Spatiotemporal electrocardiographic characterization of ventricular depolarization and repolarization abnormalities in long QT syndrome

Background and Purpose

If only a standard electrocardiogram (ECG) is available, at least 25% of patients with long QT syndrome (LQTS) may be missed. Our goal is to quantify abnormal electrical activity and to develop an ECG decision rule for the patients with LQTS.

Methods

One hundred forty-one subjects were included in this study (71 patients with LQTS and 70 healthy subjects). A 12-lead digital ECG was recorded for each subject and analyzed using the CAVIAR (comparative analysis of ECG-VCG and their interpretation with auto-reference to the patient) method.

Results

A decision tree involving criteria based on 3 spatiotemporal ECG measurements—the QT interval and the maximum amplitude of the T wave, both corrected from heart rate, and the loss of planarity of the end of QRS—identified patients with LQTS from healthy subjects with a sensitivity of 89%, a specificity of 96%, and a total accuracy of 92%.

Conclusions

This study suggests that 3-dimensional ECG analysis may improve the detection of patients with LQTS.     

Accuracy of electrocardiogram interpretation by cardiologists in the setting of incorrect computer analysis

Background

Overreading of 12 lead electrocardiograms (ECGs) is required to circumvent errors of computerized ECG interpretation. The accuracy of the overreading physician's interpretation of ECGs that were incorrectly read as atrial fibrillation by a computer algorithm has not been systematically examined.

Methods

A total of 2298 ECGs with the computerized interpretation of atrial fibrillation from 1085 patients were analyzed by 2 electrophysiologists, who identified 442 ECGs (19%) from 382 patients (35%) that were incorrectly interpreted as atrial fibrillation. Charts were reviewed to determine the interpretation of the ECG by the ordering physician (primary reader) and the overreading cardiologist.

Results

Cardiologists as primary readers more often corrected the misinterpreted ECGs as compared with internists, emergency physicians, or other specialists (94% vs 71%, P < .001). Surprisingly, interpretations by cardiologists as primary readers were more accurate than the interpretation provided by overreading cardiologists (94% vs 72%, P < .001).

Conclusion

Knowledge of an individual patient on whom an ECG is ordered may result in a more critical rhythm assessment and might account for the higher accuracy of rhythm interpretation by the cardiologist as compared with the interpretation by the overreading cardiologist who is lacking relevant clinical information.     

Electrocardiogram and B-type natriuretic peptide as screening tools for left ventricular systolic dysfunction in a population-based sample of 75-year-old men and women

Background

Plasma concentration of B-type natriuretic peptide (BNP) has been suggested as a powerful screening tool for left ventricular systolic dysfunction. However, there are reports indicating that the 12-lead electrocardiogram (ECG) could be just as powerful. We aimed to evaluate the 12-lead ECG and BNP as screening tools for left ventricular systolic dysfunction in an elderly, unselected population.

Methods

In a randomly selected population-based sample of 75-year-old men and women (n = 407), diagnostic characteristics were evaluated for the ECG and plasma concentration of BNP to detect left ventricular systolic dysfunction.

Results

Sensitivity, specificity, and negative and positive predictive values for the ECG to detect left ventricular systolic dysfunction were 96%, 79%, 100%, and 26%, respectively. The corresponding values for the BNP (cut-off value 28 pg/mL) were 93%, 55%, 99%, and 13%. In participants without major abnormalities in the ECG, left ventricular systolic dysfunction was found in <1% (1/302), irrespective of BNP concentrations. In participants with abnormal ECGs, systolic dysfunction was more prevalent in persons with abnormal BNP concentrations than in those with normal concentrations (35% vs 3%, difference 32%, 95%CI for the difference 16%-44%)

Conclusions

In 75-year-old subjects both the ECG and the plasma concentration of BNP are highly efficient in excluding left ventricular systolic dysfunction. However, compared with the BNP, the ECG yields a lower number of false positive cases. In screening for left ventricular systolic dysfunction, the BNP has a diagnostic value in addition to the ECG, but only in individuals with abnormal ECGs.     

An assessment of the electrocardiogram as a screening test for large atrial septal defects in children

Background and Purpose

The electrocardiogram (ECG) is commonly used as a screening tool for diagnosis of the ostium secundum atrial septal defect (ASD). We sought to analyze the utility of conventional ECG criteria in detecting right ventricular enlargement (RVE) due to the presence of an ASD.

