Agreement between cardiologists and fellows in interpretation of ischemic electrocardiographic changes in acute myocardial infarction.

Background: Time from symptom onset may not be the best indicator for choosing reperfusion therapy for patients presenting with acute ST-elevation myocardial infarction (STEMI); consequently ECG-based methods have been developed.

Methods: This study evaluated the inter-observer agreement between experienced cardiologists and junior doctors in identifying the ECG findings of the pre-infarction syndrome (PIS) and evolving myocardial infarction (EMI). The ECGs of 353 STEMI patients were independently analyzed by two cardiologists, one fellow in cardiology, one fellow in internal medicine and a medical student.

Enhanced recognition of ischemia by three variable analysis of the exercise stress test.

Background: ECG ST-segment deviations have been the standard measure of coronary artery disease (CAD) during the exercise stress test (EST). Our past research has shown other ECG variables to be significant in EST. This study evaluates the benefit of routinely combining these variables in the detection of CAD.

Right, but not left, bundle branch block is associated with large anteroseptal scar.

Objectives: This study sought to test the hypothesis that right bundle branch block (RBBB) patients have larger scar size than left bundle branch block (LBBB) patients do.

Background: A proximal septal perforating branch of the left anterior descending (LAD) coronary artery most commonly perfuses the right bundle branch and left anterior fascicle, but not the left posterior fascicle. Thus, proximal LAD occlusions should cause RBBB, not LBBB.

A detailed guide for quantification of myocardial scar with the Selvester QRS score in the presence of electrocardiogram confounders.

The Selvester QRS score translates subtle changes in ventricular depolarization measured by the electrocardiogram into information about myocardial scar location and size. This estimated scar has been shown to have a high degree of correlation with autopsy-measured myocardial infarct size. In addition, multiple studies have demonstrated the value of the QRS score in post-myocardial infarct patients to provide prognostic information.

Myocardial scar in sarcoidosis by 12-lead ECG and pathology.

This case demonstrates the use of QRS scoring to quantify myocardial scar in a patient with cardiac sarcoidosis and left bundle branch block who progressively received an implantable defibrillator, cardiac resynchronization therapy (CRT), left ventricular assist device and cardiac transplantation. QRS scoring has been shown to correlate with magnetic resonance imaging measurements of scar, identify arrhythmogenic substrate and predict response to CRT, but had not previously been compared to pathology-documented scar in nonischemic cardiomyopathies. Further study is warranted to assess the ability of QRS scoring to guide therapy for individual patients.

Defining left bundle branch block in the era of cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) has emerged as an attractive intervention to improve left ventricular mechanical function by changing the sequence of electrical activation. Unfortunately, many patients receiving CRT do not benefit but are subjected to device complications and costs. Thus, there is a need for better selection criteria.

An ECG index of myocardial scar enhances prediction of defibrillator shocks: an analysis of the Sudden Cardiac Death in Heart Failure Trial.

Background: Only a minority of patients receiving implantable cardioverter-defibrillators (ICDs) for the primary prevention of sudden death receive appropriate shocks, yet almost as many are subjected to inappropriate shocks and device complications. Identifying and quantifying myocardial scar, which forms the substrate for ventricular tachyarrhythmias, may improve risk stratification.

Objective: This study sought to determine whether the absence of myocardial scar detected by novel 12-lead electrocardiographic (ECG) Selvester QRS scoring criteria identifies patients with low risk for appropriate ICD shocks.

Diastolic heart sounds as an adjunctive diagnostic tool with ST criteria for acute myocardial ischemia.

Aims/methods: To investigate whether diastolic third or fourth heart sounds (S3 or S4) detect myocardial ischemia independently or in combination with the 12-lead electrocardiogram (ECG), a prospective comparison study was conducted in a group with ischemia induced by percutaneous coronary intervention (n=19) and a non-ischemia group (n=18) without coronary artery disease or ischemic ECG evidence. Diastolic heart sounds were detected by computerized acoustic cardiography.

Results: Of 37 patients, the mean age was 59.

ECG quantification of myocardial scar in cardiomyopathy patients with or without conduction defects: correlation with cardiac magnetic resonance and arrhythmogenesis.

