Can myocardial infarction be rapidly identified in emergency department patients who have left bundle-branch block?

Terminal T-wave concordance is associated with SYNTAX score among left bundle branch block patients suspected of acute coronary syndrome without modified Sgarbossa criteria

BACKGROUND

Timely and precise diagnosis of ischemic cardiac events based on electrocardiogram is challengeable among patients with Left Bundle Branch Block (LBBB). The present study aimed to assess the correlation between SYNTAX score and terminal T-wave morphologies among LBBB patients suspected of Acute Coronary Syndrome (ACS) without modified Sgarbossa criteria.

METHOD

This cross-sectional study was conducted on the LBBB patients suspected of ACS without modified Sgarbossa criteria. Binary logistic regression was used to assess the correlation of ischemic heart disease (IHD, SYNTAX score > 0) and SYNTAX score categories with terminal T-wave morphologies including T-wave direction in lead V6 and terminal T-wave concordance in leads I, V5, and V6.

RESULT

This study was done on 93 patients with the mean age of 62.4 ± 9.6 years. More than half of the patients were female (58.1%, 95% CI: 47.4% to 68.2%). Among the participants with IHD, the SYNTAX score categories were correlated to discordant terminal T-wave in leads I, V5, and V6 (OR = 5.71, 95% CI: 1.04 to 31.28, p = 0.04).

CONCLUSION

Among the LBBB patients with acute ischemic cardiac events without modified Sgarbossa criteria, those with discordant terminal T-waves in leads I, V5, or V6 had higher SYNTAX scores and might require more invasive coronary revascularization techniques such as Coronary Artery Bypass Graft (CABG) surgery.

Rare and Fascinating Case of ST-Elevation Myocardial Infarction Diagnosis From an Underlying Ventricular Paced Rhythm

This is a case of a patient diagnosed with anterior ST-elevation myocardial infarction (STEMI) with a ventricular paced rhythm after the patient underwent a femoral-femoral bypass surgery for severe peripheral vascular disease. The case highlights the diagnosis of STEMI in the setting of paced rhythm in the appropriate clinical setting.

Assessment of Smith Algorithms for the Diagnosis of Acute Myocardial Infarction in the Presence of Left Bundle Branch Block

INTRODUCTION AND OBJECTIVES

Recently, a new electrocardiography algorithm has shown promising results for the the diagnosis of acute myocardial infarction in the presence of left bundle branch block (LBBB). We aimed to assess these new electrocardiography rules in a cohort of patients referred for primary percutaneous coronary intervention (pPCI).

METHODS

Retrospective observational cohort study that included all patients with suspected myocardial infarction and LBBB on the presenting electrocardiogram, referred for pPCI to 4 tertiary hospitals in Barcelona, Spain.

RESULTS

A total of 145 patients were included. Fifty four (37%) had an ST-segment elevation myocardial infarction (STEMI) equivalent. Among patients with STEMI, 25 (46%) presented in Killip class III or IV, and in-hospital mortality was 15%. Smith I and II rules performed better than Sgarbossa algorithms and showed good specificity (90% and 97%, respectively) but their sensitivity was 67% and 54%, respectively. In a strategy guided by Smith I or Smith II rules, 18 (33%) or 25 (46%) patients with STEMI would have not received a pPCI, respectively. Moreover, the severity and prognosis of STEMI patients was similar regardless of the positivity of Smith rules. Cardiac biomarkers were positive in 54% of non-STEMI patients, limiting their usefulness for initial diagnostic screening.

CONCLUSIONS

Diagnosis of STEMI in the presence of LBBB remains a challenge. Smith rules can be useful but are limited by suboptimal sensitivity. The search for new electrocardiography algorithms should be encouraged to avoid unnecessary aggressive treatments in the majority of patients, while providing timely reperfusion to a high-risk subgroup of patients.

