Predischarge ST segment and T wave patterns in predicting left ventricular function and myocardial viability in Q wave anterior myocardial infarction patients

The aim of this study was to investigate the correlation between ECG changes prior to discharge and findings of early low dose dobutamine stress echocardiography (LDSE) performed in 6 +/- 2 days, in patients experiencing their first acute anterior MI. A total of 62 patients admitted with their first acute anterior MI were divided into three groups according to the findings of electrocardiograms performed on the 7-10th days: group A, isoelectric ST and negative or positive T wave; group B, ST elevation (> 0.1 mV) and negative T wave; and group C, ST elevation and positive T wave. There were no significant differences between the groups with respect to thrombolytic therapy and reperfusion criteria. In addition, 90% of the patients in group A (20/22), 66% in group B (12/18, P < 0.05 versus group A), and only 54% in group C (12/22, P < 0.01 versus group A) responded to LDSE. The infarct zone wall motion score index (WMSI) measured by LDSE was significantly decreased in group A compared to basal values (from 2.71 +/- 0.65 to 2.07 +/- 0.71 P = 0.02), and it was significantly different compared to groups B and C. Moreover, the serum creatinine kinase level of the patients in group C was higher (P < 0.01 versus group A), whereas the ejection fraction was inferior (group A 48%, group B 47%, and group C 41%, P = 0.04 versus group A). When the correlations between good left ventricular function and terminal QRS distortion, sum ST elevation, the number of leads with ST elevation, ST elevation shape on admission, and ST and T alterations in ECG at discharge were investigated, an independent correlation was found between ST and T alteration in ECG and a WMSI value < 2 at rest or after LDSE (P = 0.03, OR 3.08, 95%CI 1.05-8.98). At the infarct zone of patients with ST elevation and positive T waves, left ventricular function is worse and the viability is less. This simple classification may be useful in predicting left ventricular function at the time of discharge.     

Abnormal Q waves on the admission electrocardiogram of patients with first acute myocardial infarction: Prognostic implications

Background: Q waves developed in the subacute and persisting into the chronic phase of myocardial infarction (MI) usually signify myocardial necrosis. However, the mechanism and significance of Q waves that appear very early in the course of acute MI (<6 h from onset of symptoms), especially if accompanied by ST elevation, are probably different. Hypothesis: This study assesses the prognostic implications of abnormal Q waves on admission in 2,370 patients with first acute MI treated with thrombolytic therapy <6 h of onset of symptoms. Results: Patients with abnormal Q waves in ≥2 leads with ST-segment elevation (n = 923) were older than patients without early Q waves (n = 1,447) (60.6 ±11.9 vs. 58.8 ±11.9 years, respectively; p = 0.0003), and had a greater incidence of hypertension (34.3 vs. 30.5% p = 0.05) and anterior MI (60.6 vs. 41.1 % p<0.0001). Time from onset of symptoms to therapy was longer in patients with Q waves upon admission (208 ± 196 vs. 183 ± 230 min; p = 0.01). Peak serum creatine kinase (2235 ± 1544 vs. 1622 ± 1536 IU; p<0.0001), prevalence of heart failure during hospitalization (13.8 vs. 7.0%, p<0.0002), hospital mortality (8.0 vs. 4.6% p = 0.02), and cardiac mortality (6.6 vs. 4.5%, p = 0.11) were higher in patients with anterior MI and with abnormal Q waves than in those without abnormal Q waves upon admission. There was no difference in peak creatine kinase, prevalence of heart failure, in-hospital mortality, and cardiac mortality between patients with and without abnormal Q waves in inferior MI. Multivariate regression analysis confirmed that mortality is independently associated with presence of Q waves on admission (odds ratio 1.61; 95% CI 1.04–2.49; p = 0.04 for all patients; odds ratio 1.65; 95% CI 0.97–2.83; p=0.09 for anterior wall MI. Conclusion: Abnormal Q waves on the admission electrocardiogram (ECG) are associated with higher peak creatine kinase, higher prevalence of heart failure, and increased mortality in patients with anterior MI. Abnormal Q waves on the admission ECG of patients with inferior MI are not associated with adverse prognosis.     

