acute myocardial infarction was 1.5%. No one died of cardiac cause within 30 days. Troponin was more accurate than creatine kinase for diagnosing acute myocardial infarction and it was cost-effective. Myoglobin was of no value.

Conclusion

Troponin is recommended as a diagnostic tool for evaluating patients with chest pain in observation ward.

Usefulness of multiaxis echocardiography in assessment of the left ventricle in ischemic heart disease. A review

Echoventriculography, a multiaxis M-mode echocardiographic technique, was developed to examine in detail the regional wall motions of the left ventricle. The basic technical aspects and limitations are described, and experience is reviewed on 263 healthy subjects or patients with ischaemic heart disease. The reliability in detecting site and size of asynergic segments was excellent as related to electrocardiographic and thallium scintigraphic sites of acute infarction, and with left ventricular cineangiograms in chronic coronary heart disease. The correlation with pathologic anatomic size of infarct in 24 consecutive patients was r = 0.88 (p less than 0.001) when expressed by a percentage of the left ventricular horizontal circumference. 94% of 111 infarcted segments were correctly detected by echo; only the posteroseptal and the most lateral regions remain out of the methodological range. The method separated old infarct scars from fresh necrosis. Decreasing echo contraction index correlated with increasing severity of coronary obstructions in 43 patients studied for coronary artery surgery. In 15 infarct patients the M-mode technique was more sensitive than two-dimensional echocardiography in recording asynergic segments or endocardial echoes. The multiple segmental echoventriculographic index decreased parallel with clinical severity of acute infarction (r = -0.79, p less than 0.001; 30 patients). There was a 88% (p less than 0.01) concordance between the reduction of the ST segments (-30%) and the recovery of the mechanical function in the ischaemic myocardial segments (+26%) after beta blockade with pindolol in 22 patients with acute infarction. Methylprednisolone showed no improvement. With dopamine the left ventricular size decreased markedly (p less than 0.0005). Echoventriculography thus seems to be very informative in evaluation of chronic or acute left ventricular dysfunction, despite the rather demanding nature of the technique in practice.

[Myocardial perfusion (SPECT) in patients with non-Q-wave myocardial infarction]

BACKGROUND AND OBJECTIVE

The denomination non-Q-wave myocardial infarction ranges from small infarcts without scintigraphic abnormalities to severe and extensive necrosis with scintigraphic criteria of transmurality. The aim of the present study was to evaluate the severity and localization of necrosis in patients with non-Q-wave myocardial infarct, by myocardial perfusion single photon emission computed tomography (SPECT).

PATIENTS AND METHOD

We evaluated 206 patients with non-Q-wave myocardial infarct consecutively studied by myocardial perfusion 99mTc-tetrofosmin SPECT. Severity and localization of perfusion defects at stress and rest were analyzed.

RESULTS

Rest SPECT was normal in 53 patients (26%) and in 41 patients (20%) at least one segment with scintigraphic criteria of transmurality (uptake absence) was observed. Perfusion defects were more frequently localized in inferior and lateral regions. Stress-rest reversibility in peri-infarct regions was observed in 68.9% of patients, and reversibility at a distance was observed in 30% of patients.

CONCLUSIONS

Myocardial perfusion SPECT is a useful technique for the evaluation of the localization, extension and transmurality of non-Q-wave myocardial infarction, and the residual peri-infarction ischemia and ischemia at a distance of the necrosis.

[Terminology and diagnostic criteria for non-Q wave myocardial infarct]

INTRODUCTION

Non-Q myocardial infarction represents a specific entity of infarction. Many studies have shown that non-Q myocardial infarction differs from Q myocardial infarction not only electrocardiographically, but also from pathophysiological, histological, clinical and prognostic points of view. NON-Q MYOCARDIAL INFARCTION-TERMINOLOGY: Until 1980's, anatomical terminology depending on ECG changes was used in the literature. Subendocardial infarction referred to non-Q myocardial infarction, while transmural infarction referred to Q myocardial infarction. Since it was established that presence or absence of Q waves is a non-specific marker of transmural necrosis, in 1982 Spodick proposed the use of terms based on ECG findings. DIAGNOSTIC CRITERIA FOR NON-Q MYOCARDIAL INFARCTION: Elevation of markers of myocardial damage (CK, CK-MB, Troponin) is the most significant criterion for diagnosis of non-Q myocardial infarction. It cannot be made without this criterion because non-Q myocardial infarction may have ECG changes identical to those in unstable angina. Authors do not agree which type of initial ECG changes is the most frequent (ST elevation, ST depression or inverted T waves).

CONCLUSION

Non-Q myocardial infarction represents a specific entity of myocardial infarction. Anatomically, based on the extension of necrosis, non-Q myocardial infarction is subendocardial, but it can be transmural as well. ECG changes in non-Q myocardial infarction may be identical to those in unstable angina. Therefore, elevation of cardiac enzymes is the golden standard in diagnosis of non-Q myocardial infarction.

Maximal precordial ST-segment depression in leads V4-V6 in patients with inferior wall acute myocardial infarction indicates coronary artery disease involving the left anterior descending coronary artery system

BACKGROUND

In inferior wall acute myocardial infarction, maximal ST-segment depression in left precordial leads (V4-V6) has been shown to be associated with increased in-hospital mortality, presumably due to coronary artery disease involving the left anterior descending coronary artery system.

METHODS

We measured ST-segment deviation from baseline in the initial electrocardiogram of patients with inferior wall acute myocardial infarction, who subsequently underwent coronary angiography during their in-hospital stay. Patients were divided into three groups: (I) No precordial ST-segment depression (n = 34). (II) Maximal precordial ST-segment depression in leads V1-V3 (n = 44). (III) Maximal precordial ST-segment depression in leads V4-V6 (n = 14).

RESULTS

The left anterior descending coronary artery or its diagonal branch were stenosed (> 50%) in 32%, 41%, and 71% of patients in groups I, II, and III, respectively (p = 0.04), and severely stenosed (> 70%) in 18%, 18% and 57% of patients in the respective groups (p = 0.007).

CONCLUSION

In patients with inferior wall acute myocardial infarction, maximal precordial ST-segment depression in leads V4-V6 is suggestive of severe coronary artery disease involving the left anterior descending coronary artery or its diagonal branch.

An emergency department-based protocol for rapidly ruling out myocardial ischemia reduces hospital time and expense: results of a randomized study (ROMIO)

OBJECTIVES

We tested the hypothesis that an emergency department-based protocol for rapidly ruling out myocardial ischemia would reduce hospital time and expense but maintain diagnostic accuracy.