Methods

Patients who underwent transcatheter or surgical closure of an isolated ASD between 1997 and 2004 were included if an ECG was performed less than 9 months before ASD closure and had echocardiographic RVE.

Results

Of 99 children (aged 6.8 ± 4.7 years; range, 1-18 years) with RVE and ASD, 57% had an ECG that met 1 or more RVE criteria. The sensitivity of ECG increased to 70% in younger patients and to 80% for the largest defects.

Conclusions

Electrocardiographic criteria for RVE are present in just more than over half of young patients with large ASDs. Although ECG is more sensitive in younger patients, it is unreliable as a screen for this lesion.     

Methods of teaching and evaluating electrocardiogram interpretation skills among cardiology fellowship programs in the United States

Background

This study examines the methods used by cardiology training programs within the United States to teach electrocardiogram (ECG) interpretation and prepare fellows for the American Board of Internal Medicine board examination.

Methods

A link to an 18-question Web-based survey was electronically mailed to 198 fellowship directors in the United States.

Results

The response rate was 45%. Most participating programs were university hospitals or affiliates (77%) and of moderate size (at least 11 total fellows [72%]). Programs were coordinated by senior (68%) general (60%) cardiologists. Only 42% of the programs performed formal testing. The American Board of Internal Medicine answer sheet was used by most faculty (92%) when teaching ECG interpretation.

Conclusions

Teaching of ECG interpretation varies among US fellowship programs. Coordination of curricula is performed by senior faculty, likely reflecting a trend toward subspecialization and dilution of ECG expertise among younger faculty. Future endeavors should focus on curriculum standardization with regular competency assessment.     

Diagnostic accuracy of extended-length electrocardiogram in differentiating between athlete's heart and hypertrophic cardiomyopathy

Background

Standard 12-lead electrocardiogram (ECG) has several limitations in solving the differential diagnosis between physiologic left ventricular hypertrophy (PLVH) and hypertrophic cardiomyopathy (HCM), given the high rate of false-positive results in athletes. The aim of this study was to assess the usefulness of several arrhythmic risk indexes in differentiating PLVH from HCM.

Methods

A multiparametric ECG analysis (extended-length ECG) was performed on 30 male athletes with PLVH and 30 male patients with HCM, with homogeneous age distribution.

Results

The combination of 4 extended-length ECG variables, namely, corrected QT interval (Bazett), QT dispersion, mean resting heart rate, and low-amplitude signal duration at 25 Hz (low-amplitude signal duration at the end of filtered QRS) displayed remarkable diagnostic accuracy (area under receiver operating characteristic curve, 94%). The same accuracy was obtained replacing QT dispersion with T-wave complexity index.

Conclusions

Extended-length ECG can be considered an effective, low-cost, and low time-consuming clinical tool for distinguishing between PLVH and HCM.     

In search of the best method to predict acute coronary syndrome using only the electrocardiogram from the emergency department

Introduction

The aim of this study was to compare different methods to predict acute coronary syndrome (ACS) using only data from a single electrocardiogram (ECG) in the emergency department (ED).

Method

We compared the ACS prediction abilities of classical ECG criteria, human expert ECG interpretation, a logistic regression model and an artificial neural network ensemble (ANN). The ED ECG and discharge diagnoses were retrieved for 861 patient visits to the ED for chest pain. Cross-validation was used to estimate the generalization performance of the logistic regression and the ANN model.

Results

The logistic regression model had the overall best performance in predicting ACS with an area under the receiver operating characteristic curve of 0.88. The sensitivities of logistic regression, ANN, expert physicians, and classical ECG criteria were 95%, 95%, 82%, and 75%, respectively, and the specificities were 54%, 44%, 63%, and 69%.

Conclusion

Our logistic regression model was the best overall method to predict ACS, followed by our ANN. Decision support models have the potential to improve even experienced ECG readers' ability to predict ACS in the ED.     

Fibrillation atriale, description de la prise en charge par les cardiologues, étude observationnelle. Résultats de l’étude Factuel

Objectives

To describe the management of patients with atrial fibrillation (AF) and to study consistency with guidelines on management of AF.

