Factors that determine the direction and magnitude of precordial ST-segment deviations during inferior wall acute myocardial infarction

[Isolated right ventricular acute myocardial infarction mimicking anterior infarction]

Isolated right ventricular acute myocardial infarction is rare and its presentation can sometimes mimic an anterior ST-segment elevation myocardial infarction. We reported two cases of isolated right ventricular acute myocardial infarction presenting with a ST-elevation in anterior leads. The first case was admitted for an out-of-hospital cardiac arrest due to ventricular fibrillation. The patient died from neurologic consequences of the cardiac arrest, despite a successful prehospital thrombolysis, followed by a percutaneous angioplasty of the right coronary artery. The second case occurred after a complex percutaneous angioplasty of the right coronary artery, complicated by a total occlusion of a right marginal branch. These two cases illustrate the limits of the ECG for the diagnosis of isolated right ventricular acute infarction, and the difficulties of the differential diagnosis with anterior infarction, which may determine the treatment and the prognosis.

Dominant right coronary artery occlusion entailing diffuse ST-segment elevation in the precordial leads

Right ventricular infarction (RVI) during inferior myocardial infarction (MI) is readily diagnosed when ST-segment elevation (STE) is recorded in lead V4R. RVI may also yield precordial STE and such an electrocardiographic (ECG) pattern may be misinterpreted as a sign of anterior MI. We present a case of inferior-right ventricular (RV) MI due to occlusion of a dominant right coronary artery manifesting STE in the inferior, all precordial and right chest leads. RV dilation due to acute ischemic insult facilitated STE in leads V1-V4 despite the dominant opponent inferior and posterolateral left ventricular injury current. This case illustrates that dilation of an infarcted RV should be considered when such an ECG pattern is encountered during inferior MI, specifically a dominant one. Awareness of the circumstances under which this ECG pattern develops facilitates avoidance of misinterpretation as a sign of anterior MI and proper management.

Isolated right ventricular infarction presenting as anterior wall myocardial infarction on electrocardiography

Isolated right ventricle infarction is extremely rare, and its electrocardiographic (ECG) signs may be misinterpreted or even missed, especially when a typical clinical picture is lacking. This paper describes a case of isolated right ventricle infarction, recognized only by echocardiography. The patient presented with ST-segment elevation in left precordial leads together with minimal ST-segment elevation in inferior leads on a 12-lead ECG. Angiography revealed the culprit right coronary artery, which was small and nondominant. No significant obstructions were found in the left anterior descending artery. This case demonstrates that the ECG appearance of isolated right ventricle infarction may mimic anterior wall infarction and can be easily missed if not suspected.

The ECG pattern of isolated right ventricular infarction during percutaneous coronary intervention

Isolated right ventricular infarction (RVI) is a rare event. The electrocardiographic (ECG) pattern of RVI, ST-elevation in lead V4R and in anterior chest leads V1-3 is similar to that of a proximal occlusion of a small, nondominant right coronary artery (RCA). The ECG changes may be misinterpreted as signs of infarction of the anterior wall. This paper describes a case of isolated temporary occlusion of the major side branches of the RCA during percutaneous coronary intervention, recognized by angiography findings and typical ECG changes. This case demonstrates how one might avoid wrong decisions even in the catheterization laboratory by putting attention to the anatomical interpretation of the ECG.

Electrocardiographic Diagnosis of ST-elevation Myocardial Infarction

The ECG is an essential part of the initial evaluation of patients who have chest pain, especially in the immediate decision-making process in patients who have ST-elevation myocardial infarction. This article reviews and summarizes the current information that can be obtained from the admission ECG in patients who have ST-elevation acute myocardial infarction, with an emphasis on: (1) prediction of final infarct size, (2) estimation of prognosis, and (3) the correlations between various ECG patterns and the localization of the infarct and the underlying coronary anatomy.

Dynamical and cellular electrophysiological mechanisms of ECG changes during ischaemia

The interpretation of normal and pathological electrocardiographic (ECG) patterns in terms of the underlying cellular and tissue electrophysiology is rudimentary, as the existing theories rely on geometrical aspects. We relate effects of sub-endocardial ischaemia on the ST-segment depression in ECG to patterns of transmural action potential propagation in a one-dimensional virtual ventricular wall. Our computational study exposes two electrophysiological mechanisms of ST depression: dynamic-predominantly positive spatial gradients in the membrane potential during abnormal repolarization of the wall, produced by action potential duration changes in the ischaemic region; and static-a negative spatial gradient of the resting membrane potential between the normal and ischaemic regions. Hyperkalaemia is the major contributor to both these mechanisms at the cellular level. These results complement simulations of the effects of cardiac geometry on the ECG, and dissect spatio-temporal and cellular electrophysiological mechanisms of ST depression seen in sub-endocardial ischaemia.

