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Aims Previous studies have demonstrated substantial variability in manual assessment of QRS complex duration (QRSd). Disagreements in QRSd measurements were also found in several automated algorithms tested on digitized electrocardiogram (ECG) recordings. The aim of our study was to investigate the variability of automated QRSd measurements performed by two commercially available electrocardiographs. Methods and results Two GE MAC 5000 (GE-1 and GE-2) electrocardiographs and two Mortara ELI 350 (Mortara-1 and Mortara-2) electrocardiographs were used in the study. Participants for the study were recruited from patients hospitalized in the department of cardiology of a university hospital. Participants underwent up to four recording sessions within a single day with a different electrocardiograph at each session when two to four immediately successive ECG recordings were undertaken. In 76 patients, 683 ECGs were recorded; the mean QRSd was 109.0 ± 26.1 ms. The QRSd difference ≥10 ms between the first and second intra-session ECG was found in 7, 3, 20, and 14% of ECG pairs for GE-1, GE-2, Mortara-1, and Mortara-2, respectively. No inter-session difference in QRSd was found within both manufacturers. In individual patients, Mortara calculated the mean QRSd to be longer by 7.3 ms (95% CI: 6.2–8.5 ms, P < 0.0001) with a 2.1-times (95% CI: 1.9–2.4) greater standard deviation of the mean QRSd (7.1 vs. 3.3 ms, P < 0.001). Conclusion Electrocardiographs from two manufacturers measured QRSd values with a systematic difference and a significantly different level of precision. This may have important clinical implications in selection of suitable candidates for cardiac resynchronization therapy.

Scenario: This resting 12-lead electrocardiogram (ECG) was obtained from a 71-year-old male veteran in the emergency department. The patient complained of dyspnea, had a history of uncontrolled hypertension, and was taking beta blockers. His ejection fraction (EF) was 20%. A regular feature of the American Journal of Critical Care, the ECG Puzzler addresses electrocardiogram (ECG) interpretation for clinical practice. To send an eLetter or to contribute to an online discussion about this article, visit www.ajcconline.org and click “Respond to This Article” on either the full-text or PDF view of the article. We welcome letters regarding this feature.

ECG Challenge: A 76-year-old man with a nonischemic cardiomyopathy is admitted to the hospital because of progressive weight gain and worsening peripheral edema. He notes that he has gained 12 pounds over the past 2 weeks. He states that he has been compliant with all of his medications, but does admit to dietary indiscretion. ECG A shows that the first 5 QRS complexes are regular at a rate of 48 bpm. There is a P wave before each of these QRS complexes (+) with a stable PR interval (0.24 s). The P wave is positive in leads I, II, aVF, and V4 to V6. Hence, this is a sinus bradycardia with a first-degree atrioventricular (AV) block or prolonged AV conduction. The QRS complex duration is increased, but there is a beat-to-beat variation in the width (ie, 0.12 and 0.14 s). The wider QRS complex has a typical right bundle branch block morphology with an RSR′ in lead V1 (→) and a broad …

Ventricular late potentials (VLPs) are small-amplitude waves with a short duration that appear at the end part of the QRS complex, making a QRS complex duration larger. The signal-averaged electrocardiography (ECG) technique enhances VLPs and beats, assuming noise as the only random variable. However, ECG signals are not completely stationary and different elongations appear in both time and amplitude in each beat. This research proposes to use piecewise linear approximation to segment each beat and performs the alignment of the beats using the technique known as derivative dynamic time-warping to have beats better aligned and consequently enhance the presence of VLPs. We recorded high-resolution ECGs (HRECGs) from 50 subjects in supine position with no heart-stroke antecedents. VLPs were created synthetically and added to the HRECGs. Two cases were evaluated: (i) duration of the QRS complexes with VLPs without beats alignment, and (ii) duration of QRS complexes with VLPs using beats alignment in time and amplitude. Considering QRS duration as an indicative of VLP presence, results show that when using beats alignment in time and amplitude it is possible to reach a sensitivity of 0.96 and a specificity of 0.52, as opposed to 0.72 and 0.40, respectively, when using only averaging without beats alignment in time and amplitude.

