Do patients with left circumflex coronary artery-related acute myocardial infarction without ST-segment elevation benefit from reperfusion therapy?

Ischemic ST-Segment Depression Maximal in V1-V4 (Versus V5-V6) of Any Amplitude Is Specific for Occlusion Myocardial Infarction (Versus Nonocclusive Ischemia)

Background Occlusion myocardial infarctions (OMIs) of the posterolateral walls are commonly missed by ST-segment-elevation myocardial infarction (STEMI) criteria, with >50% of patients with circumflex occlusion not receiving emergent reperfusion and experiencing increased mortality. ST-segment depression maximal in leads V1-V4 (STDmaxV1-4) has been suggested as an indicator of posterior OMI. Methods and Results We retrospectively reviewed a high-risk population with acute coronary syndrome. OMI was defined from prior studies as a culprit lesion with TIMI (Thrombolysis in Myocardial Infarction) 0 to 2 flow or TIMI 3 flow plus peak troponin T >1.0 ng/mL or troponin I >10 ng/mL. STEMI was defined by the Fourth Universal Definition of Myocardial Infarction. ECGs were interpreted blinded to outcomes. Among 808 patients, there were 265 OMIs, 108 (41%) meeting STEMI criteria. A total of 118 (15%) patients had "suspected ischemic" STDmaxV1-4, of whom 106 (90%) had an acute culprit lesion, 99 (84%) had OMI, and 95 (81%) underwent percutaneous coronary intervention. Suspected ischemic STDmaxV1-4 had 97% specificity and 37% sensitivity for OMI. Of the 99 OMIs detected by STDmaxV1-4, 34% had <1 mm ST-segment depression, and only 47 (47%) had accompanying STEMI criteria, of which 17 (36%) were identified a median 1.00 hour earlier by STDmaxV1-4 than STEMI criteria. Despite similar infarct size, TIMI flow, and coronary interventions, patients with STEMI(-) OMI and STDmaxV1-4 were less likely than STEMI(+) patients to undergo catheterization within 90 minutes (46% versus 68%; P=0.028). Conclusions Among patients with high-risk acute coronary syndrome, the specificity of ischemic STDmaxV1-4 was 97% for OMI and 96% for OMI requiring emergent percutaneous coronary intervention. STEMI criteria missed half of OMIs detected by STDmaxV1-4. Ischemic STDmaxV1-V4 in acute coronary syndrome should be considered OMI until proven otherwise.

Should Non-ST-Elevation Myocardial Infarction be Treated like ST-Elevation Myocardial Infarction With Shorter Door-to-Balloon Time?

It is estimated that each year in the United States >780,000 persons will experience an acute coronary syndrome. Approximately 70% of these will have non-ST-elevation myocardial infarction (NSTEMI). Optimal timing of angiography in NSTEMI is a matter of debate. The aim of this retrospective analysis was to evaluate whether and how the timing of percutaneous coronary intervention (PCI) affects the 1-year rate of major adverse cardiac events (MACE) in patients presenting with NSTEMI. Within our PCI database, we identified 1550 patients who underwent PCI for NSTEMI. We then divided the population into 3 groups based on door-to-balloon time (D2BT) (group 1 = D2BT <90 minutes; group 2 = D2BT >90 minutes <24 hours; group 3 = D2BT >24 hours). Primary outcome was MACE, a composite of MI, death and target vessel revascularization (TVR), or TVR at 1 year. Baseline characteristics were heterogeneous among the 3 groups, with patients who underwent angiograms >24 hours from presentation being older with more cardiovascular co-morbidities. Patients with D2BT <90 minutes were more likely to present with cardiogenic shock and had higher troponin levels. In-hospital mortality was similar among the 3 groups, but 1-year MACE/TVR was significantly higher in groups 1 and 3, driven by worse mortality. In this large cohort of patients presenting with NSTEMI, patients who underwent PCI between 90 minutes to 24 hours from presentation had better 1-year outcomes but also had fewer co-morbidities and with significantly lower prevalence of cardiogenic shock and high troponin on presentation. Therefore, treatment selection bias makes causal inference concerning rapid revascularization and outcome unreliable. Randomized clinical trials are warranted to assess outcome of rapid revascularization in patients presenting with NSTEMI.

Door-to-balloon time and cardiac mortality in acute myocardial infarction by total occlusion of the left circumflex artery

BACKGROUND

Acute myocardial infarction (AMI) caused by total occlusion of the left circumflex artery (LCX) can present as non-ST-segment elevation myocardial infarction (NSTEMI). We evaluate whether door-to-balloon time (DBT) is associated with cardiac mortality in patients with total occlusion of the LCX.

PATIENTS AND METHODS

From the Korea Acute Myocardial Infarction Registry, patients with AMI who had total occlusion with a Thrombolysis In Myocardial Infarction flow grade of 0 were included. We determined the factors for delay in primary percutaneous coronary intervention (DBT>90 min) and evaluated cardiac mortality for a median period of 14 months.

RESULTS

Mean DBT was 68 min (interquartile range=50-156 min), and the achievement rate of DBT less than or equal to 90 min was 66.9% in the entire study population. More than half of patients with total occlusion of LCX were presented as NSTEMI (57.7%). Among patients with total occlusion of the LCX, the mean DBT was 136 min (interquartile range=60-484 min), and the achievement rate of DBT less than or equal to 90 min was 42.8%. On multivariate analysis, LCX occlusion was an important factor for DBT more than 90 min (odds ratio: 1.766, P<0.001). Among patients with LCX occlusion, cardiac mortality was higher in patients with ST-segment elevation (6.2 vs. 11.0%, P=0.024).