Prehospital diagnosis of patients with acute myocardial infarction

Primary percutaneous intervention (PPCI) is the preferred treatment in patients with ST elevation myocardial infarction (STEMI) if this can be performed in a timely manner. The

Diagnosis of myocardial infarction and ischemia in the setting of bundle branch block and cardiac pacing

The diagnosis of myocardial infarction (MI) in the presence of left bundle branch block (LBBB) or during ventricular pacing (VP) is challenging because of inherent changes in the sequence of ventricular depolarization and repolarization associated with both conditions. Although LBBB and right ventricular (RV) pacing may both produce abnormalities in the ECG, it is often possible to diagnose an acute MI (AMI) or an old MI based on selected morphologic changes. Primary ST-segment changes scoring 3 points or greater according to the Sgarbossa criteria are highly predictive of an AMI in patients with LBBB or RV pacing. The modified Sgarbossa criteria are useful for the diagnosis of AMI in patients with LBBB; however, these criteria have not yet been studied in the setting of RV pacing. Although changes of the QRS complex are not particularly sensitive for the diagnosis of an old MI in the setting of LBBB or RV pacing, the qR complex and Cabrera sign are highly specific for the presence of an old infarct. Diagnosing AMI in the setting of biventricular (BiV) pacing is challenging. To date there is minimal evidence suggesting that the traditional electrocardiographic criteria for diagnosis of AMI in bundle branch block may be applicable to patients with BiV pacing and positive QRS complexes on their ECG in lead V1. This report is a careful review of the electrocardiographic criteria facilitating the diagnosis of acute and remote MI in patients with LBBB and/or VP.

Electrocardiographic Predictors of Cardiovascular Mortality

Cardiovascular diseases are the main causes of mortality. Sudden cardiac death may also appear in athletes, due to underlying congenital or inherited cardiac abnormalities. The electrocardiogram is used in clinical practice and clinical trials, as a valid, reliable, accessible, inexpensive method. The aim of the present paper was to review electrocardiographic (ECG) signs associated with cardiovascular mortality and the mechanisms underlying those associations, providing a brief description of the main studies in this area, and consider their implication for clinical practice in the general population and athletes. The main ECG parameters associated with cardiovascular mortality in the present paper are the P wave (duration, interatrial block, and deep terminal negativity of the P wave in V1), prolonged QT and Tpeak-Tend intervals, QRS duration and fragmentation, bundle branch block, ST segment depression and elevation, T waves (inverted, T wave axes), spatial angles between QRS and T vectors, premature ventricular contractions, and ECG hypertrophy criteria.

Left Bundle Branch Block in Acute Cardiac Events: Insights From a 23-Year Registry

Between 1991 and 2013, we evaluated the demographics, presentations, and final diagnosis of patients hospitalized with acute cardiac events and left bundle branch block (LBBB). Of 50 992 patients, 768 (1.5%) had LBBB. Compared with non-LBBB patients, patients with LBBB were mostly older, female, diabetic, and had hypertension and chronic kidney failure (CKF; P < .001 for all). Dyspnea (P < .001) and dizziness (P = .037) were more frequent in patients with LBBB. The most frequent cause of admission with LBBB was congestive heart failure (CHF; 54.2%), followed by ST-elevation myocardial infarction (STEMI; 13.3%), valvular heart disease (9.4%), unstable angina (8.3%) and Non-STEMI (7.7%). On multivariate analysis, CKF (odds ratio [OR]: 2.02, 95% confidence interval [CI]: 1.09-3.70) and LBBB (OR: 2.96, 95% CI: 2.01-4.42) were predictors of in-hospital mortality in the entire study population. Further analysis of patients with LBBB showed that CKF (OR: 2.93, 95% CI: 1.40-6.12) was the only predictor of in-hospital mortality. Regardless the presenting symptoms, CHF was the final diagnosis in most cases with LBBB.

Left bundle branch block and suspected myocardial infarction: does chronicity of the branch block matter?

BACKGROUND

Our aim was to investigate if patients with suspected myocardial infarction (MI) and a new or presumed new left bundle branch block (nLBBB) were treated according to the ESC reperfusion guidelines and to compare them with patients having a previously known LBBB (oLBBB). Furthermore, we investigated the prevalence of ST-segment concordance in this population.

METHODS

Retrospective data was collected from the Swedeheart registry for patients admitted to the cardiac care unit at Örebro University Hospital with LBBB and suspected MI during 2009 and 2010. The patients were divided in two age groups; <80 or ≥80 years and analysed for LBBB chronicity (nLBBB or oLBBB), MI, and reperfusion treatment. We also compared our data with the national Swedeheart database for 2009.

