High-frequency QRS Research Articles

Predicting angiographic coronary artery disease using machine learning and high-frequency QRS

AimExercise stress ECG is a common diagnostic test for stable coronary artery disease, but its sensitivity and specificity need to be further improved. In this paper, we construct a machine learning model for the prediction of angiographic coronary artery disease by HFQRS analysis of cycling exercise ECG.Methods and resultsThis study prospectively included 140 inpatients and 59 healthy volunteers undergoing cycling exercise ECG. The CHD group (N=104) and non-CHD group (N=95) were determined by coronary angiography gold standard. Automated HF QRS analysis was performed by the blinded method. The coronary group was predominantly male, with a higher prevalence of age, BMI, hypertension, and diabetes than the non-coronary group (P<0.001\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P<0.001$$\\end{document}), higher lipid levels in the coronary group (P<0.005\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P<0.005$$\\end{document}), significantly longer QRS duration during exercise testing (P<0.005\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P<0.005$$\\end{document}), more positive leads (P<0.001\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P<0.001$$\\end{document}), and a greater proportion of significant changes in HFQRS (P<0.001\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P<0.001$$\\end{document}). Age, Gender, Hypertension, Diabetes, and HF QRS Conclusions were screened by correlation analysis and multifactorial retrospective analysis to construct the machine learning models of the XGBoost Classifier, Logistic Regression, LightGBM Classifier, RandomForest Classifier, Artificial Neural Network and Support Vector Machine, respectively.ConclusionMale, elderly, with hypertension, diabetes mellitus, and positive exercise stress test HFQRS conclusions suggested a high risk of CHD. The best performance of the Logistic Regression model was compared, and a column line graph for assessing the risk of CHD was further developed and validated.

Revisiting the diagnostic and prognostic significance of high-frequency QRS analysis in cardiovascular diseases: a comprehensive review.

Cardiovascular diseases (CVDs) present a significant global public health threat, contributing to a substantial number of cases involving morbidity and mortality. Therefore, the early and accurate detection of CVDs plays an indispensable role in enhancing patient outcomes. Decades of extensive research on electrocardiography at high frequencies have yielded a wealth of knowledge regarding alterations in the QRS complex during myocardial ischemia, as well as the methodologies to assess and quantify these changes. In recent years, the analysis of high-frequency QRS (HF-QRS) components has emerged as a promising non-invasive approach for diagnosing various cardiovascular conditions. Alterations in HF-QRS amplitude and morphology have demonstrated remarkable sensitivity as diagnostic indicators for myocardial ischemia, often surpassing measures of ST-T segment changes. This comprehensive review aims to provide an intricate overview of the current advancements, challenges, and prospects associated with HF-QRS analysis in the field of CVDs.

The combination of high-frequency QRS and ST-segment alterations during exercise stress tests enhanced the diagnostic efficacy for coronary artery disease.

High-frequency QRS (HF-QRS) manifests as a novel adjunct electrocardiographic marker with potential utility in coronary artery disease (CAD) detection. We hypothesize that HF-QRS analysis may be superior to conventional ST-segment analysis in detecting CAD, and the combination of these two analyses in the exercise stress test may enhance the diagnostic efficacy for CAD. The study incorporated a sample of 157 patients (mean age 62 9 years) referred for nonemergent angiography. Before angiography, patients underwent exercise stress testing utilizing an upright bicycle. High-resolution electrocardiogram (ECG) data were collected during the exercise test, facilitating both HF-QRS and conventional ST-segment analyses. The diagnostic efficacy of HF-QRS and ST-segment analysis were compared, utilizing angiographic outcomes as the gold standard. The study design integrated HF-QRS analysis and ST-segment analysis via sequential and concurrent testing protocols. In terms of CAD detection, HF-QRS analysis displayed superior sensitivity compared to conventional ST-segment analysis (63% vs. 37%, p = .002). The serial test significantly increased specificity from 79% to 97% (p = .002) compared to ST-deviation analysis alone. It showed a markedly low sensitivity of 26%. The parallel test significantly increased sensitivity from 37% to 77% (p < .001), while retaining a moderate level of specificity of 51%. The quantity of ECG leads exhibiting a positive HF-QRS response demonstrated a correlation with the severity of CAD (p < .001). HF-QRS analysis exhibited superior sensitivity in detecting angiographically confirmed CAD relative to conventional ST-segment analysis. Moreover, the combination of HF-QRS and ST-segment alterations during exercise stress test enhanced the diagnostic efficacy for CAD.