Mechanism for ST depression associated with contiguous subendocardial ischemia

INTRODUCTION

A mechanism for ST depression arising on the epicardial surface over the border between normal and ischemic tissue is proposed. Depression is caused by current flowing in a transmural loop that begins and ends at the lateral boundary between healthy and ischemic tissue and passes through the transmural boundary between healthy and ischemic tissue. The result is ST depression at the epicardium over the lateral boundary. The size and direction of current flow are dictated by differences in the magnitude and orientation of anisotropic conductivity between those boundaries.

METHODS AND RESULTS

Computer simulations verified and quantified the relationship between ST depression and conductivity differences. We used computer simulations based on an anatomically accurate, anisotropic model of canine ventricles and a bidomain representation of the effects of ischemia to verify the biophysical basis of this mechanism.

CONCLUSION

ST depression at the epicardium appears over a lateral boundary between healthy and ischemic tissue.

The electrocardiogram in ST elevation acute myocardial infarction: correlation with coronary anatomy and prognosis

The electrocardiogram is considered an essential part of the diagnosis and initial evaluation of patients with chest pain. This review summarises the information that can be obtained from the admission electrocardiogram in patients with ST elevation acute myocardial infarction, with emphasis on: (1) prediction of infarct size, (2) estimation of prognosis, and (3) the correlations between various electrocardiographic patterns and the localisation of the infarct and the underlying coronary anatomy.

ST segment elevation in leads V1 to V3 due to isolated right ventricular branch occlusion during primary right coronary angioplasty

It is rare to observe ST elevation in anterior derivations caused by isolated right ventricular branch occlusion. We described the case with acute inferior and right ventricular myocardial infarction (MI) who developed ST segment elevation in precordial leads V(1) to V(3) due to isolated right ventricular branch occlusion during primary right coronary angioplasty.

Electrocardiographic patterns in acute inferior myocardial infarction with and without right ventricle involvement: classification, diagnostic and prognostic value, masking effect

BACKGROUND

In acute inferior myocardial infarction (AIMI), the ST depression from V1 to V4 has been the subject of many papers, while the ST changes in other leads, their association, and the right ventricular (RV) involvement have been studied less.

HYPOTHESIS

This study was performed to contribute to the meaning of the ST changes and RV involvement in AIMI.

METHODS

Seventy-one patients, admitted within 6 h from symptom onset, all thrombolysed, were enrolled. We classified them according to ST patterns and RV involvement. We divided the right coronary artery into three segments, considering the origin of RV branch and the crux as dividing points. We established a coronary score attributing 2 points to each terminal branch. Comparisons were performed between the electrocardiographic (ECG) findings at onset, the creatine phosphokinase (CPK) peaks, the radionuclide ejection fractions, and the coronary angiographies.

RESULTS

We found that the ST changes give indications regarding the site, extension, and extent of AIMI; RV involvement can mask posterior extension, points to the right coronary as the culprit vessel (100%), and, with high probability, indicates the proximal segment as the site of the lesion; the ECG signs of isolated AIMI indicate a peripheral obstruction; and a collateral circulation may appear relatively early.

CONCLUSIONS

Our findings prove the diagnostic and prognostic value of the ST changes and RV involvement at the onset of AIMI and suggest that the higher in-hospital mortality and complication rates found with RV involvement and reported in the literature are related more to posterior extension, masked by RV involvement than to this involvement per se. Furthermore, these findings prove the clinical value of our classification of the AIMIs and distinction in segments of the right coronary artery.

New electrocardiographic criteria for predicting the site of coronary artery occlusion in inferior wall acute myocardial infarction

In patients with inferior wall acute myocardial infarction (AMI), the site of the culprit lesion is an important determinant of outcome. Patients with right ventricular infarction have a poor prognosis, whereas those with occlusion of the left circumflex coronary artery (LCx) have a good prognosis. Therefore, we assessed whether standard 12-lead electrocardiograms obtained on admission could identify the site of coronary artery occlusion, (i.e., a site proximal to the origin of the right ventricular branch of the right coronary artery [RCA], a site distal to the origin of the right ventricular branch of the RCA, or a site in the LCx). The ratio of ST depression in lead V3 to ST elevation in lead III (V3/III ratio) was evaluated immediately before coronary angiography in 152 patients with a first inferior wall AMI confirmed by coronary angiography within 12 hours after the onset of symptoms. For occlusion of the proximal RCA, distal RCA, and LCx, V3/III ratio was 0.2+/-0.3, 0.8+/-0.5, and 2.5+/-2.5 (p = 0.0001), respectively. The V3/III ratio <0.5 identified proximal RCA occlusion, 0.5 <V3/III ratio < or = 1.2 identified distal RCA occlusion, and 1.2 <V3/III ratio identified LCx occlusion with sensitivities of 91%, 84%, and 84%, and specificities of 91%, 93%, and 95%, respectively. We conclude that the V3/III ratio is useful in predicting the site of coronary artery occlusion in patients with inferior wall AMI.