Relationship between signal-averaged electrocardiography and dangerous ventricular arrhythmias in patients with left ventricular aneurysm after myocardial infarction

We performed signal-averaged electrocardiography (SAECG) andHolter monitoring, and subsequently followed-up 53 ambulatorypatients with left ventricular aneurysm (LVA) after myocardialinfarction (MI). A history of spontaneous episodes of sustainedventricular tachycardia (VT) v also analysed. Out of 53 patients, 25 (47%) had an abnormal SAECG. AbnormalSAECG correctly identified nine out of 10 cases with a historyof sustained VT. Complex ventricular arrhythmias were detectedon Holler monitoring in 23 patients: in five out of 28 withnormal SAECG (18%) and in 18 out of 25 with abnormal SAECG (72%)(P<0001). During follow-up (mean 19 months) sustained VTand/or sudden cardiac death (SCD) occurred in eight cases, outof which seven had an abnormal SAECG. The negative predictivevalue of SAECG (no VT or SCD during follow-up) was very high,96%. similar to the negative predictive value of a history ofsustained VT (93%). Using multivariate analysis only a historyof sustained VT twas an independent factor in predicting theoutcome of patients in this study. We conclude that an abnormal SAECG identifies those post infarctionpatients with LVA who are prone to complex ventricular arrhvthmias.A normal SAECG and an absence of a history of sustained VT stronglyindicate that the risk of developing arrhythmic events is verylow.     

Correlation of predischarge electrocardiographic patterns with left ventricular function in patients with anterior wall myocardial infarction

The aim of this prospective study was to assess the correlation between different predischarge electrocardiographic patterns and left ventricular function, evaluated by physical examination and echocardiography, in patients with first Q wave anterior acute myocardial infarction. A positive correlation was found between the electrocardiographic pattern and wall motion score assessed by echocardiography, reflecting a gradual worsening in left ventricular function among the different patterns. Patients with an isoelectric ST segment and negative T waves had a 73% decrease in the risk of clinical heart failure compared to those who continued to have ST elevation. Thus, a predischarge electrocardiogram can be used as a simple, noninvasive method for the risk stratification of patients with acute myocardial infarction.     

Predictive Value of P‐Wave Signal‐Averaged Electrocardiogram for Atrial Fibrillation in Acute Myocardial Infarction

Background: Atrial fibrillation (AF) is a common complication of acute myocardial infarction (AMI) with a reported incidence of 7–18%. Recently, P‐wave signal‐averaged electrocardiogram (P‐SAECG) has been used to assess the risk of paroxysmal AF attacks in some diseases. The aim of this study was to determine prospectively whether patients with AMI at risk for paroxysmal AF would be identified by P‐SAECG and other clinical variables. Methods: A total of 100 patients (mean age: 59 ± 12 , 77 male, 23 female) with ST segment elevation AMI were enrolled in this study. Patients with chronic AF were excluded. At entry, all patients underwent standard 12‐lead ECG and in the first 24 hours, P‐SAECG was taken, and echocardiography and coronary angiography were performed on the patients. Patients are followed for a month in terms of paroxysmal AF attacks and mortality. Results: AF was determined in 19 patients (19%). In patients with AF, abnormal P‐SAECG more frequently occurred than in patients without AF (37% vs 15%, P < 0.05) . Patients with AF were older (70 ± 14 vs 56 ± 10, P < 0.001) and had lower left ventricular ejection fraction (42%± 8 vs 49%± 11, P < 0.05) . AF was less common in thrombolysis‐treated patients (47% vs 74%, P <0.05) . Thirty‐day mortality was higher in patients with AF (16% vs 2%, P = 0.05) . Conclusions: An abnormal P‐SAECG may be a predictor of paroxysmal AF in patients with AMI. Advanced age and systolic heart failure were detected as two important clinical risk factors for the development of AF.     