Ultra-high-frequency ECG assessment of QRS fragmentation predicts sudden cardiac death risk in inherited arrhythmia syndromes

Abstract Background Fragmentation of the QRS complex, as a surrogate for scar or functionally disrupted ventricular activation, has been postulated as a risk factor for malignant ventricular arrhythmias across a range of cardiac diagnoses including cardiomyopathies, channelopathies and myocardial infarction. Fragmentation is subtle on the conventionally filtered 12-lead ECG and can easily be missed or over-diagnosed. Isolation of high-frequency (HF) QRS components could overcome this to demonstrate easily identifiable fragmentation but this has previously been limited by technological constraints resulting in a limited range of measured frequencies (150–300Hz). Ultra-high-frequency ECG (UHF-ECG) is a novel technology that utilises amplification and signal-averaging techniques to reliably measure frequencies up to 1000Hz. Purpose We explored the use of UHF-ECG in arrhythmia risk stratification. Methods We recruited 60 participants to undergo UHF-ECG recordings, including 23 healthy volunteers and 37 patients with inherited arrhythmia syndromes: 25 hypertrophic cardiomyopathy (HCM), 5 Brugada syndrome, 4 arrhythmogenic cardiomyopathy, 3 idiopathic ventricular fibrillation, 2 long QT syndrome and 1 non-ischaemic dilated cardiomyopathy. The arrhythmia risk status of patients with inherited disease was classified, by two independent researchers, into high or low risk based on their history of cardiac arrest, sustained ventricular arrhythmia, appropriate therapy, syncope and programmed ventricular stimulation result. A third researcher adjudicated disagreement. Two further researchers, blinded to aforementioned risk status, independently assessed the UHF-ECG recordings of all participants. Results 40 patients were classified as low risk, and 20 as high. Healthy volunteer UHF-ECGs showed uniform ventricular activation with single HF peaks in each lead. High-risk patients' UHF-ECGs showed multiple HF peaks, representing QRS fragmentation. The maximum number of HF peaks in any lead was used to measure severity of fragmentation. Example UHF-ECGs are shown in Figure 1. Fragmentation severity (number of peaks) correlated with arrhythmia risk status (chi-square statistic = 8.95, p-value = 0.03) across all participants (Figure 2) and when comparing high to low risk patients with inherited disease. UHF-ECG fragmentation could be observed even when the 12-lead ECG did not show any observable fragmentation. Among patients with inherited disease, patients with HCM showed the largest difference in UHF-ECG fragmentation between high and low risk. UHF-ECG fragmentation analysis showed excellent reproducibility with no difference in number of peaks identified between two independent assessors. Conclusion We demonstrate proof-of-concept that a novel ultra-high-frequency tool for measuring a broad range of high frequency QRS components can be used for sudden death risk stratification in patients with inherited cardiac conditions. Funding Acknowledgement Type of funding sources: None.

PO-626-07 VALIDATION OF A PORTABLE DEVICE FOR HF-ECG IN ISCHEMIA DETECTION DURING CORONARY BALLOON INFLATION IN ANGIOPLASTY - BRINGING THE PHYSIOLOGY LAB TO THE BEDSIDE !