Association between preinfarction angina and a lower risk of right ventricular infarction

BACKGROUND

Right ventricular infarction occurs in conjunction with inferior myocardial infarction caused by proximal occlusion of the right coronary artery. However, right ventricular infarction occurs infrequently, and the reasons for this are uncertain.

METHODS

We retrospectively assessed the association between preinfarction angina and right ventricular infarction, as well as the short-term outcome, in 113 patients with a first acute inferior myocardial infarction caused by right-coronary-artery occlusion. The association between the timing of angina during the week before infarction and the clinical outcome was also assessed.

RESULTS

The absence of preinfarction angina predicted the development of right ventricular infarction (odds ratio, 6.3; 95 percent confidence interval, 2.7 to 15.1; P<0.001), complete atrioventricular block (odds ratio, 3.6; 95 percent confidence interval, 1.4 to 10.3; P=0.01), and combined hypotension and shock (odds ratio, 12.4; 95 percent confidence interval, 4.5 to 40.6; P<0.001). Angina 24 to 72 hours before infarction was most strongly associated with reductions in the rates of right ventricular infarction (adjusted odds ratio, 0.2; 95 percent confidence interval, 0 to 0.8; P=0.02) and combined hypotension and shock (adjusted odds ratio, 0.1; 95 percent confidence interval, 0 to 0.5; P=0.02).

CONCLUSIONS

Preinfarction angina was an independent predictor of the absence of right ventricular infarction in patients with acute inferior myocardial infarction. The patients with preinfarction angina also had better short-term outcomes than those without preinfarction angina.

Significance of ST segment elevations in posterior chest leads (V7 to V9) in patients with acute inferior myocardial infarction: application for thrombolytic therapy

OBJECTIVES

This study was designed to examine whether ST segment elevation in posterior chest leads (V7 to V9) during acute inferior myocardial infarction (MI) identifies patients with a concomitant posterior infarction and whether these patients might benefit more from thrombolysis.

BACKGROUND

Because the posterior wall is faced by none of the 12 standard electrocardiographic (ECG) leads, the ECG diagnosis of posterior infarction is problematic and has often remained undiagnosed, especially in the acute phase.

METHODS

Eighty-seven patients with a first inferior infarction who were treated with recombinant tissue-type plasminogen activator were stratified according to the presence (Group A [46 patients]) or absence (Group B [41 patients]) of concomitant ST segment elevation in posterior chest leads V7 to V9.

RESULTS

Patients in Group A had a higher incidence of posterolateral wall motion abnormalities (p < 0.001) on radionuclide ventriculography, a larger infarct area (as evidenced by higher peak creatine kinase levels) (p < 0.02) and a lower left ventricular ejection fraction (LVEF) at hospital discharge (p < 0.008) than those in Group B. ST segment elevation in leads V7 to V9 was associated with a higher incidence of at least one of the following adverse clinical events: reinfarction, heart failure or death (p = 0.05). Although patency of the infarct-related artery (IRA) in Group A resulted in an improved LVEF at discharge (p < 0.012), LVEF was unchanged in Group B, regardless of the patency status of the IRA.

CONCLUSIONS

ST segment elevation in leads V7 to V9 identifies patients with a larger inferior MI because of concomitant posterolateral involvement. Such patients might benefit more from thrombolytic therapy.

Electrocardiographic criteria for the diagnosis of right ventricular involvement in the setting of acute inferior infarction

Surface electrocardiograph of twelve cases of isolated left ventricular inferior infarction and 24 cases of biventricular inferior infarction confirmed by two-dimensional echocardiography were analysed. ST segment elevation in lead III more than in lead II and ST segment depression in leads I and aVL were highly sensitive in diagnosing right ventricular involvement. ST segment depression in lead V3 equal to or greater than ST segment elevation in lead III was highly specific but had low sensitivity. These findings can be helpful in cases where right sided chest leads have not been recorded or are inconclusive.

Revisiting reperfusion therapy in inferior myocardial infarction

Although thrombolytic therapy for acute myocardial infarction (MI) is recommended without regard for infarct location, treatment results are less impressive for inferior than for anterior MI because the amount of myocardium at risk is smaller and less strategically located, and the mortality risk is lower. Whereas the risks associated with anterior MI are relatively constant, high risk subsets of patients with an inferior MI can be identified by simple electrocardiographic criteria, including left precordial ST segment depression, complete atrioventricular heart block and right precordial ST segment elevation. Unfortunately, none of the placebo-controlled, randomized trials have analyzed the benefit of thrombolytic therapy for inferior MI in high risk versus low risk subsets. Thrombolytic therapy should be more successful in reducing infarct size and decreasing mortality in high risk patients with an inferior MI. Thrombolytic therapy may not decrease hospital mortality in low risk patients (baseline risk 2% to 4%) or those with symptom duration > 6 h. Whereas it is arguable whether coronary angioplasty is superior to thrombolytic therapy in anterior MI, there are no mortality data to support using angioplasty as a primary or rescue reperfusion strategy instead of thrombolytic therapy in inferior MI, unless thrombolytic contraindications are present or the patient is in cardiogenic shock.

