Should the electrocardiogram be used to guide therapy for patients with left bundle-branch block and suspected myocardial infarction?

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.

[High-risk electrocardiographic patterns in Patients with acute coronary syndrome]

Acute myocardial infarction is the leading cause of death in the world and the electrocardiogram remains the diagnostic tool for determining an acute myocardial infarction with ST-segment elevation. In spite of this, only half of the patients present classic electrocardiogram findings compatible with the ST-elevation infarction criteria. There is a spectrum of electrocardiographic findings that may reflect a phenomenon of acute coronary occlusion, which should be promptly recognized by the clinician to offer early reperfusion therapy.

Challenges and Controversies in the Management of ACS in Elderly Patients

PURPOSE OF REVIEW

Elderly patients presenting with acute coronary syndrome (ACS) represent a challenging patient population. A high index of suspicion is needed for their diagnosis, as they are less likely to present with typical anginal symptoms compared to their younger counterparts.

RECENT FINDINGS

Disrupted coronary plaques with superimposed thrombosis are the predominant pathophysiology of ACS; however, an increased proportion of calcified nodules is encountered in elderly patients. Emergent reperfusion and revascularization remain the mainstay treatment for ST-elevation myocardial infarction or cardiogenic shock. In elderly patients with NSTE-ACS, a routine invasive strategy is generally superior to an ischemia-guided strategy, and the safety of an early invasive strategy has also been recently demonstrated. When treating elderly ACS patients with antiplatelet and antithrombotic therapies, close attention to co-morbidities, frailty and the balance of ischemia-bleeding risk should be undertaken, and medication doses should be carefully adjusted. Overall, elderly patients with ACS remain undertreated with evidence-based therapies, experience worse outcomes, and represent an opportunity for enhancing and mitigating healthcare disparities.

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.

Acute myocardial infarction in the setting of left bundle branch block: Chapman's sign

Acute myocardial infarction (AMI) diagnosis in patients with pre-existing left bundle branch block (LBBB) can be difficult. Undiagnosed or delayed diagnosis of AMI in these patients can put them at risk of having shock, mechanical complications, and death. We present a case of 77-year-old Caucasian male with a known LBBB and coronary artery bypass surgery for coronary artery disease who presented to the emergency department with a chief complaint of chest pain and shortness of breath. The patient had recurrent chest pain despite using aspirin, nitroglycerine, and morphine. An electrocardiogram (ECG) showed a new notch in the upslope of the R wave in leads I, AVL that indicated a positive Chapman's sign. Troponin levels were initially normal, but serial troponin showed elevated enzyme giving evidence of acute coronary syndrome (ACS). The patient was started on heparin drip and underwent subsequent coronary catheterization. Physicians should be aware of Chapman's sign on ECG in patients presenting with chest pain who have baseline LBBB as it might represent myocardial ischemia and warrant emergent treatment for ACS.

ST-segment elevation myocardial infarction

ST-segment elevation myocardial infarction (STEMI) is the most acute manifestation of coronary artery disease and is associated with great morbidity and mortality. A complete thrombotic occlusion developing from an atherosclerotic plaque in an epicardial coronary vessel is the cause of STEMI in the majority of cases. Early diagnosis and immediate reperfusion are the most effective ways to limit myocardial ischaemia and infarct size and thereby reduce the risk of post-STEMI complications and heart failure. Primary percutaneous coronary intervention (PCI) has become the preferred reperfusion strategy in patients with STEMI; if PCI cannot be performed within 120 minutes of STEMI diagnosis, fibrinolysis therapy should be administered to dissolve the occluding thrombus. The initiation of networks to provide around-the-clock cardiac catheterization availability and the generation of standard operating procedures within hospital systems have helped to reduce the time to reperfusion therapy. Together with new advances in antithrombotic therapy and preventive measures, these developments have resulted in a decrease in mortality from STEMI. However, a substantial amount of patients still experience recurrent cardiovascular events after STEMI. New insights have been gained regarding the pathophysiology of STEMI and feed into the development of new treatment strategies.

Influence of Left Bundle Branch Block on the Electrocardiographic Changes Induced by Acute Coronary Artery Occlusion of Distinct Location and Duration

Background: Electrocardiographic (ECG) diagnosis of acute myocardial ischemia is hampered in the presence of left bundle branch block (LBBB).