High frequency QRS (HfQRS) analysis for rapid assessment of myocardial ischemia has never been evaluated owing to the logistical challenges of signal recording. We aim to evaluate, in a pilot study, the correlation between the HFQRS changes recorded on a novel wearable Sydäntek 12 lead ECG patch with balloon inflation induced ischaemia. To document utility of a portable device, Sydäntek, in ECG and HFECG during multiple balloon inflations. 10 patients (M:F = 8:2) undergoing coronary intervention for medically refractory chronic stable angina were screened for enrollment into the study ; 9/10 patients underwent the final recording. 1 patient was excluded owing to signal noise in the device due to reluctance in chest preparation. The mean recording time per case was 60+/-15 mins. ECG including HfQRS was recordable continuously during all intended times, using Sydäntek at 2k samples/secs. In 33 balloon inflation ischemia episodes , changes were seen on the HFQRS onset ∼ 10 secs, offset ∼45 secs after deflation . No significant changes were seen in the conventional ECG analysed for these upto ∼45 secs . Decrease in the amplitude of the HFQRS, and decrease in the real time RMS voltage of QRS in leads V2-V5 and the presence of RAZ ( reduced amplitude zone ) were considered to be changes suggestive of ischemia. RAZ disappeared ∼45 secs after the balloon deflation. The mean total ischemic was 1 +/-0.5 min per patient per balloon inflation. In this study , all 9 of the conventional ECGs were reported independently by 2 docs as not having significant ST-T changes of ischaemia. RAZ presence in HFQRS was seen in all 33 of complete coronary artery occlusion by balloon, in our study .There was reduction in the amplitude of HFQRS(mean 12+/-1 μV) and RMSv2-v5 (mean 7+/-0.5 μV) from the baseline during the inflation. Post intervention, both of the above parameters had a mean increase of 22+/-1 μV and 10+/-0.3 μV respectively. HFQRS measured using our novel, portable real time 12 lead ECG recording patch can reliably detect onset of coronary ischemia in a complete coronary occlusion even in absence of ST -T changes in 12 lead ECG . We submit this proof of concept for use in detecting ischemia in a variety of clinical situations including chest pain triage and post intervention monitoring.

BS-400-27 VALIDATION OF A PORTABLE DEVICE FOR HF-ECG IN ISCHEMIA DETECTION DURING CORONARY BALLOON INFLATION IN ANGIOPLASTY - BRINGING THE PHYSIOLOGY LAB TO THE BEDSIDE !

High frequency QRS (HfQRS) analysis for rapid assessment of myocardial ischemia has never been evaluated owing to the logistical challenges of signal recording. We aim to evaluate, in a pilot study, the correlation between the HFQRS changes recorded on a novel wearable Sydäntek 12 lead ECG patch with balloon inflation induced ischaemia.

High Frequency QRS analysis to supplement ST-Analysis for Myocardial Ischemia: multi-center prospective cohort

Abstract Funding Acknowledgements Type of funding sources: None. Background Exercise testing is a well-known non-invasive assessment method for myocardial ischemia in patients with suspected coronary artery disease (CAD). Stress electrocardiography (ECG) alone is underutilized in this population despite guideline recommendations in part due to poor diagnostic accuracy. High frequency QRS analysis (HF-QRS) is a novel tool to supplement standard ST-analysis during stress ECG and has been shown in single-center retrospective analyses to identify any and substantial ischemia with high diagnostic accuracy. We sought to compare the diagnostic accuracy of HF-QRS + standard ST-analysis compared to standard ST-analysis alone for the identification of moderate to severe myocardial ischemia by exercise SPECT MPI. Methods The study population included 388 consecutive patients who underwent exercise SPECT MPI. An ischemic HF-QRS pattern was defined as an absolute reduction of ≥1 μV and a relative reduction of ≥50% between maximal and minimal values of the mean root square of the 150-250 Hz band signal in ≥3 leads. The diagnostic accuracy of HF-QRS + ST-analysis was compared with ST-analysis alone for moderate to severe myocardial ischemia using chi-square analysis and semi-quantitative gated SPECT MPI as the gold standard. The incremental diagnostic value of HF-QRS was assessed by logistic regression analysis. The likelihood of any ischemia by number of leads positive for HF-QRS was also determined. Results The study cohort was 71% male and 84% Caucasian with a mean age of 58.3 ± 11.8 years. ST- and HF-QRS analyses were positive in 96 (24.7%) and 121 (31.2%) of patients, respectively. HF-QRS had a substantially higher sensitivity than ST-analysis for moderate-severe ischemia (66.7% vs. 40.0%, p &amp;lt;0.003). There was no statistically significant difference in specificities for HF-QRS vs ST-analysis for moderate-severe ischemia. (70.5% vs 75.7%, p = 0.08). There was a stepwise increase in ischemia as number of positive HF-QRS leads increased (p = 0.0004). HF-QRS demonstrated incremental diagnostic value to clinical risk factors without ST-analysis (p = 0.006) compared to Clinical + ST depressions (p &amp;lt; 0.001) versus clinical factors. Conclusions This multicenter, prospective study expands the literature showing the benefit of HF-QRS analysis. HF-QRS analysis substantially improves detection of moderate-severe ischemia over ST-analysis and clinical risk factors in patients undergoing exercise stress ECG. This noninvasive adjunct may improve CAD risk stratification and encourage use of stress ECG without imaging, reducing costs and radiation exposure.