RESULTS

A total of 99 patients fulfilled the inclusion criteria. A diagnosis of MI was significantly more common in the group ≥80 years compared to the group <80 years (53.8 vs. 25%, p=0.007). The rate of MI was similar in the groups with nLBBB and oLBBB (33 and 37% respectively, p=0.912). Of the 36 patients with a final diagnosis of MI, only eight (22%) had nLBBB. Reperfusion treatment, defined as an acute coronary angiography with or without intervention, was significantly more often performed in patients with nLBBB compared to patients with oLBBB (42 vs. 8%, p<0.001). The rate of MI and reperfusion treatment did not differ between our institution and the Swedish national data. ST-concordance was present in only two cases, one of which did not suffer an MI.

CONCLUSIONS

The proportion of patients receiving reperfusion treatment was low, but higher in nLBBB, reflecting a partial adherence to the guidelines. We found no correlation between LBBB chronicity and MI. Furthermore, only a minority of the MIs occurred in patients with nLBBB. ST-concordance was found in only one of 36 MI cases, indicating lack of sensitivity for this test.

Left bundle branch block without concordant ST changes is rarely associated with acute coronary occlusion

BACKGROUND

The Sgarbossa score has been used to identify acute myocardial infarction on ECG in the presence of LBBB but has relied on elevated CK-MB for validation rather than angiographic evidence of vessel occlusion.

METHODS

We determined (a) the presence or absence of Sgarbossa criteria with concordant (S-con) or discordant (S-dis) ST changes, (b) the presence of acute coronary occlusion or likely recent occlusion on angiography and (c) the biochemical evidence of myocardial infarction (Troponin T >0.10 μg/L, Troponin I >1.0 μg/L) in patients field-triaged with suspected AMI and LBBB.

RESULTS

Between April 2004 and March 2009, 102 patients had field ECGs transmitted by paramedics for triage--8 with S-con, 26 with S-dis and 68 with LBBB alone. Acute coronary occlusion was present in 8/8 with S-con but none of the S-dis or LBBB alone patients, and in all 8 S-con patients reperfusion resulted in resolution of S-con changes. Likely culprit lesions with TIMI 3 flow were found in 3 S-dis patients but stenting did not result in resolution of S-dis. LBBB did not resolve in any patient. Troponin was elevated in 26 patients--11 with occlusion or likely culprit lesions, 15 with non-ischaemic causes.

CONCLUSIONS

In the absence of S-con, LBBB is not associated with acute coronary occlusion and should not be used as criteria for reperfusion therapy in myocardial infarction.

Implications of left bundle branch block in patient treatment

Left bundle branch block (LBBB) causes an abnormal pattern of cardiac activation and affects regional myocardial function. Although recognition of LBBB on the surface electrocardiogram is straightforward, dissecting its effect on patient treatment and outcome can be more challenging. The altered pattern of cardiac activation in LBBB causes electrical and mechanical ventricular dyssynchrony, influences ischemia detection on the surface electrocardiogram, and affects stress testing and imaging modalities dependent on wall motion and thickening. Restoration of synchrony by biventricular pacing can improve symptoms and longevity in carefully selected patients. The diagnostic, prognostic, and therapeutic implications of LBBB across this spectrum are discussed in this review.

Evolving considerations in the management of patients with left bundle branch block and suspected myocardial infarction

Patients with a suspected acute coronary syndrome and left bundle branch block (LBBB) present a unique diagnostic and therapeutic challenge to the clinician. Although current guidelines recommend that patients with new or presumed new LBBB undergo early reperfusion therapy, data suggest that only a minority of patients with LBBB are ultimately diagnosed with acute myocardial infarction, regardless of LBBB chronicity, and that a significant proportion of patients will not have an occluded culprit artery at cardiac catheterization. The current treatment approach exposes a significant proportion of patients to the risks of fibrinolytic therapy without the likelihood of significant benefit and leads to increased rates of false-positive cardiac catheterization laboratory activation, unnecessary risks, and costs. Therefore, alternative strategies to those for patients with ST-segment elevation myocardial infarction are needed to guide selection of appropriate patients with a suspected acute coronary syndrome and LBBB for urgent reperfusion therapy. In this article, we describe the evolving epidemiology of LBBB in acute coronary syndromes and discuss controversies related to current clinical practice. We propose a more judicious diagnostic approach among clinically stable patients with LBBB who do not have electrocardiographic findings highly specific for ST-segment elevation myocardial infarction.

