Isoelectric ST Segment Research Articles

Correlation between infarct-related coronary artery patency and predischarge electrocardiographic patterns in patients with first anterior myocardial infarction who received thrombolytic therapy.

The aim of this study was to investigate the correlation between the ST-segment and T-wave patterns in predischarge electrocardiogram and patency of left anterior descending coronary artery in patients with a first anterior myocardial infarction (AMI). One hundred and fifty-six of 175 consecutive patients who were admitted to our clinic between January 2000 and September 2002 due to a first episode of transmural AMI and who received thrombolytic therapy were enrolled. Coronary angiography was performed by the Judkins method on the 6th-10th day after the acute infarction. The corrected TIMI frame count (CTFC) was estimated according to the previously described method. According to the combination of the ST-segment and T-wave morphology on the day (6-10) of cardiac catheterization, patients were classified into four groups: group A, ST elevation <<0.1 mV and negative T waves; group B, ST elevation >or=0.1 mV and negative T waves; group C, ST elevation <<0.1 mV and positive T waves; and group D, ST elevation >or=0.1 mV and positive T waves. Of the 99 patients with negative T waves, 47 (48%) had CTFC <or=27, 32 (32%) CTFC between 27 and 40, 15 (15%) CTFC >or=40-100, and 5 (5%) CTFC >>100. Of the 57 patients with positive T waves, CTFC was <or=27 in 14 (25%), between 27 and 40 in 17 (30%), >or=40-100 in 11 (19%), and >>100 in 15 (26%) ( P << 0.001). From the 76 patients with an isoelectric ST segment, 38 (50%) had CTFC <or=27, 29 (38%) CTFC between 27 and 40, 8 (11%) CTFC >or=40-100, and 1 (1%) CTFC >>100. Of the 80 patients with an elevated ST segment, 23 (29%) had CTFC <or=27, 20 (25%) CTFC between 27 and 40, 18 (23%) CTFC >or=40-100, and 19 (23%) CTFC >>100 ( P << 0.001). Use of the combination of two electrocardiographic parameters (ST segment and T waves) also indicated that there were significant differences between groups A and D, and groups B and D ( P << 0.001 and P << 0.05, respectively). Development of an isoelectric ST segment with negative T waves may indicate a better degree of reperfusion after AMI. In contrast, patients in whom ST-segment elevation and positive T waves remain at discharge from the coronary care unit have a higher probability of a nonpatent left anterior descending artery.

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 ≤0.1 mV and negative T waves; group B, ST elevation ≤0.1 mV and positive T waves; group C, ST elevation ≥0.1 mV and negative T waves and group D, ST elevation ≥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 spesific 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 viablitiy. However, absence of these electrocardiographic patterns does not exclude the presence of viable myocardium.

Long QT syndrome and anaesthesia

Long QT syndrome (LQTS) is an arrhythmogenic cardiovascular disorder resulting from mutations in cardiac ion channels. LQTS is characterized by prolonged ventricular repolarization and frequently manifests itself as QT interval prolongation on the electrocardiogram (ECG). The age at presentation varies from in utero to adulthood. The majority of symptomatic events are related to physical activity and emotional stress. Although LQTS is characterized by recurrent syncope, cardiac arrest, and seizure-like episodes, only about 60% of patients are symptomatic at the time of diagnosis. 3 The clinical features of LQTS result from a peculiar episodic ventricular tachyarrhythmia called ‘torsade de pointes’. ‘Twisting of the points’ describes the typical sinusoidal twisting of the QRS axis around the isoelectric line of the ECG. Usually torsade de pointes start with a premature ventricular depolarization, followed by a compensatory pause. The next sinus beat often has a markedly prolonged QT interval and abnormal T wave. This is followed by a ventricular tachycardia that is characterized by variation in the QRS morphology, and a constantly changing R-R interval (Fig. 1). The ‘short-long-short’ cycle length sequence heralding torsade de pointes is a hallmark of LQTS. Commonly, the episode of torsade de pointes is self-terminating, producing a syncopal episode or pseudoseizure, secondary to the abrupt decrease in cerebral blood flow. The majority of episodes of sudden death in LQTS result from ventricular fibrillation triggered by torsade de pointes, although the mechanism of this deterioration is unknown. Traditionally, LQTS has been classified as either familial (inherited) or acquired. However, it is likely that many patients with previously labelled acquired LQTS carry a silent mutation in one of the genes responsible for congenital LQTS. 22 119 The evidence for this hypothesis has been gradually emerging over the past few years. It is important for anaesthetists to be aware of this concept, as it means that a much higher proportion of the general population may be affected by asymptomatic mutations in genes encoding cardiac ion channels than was thought previously. The prevalence of LQTS in developed countries may be as high as 1 per 1100‐3000 of the population. 32 119 About 30% of congenital LQTS carriers have an apparently normal phenotype, and thus a normal QT interval, and remain undiagnosed until an initiating event. 105 Fatal arrhythmias associated with primary electrical disease of the heart such as the Brugada and LQTS, probably account for 19% of sudden deaths in children between 1 and 13 yr of age, and 30% of sudden deaths that occur between 14 and 21 yr of age. 10 Furthermore, there is a strong association between prolonged corrected QT interval (QTc) in the first week of life and risk of sudden infant death syndrome. 86