Changes in High-Frequency Intracardiac Electrogram Indicate Cardiac Ischemia.

High-frequency QRS (HFQRS) analysis of surface ECG is a reliable marker of cardiac ischemia (CI). This study aimed to assess the response of HFQRS signals from standard intracardiac electrodes (iHFQRS) to CI in swine and compare them with conventional ST-segment deviations. Devices with three intracardiac leads were implanted in three swine in a controlled environment. CI was induced by inflating a balloon in epicardial coronary arteries. A designated signal-processing algorithm was applied to quantify the iHFQRS content before, during, and after each occlusion. iHFQRS time responses were compared to conventional ST-segment deviations. Thirty-three over thirty-nine (85%) of the occlusions presented significant reduction in the iHFQRS signal, preceding ST-segment change, being the only indicator of CI in brief occlusions. iHFQRS was found to be an early indicator for the onset of CI and demonstrated superior sensitivity to conventional ST-segment deviations during brief ischemic episodes.

High-frequency QRS analysis to supplement ST evaluation in exercise stress electrocardiography: Incremental diagnostic accuracy and net reclassification

BackgroundExercise stress electrocardiography (ECG) alone is underutilized in part due to poor diagnostic accuracy. High-frequency QRS analysis (HF-QRS) is a novel tool to supplement ST evaluation during stress ECG. We compared the diagnostic accuracy and net reclassification of HF-QRS analysis compared with ST evaluation for substantial myocardial ischemia by exercise SPECT myocardial perfusion imaging (MPI). Methods and ResultsExercise SPECT MPI was performed in 257 consecutive eligible patients (mean age 59 ± 12, 67% male). An ischemic HF-QRS pattern was defined as a ≥ 1 µV absolute reduction and a ≥ 50% relative reduction of the root-mean-square of the 150-250 Hz band signal in ≥ 3 leads. Left ventricular ischemia of ≥ 10% on SPECT MPI was the diagnostic standard for substantial myocardial ischemia. HF-QRS analysis demonstrated incremental diagnostic value to ST evaluation plus clinical risk factors (AUC 0.804 vs 0.749, P < .0001). A HF-QRS + ST -analysis strategy identified 92.3% of subjects with substantial ischemia and no abnormality in 59.9% of the cohort. No cardiac events occurred in patients without substantial ischemia identified by HF-QRS analysis. ConclusionsIn this prospective analysis, exercise stress ECG with HF-QRS analysis identified any and substantial ischemia with high diagnostic accuracy and may allow more than half of referred patients to safely avoid imaging.

The relationship between ECG predictors of cardiac resynchronization therapy benefit.

IntroductionCardiac resynchronization therapy (CRT) is an effective treatment that reduces mortality and improves cardiac function in patients with left bundle branch block (LBBB). However, about 30% of patients passing the current criteria do not benefit or benefit only a little from CRT. Three predictors of benefit based on different ECG properties were compared: 1) “strict” left bundle branch block classification (SLBBB); 2) QRS area; 3) ventricular electrical delay (VED) which defines the septal-lateral conduction delay. These predictors have never been analyzed concurrently. We analyzed the relationship between them on a subset of 602 records from the MADIT-CRT trial.Methods & resultsSLBBB classification was performed by two experts; QRS area and VED were computed fully automatically. High-frequency QRS (HFQRS) maps were used to inspect conduction abnormalities. The correlation between SLBBB and other predictors was R = 0.613, 0.523 and 0.390 for VED, QRS area in Z lead, and QRS duration, respectively. Scatter plots were used to pick up disagreement between the predictors. The majority of SLBBB subjects– 295 of 330 (89%)–are supposed to respond positively to CRT according to the VED and QRS area, though 93 of 272 (34%) non-SLBBB should also benefit from CRT according to the VED and QRS area.ConclusionSLBBB classification is limited by the proper setting of cut-off values. In addition, it is too “strict” and excludes patients that may benefit from CRT therapy. QRS area and VED are clearly defined parameters. They may be used to optimize biventricular stimulation. Detailed analysis of conduction irregularities with CRT optimization should be based on HFQRS maps.