Patients and methods

Observational study on a random sample of cardiologists from a French national database. Each cardiologist had to recruit the first five patients meeting inclusion criteria (patients diagnosed with AF between January 2004 and one month before inclusion and accepting the collection of their medical data).

Results

Between December 2006 and January 2207, 1789 patients aged 71 on average have been recruited by 481 cardiologists. Fifty-one percent were diagnosed with paroxysmal, 15% with persistent and 33% with permanent AF. Restoration of sinus rhythm was preferred in forms considered as paroxysmal or persistent forms whereas control of the ventricular rate was more frequent in AF considered as permanent. Overall, therapeutic guidelines are applied in practice, despite a frequent use of amiodarone in patients with no associated heart disease. Prevention of thromboembolism was observed in 88% of the patients.

Conclusions

FACTUEL is the biggest observational study on AF ever conducted in France. The therapeutic strategies used by the cardiologists are consistent with the objectives of preventing thromboembolism and controlling heart rhythm and/or rate. In most cases, the treatment used is consistent with the therapeutic guidelines.     

Elevated blood pressure and electrocardiographic frontal T axis and spatial QRS-T angle changes in postmenopausal women

Introduction

Frontal T axis and spatial QRS-T angle are both measures of disturbances in ventricular repolarization and depolarization. We determined whether increased blood pressure is a risk factor for changes in these parameters in postmenopausal women free of left ventricular hypertrophy.

Materials and Methods

This cross-sectional study included 969 women. A standard 12-lead electrocardiogram (ECG) was recorded, and frontal T axes and spatial QRS-T angles were computed from vectorcardiography. Logistic regression analysis was used to assess the relationship between systolic and diastolic blood pressures on the one hand and both ECG parameters on the other.

Results

Odds ratios were 1.08 (95% confidence interval [CI], 0.99-1.18) and 1.12 (95% CI, 1.03-1.23) per 10 mm Hg systolic blood pressure for frontal T axis and QRS-T angle, respectively. These values were 1.05 (95% CI, 0.95-1.16) and 1.12 (95% CI, 1.02-1.23) per 5 mm Hg diastolic blood pressure for frontal T-axis and QRS-T angle, respectively.

Conclusion

Elevated blood pressure may lead to ventricular depolarization and repolarization disturbances before overt ECG left ventricular hypertrophy has developed.     

Detection of hypertrophic cardiomyopathy is improved when using advanced rather than strictly conventional 12-lead electrocardiogram

Introduction

Twelve-lead electrocardiogram (ECG) is used to screen for hypertrophic cardiomyopathy (HCM), but up to 25% of HCM patients do not have distinctly abnormal ECGs, whereas up to 5% to 15% of healthy athletes do. We hypothesized that an approximately 5-minute resting advanced 12-lead ECG test (“A-ECG score”) could detect HCM with greater sensitivity than pooled conventional ECG criteria and distinguish healthy athletes from HCM with greater specificity.

Materials and methods

Five-minute 12-lead ECGs were obtained from 56 HCM patients, 56 age/sex-matched healthy controls, and 69 younger endurance-trained athletes. Electrocardiograms were analyzed using recently suggested pooled conventional ECG criteria and also A-ECG scoring techniques that considered results from multiple advanced and conventional ECG parameters.

Results

Compared with pooled criteria from the strictly conventional ECG, an A-ECG logistic score incorporating results from just 3 advanced ECG parameters (spatial QRS-T angle, unexplained portion of QT variability, and T-wave principal component analysis ratio) increased the sensitivity of ECG for identifying HCM from 89% (78%-96%) to 98% (89%-100%; P = .025), while increasing specificity from 90% (83%-94%) to 95% (92%-99%; P = .020).

Conclusions

Resting 12-lead A-ECG scores that are simultaneously more sensitive than pooled conventional ECG criteria for detecting HCM and more specific for distinguishing healthy athletes and other healthy controls from HCM can be constructed. Pending further prospective validation, such scores may lead to improved ECG-based screening for HCM.     

Two automatic QT algorithms compared with manual measurement in identification of long QT syndrome

Background

Long QT syndrome (LQTS) is an inherited disorder that increases the risk of syncope and malignant ventricular arrhythmias, which may result in sudden death.

Methods

We compared manual measurement by 4 observers (QT_manual) and 3 computerized measurements for QT interval accuracy in the diagnosis of LQTS:

1.