BACKGROUND

Patients with a missed diagnosis of myocardial infarction have a high mortality rate; however, providing routine hospital care to low risk patients may not be time- or cost-effective.

METHODS

One hundred low risk patients were entered into the study and randomized either to an emergency department-based rapid rule-out protocol (n = 50) or to routine hospital care (n = 50). Patients receiving routine care were managed by their attending physicians. The rapid protocol included serum enzyme testing at 0, 3, 6 and 9h, serial electrocardiograms with continuous ST segment monitoring and, if results were negative, a predischarge graded exercise test. Study patients were also compared with 160 historical control subjects.

RESULTS

Myocardial infarction or unstable angina occurred in 6% of patients within 30 days; no diagnoses were missed. By intention to treat analysis (n = 50 in each group), the hospital stay was shorter and charges were lower with the rapid protocol than with routine care (p = 0.001). Among patients in whom ischemia was ruled out, those assigned to the rapid protocol had a shorter hospital stay (median 11.9 vs. 22.8 h, p = 0.0001) and lower initial ($893 vs $1,349, p = 0.0001) and 30-day ($898 vs. $1,522, p = 0.0001) hospital charges than did patients given routine care. In historical control subjects, the hospital stay was longer (median 34.5 h, p = 0.001 vs. either group) and charges greater (median $2,063, p = 0.001, vs rapid protocol, p = 0.02, vs. routine care group).

CONCLUSIONS

In low risk patients who present to the emergency department with chest pain, the rapid protocol ruled out myocardial infarction and unstable angina more quickly and cost-effectively than did routine hospital care.

Acute infarction of the left ventricular papillary muscle: electrocardiographic pattern and recognition of its location

BACKGROUND AND HYPOTHESIS

ST-segment depression during acute myocardial infarction (AMI) is known to herald serious hemodynamic complications. Since the mechanism of this dependence is not clear, we reinvestigated the old concept of papillary muscle infarction (PMI) as a cause of marked ST depression.

METHODS

Autopsies and morpho-electrocardiographic cor-relations were performed in 53 patients with AMI involving one or both left ventricular papillary muscles, and in 10 patients with AMI, but without acute PMI.

RESULTS

ST-segment depression > or = 1 mm in at least two leads (mean 3.6 +/- 2.2 mm) was found in 46 (86.8%) patients with, and in one without acute PMI. Thus, the sensitivity and specificity in selecting patients with acute PMI from among those with AMI were 86.8 and 90%, respectively, with an overall accuracy of diagnosis of acute PMI in the course of AMI of 87.3%. Among 26 patients with ST elevation consistent with diagnosis of AMI, ST depression, recorded in 22 patients, was insignificantly greater than in 24 of 27 patients without ST elevation: 4.1 +/- 2.9 versus 3.1 +/- 1.2 mm. Localization of ST depression in the limb leads allowed recognition of which papillary muscle suffered from acute infarction: ST depression in the inferior leads was seen only in patients with anterolateral PMI, whereas in leads I and/or a VL it was seen only in cases with posteromedial PMI. This rule was also valid in patients without concomitant ST elevation.

CONCLUSION

Patients with acute PMI show marked ST-segment depression. Its location in the limb leads allows recognition of which papillary muscle has undergone necrosis. This cause of marked ST depression in patients with AMI may explain the high mortality in this particular group.

Usefulness of the 12-lead electrocardiogram in detection of myocardial infarction: electrocardiographic-anatomic correlations--Part II

Part II of this two-part series on electrocardiographic-necropsy correlation of infarct location focuses on lateral and posterior ("inferior") infarctions. The value of infarct location regarding complications and prognosis is also discussed.

Prognostic significance of the initial electrocardiographic pattern in patients with inferior wall acute myocardial infarction

The purpose of the study was to determine whether the initial electrocardiographic pattern is predictive of in-hospital mortality in inferior wall acute myocardial infarction. It is commonly perceived that patients with acute myocardial infarction presenting with greater ST elevation have a worse prognosis. The initial electrocardiogram of patients (n = 213) with inferior wall myocardial infarction was categorized based on the pattern of ST-segment elevation in inferior leads: (A) ST <1 mm with tall T waves, (B) ST > or = 1 mm with normal terminal QRS, and (C) ST > or = 1 mm with distortion of terminal QRS. ST deviation from baseline was calculated for all leads. Patients with maximal precordial ST depression in V4-V6 and pattern A had an in-hospital mortality rate of 68.8% compared with 16.9% for the entire study group. By univariate analysis, only pattern A was significantly predictive of in-hospital mortality [odds ratio = 2.91, 95% confidence interval (CI) 1.22-6.93], but by multivariate analysis adjusted for (1) age, (2) diabetes mellitus, (3) previous myocardial infarction, (4) thrombolytic therapy, (5) precordial ST-depression pattern, and (6) patterns of ST elevation, maximal ST depression in V4-V6 was significantly predictive (odds ratio = 4.93, 95% CI 1.79-13.56), whereas pattern A was not (odds ratio = 1.12, 95% CI 0.36-3.52). Contrary to popular perception, patients with inferior wall myocardial infarction presenting with minimal ST-segment elevation are at highest risk for in-hospital mortality, especially if accompanied by maximal precordial ST depression in V4-V6.

Usefulness of the 12-lead electrocardiogram in detection of myocardial infarction: electrocardiographic-anatomic correlations--part I

This two-part review evaluates a 56-year period (1938-1994) of electrocardiographic-necropsy correlation studies. Part I focuses on definitions of infarct location and evaluates anterior infarctions. Part II will focus on lateral and posterior infarcts.

Analysis of transmural trend of myocardial integrated ultrasonic backscatter in patients with old myocardial infarction

Changes in myocardial integrated backscatter (IB) reflect myocardial viability in patients with myocardial infarction. IB may be obtained separately in the subendocardial and subepicardial layers to establish a transmural trend. The purpose of this study is to examine the possibilities that the measurement of the transmural trend in myocardial IB may provide a new estimate of transmurality of infarction in patients with old myocardial infarction. A calibrated myocardial IB and its transmural trend were measured both in the septum and posterior wall in 21 normal subjects, 24 patients with anteroseptal old myocardial infarction (13 patients with Q-wave myocardial infarction and 11 patients with non-Q-wave myocardial infarction). The transmural trend in myocardial IB was assessed by measuring the acoustic parameter separately in the right and left ventricular halves of the septum, and in the endocardial and epicardial halves of the posterior wall. The magnitude of cyclic variation of IB (a difference between minimum and maximum peaks) was lower, and calibrated myocardial IB (the maximum value of myocardial IB at end diastole calibrated with the power of Doppler signals from the blood along the same ultrasound beam) was higher in patients with anteroseptal old myocardial infarction in the septum, compared with normal subjects. Among patients with myocardial infarction, the difference in these IB parameters between the right and left ventricular halves of the septum was found only in patients with non-Q-wave myocardial infarction. The transmural trend of myocardial IB was likely to reflect the transmurality of myocardial infarction. Therefore, our data give another insight into the assessment of transmural inhomogeneity of myocardial fibrosis or viability in patients with myocardial infarction.