Prevalence of acute myocardial infarction in patients with presumably new left bundle-branch block

OBJECTIVES

We assessed the prevalence of true acute myocardial infarction and the need for emergent revascularization among patients with new or presumably new left bundle branch block (nLBBB) for whom the primary percutaneous coronary intervention protocol was activated.

METHODS AND RESULTS

Among 802 patients, 69 (8.6%) had nLBBB. The chief presenting symptom was chest pain or cardiac arrest in 36 patients (52.2%) and shortness of breath in 15 (21.7%). Less than 30% of the patients had elevated cardiac troponin-I, and less than 10% had elevated creatine kinase-MB. Only 11.6% of the patients underwent emergent revascularization; the rate was higher for patients who presented with chest pain or cardiac arrest or shortness of breath than for patients who presented with other symptoms.

CONCLUSIONS

Acute myocardial infarction and the need for emergent revascularization are relatively uncommon among patients who present with nLBBB, especially when symptoms are atypical. Current guidelines for primary percutaneous coronary intervention protocol activation for nLBBB should be reconsidered.

Diagnosing acute myocardial infarction in patients with left bundle branch block

We compared the clinical features, laboratory and coronary angiographic findings, treatments, and outcomes among patients with ST-segment elevation myocardial infarction (MI) with and without left bundle branch block (LBBB). We examined 5,742 patients with ST-segment elevation MI with and without LBBB treated with primary percutaneous coronary intervention in the Assessment of Pexelizumab in Acute Myocardial Infarction trial. The main outcome measures were obstructive coronary disease, MI, positive cardiac biomarkers, angiographic Thrombolysis In Myocardial Infarction flow, and death, MI, or congestive heart failure at 90 days. LBBB was present in 98 patients (1.7%). According to the protocol, patients with LBBB were eligible only if they had ≥1 mm concordant ST-segment elevation. Obstructive coronary artery disease was present in >87% of the patients with LBBB. Documented MI (elevated biomarkers) with an initially occluded infarct artery was more common in patients with LBBB with concordant ST-segment elevation (71.4%) than in patients without (44.1%; p = 0.027). The use of ST-segment elevation concordance criteria in the presence of LBBB was more often associated with documented MI with an identifiable culprit vessel with an initially occluded infarct-related artery. In conclusion, because a substantial proportion of patients with LBBB have acute MI with a culprit lesion and positive biomarkers, these data support immediate catheterization with the intent for primary percutaneous coronary intervention for all patients presenting with suspected ST-segment elevation myocardial infarction, ischemic symptoms, and presumed new LBBB, particularly if concordant ST-segment elevation is present.

Outcomes in patients with chronicity of left bundle-branch block with possible acute myocardial infarction

INTRODUCTION

Guidelines derived from patients in clinical trials indicate that emergency department patients with likely myocardial infarction (MI) who have new left bundle-branch block (LBBB) should undergo rapid reperfusion therapy. Whether this pertains to lower risk emergency department patients with LBBB is unclear.

METHODS

A total of 401 consecutive patients with LBBB undergoing an MI rule-out protocol were included. Left bundle-branch blocks were classified as chronic; new; or, if no prior electrocardiogram (ECG) was available, as presumably new. Left bundle-branch blocks were considered concordant if there was ≥1 mm concordant ST elevation or depression. Rates of MI, peak MB values in MI patients, and 30-day mortality were compared across groups.

RESULTS

A majority of patients (64%) had new (37%) or presumably new LBBB (27%). A total of 116 patients (29%) had MI, with no significant difference in prevalence or size of MI among the 3 ECG groups. Myocardial infarction was diagnosed in 86% of patients with concordant ECG changes versus 27% of patients without concordant ECG changes (P < .01). Peak MB was >5× normal in 50% who had concordant ST changes compared to none of those who did not. Concordant ST changes were the most important predictor of MI (odds ratio 17, 95% CI 3.4-81, P < .001) and an independent predictor of mortality (odds ratio 4.3, 95% CI 1.3-15, P < .001); new or presumably new LBBB was neither.

CONCLUSIONS

Most patients with possible MI with new or presumably new LBBB do not have MI. Concordant ECG changes were an important predictor of MI and death. Current guidelines regarding early reperfusion therapy for patients with LBBB should be reconsidered.

