Real-Time 12-Lead High-Frequency QRS Electrocardiography for Enhanced Detection of Myocardial Ischemia and Coronary Artery Disease

Several studies have shown that diminution of the high-frequency (HF; 150–250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease. Several studies have shown that diminution of the high-frequency (HF; 150–250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease. In the setting of a known or suspected acute coronary syndrome (ACS), the 12-lead conventional electrocardiogram (ECG) remains the single most important initial test for revascularization triage. However, an initial 12-lead ECG may be diagnostic for acute injury in only 24% to 60% of patients with a final diagnosis of acute myocardial infarction (MI).1Fesmire FM Smith EE Continuous 12-lead electrocardiograph monitoring in the emergency department.Am J Emerg Med. 1993; 11: 54-60Abstract Full Text PDF PubMed Scopus (37) Google Scholar Although the performance of serial conventional ECGs or continuous monitoring of conventional 12-lead ST segments improves the sensitivity of the ECG for detection of ACS,2Drew BJ Krucoff MW ST-Segment Monitoring Practice Guideline International Working Group Multilead ST-segment monitoring in patients with acute coronary syndromes: a consensus statement for healthcare professionals.Am J Crit Care. 1999; 8: 372-386PubMed Google Scholar diminution of the high-frequency (HF) components present within the central QRS complex of the ECG is known to be a more sensitive indicator for the presence of ischemia than changes in conventional ST segments.3Abboud S Cohen RJ Selwyn A Ganz P Sadeh D Friedman PL Detection of transient myocardial ischemia by computer analysis of standard and signal-averaged high-frequency electrocardiograms in patients undergoing percutaneous transluminal coronary angioplasty.Circulation. 1987; 76: 585-596Crossref PubMed Scopus (126) Google Scholar, 4Aversano T Rudikoff B Washington A Traill S Coombs V Raqueno J High frequency QRS electrocardiography in the detection of reperfusion following thrombolytic therapy.Clin Cardiol. 1994; 17: 175-182Crossref PubMed Scopus (29) Google Scholar, 5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar Moreover, alterations within the HF QRS complexes of resting baseline HF QRS ECG recordings have been proposed as sensitive indicators for underlying coronary artery disease (CAD) in individuals with normal conventional 12-lead ECGs.6Abboud S Belhassen B Miller HI Sadeh D Laniado S High frequency electrocardiography using an advanced method of signal averaging for non-invasive detection of coronary artery disease in patients with normal conventional electrocardiogram.J Electrocardiol. 1986; 19: 371-380Abstract Full Text PDF PubMed Scopus (49) Google Scholar, 7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar, 8Seegobin RD Mohamed SA Ropchan G Pym J Frequency content and sex difference of the Frank lead signal-averaged ECG in a population with significant coronary artery disease: comparison with concurrent 12-lead ECG morphology.J Electrocardiol. 1995; 28: 228-233Abstract Full Text PDF PubMed Scopus (6) Google Scholar In this article, we describe a personal computer (PC)-based ECG software program recently developed at the National Aeronautics and Space Administration (NASA) that, for the first time to our knowledge, analyzes and displays, in real time during the actual patient encounter, changes in the HF QRS components in each of the 12 ECG leads during any chosen period of monitoring. Although several other programs have been designed to acquire the central HF QRS components, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. The NASA software currently is being evaluated in multiple clinical settings including emergency medicine departments (for enhanced evaluation of ACS), operating rooms (for enhanced monitoring of known or suspected myocardial ischemia in high-risk patients), cardiac catheterization laboratories (for determination of the success vs failure of percutaneous coronary interventions), and preventive medicine and cardiology clinics (for early and inexpensive diagnosis of CAD and for monitoring of heart failure). The current version of the NASA software is focused especially on the real-time isolation, analysis, and display of HF components within the entire QRS interval and between the important frequencies of 150 to 250 Hz.4Aversano T Rudikoff B Washington A Traill S Coombs V Raqueno J High frequency QRS electrocardiography in the detection of reperfusion following thrombolytic therapy.Clin Cardiol. 1994; 17: 175-182Crossref PubMed Scopus (29) Google Scholar, 5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar, 7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar, 9Beker A Pinchas A Erel J Abboud S Analysis of high frequency QRS potential during exercise testing in patients with coronary artery disease and in healthy subjects.Pacing Clin Electrophysiol. 