Prognosis in acute myocardial infarction: comparison of patients with diagnostic and nondiagnostic electrocardiograms

Prognosis in acute myocardial infarction has been compared in patients with and without diagnostic ECGs. Of 817 patients, 89.4% had ST elevation, 2.4% had left bundle branch block, and 8.2% had no ST elevation. Patients without ST elevation had a hospital mortality rate of 3.0% compared with 14.0% and 40.0%, respectively, in patients with ST elevation and left bundle branch block (p = 0.0001). Event-free survival at 6 months in patients without ST elevation was 85.6% (74.1% to 92.3%), compared with 72.9% (69.4% to 76.0%) and 31.0% (12.0% to 52.3%) in patients with ST elevation and left bundle branch block (p < 0.001). The excess risk associated with ST elevation was largely attributable to the severity of infarction: after adjustment for Q-wave development and heart failure, the hazard ratio fell from 2.24 (1.43 to 4.38) to 1.76 (0.86 to 3.59). In conclusion, acute myocardial infarction has a considerably better prognosis when it is unassociated with ST elevation or left bundle branch block. This finding may have important implications for interventional management.

Patterns of practice in emergency department management of chest pain of suspected cardiac origin: clinical utility of single stat creatine kinase (CK)

The patterns of practice and the clinical utility of a single stat creatine kinase (CK) level in the emergency department management of chest pain of suspected cardiac origin were examined by a prospective observational study using a two-part questionnaire, completed by physicians before and after availability of CK results. The results showed that of the 776 patients in the study, 135 were admitted to hospital with acute myocardial infarction (AMI), 285 were admitted for reasons other than AMI, 343 were discharged, and 13 died or were transferred to another hospital. Although initial and final diagnoses in the emergency department did not differ in 597 patients (77%), initial decisions to admit or discharge were made in only 244 (31%) patients without waiting for CK results, and in 401 (52%) cases, decisions on patient disposition were deferred. Of 218 patients who had elevated CK levels, 193 (89%) were admitted, 121 for AMI. Only five (< 1%) patients who would otherwise have been discharged were admitted because of elevated CK levels. Of the 343 discharges, 245 (71%) occurred after the physicians knew the CK results. It is concluded that emergency department physicians routinely make changes in their diagnostic and management decisions based on current information and as it becomes updated. This study also suggests that there appears to be a heavy reliance on a single CK assay, although the relative importance of this diagnostic test compared to other factors is not known. Further studies are necessary.

The role of single ECG, creatinine kinase, and CKMB in diagnosing patients with acute chest pain

The objective of this study was to determine the combined accuracy of emergency department (ED) cardiac enzymes and electrocardiograms (ECGs) in patients who were admitted to "rule-out" myocardial infarction (ROMI). A retrospective analysis of ED creatinine kinase (CK), CKMB, and ECG was performed and the results were compared with final hospital diagnosis of MI, in the ED of a medical school- and university hospital-affiliated teaching Veterans Affairs Medical Center. Approximately 222 consecutive ED patients admitted to ROMI, including 43 (19%) MI patients, 29 (67%) of whom presented to the ED within 24 hours of symptom onset were eligible to participate. Interventions included an analysis of CK and CKMB results and ECG findings. There were no statistical differences in the sensitivities, specificities, and predictive values when the two cardiac enzymes were compared. Almost all of the elevated cardiac enzyme results occurred in MI patients who presented within 24 hours of symptom onset, more than half of whom had ED cardiac enzyme elevations. For all MI patients, regardless of duration of symptoms, more than half of the ED ECGs had new ST-T changes consistent with an acute MI or acute myocardial ischemia. In the MI patients who presented within 24 hours of symptom onset, 79% had positive enzymes or ECG or both in the ED. No statistically significant difference in the sensitivity rates for MI between the CK and CKMB comparing enzymes with ECGs was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Value and limitations of current methods of evaluating patients presenting to the emergency room with cardiac-related symptoms for determining long-term prognosis

The goal of this study was to determine the value and limitations of the current approach for evaluating patients in the emergency room (ER) with cardiac-related symptoms in terms of predicting long-term outcome. Accordingly, 274 consecutive prospectively identified patients presenting to the ER with such symptoms were evaluated, and follow-up was obtained at 20 +/- 9 months in 265 of them (97%). Adverse cardiovascular events were defined as: nonfatal myocardial infarction, death, cerebrovascular accident with neurologic deficit, life-threatening arrhythmia and cardiac surgery. Eighty-three patients (31%) had a cardiovascular event during follow-up; 42 occurred within 48 hours of ER presentation, whereas 41 occurred in the ensuing months. Findings on physical examination and electrocardiogram provided additional prognostic information, compared with that of history alone, when added sequentially into a Cox model. However, by discriminant function analysis, only 63% of actual events were correctly predicted by the model. Events occurring after 48 hours of ER presentation were correctly predicted only 50% of the time compared with those occurring within 48 hours of ER presentation, which were correctly predicted 75% of the time (p = 0.04). It is concluded that patients presenting to the ER with cardiac-related symptoms are at high risk for adverse cardiovascular events. The likelihood of an event occurring after 48 hours of presentation is as high as one occurring within 48 hours. Current methods of evaluating such patients have limited prognostic value, particularly for those at long-term risk for events.

Identification of first acute Q wave and non-Q wave myocardial infarction by multivariate analysis of body surface potential maps

BACKGROUND

Patients with acute non-Q wave myocardial infarction (NQMI) appear to have more jeopardized residual myocardium at high risk for subsequent angina, reinfarction, or malignant arrhythmias than patients with acute Q wave myocardial infarction (QMI). Unfortunately, conventional electrocardiographic (ECG) criteria have limited utility in recognizing NQMI.