Association between Electrocardiographic Pattern and Level of C-Reactive Protein in Patients with First Anterior Wall Acute Myocardial Infarction

Background: Studies of prognostic markers after first anterior wall acute myocardial infarction (AMI) have reported an association between persistent ST segment elevation on the electrocardiogram (ECG) and increased levels of C-reactive protein (CRP) and worse outcome. The aim of the present study was to determine the nature of the relationship between these two factors. Methods: Twenty-three consecutive patients admitted with AMI underwent 12-lead ECG on days 1, 2, 3 and 7 and were classified into two groups according to the findings on each day’s recording: pattern A – isoelectric ST segment, or pattern B – ST segment elevation with or without a negative T wave. Serum CRP levels measured on the same days were also compared between the groups. Results: The number of patients classified as pattern A increased over time, from 8 on day 1 after AMI to 11 on day 2, 12 on day 3 and 14 on day 7, with a corresponding decrease in pattern B patients. Most of the patients with pattern B on day 1 showed a persistent pattern on day 7. For each day studied, the pattern A and pattern B patients showed a statistically significant difference in serum CRP levels on the second and third days after AMI, respectively. Values for the day 7 groups were: 3.1 ± 3.4 versus 9.6 ± 3.8 mg% (p = 0.001) (day 2) and 3.1 ± 1.2 versus 7.9 ± 3.6 mg% (p = 0.0005) (day 3). Conclusion: There was a significant association between high CRP levels on the second and third day following first AMI and ECG pattern B (ST elevation). This conclusion strengthens our earlier findings that pattern B is predictive of poor outcome in this patient population.

Clinical correlates of pr-segment depression in asymptomatic patients with pericardial effusion

ObjectivesThe purpose of this study was to determine the clinical correlates of PR-segment depression among consecutive asymptomatic patients with pericardial effusion (PE) detected by routine echocardiography. BackgroundPericardial effusion is a relatively common finding in clinical practice, but not many studies have evaluated electrocardiographic (ECG) changes associated with the occurrence of PE. MethodsAmong 4,061 consecutive patients referred to our echocardiography laboratory, 176 asymptomatic patients had PE correlated with their clinical history and ECG findings. ResultsPR-segment depression was detected in 40 patients (23%). There were no significant differences in age, gender distribution or heart rate between patients with and without PR-segment depression. Fifteen post-pericardiotomy patients (33%), 19 patients (40%) with malignant disease and 6 patients (46%) with connective tissue disease had PR-segment depression, whereas no patient with heart disease (dilated cardiomyopathy, hypertensive heart disease, old myocardial infarction, valvular heart disease), renal disease or hypothyroidism had PR-segment depression, nor widespread ST-segment elevation. Among 40 patients with PR-segment depression, 8 had ST-segment elevation in the leads of epicardial derivation, 8 had upright T waves, 20 had low to inverted T waves with an isoelectric ST-segment and 4 had ST-T–wave changes due to bundle branch block. ConclusionsPR-segment depression was a relatively common ECG sign associated with clinically silent PE, and it was an ECG indicator of inflammatory pericardial involvement.