Objectives: We analyzed the influence of location and duration of myocardial ischemia on the ECG changes in pigs with LBBB.

Methods: LBBB was acutely induced in 14 closed chest anesthetized pigs by local electrical ablation. Thereafter, episodes of 5 min catheter balloon occlusion followed by 10 min reperfusion of the left anterior descending (LAD), left circumflex (LCX), and right (RCA) coronary arteries were done sequentially in 5 pigs. Additionally, a 3-h occlusion of these arteries was performed separately in the other 9 pigs. A 15-lead ECG including leads V7 to V9 was continuously recorded.

Results: Ablation induced LBBB showed QRS widening, loss of r wave in V1, and predominant R waves in V2 to V9. After 5 min of ischemia the occluded artery could be identified in all cases: the LAD by R waves and ST elevation in V1–V3; the LCX by both ST segment elevation in II, III, aVF, V7 to V9 and ST segment depression in V1 to V4; and the RCA by ST depression and new S-waves in all precordial leads. Three hours after coronary occlusion, ST segment changes declined progressively and only the LAD occlusion could be reliably recognized.

Conclusion: LBBB did not mask the ECG recognition of the occluded coronary artery during the first 60 min of ischemia, but 3 h later only the LAD occlusion could be reliably identified. ST elevation in leads V7 to V9 is specific of LCX occlusion and it could be useful in the diagnosis of acute myocardial ischemia in the presence of LBBB.

State-of-the-art diagnosis of myocardial infarction

The current version of the Universal Definition of Myocardial Infarction (MI) was published in 2012. An acute myocardial infarction (AMI) is characterized by evidence of myocardial necrosis in a clinical setting of acute myocardial ischemia. Diagnostic criteria include a rise and/or fall of serially tested cardiac biomarkers (preferentially cardiac troponins) with at least one value above the 99th percentile of the upper reference limit combined with symptoms of ischemia, new changes on electrocardiogram (ECG), imaging evidence of a new loss of viable myocardium or new regional wall motion abnormalities or the identification of an intracoronary thrombus by angiography or autopsy. Compared to previous versions, the current definition of MI includes minor modifications regarding ECG criteria and subtypes of MI as well as the use of cardiac imaging and high sensitivity troponin assays. This article summarizes the Universal MI definition and includes recommendations from the current guidelines for the management of patients with acute coronary syndrome. Strategies for "early rule-in" and "rule-out" of non-ST-elevation MI with high sensitivity cardiac troponin assays, risk scores for assessment of ischemic and bleeding risk and criteria for optimal timing of angiography are presented.

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.

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.

[Preclinical fibrinolysis in patients with ST-segment elevation myocardial infarction in a rural region]

BACKGROUND

In the current guidelines for the treatment of patients with ST-segment elevation myocardial infarction (STEMI), the European Society of Cardiology (ESC) recommends preclinical fibrinolysis as a reperfusion therapy if, due to long transportation times, no cardiac catheterisation is available within 90-120 min. However, there is little remaining in-depth expertise in this method because fibrinolysis is presently only rarely indicated.

METHODS

In a rural area in southwestern Germany, where an emergency primary percutaneous coronary intervention was not routinely available within 90-120 min, 156 STEMI patients underwent fibrinolysis with the plasminogen activator reteplase, performed by trained emergency physicians. The practicality of the treatment, as well as complications and the mortality of the patients in the preclinical phase until arrival at the hospital, were retrospectively studied.

RESULTS

The mean time from onset of the symptoms to first medical contact was 114 ± 116 min. The mean interval to the start of fibrinolysis of 13.5 ± 6.4 min was within the 30 min mandated by the ESC. Patients with inferior STEMI represented the largest subgroup. Occurring in 39 cases (25 %), complications due to infarction were relatively common during the prehospital phase, including 15 cases (9.6 %) of cardiogenic shock, but in all cases the complications were manageable. No patient died before arrival at the hospital. As lysis-associated adverse effects, merely two uncomplicated mucosal haemorrhages and one case of mild allergic skin reactions were seen.