METHODS AND RESULTS

The present study combines the increased information content of body surface potential maps (BSPM) over the 12-lead ECG with the power of multivariate statistical procedures to identify a practical subset of leads that would allow improved diagnosis of NQMI. Discriminant analysis was performed on 120-lead data recorded simultaneously in 159 normal subjects and 308 patients with various types of myocardial infarction (MI) by using instantaneous voltages on time-normalized P, PR, QRS, and ST-T waveforms as well as the duration of these waveforms as features. Leads and features for optimal separation of 159 normals from 183 patients with recent or old QMI (group A) were selected. A total of six features from six torso sites accounted for a specificity of 96% and a sensitivity of 94%. All lead positions were outside the conventional electrode sites and selected features were voltages at mid-P, early and mid-QRS, and before and after the peak of the T wave. The discriminant function was then tested on 57 patients with acute NQMI (group B) and 68 patients with acute QMI (group C): Rates of correct classification were 91% and 93%, respectively. Because of the possible deterioration of the results caused by ST-T abnormalities also present in other clinical entities, a second classification model including an independent group of 116 patients with left ventricular hypertrophy (LVH) but without MI was developed. Two additional measurements were required, namely, P wave duration and a mid-QRS voltage on a lead located 10 cm below V1. Testing the model on both acute MI groups produced correct classification rates of 88% for acute NQMI and 93% for acute QMI. Group mean BSPM were plotted for the three MI groups at successive instants throughout the PQRST waveform. Typical patterns for each MI group were identified during PQRST by removing the corresponding normal variability at each electrode site from sequential MI maps. These standardized maps or discriminant maps provided information on the capability of each measurement at each electrode site and at each instant to separate each class of MI from the normal group (N). Striking similarities were observed between the three MI groups, particularly at mid-QRS and throughout ST-T. The closest resemblance was between acute NQMI and old QMI. Discriminant analysis was also performed on the 12-lead ECG: The first classification model (N versus MI) produced correct classification rates of 85% for acute QMI and 70% for NQMI. With the second model (MI versus N or LVH), correct rates were 81% and 65%, respectively.

CONCLUSIONS

Diagnosis of acute NQMI and QMI (also in the presence of LVH) can be improved substantially by appropriate selection of ECG leads and features. Comparison of discriminant maps from groups A, B, and C does not support the concept of acute NQMI as a distinct ECG entity but rather as a group with infarcts of smaller size. However, pathophysiological and clinical differences between acute NQMI and acute QMI influence long-term risks and may define different therapeutic approaches.

Importance of two-dimensional echocardiographic assessment of left ventricular systolic function in patients presenting to the emergency room with cardiac-related symptoms

BACKGROUND

This prospective study was designed to test the hypothesis that the assessment of left ventricular systolic function at the time of emergency room (ER) presentation provides valuable diagnostic and prognostic information in patients with cardiac-related symptoms.

METHODS AND RESULTS

The study is based on a 2-year follow-up of 171 consecutive patients evaluated in the ER for such symptoms. In the course of follow-up, one third of the patients (55 of 171) suffered a major cardiac event. For those with left ventricular systolic dysfunction (LVSD), the age-adjusted rate of early events (occurring within 48 hours of presentation) was more than eight times higher than for those without LVSD (26.9% versus 3.3%, p less than 0.01). For events occurring after 48 hours of ER presentation, LVSD was associated with a nearly fourfold excess of cardiac events (23.9% versus 6.4%, p less than 0.01). Other than advanced age, the most important confounder for early events included an abnormal electrocardiogram diagnostic for acute myocardial infarction. Confounders for late events included advanced age and a history of hypertension. LVSD on two-dimensional echocardiography (2DE) was the only finding associated with early and late events after controlling for other risk factors. In addition, the prediction of these events derived from the combination of historical, clinical, electrocardiographic, and 2DE findings was significantly improved when accounting for the presence or absence of LVSD (p less than 0.01).

CONCLUSIONS

We conclude that the 2DE assessment of left ventricular systolic function provides valuable diagnostic and prognostic information in subjects presenting to the ER with cardiac-related symptoms.

Noninvasive identification of myocardium at risk in patients with acute myocardial infarction and nondiagnostic electrocardiograms with technetium-99m-Sestamibi

BACKGROUND

Patients who have chest pain without electrocardiographic ST elevation are not candidates for thrombolytic therapy in most clinical trials. This study examined the value of technetium-99m-Sestamibi tomographic imaging to assess myocardial perfusion in patients during chest pain without ST elevation.

METHODS AND RESULTS

Tc-99m-Sestamibi was injected in 14 patients who had chest pain without ST elevation, who subsequently developed enzymatic evidence of myocardial infarction within 24 hours. Tomographic imaging was performed 1-6 hours after injection. Thirteen of 14 patients showed significant perfusion defects indicative of acute myocardial infarction consistent with absent perfusion (20 +/- 15% of the left ventricle; range, 2-53%); one patient had normal images. Because of the absence of definitive electrocardiographic changes, only five patients received reperfusion therapy within 6 hours of the onset of chest pain. Regional wall motion abnormalities were present in nine of nine patients undergoing contrast ventriculography and correlated with the location of the Tc-99m-Sestamibi perfusion defect. At the time of subsequent coronary angiography, total arterial occlusion was present in 11 of the 14 patients. The infarct-related artery could be identified in 13 of the 14 patients. In six of these 13 patients, the left circumflex was the infarct-related artery.

CONCLUSIONS

Patients who have chest pain without electrocardiographic ST elevation may have arterial occlusion and significant myocardium at risk. Tc-99m-Sestamibi imaging may be of benefit in identifying these patients early so that they can be considered for acute reperfusion therapy.

The prognostic significance of first myocardial infarction type (Q wave versus non-Q wave) and Q wave location. The Multicenter Diltiazem Post-Infarction Research Group

The prognostic significance of the type of first acute myocardial infarction (Q wave versus non-Q wave) and Q wave location (anterior versus inferoposterior) was determined from a multicenter data base involving 777 placebo-treated patients who were participants in the Multicenter Diltiazem Post-Infarction Trial. There were 224 patients (29%) with a non-Q wave infarction, 326 (42%) with an inferoposterior Q wave infarction and 227 (29%) with an anterior Q wave infarction. Mean left ventricular ejection fraction was significantly (p less than 0.001) lower in patients with an anterior Q wave infarction than in the other two groups (anterior Q wave 0.39; inferior Q wave 0.52; non-Q wave 0.53). Nevertheless, the total cardiac mortality rate during the follow-up period (average 25 months per patient) was only marginally higher (p = 0.42) in the anterior Q wave group (8.4%) than in the other two groups (inferoposterior Q wave 7.1%; non-Q wave 6.3%). The total first recurrent cardiac event was somewhat higher (p = 0.08) in the anterior Q wave group (18.1%) than in the other two groups (inferoposterior Q wave 11.7%; non-Q wave 15.6%). Survivorship analyses extending over 3 years revealed that electrocardiographic classification of the type of first infarction and Q wave location did not make significant independent contributions to the risk of postinfarction cardiac death or first recurrent cardiac event, either before or after adjustment for baseline clinical variables.