Improved diagnostic value of combined time and frequency domain analysis of the signal-averaged electrocardiogram after myocardial infarction

BackgroundTime domain analysis (TD) of the signal-averaged electrocardiogram (SAECG) presents a higher incidence of false positives in inferior myocardial infarction (MI), whereas spectral turbulence analysis (STA) suffers from a higher incidence of false positives in anterior MI. We investigated the hypothesis that a combined TD and STA (TD+STA) analysis of the SAECG could improve its predictive accuracy for major arrhythmic events (MAE) after MI.MethodsSignal-averaged electrocardiograms were prospectively recorded 10.1 ± 2.6 days after acute MI in 602 patients. Time domain analysis and STA were performed using standard parameters and criteria for abnormality. For the combined TD+STA model, stepwise discriminant analysis was utilized to optimize prediction of MAE. Receiver operating characteristic curves were utilized to optimize cutoff values for each SAECG parameter separately, and also for the combined TD+STA model.ResultsDuring a one-year follow-up period, 38 patients had MAE: 14 sustained ventricular tachycardia, 2 resuscitated ventricular fibrillation and 22 sudden cardiac deaths. The total predictive accuracy of combined TD+STA (89.9%) was significantly higher than TD (75.1%) or STA (77.6%). The negative predictive accuracy of all three analyses was high (98%). The positive predictive accuracy of TD (19.6%) or STA (18.3%) was quite low, and significantly improved to 35.8% by combined TD+STA analysis. The positive predictive accuracy of TD+STA improved to 51.2% in patients with left ventricular ejection fraction <40%.ConclusionsCombined TD+STA analysis of the SAECG significantly improves its prognostic ability for MAE in post-MI patients compared with TD or STA analyzed separately.     

Relationship between myocardial viability and the predischarge electrocardiographic pattern in patients with first anterior wall acute myocardial infarction

BACKGROUND: The assessment of residual viability in the infarcted area after an acute myocardial infarction is relevant to subsequent management and prognosis. OBJECTIVE: The aim of this study was to investigate the correlation between myocardial viability after an acute anterior myocardial infarction (AMI) as assessed by low dose dobutamine stress echocardiography (LDDSE) and the electrocardiographic patterns of ST segment and T wave abnormalities at the end of the first week of the acute event. METHODS: Sixty-nine consecutive patients (51 men, 18 women, mean age+/-standard deviation=57+/-11 years) who admitted to our clinic due to a first episode of transmural AMI were included in this study. Two-dimensional echocardiography was performed to all patients during rest and low dose dobutamine administration at the end of the first week of admission (7+/-2 days). Patients were classified into four groups according to ST segment and T wave morphology: group A, ST elevation < or =0.1 mV and negative T waves; group B, ST elevation < or =0.1 mV and positive T waves; group C, ST elevation > or =0.1 mV and negative T waves and group D, ST elevation > or =0.1 mV and positive T waves. RESULTS: Myocardial viability was detected more often in patients with isoelectric ST segments (22/24, 92%) than those with elevated ST segments (21/45, 47%) (P<0.001). Similarly patients with negative T waves had myocardial viability more frequently compared to those with positive T waves (32/45, 71% vs. 11/24, 46%, P<0.01). Seventeen (94%) of 18 patients in group A and 5 (83%) of six patients in group B had viable myocardium (P>0.05). Myocardial viability was found in 15 (56%) of 27 patients in group C and six (33%) of 18 patients in group D (P<0.01). As a marker of viable myocardium, isoelectricity of ST segment was specific (92%) but only moderately sensitive (51%), with a 92% positive predictive accuracy and a poor (53%) negative predictive value. T wave negativity was less specific but more sensitive than isoelectricity of ST segment for myocardial viability. CONCLUSION: The presence of isoelectric ST segment and negative T wave indicates a high probability of myocardial viability. However, absence of these electrocardiographic patterns does not exclude the presence of viable myocardium.     

The predictive value of the electrocardiographic pattern of acute q-wave myocardial infarction for recurrent ischemia

Atotal of 140 consecutive patients with acute Q-wave myocardial infarction was evaluated to assess the relationship between different electrocardiographic patterns of evolution and the incidence of recurrent ischemia within 10 days of infarction. Patients were allocated to three groups according to the electrocardiogram at 12 h after admission: Group A: ST elevation of < 2 mm and negative T waves (75 patients); Group B: ST elevation of > 2 mm and negative T waves (35 patients); Group C: ST elevation of > 2 mm and positive T waves (30 patients). Patients in Group C had more anterior wall infarctions (82%) than Group A (40%) or Group B (58%) (p = 0.0001). Peak creatine kinase levels were lower in Group A (782 ± 115 IU) than in Groups B (1415 ± 257 IU) and C (1501 ± 287 IU) (p<0.0001). The occurrence of post-infarction recurrent ischemia was more frequent in Group A (79.2%) than in Groups B (33.3%) and C (14.8%) (p<0.0001). Patients in Group A had relatively smaller infarctions and a higher incidence of recurrent ischemia, whereas patients in Group C had larger infarctions and a lower incidence of recurrent ischemia. The electrocardiographic pattern 12 h after admission for acute myocardial infarction is helpful in identifying a subgroup at high risk of recurrent ischemia.     