Hypertrophies and intraventricular conduction defects: causes, presentation, and significance

There is an increasing need for nurses to interpret a 12-lead electrocardiogram, both in critical care units and in other areas. This can be a challenging task, especially in the presence of hypertrophies, bundle-branch blocks, and fascicular blocks. This article reviews the pathophysiology of intraventricular blocks and hypertrophy, characteristics found in the 12-lead electrocardiogram, and discusses what the significance of these findings may be.

Appropriate cardiac cath lab activation: optimizing electrocardiogram interpretation and clinical decision-making for acute ST-elevation myocardial infarction

During the last few decades, acute ST-elevation on an electrocardiogram (ECG) in the proper clinical context has been a reliable surrogate marker of acute coronary occlusion requiring primary percutaneous coronary intervention (PPCI). In 2004, the American College of Cardiology/American Heart Association ST-elevation myocardial infarction (STEMI) guidelines specified ECG criteria that warrant immediate angiography in patients who are candidates for primary PPCI, but new findings have emerged that suggest a reappraisal is warranted. Furthermore, as part of integrated and efficient STEMI systems, emergency department and emergency medical services providers are now encouraged to routinely make the time-sensitive diagnosis of STEMI and promptly activate the cardiac catheterization laboratory (Cath Lab) team. Our primary objective is to provide a practical summary of updated ECG criteria for emergency coronary angiography with planned PPCI, thus allowing clinicians to maximize the rate of appropriate Cath Lab activation and minimize the rate of inappropriate Cath Lab activation. We review the evidence for ECG interpretation strategies that either increase diagnostic specificity for "classic" STEMI and left bundle-branch block or improve diagnostic sensitivity in identifying 4 STEMI-equivalents: posterior MI, acute left main occlusion, de Winter ST/T-wave complex, and certain scenarios of resuscitated cardiac arrest.

Acute coronary syndromes focusing on left bundle branch block

There has been extensive coverage of acute myocardial infarction (AMI) and the acute coronary syndromes (ACS) in recent years, yet heart blocks involving the right and left bundle branches have received little coverage, despite their frequent co-existence. This article will commence with an overview of the ACS with which LBBB is synonymous, discussion on the initial management of these patients, and progress into highlighting both the clinical signs and symptoms related to the pathophysiological changes associated with blocks involving the bundle branches, and the associated electrical changes that can be identified on an electrocardiogram (ECG). The overall intension of this article is to increase practitioners' awareness and knowledge base surrounding this common clinical patient presentation and enhance clinical proficiency, thereby improving patient care and the management of patient's experiencing LBBB.

Using the 12-lead ECG to diagnose acute myocardial infarction in the presence of left bundle branch block

The 12-lead ECG is a powerful clinical tool used to risk stratify patients presenting to the emergency department with chest pain. In particular the ECG is used as the diagnostic tool to instigate reperfusion therapy in patients with acute coronary syndromes. The ECG features of acute myocardial infarction (AMI) may be masked by the presence of left bundle branch block (LBBB) and the ECG may be difficult to interpret. Invariably this results in delays to the provision of thrombolysis to these patients despite the mounting body of evidence which demonstrates that patients with AMI who present with LBBB have greater in-hospital mortality than those who do not. Difficulties in interpreting the ECG in these patients can therefore delay treatment and compromise their prognosis. The utility of the ECG for the diagnosis of AMI in the presence of LBBB has recently received renewed attention. ECG criteria have been identified which have a high association with AMI in patients with LBBB and two ECG tools have been evaluated in clinical practice which utilise these ECG criteria. The use of these simple algorithmic tools is recommended for clinical practice.

Electrocardiographic Diagnosis of Myocardial Infarction during Left Bundle Branch Block

The electrocardiographic diagnosis of myocardial infarction (MI) in the presence of left bundle branch block (LBBB) has long been considered problematic or even almost impossible. Many proposed ECG markers in the old literature have now been discarded. However, the advent of reperfusion therapy has generated greater interest in the ECG diagnosis of acute MI in LBBB where ST-segment deviation is the only useful sign. As such, the ST-segment criteria cannot be used to rule out MI, but they can help to rule it in. Criteria for old MI (based on QRS changes) have not been reevaluated for almost 20 years and continue to exhibit low sensitivity, but high specificity.

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.

Intraventricular conduction abnormalities

There are multiple types of intraventricular conduction abnormalities, each with its own unique clinical significance. It is useful to categorize conduction abnormalities, or blocks, by the number of fascicles involved. This article reviews intraventricular conduction abnormalities.

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.