INCREMENTAL DIAGNOSTIC ACCURACY OF HIGH FREQUENCY QRS ANALYSIS OVER ST-ANALYSIS FOR MYOCARDIAL ISCHEMIA: MULTI-CENTER PROSPECTIVE COHORT

Background: Exercise stress electrocardiography (ECG) alone is underutilized despite guideline recommendations in part due to poor diagnostic accuracy. High frequency QRS analysis (HF-QRS) is a novel tool to supplement standard ST-analysis during stress ECG. We sought to compare the diagnostic

High-frequency QRS analysis in the evaluation of chest pain in the emergency department

ObjectivesHigh frequency QRS (HFQRS) analysis has been shown to be an accurate marker for myocardial ischemia. Our objective was to test the use of HFQRS in diagnosing ACS in the emergency department. Methods324 patients presenting to the ED with chest pain were enrolled. Resting ECG was recorded and later analyzed by an HFQRS algorithm. Results were compared to the conventional ECG diagnosis by 3 independent interpretations: treating physician, expert cardiologist and an automated computer program. ResultsThe HFQRS analysis demonstrated improved sensitivity (67.5%) for the NSTE-ACS group compared to the human interpreters (59.7% and 53.2% for the treating physician and cardiologist respectively) with similar specificity. The automatic program had significantly lower sensitivity (31%) with a higher specificity (77%). ConclusionsHFQRS which has shown great promise in diagnosing stable CAD may also be helpful in the ED for diagnosing ACS.

Ambulatory monitoring of myocardial ischemia in the 21st century—an opportunity for high frequency QRS analysis

Ambulatory monitoring represents an effective tool for the assessment of silent and transient myocardial ischemia during routine daily activities. Incidence of silent ischemia can provide important prognostic information about patients with coronary artery disease or acute coronary syndrome, as well as about post-myocardial infarction patients. The current technological progress enables development of powerful and miniaturized wearable devices for Holter monitoring. Higher sampling rates, dynamic range, and extended computational and storage capacity allow for considering of more complex methodological solutions such as high-frequency QRS analysis for diagnosing myocardial ischemia. Implementation of suitable methodologies for advanced detection of myocardial ischemia into modern ambulatory monitoring devices creates the potential of making the ambulatory myocardial ischemia monitoring a valuable diagnostic tool in clinical practice.

Advanced ECG in 2016: is there more than just a tracing?

The 12-lead electrocardiogram (ECG) is the most frequently used technology in clinical cardiology. It is critical for evidence-based management of patients with most cardiovascular conditions, including patients with acute myocardial infarction, suspected chronic cardiac ischaemia, cardiac arrhythmias, heart failure and implantable cardiac devices. In contrast to many other techniques in cardiology, the ECG is simple, small, mobile, universally available and cheap, and therefore particularly attractive. Standard ECG interpretation mainly relies on direct visual assessment. The progress in biomedical computing and signal processing, and the available computational power offer fascinating new options for ECG analysis relevant to all fields of cardiology. Several digital ECG markers and advanced ECG technologies have shown promise in preliminary studies. This article reviews promising novel surface ECG technologies in three different fields. (1) For the detection of myocardial ischaemia and infarction, QRS morphology feature analysis, the analysis of high frequency QRS components (HF-QRS) and methods using vectorcardiography as well as ECG imaging are discussed. (2) For the identification and management of patients with cardiac arrhythmias, methods of advanced P-wave analysis are discussed and the concept of ECG imaging for noninvasive localisation of cardiac arrhythmias is presented. (3) For risk stratification of sudden cardiac death and the selection of patients for medical device therapy, several novel markers including an automated QRS-score for scar quantification, the QRS-T angle or the T-wave peak-to-end-interval are discussed. Despite the existing preliminary data, none of the advanced ECG markers and technologies has yet accomplished the transition into clinical practice. Further refinement of these technologies and broader validation in large unselected patient cohorts are the critical next step needed to facilitate translation of advanced ECG technologies into clinical cardiology.

