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. The last two were given a half-hour introduction of the PIS/EMI-algorithm. RESULTS: The inter-observer reliability between all the investigators was found to be good according to kappa statistics (κ 0.632-0.790) for the whole study population. When divided into different subgroups, the inter-observer agreements were from good to very good between the cardiologists and the fellow in cardiology (κ 0.652 -0.813) and from moderate to good (κ 0.464-0.784) between the fellow in internal medicine, medical student and the others. CONCLUSIONS: The PIS and EMI ECG patterns are reliably identified by experienced cardiologists and can be easily adopted by junior doctors.

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.

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. Recent studies have demonstrated that increasing QRS score is predictive of increased implantable defibrillator shocks for ventricular tachycardia and fibrillation as well as decreased response to cardiac resynchronization therapy. Although QRS scoring has never achieved widespread clinical use, increased interest in patient selection and risk-stratification techniques for implantable defibrillators and cardiac resynchronization therapy has led to renewed interest in QRS scoring and its potential to identify which patients will benefit from device therapy. The QRS score criteria were updated in 2009 to expand their use to a broader population by accounting for the different ventricular depolarization sequences in patients with bundle-branch/fascicular blocks or ventricular hypertrophy. However, these changes also introduced additional complexity and nuance to the scoring procedure. This article provides detailed instructions and examples on how to apply the QRS score criteria in the presence of confounding conduction types to facilitate understanding and enable development and application of automated QRS scoring.

Computerized classification of proximal occlusion in the left anterior descending coronary artery.

Proximal occlusion within the left anterior descending (LAD) coronary artery in patients with acute myocardial infarction leads to higher mortality than does nonproximal occlusion. We evaluated an automated program to detect proximal LAD occlusion. All patients with suspected acute coronary syndrome (n = 7,710) presenting consecutively to the emergency department of a local hospital with a coronary angiogram­confirmed flow-limiting lesion and notation of occlusion site were included in the study (n = 711). Electrocardiograms (ECGs) that met ST-segment elevation myocardial infarction (STEMI) criteria were included in the training set (n = 183). Paired angiographic location of proximal LAD and ECGs with ST elevation in the anterolateral region were used for the computer program development (n = 36). The test set was based on ECG criteria for anterolateral STEMI only without angiographic reports (n = 162). Tested against 2 expert cardiologists' agreed reading of proximal LAD occlusion, the algorithm has a sensitivity of 95% and a specificity of 82%. The algorithm is designed to have high sensitivity rather than high specificity for the purpose of not missing any proximal LAD in the STEMI population. Our preliminary evaluation suggests that the algorithm can detect proximal LAD occlusion as an additional interpretation to STEMI detection with similar accuracy as cardiologist readers.

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. The sequence of the onset and resolution of these signs of ischemia were examined following coronary balloon inflation and deflation. RESULTS: Electrocardiographic ST amplitude and diastolic heart sound changes occurred contemporaneously, shortly after coronary occlusion (mean onset from balloon inflation; ST changes, 21 +/- 17 seconds; S4, 25 +/- 26 seconds; S3, 45 +/- 43 seconds). In 40% of patients, a new or increased S3 or S4 developed earlier than ST changes. Anginal symptoms occurred in only 2 of the 21 subjects during ischemia with a mean onset time of 68 seconds. ST-segment changes resolved earliest (33 seconds after balloon deflation) while diastolic heart sounds (89 +/- 146 seconds) and angina (586 +/- 653 seconds) resolved later. CONCLUSION: A new or intensified S3 and/or S4 occurred contemporaneously with electrocardiographic changes during ischemia. These diastolic heart sounds persisted longer than ST changes following coronary reperfusion. Acoustic cardiographic assessment of diastolic heart sounds may aid in the early detection of myocardial ischemia, particularly in those patients with an uninterpretable ECG.

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%. Ten (67%) of 15 patients without clinical ST criteria for ischemia also developed new or increased-intensity diastolic heart sounds. CONCLUSIONS: The combined use of diastolic heart sounds, as a measurement of ventricular dysfunction, with the standard ECG may improve the noninvasive diagnosis of myocardial ischemia that is likely to develop into infarction.