Predicting arrhythmic events after acute myocardial infarction using the signal-averaged electrocardiogram.

To determine if the signal-averaged (SA) electrocardiogram (ECG) predicts the occurrence of sustained ventricular arrhythmia and sudden death after acute myocardial infarction, 182 consecutive patients underwent systematic noninvasive testing, including the SAECG. Seventy-one patients (39%) had an abnormal SAECG. The presence of an abnormal SAECG was not related to underlying left ventricular dysfunction or any other clinical or measured variable. There were 16 end points (sustained ventricular arrhythmia or sudden cardiac death) during 14-month follow-up. The SAECG was a significant predictor of these events (p less than 0.02), and an abnormal SAECG conferred a 2.7-fold increase in risk. The risk associated with an abnormal SAECG was independent of both left ventricular function and ventricular arrhythmia on Holter ECG. The SAECG had excellent negative predictive accuracy (95%), but the positive predictive accuracy was low (15%). When the results of the SAECG were combined with the results of the Holter ECG, a group of very high-risk patients was identified; at 18 months, the presence of abnormal SAECG and Holter ECG was associated with a risk of 26% compared with only 4% if both tests were normal. Furthermore, all published studies with a similar design were pooled for meta-analysis. The meta-analysis revealed a sixfold increase in risk, independent of left ventricular function, and an eightfold increase in risk, independent of Holter results when the SAECG was abnormal. The SAECG is a noninvasive test that can rapidly and easily provide potent prognostic information regarding the risk of sustained ventricular arrhythmias for patients after myocardial infarction.     

Modulation of ventricular repolarization in patients with transient left ventricular apical ballooning: a case control study

Objective: Even though diffuse T wave inversion and prolongation of the QT interval in the surface electrocardiogram (ECG) have been consistently reported in patients with transient stress‐induced left ventricular apical ballooning (AB), ventricular repolarization has not yet been systematically investigated in this clinical entity. Background: AB, an emerging syndrome that mimics acute ST‐segment elevation myocardial infarction (MI), is characterized by reversible left ventricular wall motion abnormalities in the absence of obstructive coronary heart disease and significant QT interval prolongation. Methods: We prospectively enrolled 22 consecutive patients (21 women, median age 65 years) with transient left ventricular AB. A total of 22 age‐, gender‐, body‐mass‐index‐, and left‐ventricular‐function‐matched patients with acute anterior ST‐segment elevation MI undergoing successful direct percutaneous coronary intervention for a proximal occlusion of the LAD, as well as 22 healthy volunteers served as control groups. Beat‐to‐beat QT interval and QT interval dynamicity were determined from 24‐hour Holter ECGs, recorded on the third day after hospital admission. Results: There were no significant differences in baseline clinical characteristics, except higher peak enzyme release in MI patients. Compared with MI patients, AB patients exhibited significantly prolonged mean QT intervals and rate‐corrected QT intervals (QT: 418 ± 37 vs 384 ± 33 msec, P < 0.01; QTc_Bazett: 446 ± 40 vs 424 ± 35 msec, P < 0.05; QTc_Fridericia: 437 ± 35 vs 412 ± 31 msec, P < 0.05). Mean RR intervals tended to be higher in AB patients, without reaching statistical significance (877 ± 96 vs 831 ± 102 msec, P = NS). The linear regression slope of QT intervals plotted against RR intervals was significantly flatter in AB patients at both day‐ and nighttime (QT/RR slope_day: 0.18 ± 0.04 vs 0.22 ± 0.06, P < 0.01; QT/RR slope_night: 0.12 ± 0.03 vs 0.17 ± 0.05, P < 0.01). Conclusion: The present study is the first to demonstrate significant differences of QT interval modulation in patients with transient left ventricular AB and acute ST‐segment elevation MI. Even though transient AB is associated with a significant QT interval prolongation, rate adaptation of ventricular repolarization (i.e., QT dynamicity) is not significantly altered, suggesting a differential effect of autonomic nervous activity on the ventricular myocardium in transient AB and in acute MI.     