Clinical characteristics and outcome of acute myocardial infarction in patients with initially normal or nonspecific electrocardiograms (a report from the Multicenter Chest Pain Study)

To determine the prevalence and characteristics of acute myocardial infarction (AMI) patients who present to emergency departments with normal or nonspecific electrocardiograms (ECGs), data were analyzed from 7,115 consecutive patients in the Multicenter Chest Pain Study. AMI patients with normal or nonspecific initial ECGs (n = 107) were less likely to have a past history of coronary artery disease or to be diaphoretic on presentation (p less than 0.01) than AMI patients with initial ECGs highly suggestive of AMI (n = 811). The overall probability of AMI among patients with chest pain and initially normal or nonspecific ECGs was 3%, but ranged from less than 1 to 17% depending on the patient's age and sex and whether the patient had pressure-type pain or pain radiating to the shoulder, neck or arms. Among initially admitted patients, the time elapsed between onset of pain and presentation was similar in both groups. However, the time between onset of pain and definitive diagnosis of AMI by enzymes or clinical course was longer in patients with initially normal or nonspecific electrocardiograms (8.3 vs 7.5 hours, p less than 0.05), their peak creatine kinase levels were lower (mean 643 vs 1,032 mg/dl, p less than 0.001) and their mortality was slightly lower (6 vs 12%, p = 0.10). These findings suggest that AMI patients with initially normal or nonspecific ECGs may have a less severe short-term clinical outcome.

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)

"Non-Q wave," alias "nontransmural," myocardial infarction: a specific entity

Although Q wave and non-Q wave MI are often referred to as "transmural" and "nontransmural," there is no anatomic evidence to justify this distinction. Nevertheless, a distinction is important, because the two entities have a different prognosis. At the present time, between 25% and 35% of MIs are non-Q wave. They are frequently observed in patients with previous coronary events. They occur in a relatively older population and involve a slightly higher proportion of women than do Q wave MIs. The degree of cardiac damage is less, reflected by a smaller rise in enzyme level and less impairment of left ventricular ejection fraction; early reperfusion may occur, after spontaneous thrombolysis or resolution of coronary spasm. The immediate mortality rate is half that of Q wave MI but identical in the long term. Reinfarction and angina are more frequent because of a peri-infarction zone of ischemia maintained by a high-grade coronary stenosis and inadequate collateral circulation. Early characterization of those MIs likely to progress is important. Diltiazem seems effective in this context if given between 24 and 72 hours of the onset of the event. Other therapeutic approaches need further assessment.

Prognostic significance of a low peak serum creatine kinase level in acute myocardial infarction

To assess the prognostic significance of a low peak creatine kinase (CK) level, 723 consecutive patients admitted with acute myocardial infarction (AMI) within 16 hours after onset of symptoms were studied. Thrombolytic therapy was not attempted during the study. Patients were dichotomized according to their peak CK levels, determined from a cluster analysis of peak CK distribution among the population of patients who died within 3 years after hospital discharge. The 139 patients with low peak CK (less than or equal to 650 IU/liter) (group 1) were compared to the 584 patients with high peak CK (greater than 650 IU/liter) (group 2). Patients in group 1 were older and had a higher incidence of previous AMI, angina pectoris before AMI and non-Q-wave AMI. Despite a lower incidence of in-hospital complications and a nonsignificantly lower hospital mortality rate (4 vs 9%) the group 1 three-year posthospital mortality rate was higher (26 vs 17%; p less than 0.02), especially in the subgroup of patients with a Q-wave infarct (mortality 31% in group 1 vs 16% in group 2; p less than 0.001). Among the 491 patients who had a first Q-wave AMI, 55 had a peak CK less than or equal to 650 IU/liter. Compared to the 436 patients with a higher peak CK, these 55 patients had a higher incidence of early postinfarction angina (31 vs 14%; p less than 0.01), a similar hospital mortality (4 vs 7%) but a higher 3-year posthospital mortality (23 vs 12%; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

ST segment shifts are poor predictors of subsequent Q wave evolution in acute myocardial infarction. A natural history study of early non-Q wave infarction

Acute ST segment elevation is regarded generally as the sine qua non of evolving Q wave myocardial infarction (MI) because such electrocardiographic (ECG) injury is believed to be a marker of transmural ischemia and a forerunner of transmural necrosis. Alternatively, ST segment depression with or without T wave inversion is viewed as the dominant ECG feature of non-Q wave MI. However, this hypothesis has not been assessed prospectively in an acute MI population. We analyzed 2,304 serial ECGs at study entry (admission), day 2, day 3, and predischarge (mean, 10.2 +/- 2 days) from 576 patients with creatine kinase MB confirmed acute non-Q wave MI to determine what percentage of patients with early ST segment elevation culminated in subsequent Q wave development. Of this group, 187 patients (32%) exhibited 1 mm or greater ST segment elevation in two or more contiguous entry ECG leads. Of those patients whose non-Q wave MI could be localized on the basis of diagnostic admission ST segment shifts, the prevalence of early ST segment elevation was 43% (187 of 439). The sum total mean (+/- SD) peak ST segment elevation by lead group (anterior, inferior, lateral) was 4.0 +/- 2.4, 4.5 +/- 2.4, and 2.5 +/- 0.6 mm, respectively. Despite this, only 20% of patients with ST segment elevation (37 of 187) developed Q waves. Of 252 patients who exhibited early ST segment depression or T wave inversion or both, 39 (15%) evolved subsequent Q waves. Thus, while the prevalence of early ST segment elevation in acute evolving non-Q wave MI was higher than previously reported, 80% of patients with and 85% of patients without ST segment elevation and absent Q waves on the admission ECG did not develop subsequent Q waves during a 2-week period of observation (p = NS). In addition, when patients with ST segment elevation were compared with patients with ST segment depression or T wave inversions or both, there were no between-group differences in log peak creatine kinase (404 vs. 383 IU), reinfarction (6% vs. 8%), postinfarction angina (50% vs. 42%), or early recurrent ischemia (49% vs. 45%), defined as postinfarction angina with transient ECG changes. Thus, in patients who present with initial acute non-Q wave MI, ST segment shifts on admission are unreliable predictors of subsequent Q wave evolution and do not discriminate significant differences in postinfarction outcome. In particular, ST segment elevation during the early hours of evolving infarction is not an invariable harbinger of subsequent Q wave development.