Electrocardiographic T-wave inversion: Differential diagnosis in the chest pain patient

Inverted T waves produced by myocardial ischemia are classically narrow and symmetric. T-wave inversion (TWI) associated with an acute coronary syndrome (ACS) is morphologically characterized by an isoelectric ST segment that is usually bowed upward (ie, concave) and followed by a sharp symmetric downstroke. The terms coronary T wave and coved T wave have been used to describe these ischemic TWIs. Prominent, deeply inverted, and widely splayed T waves are more characteristic of non-ACS conditions such as juvenile T-wave patterns, left ventricular hypertrophy, acute myocarditis, Wolff-Parkinson-White syndrome, acute pulmonary embolism, cerebrovascular accident, bundle branch block, and later stages of pericarditis. (Am J Emerg Med 2002;20:252-262. Copyright 2002, Elsevier Science (USA). All rights reserved.)

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.

Usefulness of the Initial Electrocardiogram for Predicting the Infarct-Related Artery in Acute Inferior Myocardial Infarction

Background and Objectives:Eectrocardiogram (ECG may provide valuable informations regarding the infarct-related artery (IRA, which may be of guidance in selecting the therapeutic modality. ST segment elevation in inferior leads usually indicates occlusion of right coronary artery, less often left circumflex coronary artery or rarely occlusion of left anterior descending coronary artery may be the cause. We are to determine whether the initial ECG can differentiate the right coronary artery (RCA or left circumflex artery (LCx occlusion in acute inferior myocardial infarction (IMI. Materials and Method:We compared retrospectively the ECG recorded within 12 hours from the onset of chest pain with coronary angiograaphic findings in 85 patients(34% of all 250 patients having electrocardiographic criteria for IMI. Results:1 Angiographic characteristics. Of the 85 patients, IRA was RCA in 65 (76% (38(58%) proximal, 27(42%) distal to first right ventricular branch), and LCx in 20 (24% (nine(45%) proximal to first obtuse marginal branch or involving a high first marginal branch, eleven(55%) distal obstruction. RCA dominance was more common in RCA occlusion group (100% vs 80%, p=0.001, and LCx dominance in LCx occlusion group (15% vs 0%, p=0.001. No significant difference was noted between two groups regarding vessels diseased, involvement of left anterior descending coronary artery and contralateral artery (RCA or LCx, location of the lesion. 2 Electrocardiographic characteritics. Lateral limb leads (I, aVL:ST segment depression (≥1 mm was more common in RCA occlusion group (82% vs 45%, p=0.001. Isoelectric ST segment in I was more common in LCx occlusion group(100% vs 15%, p=0.001. Left precordial leads (V5,6:ST segment elevation (≥1 mm was more common in LCx occlusion group (60% vs 15%, p=0.001. Isoelectric ST segment was more common in RCA occlusion group (57% vs 20%, p=0.004. ST segment depression (≥1 mm was not different between two groups. Right precordial leads (V1-4:ST segment changes were not different between two groups. Lead I and left precordial leads (V5,6:Isoelectric ST segment in lead I and ST segment elevation (≥1 mm in V5 or V6 was more common in LCx occlusion group (60% vs 5%, p<0.05, sensitivity 60% specificity 95% positive/negative predictive value

The relationship between the electrocardiographic pattern with TIMI flow class and ejection fraction in patients with a first acute anterior wall myocardial infarction.