High-frequency QRS analysis superior to conventional ST-segment analysis of women with chest pain

BackgroundThe novel analysis of high-frequency QRS components (HF/QRS) has been proposed in patients with chest pain (CP) referred for exercise tolerance test (ex-ECG). We sought to evaluate the prognostic role of exercise high-frequency QRS-analysis (ex-HF/QRS) in patients with recent-onset stable CP, in the emergency setting. MethodsPatients with CP underwent ex-ECG. A decrease greater than or equal to 50% of the signal of HF/QRS intensity was considered as index of ischemia as ST-segment depression greater than or equal to 2 mm or greater than or equal to 1 mm associated with CP. Exclusion criteria were QRS duration greater than or equal to 120 milliseconds and inability to exercise. Baseline characteristics were adjusted with the propensity score matching specifying nearest-neighbor matching in cardiovascular risk factors and risk scores. The primary end point was the composite of coronary stenosis greater than or equal to 70% or acute coronary syndrome, revascularization, and cardiac death on the 6-month follow-up. ResultsOf 589 patients, 22 achieved the end point. On the univariate analysis, known cardiovascular disease, GRACE score, and ex-HF/QRS were predictors of the end point. On the multivariate analysis, only ex-HF/QRS was predictor of the end point (odd ratio, 28; 95% confidence interval [CI], 6-120; P < .001). Overall, the ex-HF/QRS when compared to ex-ECG showed higher sensitivity (91% vs 27%; P = .02), lower specificity (74% vs 86%; P = .09), and comparable negative predictive value (99% vs 97%; P = .78). Receiver operating characteristic curve analysis showed the larger area of ex-HF/QRS (0.83; 95% CI, 0.75-0.90) over ex-ECG (0.57; CI, 0.44-0.70) and GRACE score (0.65; CI, 0.54-0.76); P < .03 on C-statistic. Women showed the largest area (0.89; CI, 0.83-0.95; P < .03) vs the other clinical data. ConclusionsIn patients with CP, the novel ex-HF/QRS analysis has a valuable incremental prognostic role over ex-ECG, especially in women.

Abstract 9563: High-frequency QRS Analysis is More Specific and Accurate Than Conventional ST-segment Analysis in Diagnosing Coronary Ischaemia

Purpose: High-frequency QRS analysis (HFQRS) is a new tool for detecting stress-induced coronary ischaemia. This study aims to compare HFQRS with conventional ST-segment analysis (STA) in the diagnostic performance in patients with chest pain and no history of coronary artery disease, which has not been investigated before. Methods: One hundred and seventy-five patients (120 men; mean age 58.2±7.5) with chest pain referred for diagnostic workup of coronary ischaemia were recruited. They underwent symptom-limited exercise treadmill test with both HFQRS and STA, followed by myocardial perfusion imaging (MPI) to confirm presence or absence of ischaemia. Results: Coronary ischaemia was present in 20 (11.4%) patients by MPI. HFQRS was more specific (85.8 vs 68.4%; p=0.002) and similarly sensitive (45 vs 60%; p=0.371) compared with STA. HFQRS had a higher positive predictive value (29 vs 19.7%; p=0.01) and similar negative predictive value (92.4 vs 93%; p=0.61) compared with STA. The diagnostic accuracy for coronary ischaemia by HFQRS was significantly higher than STA (81.1 vs 67.4%; p=0.001). Conclusions: HFQRS is more specific and accurate than STA in diagnosing coronary ischaemia in patients with chest pain and no prior history of coronary artery disease.

High-resolution electrocardiography in the diagnosis of arrhythmogenic right ventricular cardiomyopathy in Boxer dogs

To evaluate the reliability of high-resolution electrocardiography in the diagnosis of arrhythmogenic right ventricular cardiomyopathy in Boxers, 20 dogs with no structural cardiac alterations at echocardiographic examination were grouped on the basis of frequency of ventricular arrhythmias, evaluated by 24-hour ambulatory ECG, and undergoing a high-resolution electrocardiography. High frequency QRS duration, duration of terminal QRS complex less than 40µV (LAS40) and root mean square voltage of the terminal 40 milliseconds of the QRS complex (RMS40) were measured. Differences in high-resolution ECG variables were not observed between groups. Therefore, the results of this investigation suggest that high-resolution electrocardiography is not a useful method for the diagnosis of arrhythmogenic right ventricular cardiomyopathy in Boxers without detectable myocardial alterations or systolic dysfunction.