Multiparametric approach to diagnosis of non-Q-wave acute myocardial infarction

The present study investigated whether the lack of enzyme increase is reason enough to exclude necrosis in patients with ischemic heart disease who develop electrocardiographic sustained ST-T changes in the absence of Q waves. In 15 consecutive patients with angina who developed sustained ST-T changes during hospitalization, the presence of myocardial necrosis was investigated by a prospective multiparametric approach. Serum enzymes and myoglobin, pyrophosphate uptake, 2-dimensional echocardiography, perfusion scintigraphy, left ventriculography and coronary angiography were evaluated. According to creatine kinase and creatine kinase-MB peak at twice the upper normal value, the diagnosis of acute myocardial infarction applied only to 40% of patients. However, myoglobin was positive in 80% and a perfusion defect could be documented by an electrocardiographic gated microsphere technique in 100% of patients. The positivity of myoglobin increased to 100% and of creatine kinase and creatine kinase-MB to 87 and 60%, respectively, when a peak value twice the individual lowest value was considered for positivity. The 100% presence of perfusion defects associated with the high prevalence of both positive pyrophosphate uptake (87%) and regional dyssynergies (87 and 73%, respectively, by left ventriculography and echocardiography) strongly suggest that sustained (greater than or equal to 7 days) ST-T changes in this population were indicative of myocardial necrosis. Thus, by conventional enzymatic approach, diagnosis of non-Q-wave infarction can be missed in a sizable number of patients and present important clinical implications.

Early peak of creatine kinase-MB in acute myocardial infarction with a nondiagnostic electrocardiogram

This study compared the time from the onset of symptoms to the peak of the creatine kinase-myocardial band (CK-MB) in 34 consecutive patients with acute myocardial infarction. Patients were separated into two groups: group 1 (n = 21) had diagnostic (greater than or equal to 0.1 mV) ST segment elevation on the initial ECG, and group 2 (n = 13) did not have diagnostic ST segment elevation on the initial ECG. In group 1 the time to the peak CK-MB was 16.2 +/- 50 hours vs 10.0 +/- 2.0 hours for group 2 (p = 0.0001). Peak CK-MB was 331 +/- 276 IU/L in group 1 vs 81 +/- 54 IU/L in group 2 (p less than 0.005). In group 1 there were 16 patients who subsequently had a Q wave myocardial infarction as opposed to one patient in group 2 (p = 0.0001). Patients who do not have diagnostic ST segment elevation on the initial ECG have an early but low peak of CK-MB and typically have a non-Q wave infarction. These findings are consistent with early spontaneous restoration of blood flow during the infarction process in these patients. This early restoration of blood flow may provide the substrate for the high incidence of recurrent ischemic events noted in patients with non-Q wave myocardial infarction.

Diagnostic value of Q waves outside standard precordial lead points in left anterior myocardial infarction undetectable by standard 12-lead electrocardiogram

Body surface potential maps were recorded for 52 patients with solitary anterior myocardial infarction and 57 normal subjects. All patients had pure anterior wall asynergy on a left ventriculogram but no diagnostic Q wave on the standard 12-lead electrocardiogram. Q wave (greater than 30 msec) distributions on the body surface of the patients and normals were compared. The frequency of Q waves in the area above V1-V2 and in the right middle chest was significantly higher in patients than in normals. The sensitivity of Q waves for asynergy in leads from both these areas was 19-60%. The positive predictive value was 67-94%. The frequency of Q waves was significantly higher in severe asynergy than in mild asynergy. A combination of two selected unipolar leads from these areas yielded a sensitivity and specificity of 33% and 95%, respectively. With a combination of three leads, these values were 42% and 93% and with four leads 48% and 88%, respectively. The results indicate that several unipolar leads from the area above V1-V2 and from the right middle chest in addition to the standard 12-lead electrocardiogram may improve the electrocardiographic diagnostic accuracy of myocardial infarction.

Q and non-Q wave myocardial infarction: current views

The new terminology "Q and non-Q wave myocardial infarction" (MI) tends to replace the traditional terms "transmural" and "subendocardial" MI since the anatomy cannot be accurately predicted by electrocardiography. Although some subtypes of non-QMI display a favorable early or in-hospital prognosis, the long-term outlook seems less benign, particularly when early or late recurrence of MI occurs. Coronary arteriograms show an equal number of diseased vessels in both types of MI, but complete coronary artery occlusion is less frequent in non-QMI. The management of patients with non-QMI should be mainly directed to preventing extension or recurrence of MI by using either drugs such as thrombolytic agents and drugs against coronary artery spasm or invasive techniques like percutaneous transluminal coronary angioplasty.

Non-Q-wave myocardial infarction

The rationale for introducing the term "non-Q-wave myocardial infarction" is identified. The incidence, pathology, pathogenesis, and diagnostic criteria for this condition, previously identified as nontransmural or subendocardial infarction, are reviewed. In reviewing the diagnostic criteria, the various noninvasive techniques that may be applied are discussed. The clinical course, prognosis, and management are discussed under the headings of early postinfarction period, late clinical course, predischarge evaluation, and long-term care. The issues of the management of infarct extension and acute interventional therapy are raised and reviewed. Suggestions regarding specific aspects of therapy in non-Q-wave myocardial infarction are included in the summary.

Coronary arteriographic findings soon after non-Q-wave myocardial infarction

Complete occlusion of the infarct-related coronary artery is a frequent finding soon after Q-wave (transmural) myocardial infarction. We performed coronary arteriography to study the frequency of total coronary occlusion and of angiographically visible collateral vessels in 341 patients within one week of non-Q-wave myocardial infarction. In this cross-sectional study, 192, 94, and 55 patients underwent coronary arteriography within 24 hours of peak symptoms, between 24 and 72 hours after peak symptoms, and between 72 hours and seven days after peak symptoms, respectively. In the three groups, total occlusion of the infarct-related vessel was found in 26 percent (49 of 192), 37 percent (35 of 94), and 42 percent (23 of 55) of the patients, respectively (P less than 0.05). The presence of visible collateral vessels increased in parallel: 27 percent (52 of 192), 34 percent (32 of 94), and 42 percent (23 of 55), respectively (P less than 0.05). The frequency of subtotal occlusion (i.e., greater than or equal to 90 percent stenosis) decreased inversely: 34 percent (65 of 192), 25.5 percent (24 of 94), and 18 percent (10 of 55), respectively (P less than 0.05). Thus, in contrast to Q-wave infarction, total coronary occlusion of the infarct-related vessel is infrequently observed in the early hours of non-Q-wave infarction, but it increases moderately in frequency over the next several days. These cross-sectional data suggest that non-Q-wave infarction may be related to a preserved but marginal blood supply, which sufficiently disrupts the relation between the supply of and the demand for myocardial oxygen to cause tissue necrosis.