Prognostic significance of electrical alternans versus signal averaged electrocardiography in predicting the outcome of electrophysiological testing and arrhythmia-free survival

Objective—To investigate the accuracy of signal averaged electrocardiography (SAECG) and measurement of microvolt level T wave alternans as predictors of susceptibility to ventricular arrhythmias.
Design—Analysis of new data from a previously published prospective investigation.
Setting—Electrophysiology laboratory of a major referral hospital.
Patients and interventions—43 patients, not on class I or class III antiarrhythmic drug treatment, undergoing invasive electrophysiological testing had SAECG and T wave alternans measurements. The SAECG was considered positive in the presence of one (SAECG-I) or two (SAECG-II) of three standard criteria. T wave alternans was considered positive if the alternans ratio exceeded 3.0.
Main outcome measures—Inducibility of sustained ventricular tachycardia or fibrillation during electrophysiological testing, and 20 month arrhythmia-free survival.
Results—The accuracy of T wave alternans in predicting the outcome of electrophysiological testing was 84% (p < 0.0001). Neither SAECG-I (accuracy 60%; p < 0.29) nor SAECG-II (accuracy 71%; p < 0.10) was a statistically significant predictor of electrophysiological testing. SAECG, T wave alternans, electrophysiological testing, and follow up data were available in 36 patients while not on class I or III antiarrhythmic agents. The accuracy of T wave alternans in predicting the outcome of arrhythmia-free survival was 86% (p < 0.030). Neither SAECG-I (accuracy 65%; p < 0.21) nor SAECG-II (accuracy 71%; p < 0.48) was a statistically significant predictor of arrhythmia-free survival.
Conclusions—T wave alternans was a highly significant predictor of the outcome of electrophysiological testing and arrhythmia-free survival, while SAECG was not a statistically significant predictor. Although these results need to be confirmed in prospective clinical studies, they suggest that T wave alternans may serve as a non-invasive probe for screening high risk populations for malignant ventricular arrhythmias.

     

Role of signal-averaged electrocardiograms for predicting the inducibility of ventricular fibrillation in the syndrome consisting of right bundle branch block and ST segment elevation in leads V1-V3

Right bundle branch block and ST segment elevation (RBBB-STE) in the right precordial leads have been reported as a distinct clinical and electrocardiographic syndrome in patients prone to ventricular fibrillation (VF) in the absence of structural heart disease (Brugada syndrome). The purpose of the study was to investigate the role of signal averaged electrocardiogram (SAECG) in identifying patients at high risk among asymptomatic RBBB-STE patients. Thirteen patients with the RBBB-STE ECG were identified. Symptoms were: syncope (n=3, cases 1, 3, and 11), atypical chest pain (n=3, cases 4, 10, and 12) and palpitations (n=2, cases 6, and 7). The other 5 patients were asymptomatic. SAECG and programmed electrical stimulation (PES) were conducted in all patients. Body surface late potentials (LPs) were present in 7 of 13 patients before PES. Vf was induced in 6 of 7 LP positive patients. Vf was induced in 3 of 6 LP negative patients, but LP became positive in 2 of 3 patients in whom Vf was induced. One patient with syncope due to VF (case 1), 1 patient without symptoms who died suddenly during follow up (case 2), and 1 asymptomatic patient (case 9) showed reproducibly positive LP. In a patient (case 9) with positive LP at baseline, LP transiently became negative during follow up. In RBBB-STE patients, reproducibly positive LP is at risk for malignant ventricular arrhythmias and sudden death. Repeated SAECG recording may be useful for screening high-risk patients who should receive electrophysiological study among asymptomatic RBBB-STE patients.     

Relationship between signal-averaged electrocardiography and dangerous ventricular arrhythmias in patients with left ventricular aneurysm after myocardial infarction.