CONCLUSION

In emergency situations with long transportation times to the nearest suitable cardiac catheterisation laboratory, preclinical fibrinolysis in STEMI still represents a workable method. Success of this strategy requires particularly strong training of the emergency physicians in ECG and lysis therapy, and co-operation with nearby cardiac centres.

Troponin I Assay for Identification of a Significant Coronary Stenosis in Patients with Suspected Acute Myocardial Infarction and Wide QRS Complex

Background

Common ECG criteria such as ST-segment changes are of limited value in patients with suspected acute myocardial infarction (AMI) and bundle branch block or wide QRS complex. A large proportion of these patients do not suffer from an AMI, whereas those with ST-elevation myocardial infarction (STEMI) equivalent AMI benefit from an aggressive treatment. Aim of the present study was to evaluate the diagnostic information of cardiac troponin I (cTnI) in hemodynamically stable patients with wide QRS complex and suspected AMI.

Methods

In 417 out of 1818 patients presenting consecutively between 01/2007 and 12/2008 in a prospective multicenter observational study with suspected AMI a prolonged QRS duration was observed. Of these, n = 117 showed significant obstructive coronary artery disease (CAD) used as diagnostic outcome variable. cTnI was determined at admission.

Results

Patients with significant CAD had higher cTnI levels compared to individuals without (median 250ng/L vs. 11ng/L; p<0.01). To identify patients needing a coronary intervention, cTnI yielded an area under the receiver operator characteristics curve of 0.849. Optimized cut-offs with respect to a sensitivity driven rule-out and specificity driven rule-in strategy were established (40ng/L/96ng/L). Application of the specificity optimized cut-off value led to a positive predictive value of 71% compared to 59% if using the 99^th percentile cut-off. The sensitivity optimized cut-off value was associated with a negative predictive value of 93% compared to 89% provided by application of the 99^th percentile threshold.

Conclusion

cTnI determined in hemodynamically stable patients with suspected AMI and wide QRS complex using optimized diagnostic thresholds improves rule-in and rule-out with respect to presence of a significant obstructive CAD.

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.

Mortality in patients with ST-segment elevation myocardial infarction who do not undergo reperfusion

Reperfusion therapy reduces mortality in patients presenting with ST-segment elevation myocardial infarctions (STEMI). However, some patients may not receive thrombolytic therapy or undergo primary percutaneous coronary intervention. The decision making and clinical outcomes of these patients have not been well described. In this study, 139 patients were identified from a total of 1,126 patients with STEMI who did not undergo reperfusion therapy at a high-volume percutaneous coronary intervention center from October 2006 to March 2011. Clinical data, reasons for no reperfusion, management, and mortality were obtained by chart review. The mean age was 80 ± 13 years (61% women, 31% diabetic, and 37% known coronary artery disease). Of the 139 patients, 72 (52%) presented with primary diagnoses other than STEMI, and 39 (28%) developed STEMI >24 hours after admission. The most common reasons for no reperfusion were advanced age, co-morbid conditions, acute or chronic kidney injury, delayed presentation, advance directives precluding reperfusion, patient preference, and dementia. Eighty-four patients (60%) had ≥ 3 reasons for no reperfusion. Factors associated with hospital mortality were cardiogenic shock, intubation, and advance directives prohibiting reperfusion after physician consultation. In hospital and 1-year mortality were 53% and 69%, respectively. In conclusion, at a high-volume percutaneous coronary intervention center, most patients presenting with STEMI underwent immediate catheterization. The decision for no reperfusion was multifactorial, with advanced age reported as the most common factor. Outcomes were poor in this population, and fewer than half of these patients survived to hospital discharge.

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.

Underuse of thrombolytic therapy in acute myocardial infarction and left bundle branch block

Thrombolytic therapy reduces mortality in patients with acute myocardial infarction (AMI) and left bundle branch block (LBBB). The difficulty in accurately diagnosing AMI in patients with LBBB, however, might result in their undertreatment. Among 3,890 patients hospitalized with chest pain, 241 (6.2%) had LBBB at presentation. The only variable independently associated with AMI among patients with LBBB was in-hospital left ventricular failure (odds ratio [OR]: 4.32, 95% confidence interval [CI]: 1.95-9.57, p < 0.0005). Only 16 (29%) of the LBBB patients with AMI received thrombolytic therapy compared with 583 (78%) of the 747 patients with ST-elevation AMI (p < 0.0005). A further 19 (10%) LBBB patients without AMI also received thrombolysis. Difficulty in making an accurate early diagnosis in patients with LBBB ensures that the majority of those with AMI fail to receive thrombolytic therapy while others without AMI are treated inappropriately. Improved diagnostic and therapeutic strategies are needed for patients with acute coronary syndromes and LBBB.