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.

Changes occurring in the postinfarction ECG in relation to age, sex, and previous myocardial infarction

Minnesota codes (MC), expressing Q-QS, ST segment, and T wave abnormalities in ECGs taken during the acute event and at a 1-year follow-up were studied in 256 survivors of myocardial infarction (MI). On the 1-year ECGs large Q waves (MC 1.1) were more common in patients with a history of previous MI than in those with a first MI. Regression of Q-QS, ST segment, and T wave changes occurred more extensively in first MIs, whereas progression of MC Q-QS and ST segment signs tended to be common in those with recurrent MI. On the acute ECGs large Q waves were more frequent in men (52%) than in women (36%), but ST segment depression of 1 mm or more (MC 4.1) was predominant in women in both the acute and 1-year ECGs. This ECG sign was related to the advanced age of the patients. There was no significant sex difference in the regression of the Q-QS signs, but the disappearance of ST and T wave changes occurred more extensively in men. The ECG returned to normal in 12% of men with a first MI but only infrequently in women and men with recurrent MI.

Inhospital prognosis of patients with their first transmural or subendocardial infarction and comparison of their coronary arteriogram and ventriculogram

The inhospital clinical course and early prognosis were studied prospectively in 500 patients who suffered their first transmural or subendocardial myocardial infarction, and were admitted in the coronary care unit of our hospital over the last four years. The coronary arteriogram and left ventriculogram of 300 patients out of the 500 was also compared. 434 patients developed transmural and 66 subendocardial infarction, as judged by electrocardiographic criteria. Both groups of patients had the same range of sex, age, coronary risk factors and history of previous angina. There was no statistical difference in in-hospital prognosis and early clinical course. There was no difference in prevalence of single, double or triple vessel coronary artery disease. The hemodynamic parameters (ejection fraction, left ventricular end-diastolic pressure), as well as the number of hypokinetic, akinetic or dyskinetic segments did not show any significant statistical difference between the two categories of patients. The same extent of coronary artery lesions and degree of left ventricular dysfunction may explain the similarity of early clinical course. 12% of patients who were admitted with subendocardial infarction developed transmural infarction during their hospitalization.

Subendocardial infarction in retrospect: pathologic, cardiographic, and ancillary features

Fifty-three patients with subendocardial infarction (SEMI) were studied at autopsy; all were elderly and the group was equally divided by sex. About half had more than one SEMI; the recurrences or extensions often involved superjacent, but not infrequently adjacent, areas. Six showed fibrinous pericarditis. This larger study showed more widespread and severe coronary narrowing than an earlier report. Six patients had thrombi in the right coronary artery. Six showed electrocardiographic evidence of concomitant anteroseptal and inferior (Roesler-Dressler) infarction, and 12 had intraventricular block generally preceding higher-grade block or arrhythmias. At some time during their terminal hospitalization, 27 patients, or half, developed distinctive protracted RS-T depression or T wave inversion. Twenty-four of the SEMIs were diagnosed on accepted criteria as transmural infarct; that diagnosis was sustained in only four. Thus neither the presence of changes in RS-T segment or T wave nor the absence of QRS changes are mandatory for the diagnosis of SEMI; this invalidates the common assumption that the diagnosis is not justified unless these conditions are met.

The clinical implications of electrocardiographic changes in first acute myocardial infarction

To assess the prognostic significance and the clinical implications of the electrocardiographic findings of the first acute myocardial infarction, the in-hospital mortality and complications and three-year follow-up of 180 patients were analyzed. The patients were divided according to the infarction type (transmural, non-transmural), the site, (anterior, inferior including posterior) and the absence or presence of ST depression in leads facing the site of infarction. The peak enzyme concentrations were significantly higher in those with transmural infarcts than in those with non-transmural infarcts, in anterior infarcts compared to inferior infarcts, and in those sites with ST depression than those without. The early complications of cardiogenic shock, congestive cardiac failure, and complete heart block were significantly higher in transmural infarcts compared to non-transmural, while late complications and mortality were the same in all groups and subgroups. This study demonstrated that ECG changes in the first acute myocardial infarction are of prognostic significance for the early clinical course, but cannot predict the late course or subsequent coronary events.

Two-dimensional echocardiography versus surface electrocardiography for the diagnosis of acute non-Q wave myocardial infarction

The initial two-dimensional echocardiogram (2DE) and electrocardiogram (ECG) of 50 consecutive patients with chest pain and a possible acute non-Q wave myocardial infarction (MI) were compared to each other to determine the value of 2DE in this type of acute MI. The ECG markers for a non-Q wave MI were (1) greater than or equal to 0.15 mV ST segment depression, (2) ST segment elevations with reciprocal ST segment depression, and (3) new symmetrical deep T wave changes as compared to a recent preadmission ECG. The 2DE was considered positive for MI if akinesia, dyskinesia, or severe hypokinesia was seen in one or more left ventricular segments. The sensitivity, specificity, and predictive value of the 2DE as compared to the ECG was 66% and 52%, respectively (sensitivity); 91% and 95%, respectivity (specificity); and 91% and 94%, respectively (predictive value). Statistically, there were no differences in the proportion of patients who had a positive 2DE as compared to the proportion of patients who had a positive ECG (p greater than 0.2). The ECG and 2DE results were combined and the sensitivity increased to 76% but the specificity decreased to 86%. Myocardial infarction size was not significantly different in infarcted subjects who had a positive 2DE (395 +/- 125 IU/L) as compared to those who had a negative 2DE (727 +/- 187 IU/L, p greater than 0.1).