QT measured from the vector magnitude calculated from the 3 averaged orthogonal leads X, Y, and Z (QT_VCG) and classified using the same predefined QTc cut-points for classification of QT prolongation as in manual measurements;

2.

QT measured by a 12-lead electrocardiogram (ECG) program (QT_ECG) and subsequently classified using the same cut-points as in (1) above;

3.

The same QT value as in (2) above, automatically classified by a 12-lead ECG program with thresholds for QT prolongation adjusted for age and sex (QT_interpret).

The population consisted of 94 genetically confirmed carriers of KCNQ1 (LQT1) and KCNH2 (LQT2) mutations and a combined control group of 28 genetically confirmed noncarriers and 66 unrelated healthy volunteers.

Results

QT_VCG provided the best combination of sensitivity (89%) and specificity (90%) in diagnosing LQTS, with 0.948 as the area under the receiver operating characteristic curve. The evaluation of QT measurement by the 4 observers revealed a high interreader variability, and only 1 of 4 observers showed acceptable level of agreement in LQTS mutation carrier identification (κ coefficient >0.75).

Conclusion

Automatic QT measurement by the Mida1000/CoroNet system (Ortivus AB, Danderyd, Sweden) is an accurate, efficient, and easily applied method for initial screening for LQTS.     

High-frequency electrocardiogram as a supplement to standard 12-lead ischemia monitoring during reperfusion therapy of acute inferior myocardial infarction

Background

Resolution of ST-segment elevation in the electrocardiogram (ECG) is used as a reperfusion sign during thrombolytic therapy in acute myocardial infarction. Analysis of high-frequency QRS components (HF-QRS) might provide additional information. The study compares changes in HF-QRS (150-250 Hz) to ST-segment changes in the standard ECG during thrombolytic therapy.

Methods

Twelve patients receiving intravenous thrombolytic therapy were included. A continuous 12-lead ECG recording was acquired for 4 hours.

Results

After 1 hour of therapy, 3 patients showed ST-elevation resolution as well as an increase in HF-QRS. These changes in ST and HF-QRS occurred simultaneously. No other patient showed significant changes in ST or HF-QRS after 1 hour. After 2 and 4 hours, there was less concordance between the standard and high-frequency ECGs.

Conclusions

In patients with early ST-elevation resolution, the standard and high-frequency ECGs show similar results. Later changes are more disparate and may provide different clinical information.     

In vivo studies of Scn5a+/− mice modeling Brugada syndrome demonstrate both conduction and repolarization abnormalities

Objectives

We investigate the extent to which the electrocardiographic (ECG) properties of intact Scn5a+/− mice reproduce the corresponding clinical Brugada syndrome phenotype and use this model to investigate the role of conduction and repolarization abnormalities in the arrhythmogenic mechanism.

Methods and Results

The ECGs were obtained from anesthetized wild-type and Scn5a+/− mice, before and after administration of the known pro- and antiarrhythmic agents flecainide and quinidine. The ECG intervals were measured and their dispersions calculated. Scn5a+/− hearts showed ventricular arrhythmias, ST elevation, and conduction disorders including increased QT dispersion, accentuated by flecainide. Quinidine did not cause ventricular arrhythmias but exerted variable effects on ST segments and worsened conduction abnormalities.

Conclusions

The ECG features in an Scn5a+/− mouse establish it as a suitable model for Brugada syndrome and demonstrate abnormal conduction and repolarization phenomena. Altered QT dispersion, taken to indicate increased transmural repolarization gradients, may be useful in clinical risk stratification.     

Conventional Cancer Screening versus PET/CT in Dermatomyositis/Polymyositis

Objective

To determine the value of whole-body [¹⁸F] fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) for diagnosing occult malignant disease in patients with myositis compared with broad conventional cancer screening.

Methods

We prospectively studied 55 consecutive patients with a recent diagnosis of myositis in 3 teaching hospitals over a 3-year period by whole-body FDG-PET/CT and compared the results with those of conventional cancer screening, which included thoracoabdominal CT, mammography, gynecologic examination, ultrasonography, and tumor marker analysis. Comparisons were made using predictive values and their 95% confidence intervals.