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. We assessed whether the vectorcardiographic ST-vector direction and magnitude derived from the ECG by the inverse-Dower method can estimate the location and size of ischemia. METHODS AND RESULTS: Thirty-two patients underwent elective coronary angioplasty with control and 5-minute balloon-occlusion ECG and sestamibi injection followed by single photon emission computed tomography (SPECT). The ST-vector direction derived from the inverse-Dower method was projected to an LV model with normal coronary artery anatomy. The graphical display of ST-vector location could discriminate among occlusions of the different coronaries. The ST-vector located ischemia within the SPECT defect in 75% (24/32) of all patients and 96% (24/25) of patients with ischemia in more than 12% of the LV. ST-vector magnitude had a Spearman correlation of r = 0.68 (P < .0001) with SPECT ischemia size. CONCLUSIONS: The 3-dimensional ST vector derived from the ECG can be graphically projected onto an LV model to localize ischemia, and ST-vector magnitude correlates with ischemia size. Further study is warranted to assess the ability of vectorcardiographic imaging to risk-stratify and provide decision-support for patients with acute myocardial infarction.

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. It has been suggested that in humans, the initial excitation of the left ventricle is a primary determinant of QRS complex characteristics, and that excitation begins at the papillary muscles and septum, where the fascicles of the left bundle branch insert. The aim of this study is to test the hypothesis that QRS duration and direction of QRS axis in the frontal plane have excellent agreement between real QRS and simulated QRS using papillary muscle position to indicate the border of the origin of early ventricular activation. METHODS: Fourteen healthy adult volunteers were included in the study. Magnetic resonance imaging data were obtained to assess the papillary muscle positions. Twelve-lead electrocardiographic (ECG) recordings were used to obtain real ECG data for assessment of QRS duration and QRS axis in each subject. Simulation software developed by ECG-TECH Corp (Huntington, NY) was used to simulate the ECG of each subject to determine simulated QRS duration and QRS frontal plane axis. QRS duration and QRS axis data were compared between simulated and real ECG and agreement between these variables was calculated. RESULTS: Seventy-nine percent of subjects had a difference of the QRS duration between real and simulated ECG of less than 10 milliseconds. The calculated strength of agreement between simulated and real QRS duration was 71% and considered as "good" (kappa statistics). In 70% of subjects, the difference in the QRS axis was less than 10 degrees . The calculated strength of agreement between simulated and real QRS axis was 80% and considered as "excellent" (kappa statistics). CONCLUSIONS: The results of this study suggest that the sites of the initiation of electrical activity in the left ventricle, as assessed by the positions of papillary muscles, may be considered as primary determinants of the QRS duration and QRS axis in humans. This knowledge may help in predicting normal QRS characteristic on a patient-specific basis. In this study, simulation of the QRS complex was based on papillary muscles from human hearts.

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. A second aim was to test the hypothesis that these different modalities display similar localization of the MaR in patients with reperfused first-time myocardial infarction. METHODS: Eleven patients with first-time myocardial infarction with ST-elevation received (99m)Tc tetrofosmin before primary percutaneous coronary intervention, SPECT imaging within 3 hours, and cardiac MRI of the left ventricle within 24 hours. The results for SPECT, MRI, and electrocardiogram (ECG) were developed into polar plots, and two expert observers designated the culprit coronary artery as assessed by angiography. RESULTS: The perfusion SPECT, MRI wall thickening, and ST changes are presented in side-by-side polar plots. In total, the culprit artery, based on the location of the MaR, was correctly designated in 91%, 82%, and 91% of cases by SPECT, MRI, and ECG, respectively. CONCLUSIONS: Polar representation for localization of the MaR by SPECT perfusion, MRI wall thickening, and ECG ST-segment deviation is feasible. All 3 modalities have the potential to be used for indirect visual designation of the culprit artery in patients with first-time acute coronary occlusion.

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. These structures could therefore serve as anatomical landmarks to indicate the borders of this fanlike distribution of primary "start points" of left ventricular activation. AIMS: The primary aim of this study is to test the hypothesis that location of both papillary muscles closer to the septum correlates with longer QRS duration. The secondary aim of the study is to test the hypothesis that the balance of the distances of the anterior and posterior papillary muscles from the septum is related to the direction of the frontal plane QRS axis. METHODS: The study population consisted of 16 healthy adult volunteers with a mean age of 26 +/- 9 years, mean height of 170 +/- 12 cm, and mean weight of 68 +/- 10 kg. Measurements were done on the magnetic resonance images from all study subjects. Positions of papillary muscles were assessed as a predictive variable of QRS duration. RESULTS: A significant correlation was found between the closer position of both papillary muscles to the septum and longer QRS duration (R = 0.7, P = .02). Subjects with higher ratio of anterior papillary muscle vs posterior papillary muscle free wall angle correlates with inferior rotation of the average axis of QRS complex in the frontal plane (R = 0.5, P = .04). CONCLUSIONS: The positions of the papillary muscles in relation to the free wall and septum wall can be predictive of both QRS duration and the direction of the QRS complex of the heart. These results might provide a new basis for prediction of QRS complex characteristics of an individual and, thus, differentiate between real QRS complex abnormalities and variants of normal.