Electrocardiographic effects of experimental nontransmural myocardial infarction

Clinical and experimental data have documented the ability of nontransmural myocardial infarction to produce abnormal Q waves on both the epicardial and body surfaces. We undertook this study to define the anatomic determinants of such Q wave development. Thirty dogs were studied before and after occlusion-reperfusion (26 dogs) or latex embolization (four dogs) of the left circumflex coronary artery. Occlusion was maintained for 60 to 240 min before reperfusion to produce nontransmural lesions of various sizes. Electrocardiographic data were registered from 84 torso electrodes by body surface mapping techniques before and 1 week after infarction. Infarct size was quantitated by computer analysis of heart slices stained with triphenyl tetrazolium chloride. Six dogs did not develop infarction. Of the remaining 24, 10 did and 14 did not develop significant changes in body surface Q wave duration and width. The incidence of Q wave changes was not different in dogs with nontransmural and those with transmural lesions. Infarct size (expressed as a percentage of the left ventricle infarcted), the percentage of endocardium subjacent to infarction, the average depth of necrosis, the percent of the four outer fifths of the ventricular wall infarcted, and the duration of occlusion were significantly (p less than .05) greater in dogs with than in those without Q wave changes. Logistic regression modeling demonstrated that only two anatomic parameters--percentage of left ventricle infarcted and average lesion depth--significantly and independently predicted Q wave development. A model including only these two variables accurately classified all 24 cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Q wave, S-T segment, and T wave myocardial infarction. Useful clinical distinction

Abundant experimental and clinical evidence now suggests that the presence or absence of Q waves on surface electrocardiography does not permit distinction between pathologic transmural and subendocardial myocardial infarction. It has been recommended, therefore, that use of certain electrocardiographic descriptors of myocardial infarction be avoided. One hundred fourteen consecutive patients with first myocardial infarction were studied. The lack of development of Q waves accompanying acute myocardial infarction delineated a group of patients with low in-hospital mortality. Left ventricular ejection fraction was less after Q wave (0.48 +/- 0.16) than after non-Q wave (0.67 +/- 0.10) infarction (p less than 0.0001). Left ventricular end-diastolic pressure was greater after Q wave (16.1 +/- 5.9 mm Hg) than after non-Q wave (11.7 +/- 2.7 mm Hg) infarction (p less than 0.02). Fixed thallium perfusion scintigraphic defects were more common in survivors of Q wave (98 percent [41 of 42]) than in survivors of non-Q wave (64 percent [seven of 11]) infarction (p less than 0.002). Objectively demonstrable myocardial ischemia was more common after non-Q wave (68 percent [13 of 19]) than after Q wave (32 percent [16 of 50]) infarction (p less than 0.01). The incidence of late cardiac events (sudden death plus reinfarction) did not differ after Q wave or non-Q wave infarction. Q wave, S-T segment, and T wave myocardial infarctions differ physiologically, clinically, and prognostically. It is of little consequence to the clinician managing patients whether such useful electrocardiographic descriptors also accurately define groups that differ anatomically with regard to the thickness of the injured myocardial wall.

Non-transmural infarction: clinical distinction between patients with ST depression and those with T wave inversion

The electrocardiograms and clinical characteristics of 152 patients with chest pain, who had changes only in their ST or T waves, were evaluated. The increase in ST depression was significantly greater (p less than 0.01) in infarction patients than in those without infarction; this was not the case with T wave inversion (p greater than 0.5). Infarction patients with ST depression had a higher incidence of previous myocardial infarction and prior digitalis usage (74% versus 35%, p less than 0.01) and a significantly greater short term (37% versus 12%, p less than 0.05) and long term (52% versus 19%, p less than 0.02) mortality than infarction patients who had T wave inversion alone. This difference was unrelated to infarct size as determined by peak enzyme levels. These two groups, therefore, appear to be clinically distinct, perhaps related to differences in ventricular function and/or extent of coronary artery disease.

High mortality early reinfarction with first nontransmural myocardial infarction

Thirty-eight patients with first nontransmural myocardial infarction were studied to determine prognosis and clinical markers of a high-risk subgroup. We found a high incidence of reinfarction (18%) at a median time of 16 days post nontransmural infarction (seven patients). Reinfarction was uniformly associated with death within 24 hours. A total of 14 patients (37%) either died (eight patients) or required urgent revascularization (six patients). Predominant ST segment depression with presenting nontransmural infarction and a history of prior angina were associated with increased mortality (p less than 0.05 and p = 0.05, respectively). We conclude that patients with nontransmural infarction are at high risk for early recurrent infarction. Patients with history of prior angina and predominant ST segment depression may be at particularly high risk. Reinfarction in these patients is frequently extensive. We recommend that these patients be considered for early coronary angiography.

Non-Q wave myocardial infarction. Pathophysiology and prognostic implications

Non-Q wave myocardial infarctions, also known as nontransmural myocardial infarctions or subendocardial myocardial infarctions, have been managed as "mild" coronary events in the past. Substantial evidence now requires modification of this approach. Because of their tendency to be associated with modest cardiac enzyme level elevations, non-Q wave infarcts often result in a favorable early or inhospital prognosis. However, their late complications include recurrent angina, transmural myocardial infarction, and sudden death. Previous myocardial infarction with residual myocardium "at risk" from recurrent ischemia probably bears responsibility for these late complications. Earlier identification of patients at risk and appropriate interventions may improve the long-term prognosis after nontransmural infarcts.

Electrocardiographic changes of acute lateral wall myocardial infarction: a reappraisal based on scintigraphic localization of the infarct

To determine how often acute lateral myocardial infarcts may be electrocardiographically "silent," a new approach was utilized in which subjects were selected by admission thallium scintigraphy. Thirty-one patients with their first infarction were identified with moderate to severe perfusion defects of the lateral and posterolateral walls, persistent over 7 days and associated with severe wall motion abnormalities. Patients with involvement of the anterior, septal or "inferior" regions were not included. In nine patients, the perfusion defect extended to the anterolateral wall: all developed ST elevation and Q waves in at least one of the "lateral" leads (I, aVL or V6) but none showed changes in the "inferior" leads (II, III or aVF). In the other 22 patients, the perfusion defect was limited to the lateral and posterolateral walls: only 12 showed ST elevations (inferior leads only in 7, lateral leads only in 2, both leads in 3) and only 9 developed Q waves (inferior in all). In 8 of these 22 patients, the infarct was silent in the sense that no ST segment elevation or Q waves were seen, although ST depressions or T wave inversions, or both, in all but one patient were compatible with subendocardial infarction. The results indicate that the standard electrocardiogram is insensitive to changes in the lateral and posterolateral regions. Additional diagnostic studies are needed for proper localization and sizing of acute myocardial infarcts.