We performed signal-averaged electrocardiography (SAECG) and Holter monitoring, and subsequently followed-up 53 ambulatory patients with left ventricular aneurysm (LVA) after myocardial infarction (MI). A history of spontaneous episodes of sustained ventricular tachycardia (VT) was also analysed. Out of 53 patients, 25 (47%) had an abnormal SAECG. Abnormal SAECG correctly identified nine out of 10 cases with a history of sustained VT. Complex ventricular arrhythmias were detected on Holter monitoring in 23 patients: in five out of 28 with normal SAECG (18%) and in 18 out of 25 with abnormal SAECG (72%) (P less than 0.001). During follow-up (mean 19 months) sustained VT and/or sudden cardiac death (SCD) occurred in eight cases, out of which seven had an abnormal SAECG. The negative predictive value of SAECG (no VT or SCD during follow-up) was very high, 96%, similar to the negative predictive value of a history of sustained VT (93%). Using multivariate analysis only a history of sustained VT was an independent factor in predicting the outcome of patients in this study. We conclude that an abnormal SAECG identifies those post infarction patients with LVA who are prone to complex ventricular arrhythmias. A normal SAECG and an absence of a history of sustained VT strongly indicate that the risk of developing arrhythmic events is very low.     

Initial presenting electrocardiogram as determinant for hospital admission in patients presenting to the emergency department with chest pain: a pilot investigation

BACKGROUND: Evaluation of chest pain accounts for millions of costly Emergency Department (ED) visits and hospital admissions annually. Of these, approximately 10-20% are myocardial infarctions (MI). HYPOTHESIS: Patients with chest pain whose initial electrocardiogram (ECG) is normal do not require hospital admission for evaluation and management of a possible myocardial infarction. METHODS: The medical records of a consecutive cohort of 250 patients who presented to the ED with chest pain and were admitted by the ED physician to a cardiology inpatient service of an academic tertiary care medical center were reviewed. Reasons for admission to hospital was to rule out an acute coronary syndrome, specifically, myocardial infarction. The initial ECG of each patient was evaluated for abnormalities and compared with the final diagnosis. RESULTS: Of the 75 patients presenting with normal ECGs (normal, upright T waves and isoelectric ST segments), 1 (1.3%) was subsequently diagnosed with a myocardial infarction by Troponin I elevation alone. Of the 55 patients presenting with abnormal ECGs but no clear evidence of ischemia [i.e., left bundle branch block (LBBB), right bundle branch block (RBBB), left anterior hemiblock (LAH)], 2 (3.6%) were diagnosed with MI. Of the 48 patients presenting with abnormal ECGs questionable for ischemia (nonspecific ST and T wave changes that were not clearly ST segment elevation or depression), 7 (14.6%) were diagnosed with an MI. Of the 72 patients who presented with abnormal ECGs showing ischemia (acute ST segment elevation and/or depression), 39 (54.2%) were shown to have evidence for MI. SUMMARY: Patients who presented with normal ECGs (category 1) were extremely low risk for acute myocardial infarction. Patients with abnormal ECGs but no evidence of definite ischemia (category 2) had a relatively low incidence of MI. Patients with abnormal ECGs questionable for ischemia (category 3) had an intermediate risk of acute myocardial infarction. The majority of patients with abnormal ECGs demonstrating ischemia (category 4) were subsequently shown to evolve an acute myocardial infarction. CONCLUSIONS: Patients with chest pain and initial ECGs with ST segment abnormalities suggestive or diagnostic for ischemia, should be admitted to the hospital for further evaluation and management. Patients with ECGs that do not display acute ST segment changes are at a lower risk for acute myocardial infarction than those with acute ST segment changes and should be admitted on the basis of cardiac risk profile. (i.e., age, gender, hypertension, diabetes, smoking, known coronary artery disease, etc.) Patients with normal ECGs (category 1) are at extremely low risk, and it may be acceptable to consider further evaluation on an outpatient basis.     

Natural course of electrocardiographic components and stages in the first twelve hours of acute myocardial infarction

Time course evolution of R, Q, T and ST components of the electrocardiogram during the first 12 hours of an acute myocardial infarction was studied. A comparison between anterior-extensive and anteroseptal wall infarctions (anterior group), and inferior-extensive and inferior wall infarction (inferior group) showed appearance of significant Q waves within two hours in both groups. R wave loss was nearly a mirror image of Q wave development in both groups. T waves became negative and ST more isoelectric earlier in the inferior than in the anterior group. When combined variations of the four electrocardiographic components were analyzed, four stages of acute infarction were delineated. Stage I--tall R, no Q, ST elevation and positive T; Stage II--significant Q wave appearance; Stage III--negativity of T waves; and Stage IV--ST isoelectric. The inferior group reached stages III-IV within 12 hours; the anterior group remained mostly in stage II. An early appearance of Q waves correlated well with rapid progression to stages III-IV within 12 hours in both infarction groups.     