The aim of this study was to assess the value of the electrocardiogram in predicting the patency of the left anterior descending artery and left ventricular ejection fraction in patients with a first acute anterior wall myocardial infarction at discharge from the coronary care unit. We included 116 consecutive patients with an acute anterior myocardial infarction who had undergone coronary angiography and left ventriculography before discharge from the coronary care unit (7th to 10th day). The ST segment, either elevated or isoelectric (< 1 mm), and the T wave (positive or negative) in precordial leads V2-V4 were analysed and compared to the TIMI flow from each patient. Out of 69 patients with negative T waves, 38 (55%) had TIMI flow 3 compared with 20 (29%) and 11 (16%) with TIMI flow 2 and 0-1, respectively; and out of 47 patients with positive T waves seven (15%) had TIMI flow 3, 17 (36%) TIMI flow 2 and 23 (49%) TIMI flow 0-1 (P < 0.001). Out of 63 patients with an isoelectric ST segment, 35 (55%) had TIMI flow 3, 18 (29%) TIMI flow 2 and 10 (16%) TIMI flow 0-1, and out of 53 with ST segment elevation, 10 (19%) had TIMI flow 3, 19 (36%) TIMI flow 2 and 24 (45%) TIMI flow 0-1 (P < 0.001). When both parameters were analysed together, we found that in 46 patients with both isoelectric ST segments and negative T waves, 30 (65%) had TIMI flow 3 compared with two of 30 (7%) patients with ST segment elevation and positive T waves (P < 0.001). Patients with isoelectric ST segments had a better degree of left ventricular ejection fraction (57.8 +/- 14.1%) than patients with ST segment elevation (41.7 +/- 13%) (P < 0.001). Patients with positive and negative T waves had a similar left ventricular ejection fraction (49 +/- 18.1% vs 51 +/- 14%). We concluded that patients with a first acute anterior myocardial infarction and an electrocardiogram pattern of an isoelectric ST segment and a negative T wave have a higher incidence of a patent left anterior descending coronary artery than similar patients with ST segment elevation and a positive T wave. An isoelectric ST segment is also related to better left ventricular function.

Relationship between late potentials and the predischarge electrocardiographic pattern in patients with acute anterior wall myocardial infarction.

The presence of late potentials on the signal-averaged electrocardiogram (SAECG) identifies patients at high risk for development of ventricular tachyarrhythmias after myocardial infarction (MI). The electrocardiogram and left ventricular function in 65 patients recovering from a first acute anterior wall MI were analyzed. We compared the pattern of the ST segment (isoelectric or elevated) and of the T wave (positive or negative) with the SAECG using an orthogonal bipolar lead configuration (X, Y, Z) with bidirectional Butterworth filtering (Simson's method). Abnormal SAECG was found in 17 (26%) patients; 11 of 18 patients with ST elevation had abnormal SAECG, and only 6 of 47 patients with isoelectric ST segment developed abnormal SAECG (p < 0.0001, odds ratio = 10.74). Of 19 patients with positive T waves, 10 had abnormal SAECG, and abnormal SAECG was found in 7 of 46 patients with negative T waves (p < 0.003, odds ratio = 5.27). When both parameters were considered together, 9 of 12 patients with ST elevation and positive T wave developed abnormal SAECG, and 35 of 40 patients with isoelectric ST and negative T wave had normal SAECG (p < 0.0002). Left ventricular ejection fraction was similar in patients with abnormal SAECG (43 +/- 14%) and normal SAECG (46 +/- 11%). These findings suggest that patients with anterior wall MI and a predischarge pattern of ST elevation and positive T wave have a higher incidence of abnormal SAECG and therefore may have a worse prognosis, especially related to the subsequent development of ventricular arrhythmias.

ST segment and T wave characteristics as indicators of coronary heart disease risk: The Zutphen study

This study evaluated the predictive value of T wave amplitude and ST segment level on lead I for angina pectoris, a first myocardial infarction, sudden death and coronary heart disease death in middle-aged and elderly men. Certain ST-T wave characteristics may reflect favorable autonomic cardiac control. Slight ST segment elevation has been reported to indicate a low risk of coronary heart disease mortality. A total of 876 men, born between 1900 and 1920, participated in periodic medical examinations and were followed up with respect to morbidity and mortality from 1960 to 1985. In 1985, the remaining cohort was extended to 836 elderly men from the same birth cohort who were followed up until 1990. Relative risks in categories of T wave amplitude and ST segment level were estimated by survival analysis. Both middle-aged and elderly men with T wave amplitudes > or = 0.15 mV had a lower risk of myocardial infarction, coronary heart disease death and sudden death than men with T wave amplitudes 0.05 to 0.15 mV. The adjusted relative risk of coronary heart disease death was 0.5 (95% confidence interval [CI] 0.2 to 1.0); in men with T wave amplitude < or = 0.05 mV, relative risk was 2.0 (95% CI 1.3 to 3.1). Slight ST segment elevation was also associated with decreased risk: relative risk 0.5 (95% CI 0.3 to 1.0) compared with the isoelectric ST segment level. In men with ST segment depression, relative risk was 2.2 (95% CI 1.4 to 3.4). The association of T wave amplitude and ST segment level were independent of each other. In addition to the elevated risk of coronary heart disease that is associated with ST-T wave abnormalities, we observed that normal variations in repolarization characteristics are predictive of future heart disease.