Significance of initial ST segment changes for thrombolytic treatment in first inferior myocardial infarction

OBJECTIVE

To evaluate the benefit to risk ratio of thrombolytic treatment in patients with small inferior acute myocardial infarction (AMI). Controlled studies relating the benefit from thrombolysis with initial electrocardiographic features are scarce and of limited sample size.

DESIGN

Retrospective study of 728 patients with a first inferior AMI of six hours' duration from the Intravenous Streptokinase in Acute Myocardial Infarction (ISAM) study comparing streptokinase with placebo stratified by the initial sum ST segment elevation (sigma ST) of 0.8 mV or less and greater than 0.8 mV, and 636 patients from the International Joint Efficacy Comparison of Thrombolytics (INJECT) trial comparing double blind streptokinase with reteplase stratified by either sigma ST or the presence of precordial ST segment depression.

RESULTS

ISAM study patients with an sigma ST of greater than 0.8 mV had a significant mortality benefit from streptokinase throughout six years, while those with an sigma ST of 0.8 mV or less showed a trend to higher mortality at six months (6.3% streptokinase v 5.1% placebo). Despite significantly smaller infarcts and fewer clinical complications in patients with an sigma ST of 0.8 mV or less (ISAM and INJECT) or the absence of precordial ST segment depression (INJECT) thrombolytic treatment was associated with higher early mortality than in those with initially larger ST segment deviations.

CONCLUSION

Thrombolytic treatment in patients with inferior AMI presenting with larger ST segment deviations is associated with improved survival throughout six years. The risk to benefit ratio, however, in terms of early mortality in patients who have an sigma ST of 0.8 mV or less and no precordial ST segment depression may be unfavourable.

Usefulness of ST-segment depression in non-infarct-related electrocardiographic leads in predicting prognosis after thrombolytic therapy for acute myocardial infarction

This study investigated both the in-hospital and long-term prognostic significance of ST-segment depression in non-infarct-related leads in patients who received thrombolytic therapy after acute myocardial infarction (AMI). We evaluated 221 consecutive patients who were admitted with their first AMI and underwent thrombolysis. Patients were followed for an average of 31 months and were classified into 3 groups: group 1 included 51 patients with persistent ST-segment depression, group 2 had 97 patients with transient ST-segment depression, and group 3 consisted of 73 patients without ST-segment depression (absent). Group 1 had significantly worse long-term survival during follow up by Kaplan-Meier analysis (55%) versus group 2 (81%) and group 3 (94%) (p = 0.0004) and higher event rates. This prognostic significance seemed to be maintained in both the anterior and inferior wall AMI groups. Multivariate analysis, using the Cox model, showed that Killip class, in-hospital left ventricular ejection fraction, and the persistence of ST-segment depression on the predischarge electrocardiogram (group 1) were independent predictors of survival. ST-segment depression in non-infarct-related leads on the predischarge electrocardiogram is an independent risk factor for worse long-term survival after anterior as well as inferior AMI treated with thrombolytic therapy.

Usefulness of the admission electrocardiogram for identifying the infarct-related artery in inferior wall acute myocardial infarction

We analyzed the admission electrocardiogram in 109 patients with inferior wall acute myocardial infarction in an attempt to determine the infarct-related artery (IRA). The presence of ST depression in leads V1 or V2 had a high sensitivity for predicting the left circumflex artery as the IRA. The lack of ST depression in V1 or V2 had a high negative predictive value for excluding the left circumflex artery as the IRA.

Prognostic significance of precordial ST segment depression on admission electrocardiogram in patients with inferior wall myocardial infarction

OBJECTIVES

This study assessed retrospectively the correlation between the pattern of precordial ST segment depression on the admission electrocardiogram (ECG) and hospital mortality in patients with an inferior myocardial infarction treated with intravenous thrombolytic therapy.

BACKGROUND

Previous studies have shown that in acute inferior myocardial infarction, ST segment depression in the precordial leads is associated with increased hospital mortality. However, the significance of the different patterns of precordial ST segment depression has been evaluated in only two previous studies.

METHODS

The study included 1,321 patients (1,020 men) who enrolled in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) trial in Israel and received intravenous thrombolytic therapy. Patients with an ST segment elevation > or = 0.1 mV in at least two of the inferior leads were included. Patients were classified into four groups on the basis of their admission ECG: group I = patients with no precordial ST segment depression (n = 346); group II = those for whom the sum of ST segment depression in leads V1 to V3 was greater than that in leads V4 to V6 (n = 700); group III = those for whom the sum of ST depression in leads V1 to V3 was equal to that in leads V4 to V6 (n = 162); group IV = those with maximal ST depression in leads V4 to V6 (n = 113).

RESULTS

The overall hospital mortality rate was 3.6% (48 patients): for groups I, II, III and IV it was 2.9%, 2.8%, 4.3% and 9.7%, respectively. Multivariable logistic regression analysis confirmed that hospital mortality was independently associated with the pattern of precordial ST segment depression. The odd ratios in group IV relative to group I was 2.78 (95% confidence interval 1.26 to 6.13, p = 0.007).