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. Currently, this program enables the user to view the activation simulation for all of the following pathology examples: normal activation; large, medium, and small anterior myocardial infarction (MI); large, medium, and small posterolateral MI; large, medium, and small inferior MI. Simulations relating to other cardiac abnormalities, such as bundle branch block and left ventricular hypertrophy fasicular block, are being developed as part of a National Institute of Health (NIH) Phase 1 Small Business Innovation Research (SBIR) program.

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. A method for comparing global and regional quantifications of MI with DE-MRI and ECG was developed. The Selvester QRS-scoring system was used for estimating MI size electrocardiographically. RESULTS: Twenty-five patients with chronic single anterior MI, documented with DE-MRI, were studied. The best agreement for mean % MI per regional segment of the left ventricle was found in the middle third (26% vs 27%), whereas the most significant discrepancy was found in the apex (56% vs 30%). The global MI size of the left ventricle averaged 21 +/- 9% with DE-MRI and 22% +/- 12% with ECG, with a correlation of r = 0.40 (P <.05). CONCLUSIONS: The current Selvester QRS scoring system performs well for quantifying anterior MI in the mid-regions of the left ventricle. The diagnostic performance of the Selvester QRS-scoring system for quantifying MI in the other regions, particularly the left ventricular apex, can potentially be improved, with DE-MRI as the gold standard.

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. Accordingly, for patients presenting 30 minutes after chest pain onset, compared with a QTc of 0.44, the risk for cardiac arrest for patients with QTc of 0.50 was more than doubled (odds ratio [OR] 2.20, 95% confidence intervals [CI] 1.17 to 4.13), whereas for those presenting after an hour, it was much lower (e.g., at 1.5 hours, OR 0.21, 95% CI 0.06 to 0.73). Patients presenting 30 minutes after chest pain onset with a sum of ST elevation of 20 mm had a threefold higher risk than patients with a sum of ST elevation of 5 mm (OR 3.37, 95% CI 1.83 to 6.20). However, if presenting 1.5 hours after chest pain onset, the risk was barely elevated (OR 1.18; 95% CI 1.09 to 1.29). Thrombolytic therapy was protective, halving the odds of cardiac arrest (OR 0.51, 95% CI 0.27 to 0.93). Thus, the relation of prolonged QTc interval and substantial ST segment elevation to cardiac arrest in AMI may be obscured because patients with these risks are more likely to die soon after AMI onset, before ED presentation, and are thereby unavailable for study. Those with prolonged QTc or substantial ST elevation who survive the initial 1.5-hour period are those less susceptible to these risks.

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. METHODS: We performed electrocardiograms and magnetic resonance imaging for scar quantification in 233 patients with left ventricular (LV) ejection fraction ≤35% who were receiving primary prevention implantable cardioverter-defibrillators (ICD cohort). Scar size and location were compared among patients with RBBB, LBBB, nonspecific LV conduction delay, and QRS <120 ms. A second cohort of 20 hypertrophic cardiomyopathy patients undergoing alcohol septal ablation was studied to determine whether controlled infarction in a proximal LAD septal perforator caused RBBB or LBBB. RESULTS: In the ICD cohort, LV ejection fraction was similar between RBBB and LBBB patients (24.9% vs. 25.0%; p = 0.98); however, RBBB patients had significantly larger scar size (24.0% vs. 6.5%; p < 0.0001). Patients with nonspecific LV conduction delay or QRS <120 ms had intermediate scar size (12.9% and 14.4%, respectively). Those with RBBB (compared with LBBB) were more likely to have ischemic heart disease (79% vs. 29%; p < 0.0001). In the alcohol septal ablation cohort, 15 of 20 patients (75%) developed RBBB, but no patients developed LBBB. CONCLUSIONS: In patients with LV ejection fraction ≤35%, RBBB is associated with significantly larger scar size than LBBB is, and occlusion of a proximal LAD septal perforator causes RBBB. In contrast, LBBB is most commonly caused by nonischemic pathologies.