Background: Myocardial scarring from infarction or nonischemic fibrosis forms an arrhythmogenic substrate. The Selvester QRS score has been extensively validated for estimating myocardial infarction scar size in the absence of ECG confounders, but has not been tested to quantify scar in patients with hypertrophy, bundle branch/fascicular blocks, or nonischemic cardiomyopathy. We assessed the hypotheses that (1) QRS scores (modified for each ECG confounder) correctly identify and quantify scar in ischemic and nonischemic patients when compared with the reference standard of cardiac magnetic resonance using late-gadolinium enhancement, and (2) QRS-estimated scar size predicts inducible sustained monomorphic ventricular tachycardia during electrophysiological testing.

Sequence of electrocardiographic and acoustic cardiographic changes and angina during coronary occlusion and reperfusion in patients undergoing percutaneous coronary intervention.

Background: Previous studies have suggested that ventricular function may be impaired without or prior to electrocardiographic changes or angina during ischemia. Understanding of temporal sequence of electrical and functional ischemic events may improve the detection of myocardial ischemia.

Methods: A prospective study was performed in 21 subjects undergoing percutaneous coronary intervention (PCI) who had both ST amplitude changes >2 standard deviations above baseline on 12-lead electrocardiography (ECG), and new or increased third or fourth heart sound (S3 or S4) intensity measured by computerized acoustic cardiography.

Vectorcardiogram synthesized from the 12-lead electrocardiogram to image ischemia.

Background: Knowledge of the location and size of ischemic myocardium at risk for infarction could impact prehospital patient triage and reperfusion therapy. The 12-lead electrocardiogram (ECG) can roughly estimate ischemia size; however, individual precordial ECG leads are at different distances from the left ventricle (LV) and certain LV walls have greater effects on the ECG. Vectorcardiographic corrected orthogonal lead systems can display the magnitude and direction of the ST-segment "injury current" vector in 3-dimensional space.

Simulation of the QRS complex using papillary muscle positions as the site of early activation in human subjects.

Background: Simulation of the electrical activation of the heart and its comparison with real in vivo activation is a promising method in testing potential determinants of excitation. Simulation of the electrical activity of the human heart is now emerging as a step forward for understanding and predicting electrophysiologic patterns in humans. Initial points of excitation and the manner in which the activation spreads from these points are important variables determining QRS complex characteristics.

Location of myocardium at risk in patients with first-time ST-elevation infarction: comparison among single photon emission computed tomography, magnetic resonance imaging, and electrocardiography.

Background: The amount of myocardium at risk (MaR) during acute coronary occlusion and the duration of occlusion are important determinants of final infarct size. The main goal of early reperfusion therapy is to salvage ischemic myocardium, thereby preserving left ventricular function. The aims of the present study were to test the feasibility of developing polar plot representations of MaR, for perfusion single photon emission computed tomography (SPECT), regional wall thickening by magnetic resonance imaging (MRI), and distribution of ST-segment changes.

Frequency of diastolic third and fourth heart sounds with myocardial ischemia induced during percutaneous coronary intervention.

Background: Although the standard 12-lead electrocardiogram (ECG) is considered the gold standard to diagnose acute myocardial ischemia, nearly half of ECGs are nondiagnostic in patients who present with chest pain and have subsequent confirmation of infarction with positive serum biomarkers.

Methods: A prospective study was performed to investigate the frequency and intensity of diastolic third and fourth heart sounds (S3 and S4), as measured by computerized acoustic cardiography, with myocardial ischemia induced by balloon occlusion during percutaneous coronary intervention.

Results: In our 24 subjects, during percutaneous coronary intervention-induced ischemia, a new or increased intensity S3 or S4 developed in 67%.

The relationship between mitral papillary muscles positions and characteristics of the QRS complex.

Background: QRS complex characteristics are considered to be one of the most significant diagnostic and prognostic determinants for assessment of several cardiac conditions. However, there is a large variability of the QRS complex even among "normal" individuals. This study was based on 2 assumptions: (1) that the portion of the left ventricular endocardium activated earliest is directly supplied by the "fanlike" distribution of the anterior, middle, and posterior fascicles of the left bundle branch, and (2) that the anterior and posterior fascicles course toward their respective mitral papillary muscles.

ST-segment deviation analysis of the admission 12-lead electrocardiogram as an aid to early diagnosis of acute myocardial infarction with a cardiac magnetic resonance imaging gold standard.

Objectives: The purpose of this study was to validate existing 12-lead electrocardiographic (ECG) ST-segment elevation myocardial infarction (STEMI) criteria in the diagnosis of acute myocardial infarction (AMI) and the application of similar ST-segment depression (STEMI-equivalent) criteria with contrast-enhanced cardiac magnetic resonance imaging (ceMRI) as the diagnostic gold standard.