CONCLUSIONS

The risk of mortality is higher in patients with an inferior myocardial infarction and maximal ST segment depression in precordial leads V4 to V6 versus precordial leads V1 to V3 on the admission ECG.

Prognostic significance of precordial ST segment depression during inferior myocardial infarction in the thrombolytic era: results in 16,521 patients

OBJECTIVES

We examined the prognostic significance of precordial ST segment depression among patients with an acute inferior myocardial infarction.

BACKGROUND

Although precordial ST segment depression has been associated with a poor prognosis, this correlation has not been adequately quantified, partly because of small sample sizes and methodologic limitations in previous studies.

METHODS

We examined the clinical and angiographic outcomes of 16,521 patients with an acute inferior myocardial infarction who underwent thrombolysis in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) study. Patients were classified into those without precordial ST segment depression (n = 6,422 [38.9%]), those with ST segment depression in leads V1 to V3 only (n = 5,850 [35.4%]), those with ST segment depression in leads V4 to V6 only (n = 876 [5.3%]) and those with ST segment depression in both leads V1 to V3 and leads V4 to V6 (n = 3,373 [20.4%]) on initial electrocardiography. Outcome measures included postinfarction complications (second- or third-degree heart block, congestive heart failure or shock) and 30-day and 1-year mortality.

RESULTS

Patients with precordial ST segment depression had larger infarctions, more postinfarction complications and a higher mortality rate than those without precordial ST segment depression (4.7% vs. 3.2% at 30 days; 5.0% vs. 3.4% at 1 year; both p < 0.001), regardless of whether ST segment depression was noted in leads V1 to V6 or in leads V4 to V6. The magnitude of precordial ST segment depression (sum of leads V1 to V6) added significant independent prognostic information after adjustment for clinical risk factors; the risk of 30-day mortality increased by 36% for every 0.5 mV of precordial ST segment depression.

CONCLUSIONS

Assessment of the magnitude of precordial ST segment depression is useful for acute risk stratification in patients with an inferior myocardial infarction.

Diagnostic value of the arithmetic sum of the ST segment of inferior and V2 leads, II + V2, III + V2 and aVF + V2 in identifying the artery responsible for inferior acute myocardial infarction

In order to evaluate electrocardiographic changes in the diagnosis of the artery responsible for inferior myocardial infarction, a prospective study was performed on inferior and V2 ST segment deviation and its correlation using the arithmetic sum: II + V2, III + V2, and aVF + V2. A group of 66 patients with inferior acute myocardial infarction (AMI) was studied. A standard 12-leads electrocardiogram was performed within six hours of the onset of chest pain. Coronary arteriography was performed on each of the patients between one and twelve weeks after infarction. Right coronary artery (RCA) lesion was found in 46 patients, 27 at a proximal level and 19 at a distal level; in 20 patients the left circumflex coronary artery was affected. The isolated value of the magnitude of the inferior ST segment is not an efficient parameter for identifying the artery responsible for inferior AMI. In lead V2 all the patients with a lesion of the left circumflex artery showed ST segment depression > or = 1 mm (P < 0.001) and all those presenting ST segment elevation had stenosis of the proximal RCA. The most useful parameters for identifying the artery responsible for inferior AMI, with 100% specificity are: (1) for occlusion of the RCA, the arithmetic sum of ST segments: aVF + V2 > 0, with 86.9% sensitivity (P < 0.001); (2) for occlusion of the left circumflex artery III + V2 < 0, with 90% sensitivity (P < 0.001); and (3) for proximal occlusion of the RCA: aVF + V2 > or = 1, with 96.2% sensitivity (P < 0.001). No specific marker was observed for distal occlusion of the RCA. The value of the arithmetic sum of the ST segment: III + V2 between 0 and 0.9 was the most significant, with 94.7% sensitivity and 95.7% specificity (P < 0.001).

Simultaneous ST-segment elevation in lead V1 and depression in lead V2. A discordant ECG pattern indicating right ventricular infarction

The major electrocardiographic change in right ventricular infarction (RVI) is ST-segment elevation in leads V4R-V6R. The authors describe a discordant electrocardiographic pattern of ST-segment elevation in lead V1 and ST-segment depression in lead V2 in five patients presenting with acute transmural (Q wave) inferior infarction and RVI. There were 51 patients with transmural inferior infarction from a thrombolytic trial. In 25 patients, the ST-segment in the right-sided precordial leads was elevated by > or = 1 mm indicating the presence of RVI. In 5 of these 25 patients, simultaneous ST-segment elevation of 1.0-8.0 mm (mean, 2.8 +/- 2.9 mm) in lead V1 and ST-segment depression of 2.5 to 4.0 mm (mean, 3.3 +/- 0.6 mm) in lead V2 were also present. The discordant pattern of the ST-segments in leads V1 and V2 is an important and specific sign for RVI.