Results

A total of 9 of 55 patients were diagnosed with paraneoplastic myositis. FDG uptake was positive in 7 patients (1 false-positive), negative in 44 patients (3 false-negative), and inconclusive in 4 patients. Positive and negative predictive values of FDG-PET/CT for the diagnosis of cancer were 85.7% and 93.8%, respectively. Conventional screening was cancer-positive in 9 patients (2 false-positive) and negative in the remaining 46 patients (2 false-negative). Positive and negative predictive values were 77.8% and 95.7%, respectively. The overall predictive value of broad conventional screening was the same as that of FDG-PET/CT (92.7 vs 92.7).

Conclusion

The performance of FDG-PET/CT, a single imaging study, for diagnosing occult malignant disease in patients with myositis was comparable to that of broad conventional screening, which includes multiple tests.     

A comparison of conductive textile-based and silver/silver chloride gel electrodes in exercise electrocardiogram recordings

Background

The goal of this study was to compare disposable silver/silver chloride and reusable conductive textile-based electrodes in electrocardiogram (ECG) signal monitoring during physical activity.

Materials and Methods

The reusable electrodes were produced using thin silver-plated nylon 117/17 2-ply conductive thread (Statex Productions & Vertriebs GmbH, Bremen, Germany) sewed with a sewing machine on a chest belt. The disposable and reusable electrodes were compared in vivo according to ECG signal baseline drift, broadband electrode noise properties, and influence of electrode area to ECG signal morphology and frequency content. Twelve volunteers were included in this study.

Results

Electroconductive textile-based ECG electrodes produce significantly more noise in a very low frequency band (0-0.67 Hz) and not significantly less of broadband noise (0-250 Hz) than disposable silver/silver chloride electrodes. Decreasing area of textile electrodes decreases fidelity of registered ECG signals at low frequencies.

Conclusion

Textile electrodes having adequate area can be used in more applications than only R-R interval monitoring.     

Defining unrecognized myocardial infarction: a call for standardized electrocardiographic diagnostic criteria

Background

Unrecognized myocardial infarctions (UMI) are detected by surveillance electrocardiograms (ECGs). In epidemiologic studies, different sets of ECG criteria have been used to define myocardial infarction, possibly contributing to significant differences in prevalence estimates and risk factor associations. We sought to summarize the rationale behind the various UMI-ECG definitions and to suggest an approach to develop uniform criteria.

Methods

A comprehensive review of relevant publications from 1966 to 2002 was conducted.

Results

Out of 14 major studies, the occurrence of UMI as a proportion of all infarctions varied from 4% to 44%, with markedly varying ECG criteria. No study directly addressed the rationale behind selection of ECG criteria. Computerized ECG analysis appears superior to visual reading due to better reliability, speed and cost while maintaining a similar predictive validity. Criteria requiring only major Q waves have the highest specificity for ECG-MI and for prediction validity for future coronary heart disease in middle-aged white men. The addition of minor Q waves and ST-T abnormalities improves predictive validity in middle-aged women and elderly men. Minor Q waves can have their diagnostic accuracy improved by several strategies, including use of ST-T wave changes, Washington Code, vector cardiogram, chronic obstructive pulmonary disease-ECG criteria, and serial ECG analysis.

Conclusion

Currently the most cost-effective and valid method for detecting UMI in epidemiologic studies appears to be computerized ECG analysis using major Q waves in middle-aged white men. Issues needing further research include morphologic validation of ECG-UMI criteria and the influence of age, sex, and race on ECG-MI criteria.     

Feedback intervention to reduce routine electrocardiogram use in primary care

Background

Although physicians frequently order non-essential diagnostic tests, including screening tests such as electrocardiograms (ECGs), effective strategies for achieving evidence-based test-ordering are not proven. Our objective was to evaluate the impact of a feedback intervention designed to reduce the rate of screening ECG use and its variation.

Methods

A non-randomized pre-post intervention trial assessed the ordering of ECGs among primary care providers affiliated with Massachusetts General Hospital. Among outpatients visiting providers, those with cardiac diagnoses or symptoms were excluded, as were providers with <120 annual visits. Data were available on 117 providers, 105,682 patients, and 511,328 patient visits. During a 9-month intervention, providers received periodic case-mix-adjusted peer-comparisons of their screening ECG use. Two computerized billing systems tracked baseline (December 1996 to March 1998), intervention (April 1998 to December 1998), and post-intervention (January 1999 to September 1999) ECG use. Our outcome measures were: 1) the likelihood of ECG ordering at office visits and 2) provider practice variation, indicated by coefficient of variation and interquartile range.