CONCLUSION

This study showed that LCX occlusion was a significant factor for the delay in primary percutaneous coronary intervention on account of presenting as NSTEMI. Cardiac mortality was not associated with DBT more than 90 min but with ST-segment elevation in AMI patients with total occlusion of the LCX.

Isolated Posterior Acute Myocardial Infarction Presenting to an Emergency Department: Diagnosis and Emergent Fibrinolytic Therapy

Objectives

Isolated posterior acute myocardial infarction (AMI) is rare and possibly underdiagnosed. The incidence of misdiagnosis in the emergency department (ED) is unknown. Delayed diagnosis may prevent timely treatment, particularly emergent fibrinolytic therapy. We describe the experience of an urban ED on this rare condition.

Methodology

A six years and seven months case series of isolated posterior AMI of initial presentation (as identified by inpatient discharge/death ICD-9-CM diagnosis code) was studied. Patients not admitted from the ED, those who developed isolated posterior AMI only after admission and/or those with concomitant ST segment elevation AMI involving other anatomical locations of the heart (e.g. inferior or lateral walls), were excluded.

Results

Eleven cases were included in the study. All the nine cases with electrocardiograms available for review demonstrated features consistent with isolated posterior AMI. Eight out of the eleven (72.7%) cases were correctly diagnosed as isolated posterior AMI in the ED. The other three cases were treated as non-ST elevation myocardial infarction (NSTEMI). Nevertheless, their lack of the typical symptoms of acute coronary syndrome and delayed presentation (more than 12 hours) precluded them from fibrinolytics. Three of the eleven cases received fibrinolytics (all streptokinase). All three cases survived to discharge and there were no haemorrhagic complications. None of the cases underwent emergent percutaneous coronary intervention.

Conclusion

The majority of cases with isolated posterior AMI (72.7%) were diagnosed in the ED. Although three cases were interpreted as NSTEMI, the use of fibrinolytic reperfusion therapy was not affected.

Acute myocardial infarction and lesion location in the left circumflex artery: importance of coronary artery dominance

AIMS

Due to the limitations of 12-lead ECG, occlusions of the left circumflex artery (LCX) are more likely to present as non-ST-elevation acute coronary syndrome (NSTEACS) compared with other coronary arteries. We aimed to study mortality in patients with LCX lesions and to assess the importance of coronary artery dominance on triage of these patients.

METHODS AND RESULTS

From the Eastern Danish Heart Registry, 3,632 NSTEACS and 3,907 ST-elevation myocardial infarction (STEMI) consecutive, single-vessel disease patients were included. LCX was the culprit in 25% of NSTEACS and 14% of STEMIs (p<0.001). LCX lesions presented predominantly as STEMI in left dominant coronary arteries compared with NSTEACS (46% vs. 30%, p<0.001). Higher 30-day mortality was found in LCX-STEMI compared with LCX-NSTEACS (HR 7.9, 95% CI: 3.2-19.7, p<0.001) with no difference in long-term mortality (HR 0.9, 95% CI: 0.7-1.2, p=0.5). LCX-NSTEACS were not associated with higher mortality compared with other NSTEACS lesions.

CONCLUSIONS

The 12-lead ECG seems sufficient for triage of patients with LCX lesions as a majority of patients with a large LCX due to a dominant left coronary artery present as STEMI. Patients with LCX-NSTEACS do not have higher mortality compared with patients with LCX-STEMI or NSTEACS with lesions in other coronary territories.

Assessment of validity of the 'Culprit Score' for predicting the culprit lesion in patients with acute inferior wall myocardial infarction

INTRODUCTION

Many electrocardiographic criteria have been developed to determine the infarct-related artery in acute inferior wall myocardial infarction. The aim of this study was to test the commonly used criteria and devise a simplified score to further improve the diagnostic accuracy.

MATERIALS AND METHODS

From 2011 to 2013, 100 patients with acute inferior wall myocardial infarction were recruited for electrocardiographic and angiographic analyses.

RESULTS

The mean age of the patients was 65±12 years with 74% of patients being male. In our study population, significantly more ST-segment depression was seen in lead aVL and ST elevation in lead III in those with right coronary artery (RCA) occlusions. In left circumflex artery (LCX) occlusions, significantly more ST depression was seen in leads V1-3 (most significantly in lead V2) and ST elevation in lead II. In addition, more prominent ST depression was seen in lead aVL and ST elevation in V1 in proximal RCA occlusions. Based on the findings, we devised a score named Culprit Score, which was defined as [II-V2/III+V1-aVL]. The sensitivity and specificity of Culprit Score ≤0.5 to predict proximal RCA occlusions; 0.5 to ≤1.5 to predict distal RCA occlusions; and score >1.5 to predict LCX occlusions were 85% and 85%; 80% and 86%; and 80% and 94%, respectively. Similarly, the negative predictive value was more than 80%.

CONCLUSION

The Culprit Score was found to have high specificity and negative predictive value to identify the infarct-related artery in inferior wall myocardial infarction.

Red cell distribution width predicts totally occluded infarct-related artery in NSTEMI

Objective Since non-ST segment elevation myocardial infarction (NSTEMI) patients with totally occluded infarct-related artery (TO-IRA) have worse prognosis, it is important to recognize TO-IRA in NSTEMI. Red cell distribution width (RDW) and mean platelet volume (MPV) are novel markers of inflammation and oxidative stress and were associated with poor clinical outcomes in acute coronary syndrome. In the present study, association of RDW and MPV with the presence of TO-IRA in NSTEMI was investigated. Methods Data of 201 consecutive patients who underwent coronary angiography with a diagnosis of NSTEMI were analyzed. Independent predictors of TO-IRA were investigated with logistic regression analysis. Results Sixty-six (32.8%) of the patients had TO-IRA. In patients with TO-IRA, RDW and troponin-T were significantly higher and left ventricular ejection fraction (LVEF) was lower. MPV did not differ between groups. Circumflex (CX) IRA was more common in TO-IRA group. The ROC curve analysis showed that the RDW at a cut-point of 13.95% has 76% sensitivity and 66% specificity in detecting TO-IRA. RDW, troponin-T, LVEF and CX-IRA were independent predictors of TO-IRA in NSTEMI, but MPV was not. Conclusion RDW is a cheap and readily available marker that may have a role to predict TO-IRA in NSTEMI.