Relation of T-wave polarity in precordial V1 lead to right or left circumflex coronary pathoanatomy in acute inferior myocardial infarction

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Usefulness of continuous ST monitoring in inferior wall acute myocardial infarction for describing the relation between precordial ST depression and inferior ST elevation

To explore the relation between precordial and inferior ST-segment changes within individual patients, continuous 12-lead electrocardiographic recording was performed in 19 patients with acute inferior infarction given intravenous thrombolytic therapy. Monitoring was performed for 519 +/- 269 minutes. The extent of inferior ST elevation varied considerably with time in all patients. With use of the maximal precordial ST depression recorded to classify patients, 11 had precordial ST depression (sigma V1-3) > 0.2 mV (group A) and 8 had < or = 0.2 mV or no precordial ST depression (group B). The maximal recorded precordial ST depression correlated inversely with the corresponding inferior ST elevation in the 19 patients (r = -0.78, p < 0.001). Within individual patients, continuous 12-lead monitoring revealed a close negative correlation between the inferior and precordial ST levels for the entire recording period in many patients, but 5 of the 19 patients (26%) (2 in group A and 3 in group B) did not have this relation. Moreover, precordial ST depression was not always present during inferior ST elevation in group A patients: 4 of 11 (36%) had some electrocardiographs showing < 0.1 mV precordial ST depression despite summed inferior ST elevation > 0.6 mV. These data indicate that precordial ST depression is not just the simple electrical reciprocal projection of the abnormal inferior wall ST vector, and its fluctuation cannot be predicted by changes in inferior ST level in every patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism and significance of precordial ST-segment depression during inferior wall acute myocardial infarction associated with severe narrowing of the dominant right coronary artery

The mechanism and significance of precordial ST depression during inferior wall acute myocardial infarction (AMI) is debated. This study assessed the location and extent of arterial perfusion distribution responsible for this electrocardiographic finding. Intracoronary thallium-201 was injected in 11 patients with 1-vessel right coronary disease to delineate perfusion distribution that was quantitated by a new angiographic distribution score. The angiographic score correlated with posterior (r = 0.84), posterolateral (r = 0.88) and total (r = 0.73) extent of intracoronary thallium distribution. The angiographic distribution score was related to electrocardiographic changes in 16 patients showing an inferior ST-segment elevation during angioplasty (7 with and 9 without precordial ST depression), of which 6 received intracoronary thallium injection. None had thallium distribution in the anterior or septal segment, but there was a trend toward a greater angiographic distribution score and posterior segment thallium score in patients with precordial ST depression. In another 77 patients with inferior wall AMI due to right coronary occlusion (24 with concomitant left anterior descending narrowing), precordial ST depression was present in 16 with and 31 without left anterior descending narrowing (p = NS). The angiographic distribution score was higher in those with than without precordial ST depression (0.59 +/- 0.10 vs 0.44 +/- 0.11, p < 0.001) in both patients with and without left anterior descending disease. The magnitude of both inferior ST elevation and precordial ST depression correlated with the angiographic distribution score, but only precordial ST depression was independently related in multivariate analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of right ventricular acute myocardial infarction by dual isotope thallium-201 and indium-111 antimyosin SPECT imaging

To assess the diagnostic value of indium-111 antimyosin for detecting right ventricular (RV) wall acute infarction, 30 patients with electrocardiographic-documented left ventricular inferior (posterior) wall acute myocardial infarction underwent simultaneous dual isotope indium-111 antimyosin and thallium-201 single-photon emission computed tomography (SPECT) within 2 days of admission. RV necrosis was defined as uptake of indium-111 antimyosin anterior and to the right of septal thallium uptake. Twenty-nine of the 30 patients (97%) had indium-111 antimyosin uptake in the inferior, posterior or lateral walls of the left ventricle and 14 of 30 (47%) had additional RV antimyosin uptake. Three different patterns of RV uptake of indium-111 antimyosin were observed: crescent-shaped, focal and apical. Twenty-seven patients underwent gated blood pool scanning before hospital discharge. Twelve of the 14 patients with RV antimyosin uptake had gated blood pool scintigraphy and 7 of 12 had RV dysfunction; 5 had normal RV function. Except for 1 patient who had questionable RV antimyosin uptake and had RV dysfunction, no patient without RV antimyosin uptake had RV dysfunction. In summary, right and left ventricular necrosis can be detected on tomographic images of indium-111 antimyosin uptake in patients with inferior infarctions when simultaneous uptake of a perfusion tracer, thallium-201, is imaged and used as an aid to reconstruction and anatomic localization.