Diagnostic Value of aVL Derivation for Right Ventricular Involvement in Patients with Acute Inferior Myocardial Infarction

Background: Right ventricular (RV) involvement is associated with increased morbidity and mortality in patients with acute inferior myocardial infarction (MI). Although electrocardiography is probably the most useful, simple, and objective tool for the diagnosis of acute MI, there are no well‐defined criteria in the standard 12‐lead electrocardiogram to properly identify RV involvement in patients with acute inferior MI. Our objective was to evaluate the value of ST‐segment depression in lead aVL in diagnosing RV involvement in patients with acute inferior MI. Materials and Methods: Sixty‐seven patients, hospitalized with acute inferior myocardial infarction, were included in this study. The diagnosis of acute inferior myocardial infarction was based on the clinical history, characteristic enzyme pattern of CK‐MB values, and the appearance of ST‐segment elevation ≥ 1 mm in at least two of the leads (leads II, III, aVF). RV infarction was defined by ST‐segment elevation ≥ 1mm in lead V4R. ST‐segment depression in lead aVL that is more than 1 mm was accepted as a diagnostic criterion for RV involvement in patients with acute inferior MI. Results: Thirty‐one patients had >1 mm ST‐segment depression and 28 of them had right ventricular infarction according to lead V4R. Thirthy‐six patients showed ≤1 mm ST‐segment depression indicating no right ventricular involvement but four of them also had right ventricular infarction according to V4R. Conclusion: More than 1 mm ST‐segment depression in lead aVL was found to have high sensitivity (87%), specificity (91%), high positive and negative predictive value (90%, 88%, respectively), and high diagnostic accuracy (89%) in diagnosing RV involvement in patients with acute inferior MI. Therefore, by using a simple 12‐lead electrocardiographic sign, ST‐segment depression >1 mm in lead aVL, obtained on admission, it is possible to identify RV involvement in patients with acute inferior MI.     

T wave positivity in resting electrocardiogram predicts preserved systolic thickening in chronic anterior Q wave myocardial infarction: an echocardiographic study.

AIM: After ST elevation myocardial infarction, ST segment and T wave changes generally resolve, but in some patients T waves keep their negative components for a long time. The aim of this study is to evaluate the pathophysiological implications of persistent negative T waves and restored positive T waves in the chronic stage of Q wave myocardial infarction. METHODS: We studied 30 patients with a previous anterior wall ST elevation myocardial infarction (more than one year follow-up) and presenting Q waves in at least three consecutive precordial leads in the standard 12-lead electrocardiogram at rest. Patients were divided into two groups according to the T wave pattern in leads with Q waves: positive T group consisting of patients in whom all T wave components showed an upright configuration; and a negative T group consisting of patients in whom T waves were are least partly inverted. We used echocardiography to measure systolic thickening of the interventricular septum within the infarction area. Systolic thickening was considered significant when end-systolic thickness was greater than end-diastolic thickness by > 25% in proportion and > 1 mm in absolute value. RESULTS: Significant systolic thickening was demonstrated in 14 (74%) of the 19 positive T patients and in one (9%) of the 11 negative T patients (odds ratio 8.1; 95% CI, 1.2 to 53.5; p = 0.002). CONCLUSION: In the chronic stage of a myocardial infarction, restored T wave positivity predicts preserved systolic thickening, suggesting the presence of viable and normally contracting myocytes within the infarction area. Further studies are needed to establish the prognostic value of T wave characteristics in patients with a past history of myocardial infarction.     