Background: The admission ECG is the cornerstone in the diagnosis of AMI, and ceMRI is a new diagnostic gold standard that can be used to validate existing and novel 12-lead ECG criteria.

Methods: One hundred fifty-one consecutive patients with their first hospital admission for chest pain underwent ceMRI.

3D Heart: a new visual training method for electrocardiographic analysis.

This new training method is based on developing a sound understanding of the sequence in which electrical excitation spreads through both the normal and the infarcted myocardium. The student is made aware of the cardiac electrical performance through a series of 3-dimensional pictures during the excitation process. The electrocardiogram 3D Heart 3-dimensional program contains a variety of different activation simulations.

Consideration of pitfalls in and omissions from the current ECG standards for diagnosis of myocardial ischemia/infarction in patients who have acute coronary syndromes.

The ECG is the key clinical test available for the emergency determination of which patients who presenting with acute coronary syndromes indeed have acute myocardial ischemia/infarction. Because typically the etiology is thrombosis, the correct clinical decision regarding reperfusion therapy is crucial. This review follows the efforts of an AHA working group to develop new standards for clinical application of electrocardiology.

Where is the central terminal located? In search of understanding the use of the Wilson central terminal for production of 9 of the standard 12 electrocardiogram leads.

The aim of this study was to evaluate the understanding of the term central terminal (CT) and to consider the consequences of this level of understanding. A total of 150 questionnaires was distributed during the 30th International Congress of Electrocardiology 2003, Helsinki, Finland; 42 (28%) of the anonymous questionnaires returned were considered adequate for the purpose of this study. The questionnaire addressed the following areas of interest: (1) the location of the CT; (2) the location of the negative poles of unipolar leads ; (3) the naming of the electrocardiogram lead groups; (4) the relationship between the leads and cardiac electrical views; and (5) impact on accuracy of clinical diagnosis.

Clinical and angiographic characteristics of patients with combined anterior and inferior ST-segment elevation on the initial electrocardiogram during acute myocardial infarction.

Objective: We evaluated the significance of combined anterior and inferior ST-segment elevation on the initial electrocardiogram (EKG) in patients with acute myocardial infarction (AMI) and correlated it with AMI size and left ventricular (LV) function.

Methods: We analyzed admission EKGs of 2996 patients with AMI from the GUSTO-I angiographic substudy and the GUSTO-IIb angioplasty substudy who underwent immediate angiography. In all, we identified 1046 patients with anterior ST elevation (ST-segment elevation in > or =2 of leads V1-V4) and divided them into 3 groups: Group 1, anterior + inferior ST elevation (ST elevation in > or =2 of leads II, III, aVF, n =179); Group 2, anterior ST elevation only (<2 of leads II, III, aVF with ST elevation or depression, n = 447); Group 3, anterior ST elevation + superior ST elevation (ST depression in > or =2 of leads II, III, aVF, n = 420).

Quantitative clinical assessment of chronic anterior myocardial infarction with delayed enhancement magnetic resonance imaging and QRS scoring.

Background: Both the regional and global myocardial extent of chronic myocardial infarction (MI) are important prognostic factors for length and quality of life and also crucial for the choice of therapy in patients with ischemic heart disease. Our aim was to develop and validate techniques for comparison between regional and global size of remote anterior MI in the left ventricle quantified with both magnetic resonance imaging (MRI) and electrocardiogram (ECG).

Methods: Delayed-enhancement (DE) MRI was used as a clinical "gold standard" for MI size to evaluate the extent of MI estimated with the commonly available standard 12-lead ECG.

Time-dependent predictors of primary cardiac arrest in patients with acute myocardial infarction.

To understand predictors of cardiac arrest early in acute myocardial infarction (AMI), for the Thrombolytic Predictive Instrument, we developed a multivariable regression model predicting primary cardiac arrest using time-dependent variables based on a case-control study of emergency department (ED) patients with AMI: 65 cases with sudden cardiac arrest and 258 without cardiac arrest. Within the first hour of AMI symptom onset, adjusting for age, systolic blood pressure, serum potassium, and infarct size, increased risk of cardiac arrest was associated with electrocardiographic prolonged QTc interval and a greater sum of ST-segment elevation. After 1 hour, the effect of ST-segment elevation was much reduced and the effect of the QTc interval was reversed, so prolonged QTc appeared protective.