Evaluation of formulas for estimating the final size of acute myocardial infarcts from quantitative ST-segment elevation on the initial standard 12-lead ECG

Previously developed formulas for predicting the final QRS estimated sizes of acute myocardial infarcts from the initial ST segment deviation are tested. The population contains patients with either anterior or inferior infarcts from two hospitals in Copenhagen, Denmark. The formula for anterior location that considers only the number of ECG leads with ST elevation achieved a high correlation (r = 0.70). However, the formula for inferior location that considers the quantity of ST elevation in inferior leads achieved a lower value (r = 0.52). Empiric modifications of this formula were constructed that considered either the quantity of ST elevation in (A) or the number of (B) involved non-inferior leads. Each modification achieved improvement in correlation with QRS estimated MI size in the original population (A: r = 0.63 and B: r = 0.65), and also in an independent test population (A: r = 0.57 and B: r = 0.62). These results suggest that the formula of Aldrich et al. for anterior location is valid for clinical application, but that further studies are required to determine if a comparably accurate method can be developed for inferior MI.

Precordial ST segment depression predicts a worse prognosis in inferior infarction despite reperfusion therapy. The Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) Study Group

The impact of associated precordial ST segment depression in inferior myocardial infarction on angiographic and clinical outcomes after thrombolytic therapy and selective coronary angioplasty was studied in 583 patients with acute myocardial infarction. Anterior infarction (Group I), inferior infarction with precordial ST segment depression (Group II) and inferior infarction without precordial ST segment depression (Group III) were present in 289, 135 and 159 patients, respectively. Precordial ST segment depression was more frequent in circumflex than right coronary infarct-related arteries (44 [71%] of 62 versus 91 [40%] of 230; p = 0.000). Although acute patency rates were not statistically different, there was a trend toward different patency rates at day 7 (Group I 88%, Group II 84%, Group III 80%; p = 0.089) partly because of insignificantly higher reocclusion rates in inferior infarction without precordial ST segment depression (Group I 11%, Group II 10%, Group III 18%, p = 0.104). Infarct zone regional wall motion (standard deviations/chord) in inferior infarction was lower with precordial ST segment depression, both acutely (Group I -2.8 +/- 0.9, Group II -2.5 +/- 1.2, Group III 2.0 +/- 1.1; p = 0.000) and at day 7 (Group I -2.2 +/- 1.1, Group II -2.3 +/- 1.1, Group III -1.9 +/- 1.3; p = 0.011). Precordial ST segment depression was associated with a lower ejection fraction in inferior infarction both acutely (Group I 47 +/- 11%, Group II 53 +/- 11%, Group III 58 +/- 9%; p = 0.000) and at day 7 (Group I 49 +/- 12%, Group II 53 +/- 10%, Group III 58 +/- 8%; p = 0.000). Complication rates tended to be higher in inferior infarction when precordial ST segment depression was present. Mortality rates for Groups I, II and III were 8%, 6% and 5%, respectively. These results suggest that precordial ST segment depression in inferior infarction predicts a worse ventriculographic and clinical outcome despite reperfusion therapy.

Importance of reciprocal ST segment depression in leads V5 and V6 as an indicator of disease of the left anterior descending coronary artery in acute inferior wall myocardial infarction

The purpose of this study was to determine the coronary angiographic correlations (specifically disease of the left anterior descending coronary artery) of reciprocal ST segment depression appearing during inferior acute myocardial infarction. Forty six patients (41 men and five women; mean age 56 years) were allocated into two groups based on the extent of precordial ST segment depression: widespread (V1-V6) ST depression v localised (V1-V4) ST depression. Patients with no reciprocal ST depression or patients with ST depression in V1-V4 but with ST elevation in V5 and V6 (inferolateral acute myocardial infarction) were excluded. All patients were catheterised during hospital admission for infarction. Twenty four of the 28 patients with ST depression in V1-V6 had significant lesions in the left anterior descending coronary artery whereas 16 of the 18 patients with ST depression in V1-V4 had insignificant or no lesions in the left anterior descending artery. The sensitivity, specificity, and positive and negative predictive values of widespread ST depression in predicting disease in the left anterior descending coronary artery were 92%, 80%, and 86% and 89% respectively. In patients with inferior acute myocardial infarction and precordial ST depression, the extent of ST depression is of clinical significance. Widespread (V1-V6) ST depression suggests disease of the left anterior descending coronary artery, whereas localised ST depression (V1-V4) indicates its absence.

The electrocardiographic diagnosis of acute myocardial infarction in the thrombolytic era

The 12-lead ECG remains a simple and inexpensive technique to diagnose AMI in its early phases. The diagnostic accuracy of the ECG depends upon the extent of myocardial necrosis and its localization. The ECG is most sensitive in patients with occlusion of the LAD artery, followed by the RCA and the left CFA. In 10% to 20% of patients with AMI the initial ECG either shows nonspecific changes or is normal. The correlation between the ECG and infarct-related artery varies according to the involved vessel. Classic ECG changes are seen in 90% of the LAD artery, in 70% to 80% of RCA, and in only 50% of CFA occlusions. A second important issue is the mechanism and clinical significance of reciprocal ST segment changes, which usually indicate larger MI, more impaired ventricular function, worse prognosis, and in some patients, significant disease of a noninfarct-related artery. Furthermore, the value of the ECG in estimating myocardial injury and infarct size remains controversial. The ECG plays an important role in coronary reperfusion. ST segment elevation is one of the principal criteria for instituting thrombolytic therapy, and helps predict those who will most likely benefit from coronary reperfusion. The role of the ECG in evaluating the reperfusion status after coronary thrombolysis is not clear. Rapid return to baseline or normalization of the ST segment suggests opening of the occluded vessel, though a small or negligible change does not exclude successful reperfusion.