Infarct artery distribution and clinical outcomes in occluded artery trial subjects presenting with non-ST-segment elevation myocardial infarction (from the long-term follow-up of Occluded Artery Trial [OAT])

We hypothesized that the insensitivity of the electrocardiogram in identifying acute circumflex occlusion would result in differences in the distribution of the infarct-related artery (IRA) between patients with non-ST-segment elevation myocardial infarction (NSTEMI) and STEMI enrolled in the Occluded Artery Trial. We also sought to evaluate the effect of percutaneous coronary intervention to the IRA on the clinical outcomes for patients with NSTEMI. Overall, those with NSTEMI constituted 13% (n = 283) of the trial population. The circumflex IRA was overrepresented in the NSTEMI group compared to the STEMI group (42.5 vs 11.2%; p <0.0001). The 7-year clinical outcomes for the patients with NSTEMI randomized to percutaneous coronary intervention and optimal medical therapy versus optimal medical therapy alone were similar for the primary composite of death, myocardial infarction, and class IV congestive heart failure (22.3% vs 20.2%, hazard ratio 1.20, 99% confidence interval 0.60 to 2.40; p = 0.51) and the individual end points of death (13.8% vs 17.0%, hazard ratio 0.82, 99% confidence interval 0.37 to 1.84; p = 0.53), myocardial infarction (6.1 vs 5.1%, hazard ratio 1.11, 99% confidence interval 0.28 to 4.41; p = 0.84), and class IV congestive heart failure (6.7% vs 6.0%, hazard ratio 1.50, 99% confidence interval 0.37 to 6.02; p = 0.45). No interaction was seen between the electrocardiographically determined myocardial infarction type and treatment effect (p = NS). In conclusion, the occluded circumflex IRA is overrepresented in the NSTEMI population. Consistent with the overall trial results, stable patients with NSTEMI and a totally occluded IRA did not benefit from randomization to percutaneous coronary intervention.

Left circumflex occlusion in acute myocardial infarction (from the National Cardiovascular Data Registry)

Compared to occlusions of other major coronary arteries, patients presenting with acute left circumflex (LCx) occlusion usually have ST-segment elevation on the electrocardiogram <50% of the time, potentially delaying treatment and resulting in worse outcomes. In contemporary practice, little is known about the clinical outcomes of patients with LCx territory occlusion without ST-segment elevation myocardial infarction (STEMI). We identified patients with myocardial infarction from April 2004 to June 2009 in the CathPCI Registry treated with percutaneous coronary intervention for culprit LCx territory occlusion, excluding those with previous coronary artery bypass grafting. Logistic generalized estimating equation modeling was used to compare the outcomes, including in-hospital mortality between patients with STEMI and non-STEMI (NSTEMI) adjusting for differences in the baseline characteristics. Of the 27,711 patients with myocardial infarction and acute LCx territory occlusion, 18,548 (67%) presented with STEMI and 9,163 (33%) with NSTEMI. With the exception of a greater proportion of cardiac risk factors and cardiac history in the NSTEMI group, the demographic and baseline characteristics were clinically similar between the 2 groups, despite the statistical significance resulting from the large population. The patients with STEMI were more likely to have a proximal LCx culprit lesion (63% vs 27%, p <0.0001) and had greater risk-adjusted in-hospital mortality (odds ratio 1.36, 95% confidence interval 1.12 to 1.65, p = 0.002) compared to patients with NSTEMI. In conclusion, acute LCx territory occlusion often presents as NSTEMI, but patients with NSTEMI and occlusion have a lower mortality risk than those with STEMI, possibly because of factors such as the amount of myocardium involved, the lesion location along the vessel, and/or a dual blood supply.

Acute myocardial infarction due to left circumflex artery occlusion and significance of ST-segment elevation

Acute occlusion of the left circumflex (LC) artery can be difficult to diagnose. The aim of the present study was to assess the incidence of LC occlusion in patients with acute myocardial infarction (AMI) requiring percutaneous coronary intervention (PCI), the frequency of ST-segment versus non-ST-segment elevation presentation among them, and to correlate the electrocardiographic findings with the outcomes. The clinical characteristics and outcomes of consecutive patients from November 2001 through December 2007 with AMI within 7 days before PCI of a single acutely occluded culprit vessel were included in the present analysis. Of the 1,500 patients, the culprit lesion was located in the right coronary artery, left anterior descending artery, or LC artery in 44.7%, 35.8%, and 19.5% of patients, respectively. Of the 1,500 patients, 72% presented with ST-segment elevation AMI, but only 43% were patients with a LC lesion (n = 127). PCI was significantly less likely (80%, 83%, and 70% for right coronary, left anterior descending, and LC artery, respectively; p < 0.001) to be performed within 24 hours for LC occlusions than for occlusions in the other territories. Among those with a non-ST-segment elevation AMI, the highest post-PCI troponin levels were in patients with a LC artery occlusion (median 1.4, 1.3, and 2.5 ng/ml; p < 0.001). No significant difference was found in the in-hospital mortality (4.4%, 7.4%, and 6.5%; p = 0.66) or major adverse cardiovascular event (9.2%, 13.9%, and 11.6%; p = 0.53) rates for right, left anterior descending, and LC occlusions, respectively. In conclusion, our results have demonstrated that in clinical practice, the LC artery is the least frequent culprit vessel among patients treated invasively for AMI. Patients with LC occlusion are less likely to present with ST-segment elevation AMI and have emergency PCI. The study results suggest that detection of these patients has been suboptimal, highlighting the need to improve the diagnostic approach toward the detection of an acutely occluded LC artery.