1996; 19: 2040-2050Crossref PubMed Scopus (22) Google Scholar These HF components should be distinguished from the more familiar "late potentials," which are signals of higher amplitude that are isolated in a broader frequency band (generally 40–250 Hz) in only the very latest portion of the QRS interval and not in the central QRS itself.10Signal-averaged electrocardiography.J Am Coll Cardiol. 1996; 27: 238-249PubMed Google Scholar The term HF QRS therefore refers to those signals between 150 and 250 Hz located throughout the signal-averaged QRS interval that are isolated by software via digital filtering. To visualize the HF QRS components in real time, the following steps are taken: First, using PC-based ECG hardware and software (eg, CardioSoft, Houston, Tex, or Cardiax, IMED Co Ltd, Budapest, Hungary) plus any modern Windows-compatible PC, amplified ECG signals are continuously acquired at a rate of 1000 samples/s or faster. Next, the amplified, R-wave-detected incoming conventional QRS complexes are signal-averaged by the software to improve the signal-to-noise ratio. Premature complexes and noisy beats are automatically eliminated in real time (ie, not added to a growing template beat in each ECG channel) by a software-based cross-correlation function that rejects any incoming beat that is not at least 97% cross-correlated5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar to the existing templates. The averaged complexes of the accepted beats are then bandpass-filtered by the software in real time using a digital filter that allows only those frequencies between 150 and 250 Hz to pass. The resulting microvolt-level HF QRS signals for each lead are then plotted in real time on the computer monitor and updated on a beat-to-beat basis adjacent to the higher-amplitude conventional ECG complexes. An example of a normal HF QRS complex from a healthy person derived from a lead I signal average is shown in Figure 1, A. The 2 most commonly measured parameters of HF QRS signals are the root mean squared (RMS) voltage4Aversano T Rudikoff B Washington A Traill S Coombs V Raqueno J High frequency QRS electrocardiography in the detection of reperfusion following thrombolytic therapy.Clin Cardiol. 1994; 17: 175-182Crossref PubMed Scopus (29) Google Scholar, 5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar, 7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar, 8Seegobin RD Mohamed SA Ropchan G Pym J Frequency content and sex difference of the Frank lead signal-averaged ECG in a population with significant coronary artery disease: comparison with concurrent 12-lead ECG morphology.J Electrocardiol. 1995; 28: 228-233Abstract Full Text PDF PubMed Scopus (6) Google Scholar, 9Beker A Pinchas A Erel J Abboud S Analysis of high frequency QRS potential during exercise testing in patients with coronary artery disease and in healthy subjects.Pacing Clin Electrophysiol. 1996; 19: 2040-2050Crossref PubMed Scopus (22) Google Scholar, 11Pettersson J Carro E Edenbrandt L et al.Spatial, individual, and temporal variation of the high-frequency QRS amplitudes in the 12 standard electrocardiographic leads.Am Heart J. 2000; 139: 352-358PubMed Scopus (44) Google Scholar, 12Seegobin RD Mohamed SA Sex differences and frequency content of the Frank lead signal-averaged ECG in a normal population.J Electrocardiol. 1996; 29: 105-109Abstract Full Text PDF PubMed Scopus (8) Google Scholar and the presence vs the absence of a splitting phenomenon known as a reduced-amplitude zone (RAZ).6Abboud S Belhassen B Miller HI Sadeh D Laniado S High frequency electrocardiography using an advanced method of signal averaging for non-invasive detection of coronary artery disease in patients with normal conventional electrocardiogram.J Electrocardiol. 1986; 19: 371-380Abstract Full Text PDF PubMed Scopus (49) Google Scholar, 7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar, 8Seegobin RD Mohamed SA Ropchan G Pym J Frequency content and sex difference of the Frank lead signal-averaged ECG in a population with significant coronary artery disease: comparison with concurrent 12-lead ECG morphology.J Electrocardiol. 1995; 28: 228-233Abstract Full Text PDF PubMed Scopus (6) Google Scholar, 12Seegobin RD Mohamed SA Sex differences and frequency content of the Frank lead signal-averaged ECG in a normal population.J Electrocardiol. 1996; 29: 105-109Abstract Full Text PDF PubMed Scopus (8) Google Scholar, 13Mor-Avi V Akselrod S Spectral analysis of canine epicardial electrogram: short-term variations in the frequency content induced by myocardial ischemia.Circ Res. 1990; 66: 1681-1691Crossref PubMed Scopus (16) Google Scholar, 14Mor-Avi V Akselrod S Some aspects of the wideband recording of the electrocardiogram.Clin Cardiol. 1990; 13: 120-126Crossref PubMed Scopus (6) Google Scholar, 15Akselrod S Mor-Avi V Oz O David D Effect of localized surface cooling of the heart muscle on the high-frequency content of ECG waveforms in dogs.Clin Cardiol. 