Relation of T-Wave Polarity in Precordial V1Lead to Right or Left Circumflex Coronary Pathoanatomy in Acute Inferior Myocardial Infarction

To test the hypothesis that right ventricular (RV) involvement in inferoposterior wall acute myocardial infarction (AMI) may affect precordial T-wave polarity, relation of T-wave polarity in lead V1 to right (RCA) or left circumflex (LCX) coronary pathoanatomy was examined. The study population included the patients with initial inferoposterior wall AMI due to RCA (n = 61) or LCX (n = 19) occlusion within 5 h of symptom onset and 100 normal controls. The patients with RCA disease were further divided into four subgroups based on the site of coronary occlusion and the direction of the ST shift in lead V1: group A1 (n = 27), proximal RCA occlusion with isoelectric or elevated ST segment; group A2 (n = 7), proximal occlusion with ST depression; group B1 (n = 8), distal RCA occlusion with isoelectric or elevated ST segment; group B2 (n = 19), distal occlusion with ST depression. Presence or absence of an upright T wave in lead V1 (> or = 0.15 mV) was evaluated. The patients with proximal RCA disease showed a higher incidence of upright T wave (71 percent) than the controls (27 percent) (p < 0.001), patients with LCX disease (26 percent) (p < 0.01), and those with distal RCA disease (19 percent) (p < 0.001). Among the four subgroups of RCA disease, the incidence of upright T wave was highest in group A1 (90 percent), lowest in group B2 (6 percent), and intermediate in controls (27 percent) (p < 0.001) for group A1 vs controls, and p < 0.05 for controls vs group B2). These findings suggest that concomitant RV involvement in inferoposterior wall AMI modifies T-wave polarity of lead V1, which is ordinarily expected to be reciprocally drawn to negativity when infarct is limited to the inferoposterior wall of the left ventricle, to the positivity.

Well shaped ST segment and risk of cardiovascular mortality.

To investigate the prognostic value of frequently occurring slight variations in the ST segment for cardiovascular mortality in healthy subjects. Follow up study of mortality in relation to variations in ST segment level in a cohort over the 28 years from 1953 to 1981. A case-cohort sampling design was applied to limit the number of electrocardiograms that had to be coded by hand. General health examination carried out in 1953 of civil servants in Amsterdam and assessment of subsequent mortality. Apparently healthy civil servants aged 40 to 65 years: 1583 men and 1508 women. Relative risk of variations in ST segment level for mortality from all causes, cardiovascular disease, and coronary heart disease. In men the multivariate relative risks of 15 year mortality from cardiovascular disease and coronary heart disease of slight ST elevation at 80 ms past the J point (compared with isoelectric ST segment) were 0.5 (95% confidence interval 0.3 to 0.9) and 0.4 (0.2 to 0.8), respectively. As expected, ST segment depression (greater than 0.25 mm) was associated with increased risk: 1.9 (1.1 to 3.0) and 2.2 (1.2 to 3.9), respectively. In women associations were weaker. The full 28 year period showed a similar pattern of somewhat weaker associations for men; among women, however, no predictive value was apparent. These results are empirical evidence for the intuitive opinion among doctors that a curved, upward sloping ST segment, resulting in slight ST elevation at 80 ms, indicates low risk compared with the isoelectric flat, stretched ST segment.

Precordial T-wave Polarity Changes in Acute Inferior Infarction: A Poor Indicator of Associated Disease of the Left Anterior Descending Coronary Artery

T-wave polarity in V1 to V3 was examined in 70 patients with acute inferior wall myocardial infarctions (IWMI) as an indicator of significant disease in the left anterior descending coronary artery (LAD). Fifty-three percent (37/70) had precordial T-wave inversions, and of these 38 percent (14/37) had angiographically significant LAD disease. Conversely, 47 percent (33/70) had upright T waves in V1 to V3, and of these, 52 percent (17/33) had significant LAD disease. Likewise, 41 percent of the patients with ST segment depression in V1 to V3 had significant LAD disease, while 50 percent of those with isoelectric ST segments were similarly affected. Finally only 39 percent of those patients with both precordial ST segment depression and T-wave inversion had significant LAD disease. We conclude that neither anterior ST depression, T-wave inversion, nor a combination of both is a sensitive or specific indicator of LAD disease in patients with acute IWMI.