Magnitude and consequences of missing the acute infarct-related circumflex artery

Emergent reperfusion strategies are integral to providing optimal patient outcomes in the setting of acute coronary artery occlusion. ST-segment elevation on the surface 12-lead electrocardiogram, although specific as a surrogate marker, is insensitive to acute posterior circulation coronary artery occlusion. Studies of non-ST-segment elevation acute coronary syndrome consistently identify patients who have epicardial vessel occlusion at the time of initial angiography, which is usually delayed for hours or days after the initial presentation. In addition, studies of ST-segment elevation myocardial infarction often divulge a disparity in identification of the infarct-related artery, with an underrepresentation of the left circumflex artery. Taken together, it is likely that many patients with left circumflex artery occlusion are "missed" during the early phases of myocardial infarction due to the electrocardiographically silent nature of the posterior territory, resulting in delayed myocardial salvage and worse cardiovascular outcomes. In this review, we report on the magnitude of missed left circumflex infarction and the consequences of this delay in diagnosis. We review the electrocardiographic findings of left circumflex occlusion and discuss strategies to enhance early identification. Heightened awareness of this clinical scenario and the available methods to avoid missing this elusive diagnosis are imperative in our quest to further improve the outcomes of patients with acute myocardial infarction.

Comparison of value of leads from body surface maps to 12-lead electrocardiogram for diagnosis of acute myocardial infarction

We aimed to develop 12-lead electrocardiographic (ECG) models testing ST-elevation criteria with QRST variables and compare their performance with the 80-lead body surface map (BSM) in detection of acute myocardial infarction (AMI). Because the prevalence of non-ST-elevation AMI is increasing worldwide, advances in early ECG detection of AMI are urgently needed. The study population was 755 consecutive patients presenting with ischemic chest pain from January 2002 to June 2004. All patients had electrocardiography and body surface mapping performed at initial presentation. AMI occurred in 519 patients (69%, cardiac troponin T or I level > or =0.1 ng/ml). Of these 519 patients, 303 (58%) had no ST-elevation on the initial 12-lead electrocardiogram. Ten patients were classified as having an "aborted AMI" and were included in the AMI analysis. The American College of Cardiology/European Society of Cardiology criteria for ST-elevation on 12-lead electrocardiogram identified 236 patients with AMI (sensitivity 45%, specificity 92%). Additional QRST features improved sensitivity (51% to 68%) but with decreased specificity (71% to 89%), with the optimal multivariate ECG model having a c-statistic of 0.75. The optimal BSM model identified 402 patients as having AMI (sensitivity 76%, specificity 92%, c-statistic 0.84). This improvement in sensitivity over the 12-lead electrocardiogram was due mainly to detection of ST-elevation in the high right anterior, posterior, and right ventricular territories and AMI in the presence of left bundle branch block. In conclusion, QRST variables added to criteria for ST-elevation result in improvement in sensitivity of the 12-lead electrocardiogram, although with decreased specificity. The BSM is superior in detecting AMI and demonstrates the importance of electroanatomic evaluation of patients with acute coronary syndromes.

Mechanisms of exercise-induced ST-segment depression in patients without typical angina pectoris

OBJECTIVE

To evaluate if exercise-induced ST-segment depression without typical angina pectoris is related to increases in sympatho-adrenal activity or beta-adrenoceptor sensitivity.

PATIENTS

Thirteen patients (four men) aged 35-62 years with ST-segment depression during exercise but atypical symptoms and normal myocardial scintigraphy, and 13 matched controls.

DESIGN AND INTERVENTIONS

Patients and controls were compared regarding responses with: (i) exercise testing without treatment, (ii) exercise testing following beta-adrenoceptor blockade by propranolol (0.15 mg kg(-1) i.v.), (iii) incremental adrenaline infusions (0.1, 0.2, 0.4 and 0.8 nmol kg(-1) min(-1)) and (iv) adrenaline infusions during alpha-adrenoceptor blockade by phentolamine (0.5 mg min(-1)).

MAIN OUTCOME MEASURES

ST-segment depression and tissue Doppler parameters reflecting contractility.

RESULTS

Exercise lowered the ST-segment by 2.44 mm without and 0.87 mm with beta-adrenoceptor blockade (P < 0.001 for difference) amongst patients, but not amongst controls. Maximal heart rate was slightly higher amongst patients (P < 0.05), despite similar loads and plasma catecholamine responses to exercise in the two groups; this difference disappeared after beta-adrenoceptor blockade with propranolol. ST-segment depression during adrenaline infusion was greater in patients compared with controls (P < 0.01) despite similar increases in heart rate. alpha-Blockade enhanced the ST-segment depression (P < 0.001) and heart rate (P < 0.001) responses to adrenaline infusion more markedly amongst patients. Tissue Doppler imaging showed similar contractility and diastolic relaxation responses of patients and controls to adrenaline, but early diastolic movements did not increase amongst patients after phentolamine (P < 0.01).

CONCLUSIONS

Exercise-induced ST-segment depression in patients with a low likelihood of ischaemic heart disease is related to increased beta-adrenergic sensitivity regarding chronotropic and electrophysiological, but not inotropic responses.