1988; 11: 112-118Crossref PubMed Scopus (6) Google Scholar Whereas RMS voltage provides an estimate of the total energy or amplitude of an HF QRS signal, the presence of a RAZ provides a morphologic indicator of potential pathology. As originally defined by Abboud,7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar a RAZ occurs in an HF QRS signal when at least 2 local maxima of the signal's upper envelope or 2 local minima of the signal's lower envelope are present (Figure 1, B-D). A local maximum or minimum (darkened circles in the HF QRS signals in Figure 1, A–D) is in turn defined as an HF envelope sample point (peak or trough) within the QRS interval wherein the absolute value of its voltage exceeds that of the 3 envelope sample points (peaks or troughs) immediately preceding and following it. The RAZ (arrows, Figure 1, B–D) is thus the region lying between the 2 neighboring maxima or minima. Reduced-amplitude zones are important because they often are formed in the HF QRS complexes of individuals with CAD and during ischemia, even when there is no simultaneous change in the conventional ST segments.3Abboud S Cohen RJ Selwyn A Ganz P Sadeh D Friedman PL Detection of transient myocardial ischemia by computer analysis of standard and signal-averaged high-frequency electrocardiograms in patients undergoing percutaneous transluminal coronary angioplasty.Circulation. 1987; 76: 585-596Crossref PubMed Scopus (126) Google Scholar, 7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar, 13Mor-Avi V Akselrod S Spectral analysis of canine epicardial electrogram: short-term variations in the frequency content induced by myocardial ischemia.Circ Res. 1990; 66: 1681-1691Crossref PubMed Scopus (16) Google Scholar, 14Mor-Avi V Akselrod S Some aspects of the wideband recording of the electrocardiogram.Clin Cardiol. 1990; 13: 120-126Crossref PubMed Scopus (6) Google Scholar, 16Abboud S Subtle alterations in the high-frequency QRS potentials during myocardial ischemia in dogs.Comput Biomed Res. 1987; 20: 384-395Crossref PubMed Scopus (30) Google Scholar, 17Abboud S Smith JM Shargorodsky B Laniado S Sadeh D Cohen RJ High frequency electrocardiography of three orthogonal leads in dogs during a coronary artery occlusion.Pacing Clin Electrophysiol. 1989; 12: 574-581Crossref PubMed Scopus (29) Google Scholar, 18Abboud S Cohen RJ Sadeh D A spectral analysis of the high frequency QRS potentials observed during acute myocardial ischemia in dogs.Int J Cardiol. 1990; 26: 285-290Abstract Full Text PDF PubMed Scopus (24) Google Scholar Abboud et al19Abboud S Berenfeld O Sadeh D Simulation of high-resolution QRS complex using a ventricular model with a fractal conduction system: effects of ischemia on high-frequency QRS potentials.Circ Res. 1991; 68: 1751-1760Crossref PubMed Scopus (109) Google Scholar have successfully modeled both HF QRS complexes and the generation of RAZ phenomena using a computer simulation that includes the torso as a volume conductor, the cells of the myocardium, and a ventricular conduction system that branches 7 or more times in a fractal (self-similar) fashion. When an ischemic activation process is simulated in the model by reducing the conduction velocity in a small ventricular region that includes the late-branching Purkinje fibers, the local myocardial cells, or both, a RAZ is formed.19Abboud S Berenfeld O Sadeh D Simulation of high-resolution QRS complex using a ventricular model with a fractal conduction system: effects of ischemia on high-frequency QRS potentials.Circ Res. 1991; 68: 1751-1760Crossref PubMed Scopus (109) Google Scholar The NASA software automatically searches in real time for local maxima and minima of the HF QRS envelope, not only according to the original criteria of Abboud but also separately according to stricter criteria that were developed to improve the usefulness of RAZ detection for clinical diagnoses. These empirical criteria identify, in addition to the generic RAZ described previously (ie, what we have termed the Abboud RAZ [RAZ A], after its original descriptor [Figure 1, B]), stricter RAZs that we have termed the Abboud Percent RAZ (RAZ AP) and the NASA RAZ (RAZ N). A RAZ AP (Figure 1, C) is simply a RAZ A that meets one additional criterion: its secondary local maximum (or minimum) has an absolute voltage that is at least X% of the absolute voltage of the primary local maximum (or minimum) located on the same side of the HF QRS envelope. The variable "X%" is user-adjustable in the software but currently defaults to a number between 25% and 33% (commonly 30%), depending on the exact clinical situation and based on prior analyses of several hundred HF QRS ECGs. In turn, the strictest type of RAZ (the RAZ N [Figure 1, D]) has both a secondary local maximum and a secondary local minimum, both