Inferior ST segment changes during acute anterior myocardial infarction: A marker of the presence or absence of concomitant inferior wall ischemia

The significance of inferior ST segment changes during acute anterior myocardial infarction was studied in 60 patients with acute anterior infarction who had angiographic visualization of the entire distribution of the left anterior descending artery after thrombolytic therapy with streptokinase. In 34 patients (Group 1) this artery supplied the anterior wall of the left ventricle up to or including the apex but did not reach the inferior wall; in 16 patients (Group 2) it continued beyond the apex onto the inferior wall of the left ventricle; and in 10 patients with prior inferior infarction (Group 3) it partially supplied the inferior wall of the left ventricle through collateral channels to an occluded right or dominant circumflex coronary artery. Consistent with this anatomy, evidence of inferior wall ischemia was significantly more frequent in Groups 2 and 3 than in Group 1 by thallium-201 scintigraphy (91 versus 7%) and by contrast left ventriculography (91 versus 13%). There was no difference in the magnitude of precordial ST segment elevation among the three groups but the inferior ST segment depression was significantly smaller in Groups 2 and 3 with concomitant inferior wall ischemia than in Group 1 (aVF: -0.5 +/- 0.7; -0.5 +/- 1.0; -1.8 +/- 0.8 mm, respectively; p less than 0.001) with 10 of the 26 patients in Groups 2 and 3 having an elevated or isoelectric ST segment in aVF compared with none of the 34 patients in Group 1 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic differentiation of occlusion of the left circumflex versus the right coronary artery as a cause of inferior acute myocardial infarction

To determine whether the admission electrocardiogram can identify left circumflex or right coronary artery occlusion as the cause of an inferior acute myocardial infarction (AMI), findings from electrocardiography and coronary angiography performed within 12 hours of each other were retrospectively assessed in 41 consecutive patients with inferior AMI. All patients had ST-segment elevation in 1 or more inferior leads (II, III or aVF). Of the 12 patients with circumflex coronary artery occlusion, 10 (83%) had ST-segment elevation in 1 or more lateral leads (aVL, V 5 or V 6) without ST-segment depression in lead I. Similar electrocardiographic findings were noted in only 1 of 29 patients (4%) with right coronary occlusion (p < 0.001). ST-segment depression in precordial leads V 1–V 3 was equally prevalent in both groups. Thus, the presence of both ST-segment elevation in 2 or more inferior leads and ST-segment elevation in 1 or more lateral leads with an isoelectric or elevated ST segment in lead I identified circumflex coronary occlusion with a sensitivity of 83%, specificity of 96%, positive predictive accuracy of 91% and negative predictive accuracy of 93%. When these criteria were prospectively applied to an additional cohort of 19 consecutive patients with inferior AMI (5 with left circumflex and 14 with right coronary artery occlusion), presence of left circumflex coronary artery occlusion was predicted with a sensitivity of 80%, specificity of 93%, positive predictive accuracy of 100% and negative predictive accuracy of 93%. Thus, the admission 12-lead electrocardiogram can assist in differentiating left circumflex from right coronary artery occlusion in patients with inferior AMI.

Transient right axis deviation during acute anterior wall infarction or ischemia: Electrocardiographic and angiographic correlation

Eleven patients, three with acute anterior myocardial infarction and eight with anterior ischemia, who developed transient right axis deviation with a left posterior hemiblock pattern during the acute phase of myocardial infarction or ischemia are described (study group). A correlation between their electrocardiographic pattern and the angiographic findings was made. The arteriographic findings were compared with those of a group of 24 patients with acute anterior myocardial infarction or ischemia without transient right axis deviation (control group). The main electrocardiographic characteristics of the right axis deviation pattern were: an average shift of the mean frontal axis to the right of 42 degrees (10 degrees to 94 degrees); increased voltage of R waves in leads II, III and a VF and appearance of small Q waves or decreased voltage of Q waves if previously present in the same leads; decreased voltage of R waves and appearance of deep S waves in lead aVL; and inverted T waves and isoelectric ST segments in leads II, III and aVF. Coronary angiography revealed that the study group had a higher incidence of significant right coronary artery obstruction and collateral circulation between the left coronary system and the posterior descending artery than did the control group (100 versus 25% and 73 versus 0%, respectively; p less than 0.01). There were no differences between the groups regarding left anterior descending and circumflex artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Anterior ST segment depression in inferior myocardial infarction: effect on complications and long-term survival.