Unraveling the spectrum of left bundle branch block in acute myocardial infarction: insights from the Assessment of the Safety and Efficacy of a New Thrombolytic (ASSENT 2 and 3) trials

BACKGROUND

Left bundle branch block (LBBB) complicates the diagnosis of acute myocardial infarction (AMI). The Sgarbossa criteria were developed from GUSTO I to surmount this diagnostic challenge but have not been prospectively validated in a large population with presumed AMI. We evaluated their utility in the diagnosis and risk stratification of AMI patients in ASSENT 2 & 3.

METHODS

Baseline electrocardiograms (ECG) of LBBB patients were scored using Sgarbossa's criteria (0-10) by 2 readers blinded to the CK/CK-MB data and clinical outcomes; 267 (1.2%) patients had LBBB on their baseline ECG.

RESULTS

Among 253 LBBB patients with available peak CK/CK-MB data, 158 (62.5%) had peak CK/CK-MB levels > 2x ULN, thereby qualifying for the diagnosis of AMI. A Sgarbossa score of 3 was shown in 48.7% of LBBB patients with elevated CK/CK-MB versus in 12.6% of those without a CK/CK-MB rise (P < .001). Patients with higher Sgarbossa scores, ie, 3, had a higher mortality compared with those with a score < 3, (23.5% vs 7.7% at 30 days P < .001; and 33.7% vs 20.2% at 1 year, P < .001, respectively).

CONCLUSIONS

Our findings validate the utility of Sgarbossa criteria for diagnosing AMI in the setting of LBBB. These criteria provide a simple and practical diagnostic approach to risk stratify this diagnostically challenging high-risk group and optimize risk-benefit of acute therapy.

Prognostic differences between different types of bundle branch block during the early phase of acute myocardial infarction: insights from the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial

AIMS

Bundle branch block (BBB) early during acute myocardial infarction (AMI) is often considered high risk for mortality. Little is known about how different BBB types influence prognosis.

METHODS AND RESULTS

The HERO-2 trial recruited 17 073 patients with ischaemic symptoms lasting >30 min and either ST elevation with or without right bundle branch block (RBBB) or presumed-new left bundle branch block (LBBB). Electrocardiograms were performed before and 60 min after the start of fibrinolytic therapy. Using patients with normal intraventricular conduction as a reference, odds ratios (ORs) for 30-day mortality were calculated for different BBB types (LBBB, RBBB with anterior AMI, and RBBB with inferior AMI) present at randomization and/or 60 min, with adjustment for recruitment region, pre-infarction characteristics, time to randomization, hemodynamics, and Killip class. At randomization, the 873 patients (5.11%) with BBB had worse baseline characteristics than patients without BBB. In patients presenting with LBBB (n=300), the ORs for 30-day mortality were 1.90 (95% CI 1.39-2.59) before and 0.68 (0.48-0.99) after adjustment for other prognosticators. In patients presenting with RBBB (n=415) and anterior AMI, the ORs were 3.52 (2.82-4.38) before and 2.48 (1.93-3.19) after adjustment. In patients presenting with RBBB and inferior AMI (n=158), the ORs were 1.74 (1.06-2.86) before and 1.22 (0.71-2.08) after adjustment. Within 60 min, 143 patients (0.92%) developed new BBB. The adjusted ORs for 30-day mortality were 2.97 (1.16-7.57) in the 25 patients with new LBBB, 3.84 (2.38-6.22) in the 100 with new RBBB and anterior AMI, and 2.23 (0.54-9.21) in the 18 with new RBBB and inferior AMI.

CONCLUSION

RBBB accompanying anterior AMI at presentation and new BBB (including LBBB) early after fibrinolytic therapy are independent predictors of high 30-day mortality. These electrocardiographic features should be considered in risk stratification to identify high-risk patients.

ECG Patterns Confounding the ECG Diagnosis of Acute Coronary Syndrome: Left Bundle Branch Block, Right Ventricular Paced Rhythms, and Left Ventricular Hypertrophy

The ECG has limitations in the evaluation of the chest-pain patient, including the presence of confounding ECG patterns; the ECG patterns that confound the diagnosis of acute myocardial infarction(AMI) include left bundle branch block (LBBB), ventricular paced rhythms (VPR), and left ventricular hypertrophy (LVH). These patterns produce new ST-segment/T-wave abnormalities, which are the new normal findings in these patients and may lead the clinician astray in two distinct instances: (1) diagnosing ECG change related to acute coronary syndromes (ACS) when the abnormality results solely from the confounding pattern; and (2) not acknowledging the confounding nature of these ECG patterns in the evaluation of potential ACS, thereby placing excessive diagnostic confidence in the ECG. This article highlights the diagnostic dilemma encountered in these confounding ECG patterns; the discussion focuses on the expected ECG abnormalities in these patients and the findings seen in ACS.