having an absolute voltage of at least X% of their respective primary local maximum and minimum. The RAZ nomenclature is such that when a RAZ N is present in any given HF QRS complex, a RAZ AP and a RAZ A also must be present in the same complex by definition. Similarly, whenever a RAZ AP is present, a RAZ A must be present by definition. As noted previously, the RMS voltage is a measure of HF QRS amplitude rather than morphology. The RMS voltage is calculated by squaring the amplitude of each sample point within the QRS interval, determining the mean of these squares, and then taking the square root of this mean.5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar The RMS voltage and related measures of amplitude are important because they often are decreased during acute myocardial ischemia, even when conventional ST segments are unchanged.4Aversano T Rudikoff B Washington A Traill S Coombs V Raqueno J High frequency QRS electrocardiography in the detection of reperfusion following thrombolytic therapy.Clin Cardiol. 1994; 17: 175-182Crossref PubMed Scopus (29) Google Scholar, 5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar, 7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar Nevertheless, RMS voltage levels in single-baseline 12-lead HF QRS ECG recordings are subject to wide interindividual (and interlead) variability.6Abboud S Belhassen B Miller HI Sadeh D Laniado S High frequency electrocardiography using an advanced method of signal averaging for non-invasive detection of coronary artery disease in patients with normal conventional electrocardiogram.J Electrocardiol. 1986; 19: 371-380Abstract Full Text PDF PubMed Scopus (49) Google Scholar, 11Pettersson J Carro E Edenbrandt L et al.Spatial, individual, and temporal variation of the high-frequency QRS amplitudes in the 12 standard electrocardiographic leads.Am Heart J. 2000; 139: 352-358PubMed Scopus (44) Google Scholar Thus, although serial measurements of RMS voltage in a given individual are potentially useful for monitoring ischemia over time,4Aversano T Rudikoff B Washington A Traill S Coombs V Raqueno J High frequency QRS electrocardiography in the detection of reperfusion following thrombolytic therapy.Clin Cardiol. 1994; 17: 175-182Crossref PubMed Scopus (29) Google Scholar, 5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar, 7Abboud S High-frequency electrocardiogram analysis of the entire QRS in the diagnosis and assessment of coronary artery disease.Prog Cardiovasc Dis. 1993; 35: 311-328Abstract Full Text PDF PubMed Scopus (40) Google Scholar RMS voltage levels alone in single resting recordings are probably insufficient to distinguish between individuals with and without CAD6Abboud S Belhassen B Miller HI Sadeh D Laniado S High frequency electrocardiography using an advanced method of signal averaging for non-invasive detection of coronary artery disease in patients with normal conventional electrocardiogram.J Electrocardiol. 1986; 19: 371-380Abstract Full Text PDF PubMed Scopus (49) Google Scholar and between individuals with and without prior MI.20Ringborn M Pahlm O Wagner GS Warren SG Pettersson J The absence of high-frequency QRS changes in the presence of standard electrocardiographic QRS changes of old myocardial infarction.Am Heart J. 2001; 141: 573-579Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar However, Seegobin et al8Seegobin RD Mohamed SA Ropchan G Pym J Frequency content and sex difference of the Frank lead signal-averaged ECG in a population with significant coronary artery disease: comparison with concurrent 12-lead ECG morphology.J Electrocardiol. 1995; 28: 228-233Abstract Full Text PDF PubMed Scopus (6) Google Scholar, 12Seegobin RD Mohamed SA Sex differences and frequency content of the Frank lead signal-averaged ECG in a normal population.J Electrocardiol. 1996; 29: 105-109Abstract Full Text PDF PubMed Scopus (8) Google Scholar have claimed the contrary. In contrast, Abboud et al6Abboud S Belhassen B Miller HI Sadeh D Laniado S High frequency electrocardiography using an advanced method of signal averaging for non-invasive detection of coronary artery disease in patients with normal conventional electrocardiogram.J Electrocardiol. 1986; 19: 371-380Abstract Full Text PDF PubMed Scopus (49) Google Scholar have shown that a measure of morphology (ie, presence vs absence of RAZ) is potentially more useful than a measure of voltage (RMS) for identifying CAD from single-baseline multichannel HF QRS ECGs. This may not be surprising given that, in an isolated conventional 12-lead ECG, it is also generally the morphology of a QRS complex, rather than its total voltage, that is diagnostically most useful for identifying MI and myocardial ischemia. Although the concept of RAZ has limitations (eg, the appearance of a RAZ sometimes may represent an improvement rather than a deterioration in physiology if the basis for the RAZ appearance is the addition of energy, and therefore new envelope sample points, to an area where the HF voltage had previously been "zero"21Berkalp B Baykal E Caglar N Erol C Akgun G Gurel T Analysis of high frequency QRS potentials observed during acute myocardial infarction.Int J Cardiol. 