The effect of anterior ST segment depression in inferior myocardial infarction on early complications and long-term prognosis was studied. A modification of the Minnesota Code was used for grading the extent of ST segment depression in leads V2 to V4 on the first hospital electrocardiogram. In 267 patients with acute inferior myocardial infarction, 107 had isoelectric anterior ST segments, 84 had minor (less than or equal to 0.5 mm) depression, and 76 had major (greater than 0.5 mm) depression. Patients with anterior ST segment depression had higher serum enzyme levels, higher Norris coronary prognostic indices, and more frequent cardiac failure during the acute stages, but similar 28 day case fatality rate (11.1%) compared with patients without anterior ST segment depression (12.6%). In the subsequent four years total cardiac death rates were not significantly different and the pattern of survival was not influenced, but there was a higher fatal re-infarction rate in patients with major anterior ST segment depression. Thus, anterior ST segment depression in inferior myocardial infarction was associated with more severe infarction in the early phase but was not a reliable marker of high risk after recovery. Selection of patients for further investigation should not be based on this observation alone.

Ischemia at a distance—So close yet so far

ST segment elevation in characteristic electrocardiographic leads during an acute myocardial infarction generally allows correct identification of the coronary artery occluded (1). Electrocardiographic changes, usually ST segment depression, are often noted in other leads, presumably representing myocardium sub served by other coronary arteries. What do such changes mean? Are they a benign electrical phenomenon or a harbinger of trouble ahead? Ekmekci et al. (2) noted that ST segment elevation recorded directly from the anterior epicardial surface after left anterior descending coronary artery ligation in the dog was immediately associated with ST segment depression recorded from the epicardial surface of the posterior left ventricular wall, directly opposite the evolving infarct (Fig. 1). Approximately 15 to 20 minutes later, electrodes from the periphery of the infarct, initially recording mild ST elevation, began recording ST depression as well, with the surrounding normal tissue demonstrating isoelectric ST segments. Hence, ST depression was not only a secondary electrical phenomenon, as evidenced over the posterior wall opposite the infarct, but also a marker of injury or infarction, most likely subendocardial in location, at the margins of the infarct. Nonetheless, the concept that ST depression represented only a secondary or reciprocal change in the presence of an acute myocardial infarction became firmly entrenched in electrocardiographic parlance. Review of hypotheses based on previous clinical studies. Recently there has been renewed interest in the significance of ST segment depression in electrocardiographic leads presumably remote from the zone of the acute infarction. Schuster and Bulkley (3) noted multivessel coronary disease in 20 autopsy patients with postinfarction chest pain associated with electrocardiographic changes (usually ST depression), recorded in leads remote from the zone of the occluded vessel. They coined the phrase ischemia at a

Normalization of Abnormal T Waves in Ischemia

Inverted T waves due to coronary artery disease and previous myocardial infarction were observed to revert ot normal, upright position during ischemia in 38 patients. The normalization of inverted T waves was seen on the electroencephalograms of 19 patients during spontaneously occurring angina pectoris and of 11 patients when ischemia was provoked by treadmill exercise; for 8 patients, normalization occurred during the administration of isoproterenol hydrochloride and during the consequent episode of angina pectoris. The mechanism for normalization may be the algebraic sum of the extent of ST segment elevation and the amplitude of the T waves of acute ischemia plus the extent of preexisting ST segment depression and the degree of T wave inversion, to result in isoelectric ST segment and upright T wave. As with myocardial infarction, reciprocal changes may also be recorded. However, the reciprocal nature may be masked since either acute ST segment elevation of T wave inversion, or both, may not be recorded in the leads reflecting the ischemic area because of normalization.