Electrocardiographic diagnosis of non–ST-segment elevation acute coronary syndromes: current concepts for the physician

With several myocardial infarction (MI) registries reporting a decline in the incidence of ST-elevation MI (STEMI) and an increase in non-ST-elevation MI (NSTEMI) and unstable angina (UA), it is important that future healthcare resources are directed towards this increased volume of patients, ECG technology, core to the early diagnosis of these patients, has lagged behind relative to other techniques and little progress has been as far as acute coronary syndrome triage is concerned beyond ST-segment deviation. We present a review of the literature on current electrocardiographic changes which will allow admitting physicians to better risk stratify those patients with "non-diagnostic ECGs." These ECGs may become diagnostic with careful evaluation, use of serial ECGs and when additional lead sets are used.

Imaging in the evaluation of the patient with suspected acute coronary syndrome

Over the last decade, major advances have been made in the treatment of acute coronary syndromes (ACSs). However, effective implementation of these treatments requires timely and accurate identification of the high-risk patient among all those presenting to the emergency department (ED) with symptoms suggestive of ACS. The opportunity for improving outcomes is time-dependent, so that early identification of the patient who has true ACS is essential. This necessity further increases the need for rapid triage tools, especially in the current setting of ED and hospital overcrowding that has become the norm in large urban centers.

Acute coronary syndromes

Despite technologic advances in many diagnostic fields, the 12-lead ECG remains the basis for early identification and management of an acute coronary syndrome. This article reviews the use of the ECG in acute coronary syndromes.

Consideration of the total ST-segment deviation on the initial electrocardiogram for predicting final acute posterior myocardial infarct size in patients with maximum ST-segment deviation as depression in leads V1 through V3. A FRISC II substudy

BACKGROUND

Because patients with acute left circumflex occlusion are typically characterized primarily on the standard 12-lead electrocardiogram (ECG) by ST depression, they do not qualify to receive reperfusion therapy. Documentation of a relationship between the quantities of acute ST change and final QRS estimated acute myocardial infarction (AMI) size could form the basis for clinical trials to determine the value of reperfusion therapy.

METHOD

The Fragmin and Fast Revascularization during Instability in Coronary artery disease trial included 3214 patients with unstable coronary artery disease. Two percent of the patients (n = 69) had maximum ST-segment depression in leads V 1 through V 3 and were selected for this study. Initial ECG changes were compared to final myocardial infarction size, using the Selvester QRS score as the end point.

RESULTS

The quantity of initial ST-segment deviation correlated with the final AMI size (r = 0.43, P < .0005). The formula 3[0.22 (SigmaST downward arrow + SigmaST upward arrow) -0.02], where downward arrow indicates depression and upward arrow elevation, derived from measurements on the initial ECG, predicted the size of the AMI in percentage of the left ventricle as estimated on the final ECG. The study population had a large proportion of AMI (73%) indicated to be in or adjacent to the posterior left ventricular wall.

CONCLUSION

The quantitative initial ST-segment deviation correlates linearly to the final AMI size in patients with maximum ST-segment depression in leads V 1 through V 3. The formula derived could be valuable for selecting patients who fail to meet strict ST-elevation AMI criteria for emergency intravenous or intracoronary reperfusion therapy.

Absence of ST elevation in ECG leads V7, V8, V9 in ischaemia of non-occlusive aetiologies

BACKGROUND AND OBJECTIVE

Occlusion of the circumflex coronary artery may present with either ST elevation typical of inferior or lateral myocardial infarction, ST depression or a normal 12-lead electrocardiogram (ECG). In patients presenting with ST depression, concomitant ST elevation in the posterior leads V7, V8 and V9 is believed to reflect ST-elevation myocardial infarction of the posterior wall. However, to be confident of this diagnosis, it is necessary to know that posterior ST depression does not occur in acute subendocardial ischaemia.

METHODS AND RESULTS

We have prospectively recorded leads V7, V8 and V9 simultaneously with the standard 12-lead ECG in patients who underwent treadmill stress test. Group A consists of 35 patients who showed ischaemic praecordial ST depression in their 12-lead ECGs during treadmill stress test and subsequent angiographic documentation of significant coronary artery disease. Group B consists of 35 subjects who showed normal ECG findings during treadmill stress test. In none of the Group A or B patients was there ST elevation in leads V7, V8 or V9 either at rest or at peak exercise. ST depression was seen in 69% in V7, 31% in V8 and 11% in V9 in the Group A patients at peak exercise.

CONCLUSION

ST elevation in leads V7, V8 and V9 is uncommon in patients presenting with subendocardial ischaemia. Therefore, in patients presenting with acute chest pain and ST depression in the 12-lead ECG, concomitant posterior ST elevation may be a reliable indicator of ST elevation posterior MI. This is likely due to circumflex artery occlusion and may require thrombolytic therapy.

Acute angiographic analysis of non-ST-segment elevation acute myocardial infarction

Most revascularization studies on acute myocardial infarction have included patients who have ST-segment elevation or new-onset left bundle branch block. However, the characteristics of patients who have non-ST-segment elevation acute myocardial infarction and who have undergone angiographic analysis of their infarct-related arteries have not been adequately described. This study suggests that these patients are likely to have had coronary bypass surgery (odds ratio 4.58, 95% confidence interval 1.83 to 11.5, p = 0.0012) and that circumflex artery occlusions are more likely to present as non-ST-segment elevation than as acute myocardial infarction with ST-segment elevation and/or left bundle branch block (odds ratio 2.91, 95% confidence interval 1.62 to 5.22, p = 0.0003).

Prehospital 80-LAD mapping: Does it add significantly to the diagnosis of acute coronary syndromes?

Early detection of acute myocardial infarction (MI) is vital in the management of acute coronary syndromes (ACS). Hence we compared the diagnostic capability of the standard 12-lead electrocardiogram (ECG) with the 80-lead ECG body surface map (BSM) prehospital.