1993; 42: 147-153Abstract Full Text PDF PubMed Scopus (15) Google Scholar), the importance of determining the presence or absence of RAZ needs to be reiterated. Several examples of the diagnostic utility of the 12-lead HF QRS ECG are discussed subsequently. Some of the device requirements (hardware and software) necessary for real-time 12-lead HF QRS monitoring are detailed in the Appendix. Figure 2, A shows the main HF QRS ECG screen of a healthy 25-year-old man with no history of cardiovascular disease. The HF QRS ECG complexes are shown below their respective signal-averaged ECG conventional QRS complexes. This snapshot was obtained with the NASA software's autoscaling function in an "on" position, a setting that allows HF QRS morphology to be most readily evaluated by ignoring absolute voltages. Figure 2, B shows the same tracing as Figure 2, A but with the software's autoscaling function switched to the alternative "off " position, allowing the absolute voltages rather than the morphologies of the HF QRS complexes to be compared. In this view, the RAZs are less visible because the 2 leads that contain them have relatively low RMS voltages. Overall, the 12-lead HF QRS ECG shown in Figure 2 is normal and is typical for a healthy young individual. Figure 3 shows a morphology-optimized snapshot from the main HF QRS ECG screen of a 65-year-old man who had a normal conventional 12-lead ECG but advanced 2-vessel CAD, which was verified later the same day by cardiac catheterization performed as part of a work-up for chest pain. This individual had widespread RAZ formation, with a RAZ N present in HF leads II, aVR, V1, and V4 through V6 and a RAZ A present in HF leads III, aVF, and V3. His case illustrates the fact that resting 12-lead HF QRS ECG often can distinguish between individuals with (Figure 3) vs without (Figure 2) CAD, whereas conventional 12-lead ECG performed at the same time provides no such distinction. An ECG from a 57-year-old man who had 2-vessel CAD and a prior inferior MI is shown in Figure 4. This patient had even more extensive RAZ formation, with RAZ Ns present in all leads except for I (which has a RAZ AP) and V1.Figure 4Morphology-optimized 12-lead high-frequency QRS electrocardiogram from a 57-year-old man with 2-vessel coronary artery disease and a prior inferior myocardial infarction and right coronary artery stent placement. Nearly every lead has a NASA (National Aeronautics and Space Administration)-type reduced-amplitude zone. Kurt = kurtosis values; rms = root mean squared voltage in microvolts.View Large Image Figure ViewerDownload (PPT) In our experience, we have found that referencing the HF precordial leads to the right arm electrode rather than to the Wilson central terminal (via a user's switch in software), and thus using the CR precordial leads rather than the V precordial leads for HF QRS analysis (which maximizes QRS voltages22De Gasperi RN McCulloh DH CR leads in cardiac emergencies: a preliminary study.Chest. 1991; 99: 904-910Crossref PubMed Scopus (12) Google Scholar, 23De Gasperi RN Ezzudin SH Bauerlein EJ Sequeira R Lemberg L Duncan RC Digitized electrocardiograms recorded with bipolar right-infraclavicular leads compared to electrocardiograms recorded with unipolar chest V leads and bipolar lead II.J Electrocardiol. 2002; 35: 125-134Abstract Full Text PDF PubMed Scopus (5) Google Scholar), often allows an even better distinction between individuals with and without CAD. Some of the promising results of an observational study at the University of Texas using the standard limb HF QRS leads plus the CR precordial HF QRS leads for diagnosis of CAD are discussed subsequently. Pettersson et al5Pettersson J Pahlm O Carro E et al.Changes in high-frequency QRS components are more sensitive than ST-segment deviation for detecting acute coronary artery occlusion.J Am Coll Cardiol. 2000; 36: 1827-1834Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar found that during percutaneous transluminal coronary angioplasty, changes in RMS voltages in 12-lead surface HF QRS ECGs are 100% sensitive for detecting acute left anterior descending artery occlusion, 87% sensitive for detecting acute right coronary artery occlusion, and 73% sensitive for detecting acute left circumflex artery occlusion, for an overall sensitivity of 88%. This sensitivity was substantially higher than that obtained from an analysis of the changes in the conventional ST segments during the same study (71%-79%), even considering the fact that the conventional ST segment change criteria were clinically liberal. Similarly, Aversano et al4Aversano