Results

ECGs were ordered in 4.6% of visits before the intervention. Provider variation in case-mix adjusted ECG ordering was substantial (coefficient of variation, 101.6%; interquartile range, 3.2% [1.5%-4.7%]). ECG ordering averaged 3.5% during the intervention and 2.8% post-intervention (P < .001). Variation in ECG ordering narrowed considerably (coefficient of variation, 92.5%; interquartile range, 2.0% [1.0%-3.0%]) after the intervention. Multivariate analysis confirmed a persistent impact of the intervention.

Conclusions

Feedback to primary care providers successfully reduced ECG use and its variation. This approach may be applicable to other physician behaviors that remain contrary to evidence, but are not questioned because peer comparisons are unavailable.     

Risk factor associations with clinical distal symmetrical polyneuropathy and various neuropathy screening instruments and protocols in type 1 diabetes

Objective

To determine whether DSP and neuropathy-assessment instruments used by non-physicians have similar risk factors.

Research design and methods

Analyses were cross-sectional (n = 176).

Results

Risk factors were similar for DSP and screening devices.

Conclusions

These data support the clinical utility of neuropathy screening devices used by non-physician personnel.     

Diagnostic accuracy of a new detection algorithm for atrial fibrillation in cardiac telemonitoring with portable electrocardiogram devices

Background

Telemedical approaches targeting cardiac outpatients try to include electrocardiogram (ECG) analysis. Increasing numbers of monitored patients require automated preanalysis of the ECG to prioritize the evaluation for the clinical professional to enable an efficient intervention.

Methods

ECGs were recorded from 60 patients, both with a standard 12-lead ECG and with a new handheld ECG device having dry electrodes for direct skin contact. Recordings of the handheld device were automatically analyzed by a new algorithm. The 12-lead recordings were evaluated by a blinded cardiologist and then compared to the automated analysis of the handheld ECG. Sensitivity and specificity of the algorithm for the detection of atrial fibrillation (AF) were calculated.

Results

A total of 60 ECG strips having 122 ± 36 beats were registered. One hundred percent of the ECG strips were sufficient for automated heart rate count; 96.6%, for automated AF analysis; and 80%, for PQ, QRS, and QTc time measurements. AF detection had a sensitivity of 92.9% and a specificity of 90.9%. There was no difference in heart rate count between automated and manual analysis (median, 71 vs 70 beats per minute; P = .51). Automated measurements of a summary complex showed no difference for PQ time (165 vs 161 milliseconds, P = .50) but overestimated QRS (119 vs 90 milliseconds, P = .001) and QTc (489 vs 417 milliseconds, P < .001) times as compared to the 12-lead recordings analyzed manually.

Conclusion

The new algorithm is suitable for automated preanalysis of the ECG data with regard to AF. It could be used for rapid selection of ECGs with relevant rhythm abnormalities from a large pool. Electrocardiographic data remain to be evaluated by health care professionals for exact diagnosis.     

Comparison of 5 methods of QT interval measurements on electrocardiograms from a thorough QT/QTc study: effect on assay sensitivity and categorical outliers

Introduction

We studied moxifloxacin-induced QT prolongation and proportion of categorical QTc outliers when 5 methods of QT measurement were used to analyze electrocardiograms (ECGs) from a thorough QT study.

Methods

QT interval was measured by the threshold, tangent, superimposed median beat, automated global median beat, and longest QT methods in a central ECG laboratory in 2730 digital ECGs from 39 subjects during placebo and moxifloxacin treatment.

Results

All 5 methods were able to demonstrate statistically significant moxifloxacin-induced QTcF prolongation. However, lower bound of 95% 1-sided confidence interval of QTcF prolongation did not exceed 5 milliseconds with the longest QT method. More QTcF outliers were observed with the longest QT and tangent methods, whereas the other 3 methods were comparable. QTcF values greater than 500 milliseconds were observed only with moxifloxacin by the tangent method, and with moxifloxacin and placebo by the longest QT method.

Conclusion

The method of QT measurement must be considered when interpreting individual thorough QT/QTc studies.