METHODS

Consecutive patients (n = 294) presenting prehospital with ischemic type chest pain were included. All had an ECG and BSM pretreatment and a baseline and 12-hour cardiac troponin-T or I (cTnT or cTnI). Acute MI was defined as cTnT > 0.09 or cTnI > 0.1 ng/mL. Acute MI on the BSM was defined as ST elevation measured at the J-point, > or = 1 mm inferior/right ventricular/high right anterior/lateral regions, > or = 2 mm anterior region, > or = 0.5 mm posterior region.

RESULTS

Acute MI occurred in 182/294 (62%) based on cTnT or I. ST elevation on the standard ECG predicted acute MI in 103 (sensitivity 57%, specificity 94%; c-statistic 0.73). The optimal model for the standard ECG included ST elevation, summed ST depression and past history of MI (c-statistic 0.82; Chi-square (Wald) 120.7, 3df). The BSM predicted acute MI in 146 (sensitivity 80%, specificity 92%; c-statistic 0.86). The optimal model for the BSM included BSM criteria for acute MI and past history of MI (c-statistic 0.91; Chi-square (Wald) 180.3, 2df).

CONCLUSION

The 80-lead BSM is superior to the standard 12-lead ECG in predicting acute MI prehospital.

Identification of the Culprit Artery Involved in Inferior Wall Acute Myocardial Infarction Using Electrocardiographic Criteria

We tested whether particular electrocardiogram (ECG) changes can identify the right coronary (RCA) or left circumflex (LCX) artery as the responsible vessel in inferior wall acute myocardial infarction (AMI) in 73 patients. A standard 12-lead ECG was performed within 6 h of onset of chest pain. Coronary angiography was performed between 1 week and 6 weeks after the infarction. RCA and LCX lesions were detected in 53 and 20 patients, respectively.

The most useful ECG parameters for implicating the RCA were a higher ST elevation in lead III than lead II (specificity 94%, sensitivity 86%) and an S/R wave ratio > 0.33 plus ST segment depression > 1 mm in lead aVL (specificity 94%, sensitivity 92%). Absence of these criteria was associated with LCX occlusion (specificity 100%, sensitivity 87%). These results indicate that composite ECG criteria are useful in predicting the artery involved in inferior wall AMI.

Posterior myocardial infarction with isolated ST elevations in V8 and V9: Is this an "ST elevation MI"?

We report a case of a 53-year-old man whose first manifestation of coronary artery disease was an acute isolated posterior myocardial infarction (IPMI). Acute IPMI is relatively uncommon and predominantly due to occlusion of the left circumflex coronary artery. IPMI is challenging to diagnose due to the absence of ST segment elevation on a standard 12-lead electrocardiogram (ECG) even in the setting of total coronary artery occlusion and transmural (Q-wave) infarct. We discuss the diagnostic implications of the absence of tall R waves in leads V1 and V2 on this patient's ECG. The utility of posterior leads (V7 through V9) is demonstrated. The controversy surrounding the use of thrombolytic therapy or primary angioplasty in the setting of acute IPMI without ST segment elevation on a standard 12-lead ECG is reviewed.

Electrocardiographic diagnosis of acute myocardial infarction: Current concepts for the clinician

BACKGROUND

Over the past 2 decades, the 12-lead electrocardiogram has attained special significance for the diagnosis and triage of patients with chest pain because timely detection of myocardial injury and a rapid assessment of myocardium at risk proved pivotal to implementing effective reperfusion therapies during acute myocardial infarction. However, this wealth of information could still be underutilized by clinicians who may restrict their diagnostic quest in patients with chest pain to the more classic electrocardiographic signs.

METHODS

The medical literature on electrocardiographic manifestations of acute myocardial infarction was extensively reviewed.

RESULTS

The widespread utilization of both coronary angiography and methods to determine myocardial function and metabolism in patients with acute myocardial infarction over the last 10 years has provided the means for rigorous comparisons with electrocardiographic information. We summarize these electrocardiographic signs and patterns in terms of their relevance to the clinician to help reduce the incidence of "nondiagnostic electrocardiograms" and improve timely decision-making.

CONCLUSIONS

The electrocardiogram continues to be an invaluable tool in the initial evaluation of patients with chest pain. The plethora of data currently available on electrocardiographic changes correlating with myocardial injury allows clinicians to make faster and better decisions than ever before.

A nonischemic electrocardiogram does not always predict a small myocardial infarction: results with acute myocardial perfusion imaging

BACKGROUND

A nonischemic electrocardiogram (ECG) in association with myocardial infarction (MI) indicates a small MI in some but not all cases. Myocardial perfusion imaging using technetium-99m sestamibi offers the ability to better characterize these "electrically silent" infarctions.

METHODS

Patients considered low risk for myocardial infarction with a normal or nonischemic ECG (no significant ST elevation, ST depression, ischemic T-wave inversion, or left bundle branch block) underwent early emergency department perfusion imaging, followed by serial myocardial marker sampling. Risk area (defect size) was quantitated by use of a 50% threshold from multiple short-axis slices.

RESULTS

A total of 87 patients with nonischemic ECGs had myocardial infarction (mean peak creatine kinase [CK] 710 +/- 720 U/L, range 111-3196 U/L). Peak CKs were lower in the 7 patients with negative perfusion imaging (420 +/- 290 U/L vs 730 +/- 740 U/L, P =.06). Mean risk area was 18% +/- 11% of the left ventricle (range 0%-62%) and was not significantly different among the different infarct-related arteries. Patients with normal ECGs had a similar risk area compared with other patients (16% +/- 12% vs 19 +/- 12%, P =.25). Coronary angiography was performed in 81 patients, with significant stenoses in 74 (91%) (37 one-vessel, 19 two-vessel, 18 three-vessel), with the infarct related artery most commonly the left circumflex (n = 32 [38%]).