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.

Acute reperfusion therapy in ST-elevation myocardial infarction from 1994-2003

BACKGROUND

Appropriate utilization of acute reperfusion therapy is not a national performance measure for ST-elevation myocardial infarction at this time, and the extent of its contemporary use among ideal patients is unknown.

METHODS

From the National Registry of Myocardial Infarction, we identified 238,291 patients enrolled from June 1994 to May 2003 who were ideally suited for acute reperfusion therapy with fibrinolytic therapy or primary percutaneous coronary intervention. We determined rates of not receiving therapy across 3 time periods (June 1994-May 1997, June 1997-May 2000, June 2000-May 2003) and evaluated factors associated with underutilization.

RESULTS

The proportion of ideal patients not receiving acute reperfusion therapy decreased by one half throughout the past decade (time period 1: 20.6%; time period 2: 11.4%; time period 3: 11.6%; P <.001). Utilization remained significantly lower in key subgroups in the most recent time period: those without chest pain (odds ratio [OR] 0.29; 95% confidence interval [CI], 0.27-0.32); those presenting 6 to 12 hours after symptom onset (OR 0.57; 95% CI, 0.52-0.61); those 75 years or older (OR 0.63 compared with patients <55 years old; 95% CI, 0.58-0.68); women (OR 0.88; 95% CI, 0.84-0.93); and non-whites (OR 0.90; 95% CI, 0.83-0.97).

CONCLUSIONS

Utilization of acute reperfusion therapy in ideal patients has improved over the last decade, but more than 10% remain untreated. Measuring and improving its use in this cohort represents an important opportunity to improve care.

Evaluating the validity of blood-based membrane potential changes for the identification of bipolar disorder I

OBJECTIVE

The objective of this study was to develop a diagnostic blood test for bipolar disorder I using membrane potentials as biological markers.

METHODS

We measured the fluorescence intensity of a dye sensitive to membrane potential in whole blood samples from bipolar I, unipolar, schizophrenic patients, and psychiatrically normal controls. Patients were diagnosed through structured clinical interviews according to DSM-IV. Both the t-test and logistic regression analysis were used to analyze the data.

RESULTS

The membrane potential as indicated by the fluorescence intensity of the membrane potential dye in blood cells drawn from patients with bipolar disorder I was significantly different from the blood cells drawn from unipolar and schizophrenic patients, and from psychiatrically normal controls (P<0.001). The specificity and sensitivity were determined to be 0.88 and 0.78 respectively which compared well with the state of the art diagnostic techniques for other diseases. Logistic regression analysis revealed that the membrane potential was a reliable predictor which could be used as a diagnostic marker for bipolar I.

CONCLUSIONS

These results indicate that the membrane potential of blood cells can be used as a diagnostic marker to augment the DSM-IV diagnosis of bipolar disorder I. Expanded clinical trials are needed to establish this technique for general use.

Implications of the failure to identify high-risk electrocardiogram findings for the quality of care of patients with acute myocardial infarction: results of the Emergency Department Quality in Myocardial Infarction (EDQMI) study

BACKGROUND

The impact of misinterpretation of the ECG in patients with acute myocardial infarction (AMI) in the emergency department (ED) setting is not well known. Our goal was to assess the prevalence of the failure to identify high-risk ECG findings in ED patients with AMI and to determine whether this failure is associated with lower-quality care.