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. Current criteria for CRT eligibility include a QRS duration ≥ 120 ms. However, QRS morphology is not considered, although it can indicate the cause of delayed conduction. Recent studies have suggested that only patients with left bundle branch block (LBBB) benefit from CRT, and not patients with right bundle branch block or nonspecific intraventricular conduction delay. The authors review the pathophysiologic and clinical evidence supporting why only patients with complete LBBB benefit from CRT. Furthermore, they review how the threshold of 120 ms to define LBBB was derived subjectively at a time when criteria for LBBB and right bundle branch block were mistakenly reversed. Three key studies over the past 65 years have suggested that 1/3 of patients diagnosed with LBBB by conventional electrocardiographic criteria may not have true complete LBBB, but likely have a combination of left ventricular hypertrophy and left anterior fascicular block. On the basis of additional insights from computer simulations, the investigators propose stricter criteria for complete LBBB that include a QRS duration ≥ 140 ms for men and ≥ 130 ms for women, along with mid-QRS notching or slurring in ≥ 2 contiguous leads. Further studies are needed to reinvestigate the electrocardiographic criteria for complete LBBB and the implications of these criteria for selecting patients for CRT.

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. METHODS: We applied QRS scoring to 797 patients from the ICD arm of the Sudden Cardiac Death in Heart Failure Trial. Patients were followed up for a median of 45.5 months for ventricular tachycardia/fibrillation treated by the ICD or sudden tachyarrhythmic death (combined group referred to as VT/VF). RESULTS: Increasing QRS score scar size predicted higher rates of VT/VF. Patients with no scar (QRS score = 0) represented a particularly low-risk cohort with 48% fewer VT/VF events than the rest of the population (absolute difference 11%; hazard ratio 0.52, 95% confidence interval 0.31 to 0.88). QRS score scar absence versus presence remained a significant prognostic factor after controlling for 10 clinically relevant variables. Combining QRS score (scar absence versus presence) with ejection fraction (≥ 25% versus < 25%) distinguished low-, middle-, and high-risk subgroups with 73% fewer VT/VF events in the low-risk versus high-risk group (absolute difference 22%; hazard ratio = 0.27, 95% confidence interval 0.12 to 0.62). CONCLUSION: Patients with no scar by QRS scoring have significantly fewer VT/VF events. This inexpensive 12-lead ECG tool provides unique, incremental prognostic information and should be considered in risk-stratifying algorithms for selecting patients for ICDs.

Usefulness of p-wave duration to identify myocardial ischemia during exercise testing.

It is well recognized that ST-segment depression is due to subendocardial ischemia secondary to an increase in left ventricular end-diastolic pressure. The increase in left ventricular end-diastolic pressure is associated with increased left atrial pressure, resulting in left atrial wall distension that contributes to increasing P-wave duration (PWD). The objective of this study was to determine if PWD measured in leads II and V(5) during maximum exercise stress testing could be a reliable predictor of myocardial ischemia. Patients with suspected coronary disease underwent maximum exercise stress testing with myocardial perfusion imaging. PWD was measured using leads II and V(5) at rest and after exercise, with electrocardiographic complexes magnified 4 times (100 mm/s, 40 mm/mV). The change in PWD was calculated as Delta = PWD(recovery) - PWD(rest). DeltaPWD and ST-segment changes were related to the absence or presence of ischemia (localized reversible perfusion abnormalities) on myocardial perfusion imaging scans. DeltaPWD had sensitivity of 72%, specificity of 82%, negative predictive power (NPP) of 90%, and positive predictive power of 57%. ST-segment change had sensitivity of 34%, specificity of 87%, NPP of 80%, and positive predictive power of 47%. When DeltaPWD and ST changes were combined, sensitivity increased to 79% and NPP increased to 91%. In conclusion, DeltaPWD outperformed ST-segment changes in predicting myocardial ischemia on myocardial perfusion imaging scans. Furthermore, when DeltaPWD and ST-segment changes were combined, sensitivity and NPP were also significantly increased. In this study population, measuring DeltaPWD substantially increased the diagnostic value of maximum exercise stress testing.