Role of myocardial ischemia in the genesis of stress-induced S-T segment elevation in previous anterior myocardial infarction

This study tests the hypothesis that myocardial ischemia is responsible for exercise-induced S-T segment elevation in patients with previous anterior myocardial infarction (MI). Exercise stress testing in conjunction with thallium imaging of the myocardium was performed in 28 patients with previously documented anterior MI. Thallium images were analyzed by computer for the presence of initial uptake defects and evidence of abnormal clearance of the isotope from the myocardium (that is, imaging evidence of ischemia). Total S-T segment elevation (∑ST) in precordial leads V₁ to V₆ at rest was subtracted from ∑ST at peak stress in order to quantitate the extent of S-T elevation induced by stress (ΔST). Two groups of patients were identified; 1 with stress-induced S-T elevation (Group I, ΔST ≥ 4.0 mm) and 1 without this abnormality (Group II, ΔST < 4.0 mm). Evidence of abnormal thallium washout from myocardial scan segments occurred in 12 of 15 Group I patients versus 9 of 13 Group II patients (difference not significant). In addition, abnormal tracer washout from anterolateral or septal scan segments occurred in 5 patients in each group. Likewise, abnormal thallium clearance from inferior or posterior scan segments occurred in 8 of 15 Group I patients versus 7 of 13 Group II patients (difference not significant). The patient with the greatest amount of stress-induced S-T elevation (S-T 11.5 mm) had no evidence of ischemia during the stress test. However, Group I patients did have larger anterolateral plus septal initial thallium uptake defect scores than did those of Group II (10 of 15 with defect score ≥ 350 in Group I versus 1 of 13 in Group II, p <0.002). Similarly, resting left ventricular ejection fraction ≥ 30% was present in only 4 of 15 Group I patients versus 13 of 13 in Group II (p <0.001). Finally, multiple stepwise linear regression analysis demonstrated that ΔST correlated best with the extent of initial anterolateral plus septal thallium uptake defect score (F = 17.3, p < 0.001) and to a lesser extent with resting ejection fraction (F = 5.2, p < 0.05) and change in heart rate from rest to peak stress (F = 8.1, p < 0.01; corrected multiple correlation coefficient = 0.76, p < 0.001). Thus, in patients with previous anterior MI (1) exercise-induced myocardial ischemia occurs as often with as without S-T segment elevation, (2) myocardial ischemia is not required for the production of stress-induced S-T segment elevation, and (3) stress-induced S-T elevation primarily reflects the extent of previous anterior wall damage and to a lesser extent an increase in heart rate between rest and peak stress.     

Right ventricular infarction. The evolution of ST-segment elevation and Q wave in right chest leads

ST-segment elevation in right chest leads V3R-V7R and Q wave in V3R was measured early (1-4 hours) and late (18-24 hours) after the onset of infarction in six patients. The patients died within 9 days of infarction, and autopsy demonstrated more than 50% necrosis of the right ventricle (inclusion criterion). Abnormal ST elevation was recorded in all patients in the early and late electrocardiograms, but mean ST elevation decreased significantly between these recordings. ST elevation greater than or equal to 1 mm was recorded in all patients in the early electrocardiogram but was present in only three (50%) in the second electrocardiogram. The number of leads exhibiting abnormal ST elevation decreased from 27 (90%) to 24 (80%) (NS), and those exhibiting ST elevation greater than or equal to 1 mm decreased from 24 (80%) to 15 (50%), (p less than 0.05). Q wave in V3R was present in both electrocardiograms in three patients. Evolution of Q wave was seen in only one patient, whereas two patients were without Q wave in both electrocardiograms. These results indicate that ST elevation in V3R-V7R may vanish within the initial 24 hours despite large right ventricular infarction. Furthermore, Q wave in V3R may evolve very early after the onset of right ventricular infarction.     

肥厚型心肌病的超声心动图及心电图分析

目的观察肥厚型心肌病的心电图和超声心动图特点。方法对临床确诊的32例肥厚型心肌病患者心电图、超声心动图资料进行回顾性分析。结果所有患者心电图均有异常,以ST-T改变、左室高电压和异常Q波为多见。Q波深度与室间隔厚度、ST压低深度与心尖部室壁厚度均呈正相关,而T波深度与心尖部室壁厚度无相关性,但与心尖部和室间隔的室壁厚度差呈正相关,左房大小与平均室壁厚度呈正相关。结论在肥厚型心肌病中,心电图和超声心动图中的许多异常指标具有相关性,两者结合可提高本病诊断率。