CONCLUSIONS

The ischemic risk area in patients with a nonischemic ECG was comparable to patients with inferior ST-elevation myocardial infarction found in previous studies. A nonischemic ECG does not predict a small ischemic risk area.

Usefulness of ST elevation II/III ratio and ST deviation in lead I for identifying the culprit artery in inferior wall acute myocardial infarction

In a study of 92 patients presenting with inferior wall acute myocardial infarction, the infarct-related artery was the right coronary artery in 72 patients (78%) and the left circumflex artery in 20 (22%). An ST II/III ratio of 1 or an isoelectric ST in lead I are sensitive and specific markers of left circumflex artery occlusion, whereas an ST II/III ratio <1 (ST elevation in lead III >II) or ST depression in lead I are sensitive and specific markers of right coronary artery occlusion.

Improved detection of posterior myocardial wall ischemia with the 15-lead electrocardiogram

BACKGROUND

A routine 12-lead electrocardiogram is commonly obtained to evaluate for possible acute myocardial infarction during the initial screening of patients with chest discomfort. Posterior myocardial infarction is commonly missed because it is not usually visible in the standard leads. In this study, we compared the sensitivity and specificity of posterior chest leads (V(7), V(8), and V(9)) and 12-lead electrocardiography in detecting posterior injury pattern during single-vessel percutaneous transluminal coronary angioplasty.

METHODS AND RESULTS

Three posterior chest leads in addition to the routine 12-lead electrocardiogram were monitored simultaneously during single-vessel percutaneous transluminal coronary angioplasty of the right, circumflex, and left anterior descending coronary arteries in a total of 223 patients. Posterior injury patterns (95%) were detected mostly during circumflex coronary occlusion. Posterior leads were able to detect injury pattern in 49% (36 of 74) of patients, whereas the 12-lead electrocardiogram was able to detect only 32% (P <.04). When all 15 leads were used to detect all ST elevations, sensitivity increased to 57%, with a specificity of 98% for the circumflex coronary artery. If maximal ST depressions in leads V(2) to V(3) are considered to be from posterior myocardial injury, then the overall sensitivity is increased to 69%.

CONCLUSIONS

Posterior leads significantly increased the detection of posterior injury pattern compared with the standard 12-lead electrocardiogram. Using all 15 leads significantly further improved the detection of circumflex coronary-related injury pattern over the standard 12-lead electrocardiogram.

Optimal management of acute myocardial infarction at the dawn of the next millennium

At the dawn of the next millennium, the optimal management of acute myocardial infarction will have been defined by multiple clinical trials of acute reperfusion strategies, in conjunction with adjunctive pharmacotherapy. Reperfusion therapy with thrombolytic agents or primary angioplasty is the standard of care for many patients examined with ST-segment elevation or left bundle branch block within approximately 12 hours of symptoms. The superiority of fibrin-specific agents over streptokinase has been established, as have the advantages of primary angioplasty in selected institutions with the requisite expertise and logistical capabilities. The key to successful reperfusion lies more in the efficiency of delivery than in the choice of modality. Reocclusion remains the "Achilles' heel" of reperfusion therapy, as does the presence of reperfusion injury microvascular dysfunction and the "no-reflow" phenomenon. These entities are major targets for further investigation in the next 5 years. The wealth of adjunctive pharmacologic agents currently available presents a challenge to the optimal treatment of myocardial infarction. A major objective is to define the magnitude of the incremental benefits and risks of using the available and new drugs, both alone and in combination. Moreover, community-wide studies indicate a marked underutilization of therapies that are available and are of proven effectiveness. The key to optimal management, as we enter the new millennium, lies in the search for new therapies in concert with the most effective use of those agents already at our disposal.

Importance of posterior chest leads in patients with suspected myocardial infarction, but nondiagnostic, routine 12-lead electrocardiogram

Criteria for reperfusion therapy in acute myocardial infarction require the presence of ST elevation in 2 contiguous leads. However, many patients with myocardial infarction do not show these changes on a routine 12-lead electrocardiogram and hence are denied reperfusion therapy. Posterior chest leads (V7 to V9) were recorded in 58 patients with clinically suspected myocardial infarction, but nondiagnostic routine electrocardiogram. ST elevation >0.1 mV or Q waves in > or =2 posterior chest leads were considered to be diagnostic of posterior myocardial infarction. Eighteen patients had these changes of posterior myocardial infarction. All 18 patients were confirmed to have myocardial infarction by creatine phosphokinase criteria or cardiac catheterization. Of the 17 patients who had cardiac catheterization, 16 had left circumflex as the culprit vessel. We conclude that posterior chest leads should be routinely recorded in patients with suspected myocardial infarction and nondiagnostic, routine electrocardiogram. This simple bedside technique may help proper treatment of some of these patients now classified as having unstable angina or non-Q-wave myocardial infarction.

Current issues in reperfusion therapy

With the establishment of thrombosis as the cause of myocardial infarction, the pivotal role of thrombolytics and primary angioplasty has evolved. Large randomized trials with innovative methodologies have examined the role of these reperfusion therapies in the management of acute coronary syndromes. Intravenous thrombolytic therapy decreases mortality in a broad group of patients with acute myocardial infarction. The GUSTO trial established intravenous tissue plasminogen activator (tPA) used in combination with intravenous heparin as the most effective thrombolytic therapy. Importantly, the time to achieve reperfusion is crucial to the mortality benefit observed, and rapid attainment of Thrombolysis in Myocardial Infarction (TIMI) trial grade 3 flow is achieved in only approximately 55% of patients who receive thrombolytics. Reocclusion, cellular damage, and microvascular dysfunction may contribute to less than optimal results. Percutaneous transluminal coronary angioplasty (PTCA) may be the preferred method of acute reperfusion therapy based on higher rates of TIMI grade 3 flow and lower rates of reocclusion and recurrent myocardial infarction. However, marked variation exists in outcomes and utilization rates among individual institutions, and the benefits of PTCA have not been consistently maintained at 6 months. The use of stents and anticoagulants may improve results, and pre-PTCA strategies also are under investigation. Limitations remain in the efficacy of current reperfusion therapies, supporting the search for improved thrombolytic agents, primary angioplasty, stents, and antithrombotics with the goal of improving TIMI 3 flow rates and achieving reperfusion more rapidly.