The cost-effectiveness of stress testing using high-frequency QRS analysis

Exercise ECG testing (EET) has limited accuracy in diagnosing coronary heart disease (CHD). High-frequency QRS (HFQRS) analysis is a new technology that improves the diagnostic performance of EET. We analysed the potential economic and healthcare benefits of HFQRS technology. The changes in utilisation of cardiac imaging tests and expenditures on medical treatment were studied using probabilistic models. A decision tree model was used to assess the expected costs of CHD workup and a prognostic Markov model was used to estimate long-term consequences. The models indicated that compared with EET, HFQRS-based workup results in a reduction in superfluous imaging tests. Analysis of long-term changes indicated a reduction in adverse events among CHD patients, with a decrease in overall medical costs and an increase in quality-adjusted life years. HFQRS technology is a promising tool for diagnosing CHD that may reduce medical costs while providing favourable prognostic outcomes.

High-frequency QRS analysis improves the specificity of exercise ECG testing in women referred for angiography

BackgroundExercise ECG testing in women for the diagnosis of coronary artery disease (CAD) has a higher false-positive rate compared to men. Consequently, women referred for coronary angiography following a positive exercise test often have normal coronary arteries or non-obstructive lesions. Analysis of the high-frequency components of the QRS complexes (HFQRS) has been reported to provide a sensitive means of detecting myocardial ischemia, independent of gender. The aim of the present study was to prospectively test the diagnostic performance of HFQRS and conventional exercise ECG in detecting stress-induced ischemia in women referred for coronary angiography. MethodsThe study included 113 female patients (age 64±9years) referred for non-urgent angiography. Patients performed a symptom-limited treadmill exercise test prior to angiography. High-resolution ECG was acquired during the test and used for both HFQRS and conventional ST-segment analyses. HFQRS diagnosis was determined by computerized analysis, measuring the stress-induced reduction in HFQRS intensity. The diagnostic performance of HFQRS, ST-segment analysis and clinical interpretation of the exercise test were compared, using angiography as a gold standard. ResultsHFQRS provided sensitivity of 70% and specificity of 80% for detection of angiographically significant coronary obstruction (≥70% stenosis in a single vessel or ≥50% in the left main artery). HFQRS was more specific than exercise ECG test (80% vs. 55%, P<.005), as well as more accurate (76% vs. 62%, P<.01). The number of ECG leads with ischemic HFQRS response correlated with the severity of CAD. HFQRS was highly specific (93%) in patients who achieved their age-predicted target heart rate, and retained its diagnostic accuracy in subgroups of patients with resting ECG abnormalities or inconclusive exercise ECG. ConclusionsHFQRS analysis, as an adjunct technology to exercise stress testing, may improve the diagnostic value of the ECG, and reduce the number of unnecessary imaging and invasive procedures.

High‐Frequency QRS Analysis in Patients with Acute Myocardial Infarction: A Preliminary Study

The 12-lead electrocardiogram (ECG) is a primary tool in the evaluation and risk stratification of patients with suspected acute myocardial infarction (AMI), even though the initial ECG of these patients is often normal or nondiagnostic. Myocardial ischemia induces depolarization changes that can be quantified by analysis of high-frequency QRS (HFQRS) components. We aimed to demonstrate the potential usefulness of HFQRS analysis in diagnosing myocardial ischemia by characterizing the morphological patterns of the HFQRS signals in patients with AMI before and following reperfusion. Five-minute high-resolution ECG was acquired from 30 patients with AMI (age 55 ± 11 years, 26 men) upon their admission to the intensive coronary care unit (ICCU). Serial ECGs were acquired following coronary revascularization and after additional 24 hours (24h). High-frequency morphology index (HFMI), quantifying the extent of ischemic patterns was computed by a custom software, and its values were compared between the serial ECG measurements. HFMI values were significantly higher on the admission ECG as compared to the post intervention ECG (4.6 ± 2.9% vs 3.4 ± 2.3%, P < 0.05) and to the 24h ECG (4.6 ± 2.9% vs 2.8 ± 2.1%, P < 0.01). In 79% of the patients who were successfully revascularized HFMI value decreased from admission ECG to 24h ECG. Analysis of HFQRS morphology in patients with AMI provides information about the existence and severity of myocardial ischemia. HFQRS analysis may aid in risk stratification of patients with suspected myocardial ischemia, complementarily to conventional ECG.