Simplifying thrombolysis decisions in patients with left bundle branch block

OBJECTIVES

To redesign and simplify an existing decision algorithm for the management of patients who present to the emergency department with chest pain and left bundle branch block (LBBB) based on the Sgarbossa criteria. To compare its reliability with the current algorithm.

METHODS

A simplified algorithm was created and tested against the existing algorithm. Electrocardiograms (ECGs) of patients with LBBB were presented to 10 emergency department doctors with both old and new algorithms a week apart. Six ECGs displayed the relevant criteria for thrombolysis and had proven acute myocardial infarction (AMI) based on a gold standard of enzyme measurements. Subjects were asked whether or not they would thrombolyse a patient presenting with the given ECG using each of the algorithms as a guide.

RESULTS

The new algorithm has demonstrated improvements in terms of an increase in appropriate thrombolysis and a reduction in inappropriate thrombolysis. Specificity for AMI rose from 0.85 to 0.99 and sensitivity from 0.38 to 0.6. kappa score showed greater agreement with the gold standard.

CONCLUSION

Patients with AMI and LBBB have a significantly poorer outcome than those without LBBB. Despite this, thrombolysis is less likely to be given to patients with AMI and LBBB. This study demonstrates that in part this is because of cognitive difficulties using the current algorithm. The proposed proforma addresses these issues and provides a simple tool to aid appropriate treatment in this group of patients.

Patients With Prolonged Ischemic Chest Pain and Presumed-New Left Bundle Branch Block Have Heterogeneous Outcomes Depending on the Presence of ST-Segment Changes

OBJECTIVES

The purpose of this research was to examine the prognostic value of ST-segment changes (concordant ST-segment elevation and/or precordial V1 to V3 ST-segment depression) during presumed-new left bundle branch block (LBBB) in patients receiving fibrinolytic therapy.

BACKGROUND

These patients are often considered high-risk, but their outcome is not well-defined.

METHODS

The Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial compared bivalirudin with heparin in patients receiving streptokinase for ST-segment elevation or presumed-new LBBB. Each patient with LBBB was matched with a control (with normal intraventricular conduction) for age, gender, pulse rate, systolic blood pressure, Killip class, and region.

RESULTS

A total of 300 patients had LBBB (92 with and 208 without ST-segment changes) and 15,340 had normal conduction. Acute myocardial infarction (AMI) occurred in 80.7% of LBBB patients and 88.7% of controls (p = 0.006). ST-segment changes were specific (96.6%) but not sensitive (37.8%) for enzymatic diagnosis of AMI. Mortality at 30 days was similar in LBBB patients with ST-segment changes (21.7%) and controls (25.0%, p = 0.563), but lower in LBBB patients without ST-segment changes than in controls (13.5% vs. 21.6%, p = 0.022). In the whole HERO-2 cohort, the LBBB patients with ST-segment changes had higher mortality than patients with normal conduction (odds ratio [OR] 1.37, 95% confidence interval [CI] 0.78 to 2.42). The LBBB patients without ST-segment changes had lower mortality than patients with normal conduction (OR 0.52, 95% CI 0.33 to 0.80).

CONCLUSIONS

ST-segment changes during LBBB are specific for the diagnosis of AMI and predict 30-day mortality; LBBB patients without ST-segment changes have lower adjusted 30-day mortality than those with normal conduction. Trials are required to determine the best treatment for high-risk and low-risk patients with LBBB.

Role of "Ischemia modified albumin", a new biochemical marker of myocardial ischaemia, in the early diagnosis of acute coronary syndromes

BACKGROUND

Diagnosis of cardiac ischaemia in patients attending emergency departments (ED) with symptoms of acute coronary syndromes is often difficult. Cardiac troponin (cTn) is sensitive and specific for the detection of myocardial damage but may not rise during reversible myocardial ischaemia. Ischemia Modified Albumin (IMA) has recently been shown to be a sensitive and early biochemical marker of ischaemia.