METHODS AND RESULTS

In a retrospective cohort study of consecutive patients presenting to 5 EDs in California and Colorado from July 1, 2000, through June 30, 2002, with confirmed AMI (n=1684), we determined the frequency of the failure by the treating provider to identify significant ST-segment depressions, ST-segment elevations, or T-wave inversions on the presenting ECG. In multivariable models, we assessed the relationship between missed high-risk ECG findings and evidence-based therapy in the ED after adjustment for patient characteristics and site of care. High-risk ECG findings were not documented in 201 patients (12%). The failure to identify high-risk findings was independently associated with a higher odds of not receiving treatment among ideal candidates for aspirin (odds ratio [OR], 2.13; 95% confidence interval [CI], 1.51 to 2.94), beta-blockers (OR, 1.85; 95% CI, 1.14 to 3.03), and reperfusion therapy (OR, 7.69; 95% CI, 3.57 to 16.67). Among patients with missed high-risk ECG findings, in-hospital mortality was 7.9% compared with 4.9% among those without missed findings (P=0.1).

CONCLUSIONS

The failure to identify high-risk ECG findings in patients with AMI results in lower-quality care in the ED. Systematic processes to improve ECG interpretation may have important implications for patient treatment and outcomes.

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.

Chest pain and associated symptoms of acute coronary syndromes

Coronary heart disease is the primary health risk for all Americans. Acute coronary syndromes (ACS) is the term used to denote any 1 of 3 clinical manifestations of coronary heart disease: unstable angina, non-ST elevation myocardial infarction, and ST-elevation MI. The major challenge to healthcare providers is the rapid and accurate identification of patients with ACS who would benefit from immediate thrombolysis or percutaneous coronary interventions. The purpose of this article is to describe the incidence, causes, risk factors, assessment, and diagnosis of patients presenting with ACS as well as current recommendations for nurses who treat patients with 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.

The impact of electrocardiographic left ventricular hypertrophy and bundle branch block on the triage and outcome of ED patients with a suspected acute coronary syndrome: a multicenter study

We studied the impact on triage and outcome of the presence of left ventricular hypertrophy (LVH) and left/right bundle branch block (LBBB/RBBB) on the initial ED electrocardiogram (ECG) for patients with symptoms suggestive of an acute coronary syndrome (ACS). Secondary analysis of data from a prospective clinical trial of patients with chest pain or other symptoms suggesting ACS in six U.S. hospitals comparing patient demographics, clinical variables, and outcomes was used. Of 5,324 study patients, 3% had ECG-LVH, 3% had LBBB, 3% had RBBB, and 43% had ischemic ST segment or T wave abnormalities. Compared with patients without ST segment or T wave abnormalities, patients with ECG-LVH or BBB were older and were more likely to have a chief complaint of shortness of breath or a history of cardiac or related diseases. Patients with ECG-LVH or BBB had more diagnoses of congestive heart failure (CHF) and ACS compared with patients without these ECG abnormalities and were just as likely to have ACS as their diagnosis compared with patients with ischemic ST segment or T wave abnormalities. Having ECG-LVH or BBB did not alter the true-positive rate for ACS but increased the false-positive rate by almost 50%. Patients with ECG-LVH had approximately 3.5 times the 30-day mortality rate as those without these ECG abnormalities. It appears that for patients with symptoms suggestive of ACS, the presence of ECG-LVH or BBB did not alter the ability of ED clinicians to identify patients with ACS but was associated with a 50% higher false-positive admission rate compared with similar patients without these ECG abnormalities. With a short-term mortality rate 3.5 times that for patients without ECG-LVH, selected patients with ECG-LVH and symptoms suggesting ACS might benefit from hospitalization for further evaluation.

Continuous ST-segment monitoring of patients with left bundle branch block and suspicion of acute myocardial infarction

OBJECTIVES

Patients with left bundle branch block comprise 5-9% of all patients with acute myocardial infarction. Limited data exist on the usefulness of continuous electrocardiographic monitoring of these patients. We have investigated prospectively the usefulness of real-time continuous vectorcardiography for monitoring patients with left bundle branch block and suspicion of acute myocardial infarction.

DESIGN

A prospective multi-centre study.

SETTING

Fourteen Swedish coronary care units.

SUBJECTS

Patients with left bundle branch block and suspicion of acute myocardial infarction with <6-h symptom duration were included.

MAIN OUTCOME MEASURES

All patients were monitored with continuous vectorcardiography for 12-24 h.