Electrocardiographic manifestations of right ventricular infarction

RVI is a frequent occurrence in the setting of an acute inferoposterior myocardial infarction and its early recognition has important therapeutic and prognostic implications. Because of this, diverse invasive and noninvasive diagnostic techniques have been investigated to identify patients with RVI. Electrocardiography is the most available, simple, and objective of these techniques. Numerous ECG signs of RVI have been described and some of them, especially ST segment elevation and patterns of necrosis (QS, QR) in the right precordial leads (V3R to V5R), have a very high sensitivity, specificity, and positive predictive value for the detection of RVI. ST segment elevation in lead V4R is also helpful in identifying the occluded coronary artery in patients with acute myocardial infarction, which could have great importance in their management. Hence, a 12-lead ECG with the right precordial leads (V3R to V6R) should be a routine part of the initial evaluation of patients with clinical suspicion of acute inferior myocardial infarction. This article reviews the value, limitations, and pathogenesis of the ECG manifestations of RVI.

Right ventricular infarction: diagnostic value of ST elevation in lead III exceeding that of lead II during inferior/posterior infarction and comparison with right-chest leads V3R to V7R

The diagnostic accuracy of ST elevation in lead III exceeding that of lead II (ratio III/II greater than 1) in the diagnosis of right ventricular infarction was investigated in 24 autopsied patients with inferior/posterior myocardial infarction on ECG. The results were compared with the diagnostic accuracy of ST elevation greater than or equal to 1 mm in right-chest leads V3R to V7R recorded in the same patients. All had left ventricular infarction documented at autopsy, and 17 (71%) had concomitant right ventricular involvement. The highest specificity (100%) and positive predictive value (100%) were calculated for the right-chest leads, whereas values for ratio III/II greater than 1 were 88% and 91%, respectively. The differences were not statistically significant. It is concluded that differences in ST elevation in leads III and II can be the basis for a diagnosis of right ventricular involvement in ECG-diagnosed inferior/posterior infarction. The diagnosis, however, may be achieved more easily with right-chest leads.

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)

Ischemic ST segment depression in leads V2-V3 as the presenting electrocardiographic feature of posterolateral wall myocardial infarction

In this study of 14 patients hospitalized with a first event of myocardial infarction, maximal ST segment depression in precordial leads V2 and V3 was the sole ECG finding during chest pain in the first 24 hours of evolving posterolateral infarction, based upon further two-dimensional echocardiographic examination and cardionuclear imaging. Other ECG findings compatible with posterolateral infarction such as the appearance of Q waves in leads V5 and V6, increased R/S ratio in leads V1 and V2, and a diminution of R wave amplitude in leads 1, aVL, V5, and V6 were relatively delayed manifestations in the majority of patients. The clinical course of all patients was benign. It therefore seems reasonable to conclude that ST segment depression in leads V2 and V3 in the absence of reciprocal ECG changes may represent the initial ECG finding of posterolateral infarction in the suitable clinical context of an acute coronary event.

Ratio of ST-segment depression in lead V2 to ST-segment elevation in lead aVF in evolving inferior acute myocardial infarction: an aid to the early recognition of right ventricular ischemia

The potential value of the ratio of precordial ST-segment depression to inferior ST-segment elevation as a sign of concomitant right ventricular (RV) ischemia was examined. The study group consisted of 68 patients, admitted within 3 hours of the onset of inferior acute myocardial infarction (AMI), in whom there was no evidence of prior AMI. In 27 of the 34 patients in whom inferior AMI was the result of right coronary artery occlusion proximal to the RV branch, the magnitude of ST-segment depression in lead V2 was 50% or less of the magnitude of ST-segment elevation in lead aVF, whereas in only 3 of the 34 patients in whom the site of occlusion was either distal to the RV branch (n = 23) or in the left circumflex artery (n = 11) was this ratio 50%; in no patient was it less than 50% (p less than 0.001). All 34 patients with occlusion of the right coronary artery proximal to the RV branch also had regional or global ischemic RV dysfunction by radionuclide ventriculography, with a mean RV ejection fraction of 30 +/- 10% compared with 42 +/- 6% in patients with occlusion distal to the RV branch or in the left circumflex artery (p less than 0.001). In conclusion, in patients with evolving inferior AMI, ST-segment depression in lead V2 of 50% or less of the magnitude of ST-segment elevation in lead aVF may be a useful sign (sensitivity 79%, specificity 91%, positive predictive value 90% and negative predictive value 82%) for identifying patients with concomitant RV ischemia.