Heterogeneity of prognosis in patient subsets treated by primary coronary angioplasty during acute myocardial infarction

Among 377 patients consecutively treated with primary coronary angioplasty for acute myocardial infarction, in-hospital mortality was higher in patients ineligible than in patients eligible for thrombolysis (14.4% vs 7.8%, p <0.05). It remained dismal (75.9%) in patients with cardiogenic shock, but was similar in lytic-eligible patients and in those who were ineligible because of an increased bleeding risk (7.8% vs 7.2%, p = NS), and was zero in patients with nondiagnostic electrocardiograms.

Electrocardiographic differentiation of the ST-segment depression of acute myocardial injury due to the left circumflex artery occlusion from that of myocardial ischemia of nonocclusive etiologies

Lead distributions of peak ST-segment depression were compared between patients undergoing left circumflex artery percutaneous transluminal coronary angioplasty and exercise tolerance test. Localization of peak ST-segment depression to leads V2 or V3 was 96% specific and 70% sensitive for differentiating ischemia due to occlusion of left circumflex artery occlusion from nonocclusive ischemia.

Use of the combination of myoglobin and CK-MB mass for the rapid diagnosis of acute myocardial infarction

Early identification of patients presenting with myocardial infarction (MI) is necessary for rapid initiation of treatment. Currently, MI has been diagnosed using the combination of the history, electrocardiogram (ECG), and biochemical markers of myocardial necrosis. Unfortunately, all lack sufficient sensitivity and specificity to confidently identify most patients with MI in a timely enough fashion to influence early intervention. Development of newer immunochemical assays for CK-MB mass and myoglobin have allowed for earlier, more rapid diagnosis; however, each has important limitations. The diagnostic sensitivity of CK-MB mass, myoglobin, and the combination of both were analyzed at the time of presentation (0 hours) and again 4 hours later in 101 patients admitted from the emergency department (ED) with possible MI. Twenty patients were subsequently diagnosed as having MI. The sensitivity of the initial ECG was 60%, compared with the sensitivities of the initial myoglobin and CK-MB mass of 70% and 30%, respectively. By 4 hours the sensitivity of myoglobin had increased to 85% and CK-MB mass to 90%. The combination of the initial myoglobin and CK-MB mass had a sensitivity of 85%. Combining these two markers, using both the initial and 4-hour samples, raised the sensitivity to 100%, with a specificity of 100% and negative predictive value of 100%. When patients with diagnostic ECGs were excluded, the sensitivity of the combination at 0 hours was 80% with a specificity of 84%, while the use of the 0- and 4-hour markers had a sensitivity and specificity of 100% and 100%, respectively. We conclude that the combination of CK-MB mass and myoglobin can rapidly diagnose or exclude MI in as short as 4 hours after ED presentation, and accuracy is not different in patients without diagnostic ECGs. Application of this strategy could potentially lead to more rapid intervention in patients with MI, while also allowing early identification of lower risk patients.

Comprehensive strategy for the evaluation and triage of the chest pain patient

STUDY OBJECTIVE

To evaluate the safety and efficacy of a systematic evaluation and triage strategy including immediate resting myocardial perfusion imaging in patients presenting to the emergency department with chest pain of possible ischemic origin.

METHODS

We conducted an observational study of 1,187 consecutive patients seen in the ED of an urban tertiary care hospital with the chief complaint of chest pain. Within 60 minutes of presentation, each patient was assigned to one of five levels on the basis of his or her risk of myocardial infarction (MI) or unstable angina (UA): level 1, MI; level 2, MI/UA; level 3, probable UA; level 4, possible UA; and level 5, noncardiac chest pain. In the lower risk levels (3 and 4), immediate resting myocardial perfusion imaging was used as a risk-stratification tool alone (level 4) or in combination with serial markers (level 3).

RESULTS

Acute MI, early revascularization indicative of acute coronary syndrome, or both were consistent with risk designations: level 1: 96% MI, 56% revascularization; level 2: 13% MI, 29% revascularization; level 3: 3% MI, 17% revascularization; level 4: .7% MI; 2.5% revascularization. Sensitivity of immediate resting myocardial perfusion imaging for MI was 100% (95% confidence interval [CI], 64% to 100%) and specificity 78% (74% to 82%). In patients with abnormal imaging findings, risk for MI (7% versus 0%, P < .001; relative risk [RR], 50; 95% CI, 2.8 to 889) and for MI or revascularization (32% vs 2%, P < .001; RR, 15.5; 95% CI, 6.4 to 36) were significantly higher than in patients with normal imaging findings. During 1-year follow-up, patients with normal imaging findings (n = 338) had an event rate of 3% (revascularization) with no MI or death (combined events: negative predictive value, 97%; 95% CI, 95% to 98%). Patients with abnormal imaging findings (n = 100) had a 42% event rate (combined events: RR, 14.2; 95% CI, 6.5 to 30; P < .001), with 11% experiencing MI and 8% cardiac death.

CONCLUSION

This strategy is a safe, effective method for rapid triage of chest pain patients. Rapid perfusion imaging plays a key role in the risk stratification of low-risk patients, allowing discrimination of unsuspected high risk patients who require prompt admission and possible intervention from those who are truly at low risk.