RESULTS

One hundred thirty-three patients were included, 47% had acute myocardial infarction. Patients with acute myocardial infarction showed a marked relative decrease in ST-vector than those without (P = 0.0002). These changes were most marked in the first 90 min. When comparing patients with acute myocardial infarction receiving thrombolytic therapy or not, those treated with thrombolytics showed more marked decline in ST-vector magnitude (P < 0.0001) and in shorter time (P = 0.0017). All patients showed STC-vector magnitude changes that were more marked in patients with acute myocardial infarction (P = 0.0002). An STC-vector magnitude cut-off value of 65 microV after 90 min of monitoring gave 54% sensitivity and 72% specificity for diagnosis of acute myocardial infarction.

CONCLUSION

Real-time continuous vectorcardiographic monitoring of patients with left bundle branch and suspicion of acute myocardial infarction shows significant differences between those with and without acute myocardial infarction and could be of use for early diagnosis and subsequent monitoring.

12-lead ECG interpretation 2: right ventricular and posterior infarcts

Some myocardial abnormalities can have serious consequences if not detected, and may negatively affect overall patient outcomes. Right ventricular and posterior myocardial infarction are two types of myocardial injury that may seriously affect the patient's haemodynamics status, but can be recognized easily if appropriate specialized 12-lead electrocardiograms (ECGs) are recorded and analysed. The nurse is best-placed to conduct advanced ECG interpretation, in partnership with medical colleagues, and taking into account the patient's clinical symptoms and cardiac risk factors. This article should be read in conjunction with the first article (Vol 12(21): 1248-55).

Body surface mapping improves early diagnosis of acute myocardial infarction in patients with chest pain and left bundle branch block

OBJECTIVE

To test prospectively depolarisation and repolarisation body surface maps (BSMs) for mirror image reversal, which is less susceptible to artefact, in patients with acute ischaemic-type chest pain, and to compare these BSM criteria with previously published 12 lead ECG criteria.

METHODS

An 80 lead portable BSM system was used to map patients presenting with acute ischaemic-type chest pain and a 12 lead ECG with left bundle branch block (LBBB). Acute myocardial infarction (AMI) was defined by serial cardiac enzymes. Each 12 lead ECG was assessed by the criteria of Sgarbossa et al and Hands et al for diagnosis of AMI. Depolarisation and repolarisation BSMs were assessed for loss of mirror image reversal of QRS with ST-T isointegral map patterns and a change in vector angle from QRS to ST-T outside 180+/-15 degrees -findings typically seen in LBBB with AMI.

RESULTS

Of 56 patients with chest pain and LBBB, 18 had enzymatically confirmed AMI. Patients with loss of BSM image reversal were significantly more likely to have AMI (odds ratio 4.9, 95% confidence interval 1.5 to 16.4, p = 0.007). Loss of BSM image reversal was significantly more sensitive (67%) for AMI than either 12 lead ECG method (17%, 33%) albeit with some loss in specificity (BSM 71%, 12 lead ECG 87%, 97%). Patients with AMI compared with those without AMI had a greater mean change in vector angle outside the normal range (180+/-15 degrees ), particularly between QRS isointegral and ST60 isopotential (the potential 60 ms after the J point at each electrode site) BSMs (19 degrees v 9 degrees, p = 0.038). Loss of image reversal and QRS-ST60 vector change outside 180+/-15 degrees had 61% sensitivity and 82% specificity for AMI (odds ratio 7.0, 95% confidence interval 2.0 to 24.4, p = 0.001).

CONCLUSIONS

BSM compared with the 12 lead ECG improved the early diagnosis of AMI in the presence of LBBB.

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.

Electrocardiographic manifestations: bundle branch blocks and fascicular blocks

Intraventricular conduction block is the general name given to a varied group of electrocardiographic entities. All share a common finding of some degree of delay in ventricular activation; recognition of these blocks hinges upon analysis of the QRS complex, as well as the ST-T changes associated with them. Bundle branch block (right or left), and fascicular block (left anterior or left posterior) are all examples of intraventricular conduction block. Causation of intraventricular conduction block may be cardiac or noncardiac; early recognition of the etiology may be of clinical importance. This article reviews the basic anatomy and physiology related to intraventricular conduction blocks, and then examines each in terms of electrocardiographic definition and clinical correlation.

The electrocardiographic differential diagnosis of ST segment depression

The importance of the electrocardiographic differential diagnosis of ST segment depression in patients presenting with acute chest pain is discussed.