METHODS AND RESULTS

This study evaluated IMA in conjunction with ECG and cTn in 208 patients presenting to the ED within three hours of acute chest pain. At presentation, a 12-lead ECG was recorded and blood taken for IMA and cardiac troponin T (cTnT). Patients underwent standardised triage, diagnostic procedures, and treatment. Results of IMA, ECG, and cTnT, alone and in combination, were correlated with final diagnoses of non-ischaemic chest pain, unstable angina, ST segment elevation, and non-ST segment elevation myocardial infarction. In the whole patient group, sensitivity of IMA at presentation for an ischaemic origin of chest pain was 82%, compared with 45% of ECG and 20% of cTnT. IMA used together with cTnT or ECG, had a sensitivity of 90% and 92%, respectively. All three tests combined identified 95% of patients whose chest pain was attributable to ischaemic heart disease. In patients with unstable angina, sensitivity of IMA used alone was equivalent to that of IMA and ECG combined.

CONCLUSIONS

IMA is highly sensitive for the diagnosis of myocardial ischaemia in patients presenting with symptoms of acute chest pain.

A case of acute pancreatitis presenting with electrocardiographic signs of acute myocardial infarction

A 71-year-old man presented with left upper quadrant abdominal pain. Serial electrocardiograms (ECGs) demonstrated an evolving left bundle branch block, a sign of acute myocardial infarction (AMI). However, a coronary angiogram demonstrated minimal coronary artery disease, and serum troponin T was undetectable in serial serum measurements. Later, serum pancreatic enzyme levels were elevated and a computed tomography scan of the abdomen was consistent with pancreatitis. In patients presenting with acute pancreatitis and ECG changes suggesting AMI, measurement of serum troponin T concentrations can aid in differentiating ECG changes driven by acute pancreatitis from those of true myocardial ischemia or infarction.

Diagnosing acute myocardial infarction in the setting of left bundle branch block: prevalence and observer variability from a large community study

BACKGROUND

Despite the known benefit of thrombolysis it remains under-utilized among eligible patients with acute myocardial infarction (AMI) and left bundle branch block (LBBB). We sought to determine the test characteristics and observer reliability of well-known criteria for the diagnosis of AMI when LBBB is present on the electrocardiogram (ECG).

METHODS

Four hundred and fourteen ECGs with LBBB from a large cohort of AMI patients (7.4% of the total) and 85 ECGs with LBBB not in the setting of acute coronary syndromes were interpreted for the presence of the Sgarbossa criteria.

RESULTS

Agreement for the various Sgarbossa criteria ranged from only fair to moderate. The three-way comparison kappa values were significantly better for ST depression than for both discordant (P<0.001) and concordant (P=0.001) ST-segment elevation. Concordant ST-segment elevation [6.3%, 95% confidence interval (CI) 4.3-9.1%] and depression (3.1%, 95% CI 1.8-5.4%) were infrequently seen in the setting of AMI and rarely seen otherwise. Discordant ST-segment elevation was seen more frequently (19.0%, 95% CI 15.5-23.1%). Concordant ST elevation and ST depression in V1-V3 were highly specific, but insensitive, for the diagnosis of AMI. The presence of discordant ST elevation was neither sensitive nor specific.

CONCLUSION

The low prevalence, poor sensitivity and marked observer variability make the Sgarbossa criteria for AMI in the setting of LBBB less than adequate. Although use of these criteria would be an advance over contemporary practice, it would still fall short among this high-risk subset.

Cardiac memory-persistent T wave changes after ventricular pacing

Cardiac memory is an uncommonly recognized entity in which T wave inversions on electrocardiogram (EKG) appear consistent with ischemia. Persistent deep T wave inversions are seen after return of normal depolarization in leads where the T waves were normal before pacing. These changes are generally recognized to occur in association with artificial pacemakers but may occur with other entities with intrinsic ventricular ectopic focus of depolarization, such as intermittent left bundle branch block. Although consideration of ischemia should be given priority, awareness of the benign nature of cardiac memory may allow some patients to avoid unnecessary work-up and admission. Sometimes the diagnosis cannot be confirmed definitively in the Emergency Department (ED) because many patients who have pacemakers also have coronary artery disease and only after a negative work-up for ischemia can one retrospectively presume cardiac memory as the likely etiology.