ECG Challenge: A 47-year-old woman with a history of palpitations that occur after exercise presents to an emergency department with palpitations that have persisted for several hours. An ECG (A) is obtained. Several minutes later the palpitations abruptly stop and an ECG (B) is repeated. ECG A shows a regular rhythm at a rate of 120 bpm. The QRS complex duration is increased (0.12 s) and there is a morphology consistent with a right bundle-branch block with a tall an RR′ wave in V1 (←) and a broad terminal S wave in leads I and V5 to V6 (→). The axis is extremely leftward between –30° and –90° (positive QRS complex in lead I and negative complex in leads II and aVF). There are 2 causes for an extreme left axis; that is, an old inferior wall myocardial …

To investigate the association between the QRS complex duration (QRSd) on admission and the prognosis of in-patient in people who suffered acute myocardial infarction. In retrospective method, enroll patients of cardiovascular department of the first hospital attached to Jilin university from 01/01

ECG Challenge: A 59-year-old woman has a history of lupus with renal involvement for which she is taking glucocorticoids. She has no known heart disease. She presents to her rheumatologist with concerns of intermittent palpitations that first began ≈1 month ago. She was referred to a cardiologist and an ECG was obtained. The ECG shows a regular rhythm with 2 different rates. The initial portion of the ECG shows a regular rhythm with a rate of 72 bpm. The second part of the ECG shows a regular rhythm at a rate of 160 bpm. All the QRS complexes (except for the 8th QRS complex; ↓) have the same morphology. The QRS complex duration is normal (0.08 s), and there is a normal morphology and a normal axis between 0° and +90° (positive QRS complex in leads I and aVF). The …

Compared to the natural electrical activation of the myocardium through the His-Purkinje system, right ventricular pacing is associated with prolonged QRS complex duration, thereby impeding the synchronicity of contractions. In left ventricular pacing, a higher pacing voltage decreases the QRS complex duration. The aim of our study was to describe the relation between the right ventricular pacing voltage and the QRS complex duration. Fourteen patients (73.6 +/- 7.6 years) with AV block and implanted pacemakers were paced at a frequency of 100 bpm with various pacing voltages. A signal-averaged QRS vector length was calculated at each degree of pacing voltage. The changes in the QRS complex duration were measured as a relative shift of the terminal region of the vectorcardiographic QRS complex (end-shift) and its most prominent peak (peak-shift) using the cross-correlation method. The nonlinear relationship between stimulation voltage and QRS duration was observed with the highest impact of stimulation voltage changes near the threshold value. The fourfold increase in the stimulation voltage above the threshold caused QRS complex shortening by 3.7 +/- 2.1 ms (range 0.19-7.76 ms). Similar peak- and end-shift responses to altered stimulation energy demonstrated that the acceleration of depolarization occurred in the initial portion of the QRS complex. Older electrodes exhibited smaller and more linear changes in the QRS complex duration.

In this paper, learning vector quantization artificial neural network method was used for designing decision support system for Electrocardiogram (ECG) analysis. Four types of ECG patterns were chosen from the data obtained from ECG simulator device to be recognized, including Bradycardia, tachycardia, monomorphic preventricular contraction, myocardial infraction R-R interval, QRS complex duration, ST-segment slope change features were performed as the characteristic representation of the original ECG signals to be fed into the neural network models. LVQ network was trained and tested for ECG pattern recognition and the experimental results, performance graphs are plotted for varying number of samples. The LVQ network exhibited the best performance and reached an overall accuracy of 95.5% when. trained with 200 samples with learning rate at 0.9.

The precise measurement of QT interval and QRS complex duration is important to characterize the electrical cardiac activity of the surface ECG. Variations of these intervals were evaluated when ECG sampling rate changes. The ECG recordings used in this study (n=78) were obtained from a combination of pharmacological blockage and postural changes. The ECG recordings were originally sampled at 500 Hz, and then were down-sampled by intervals of 25 Hz until the minimum sampling rate of 75 Hz. In all cases the down-sampling was implemented using cubic spline interpolation. The QRS complex duration, RR and QT intervals for each subject, condition and sampling rate were measured. The QT interval was corrected using two different techniques: Bazzett and individualized QT corrections. The effect of the sampling rate was modeled with an exponential decay function, which was used later to measure where the exponential reaches an asymptotic value (at 5tau). The 5tau value for uncorrected QT was at 290 Hz, corrected QT with Bazzett was at 303 Hz, and corrected QT with Individual method was at 253 Hz, finally QRS complex duration was at 297 Hz. An overestimation of the QT interval and QRS complex duration was observed when decreasing the sampling rate below 300 Hz

ECG Challenge: A 65-year-old man with a known idiopathic dilated cardiomyopathy treated with a β-blocker, angiotensin-converting-enzyme inhibitor, spironolactone, and daily diuretics was recently admitted to another hospital for decompensated heart failure that occurred while he was visiting his daughter. Upon returning, he presented to his cardiologist for a follow-up visit and reports that he had a surgical procedure performed, but he does not know any further details. The rhythm is for the most part regular, but there are 2 longer RR intervals noted (↔). The rate is 110 bpm. The QRS complex duration is increased (0.12 s). Although it has a morphology that resembles a right bundle-branch block, with a tall R wave in V1 (↓) and terminal S waves in leads V5-V6, it is not a typical looking right bundle-branch block. In addition, the axis is indeterminate (ie, between −90° and ±180°; negative QRS complex in leads I and aVF). It cannot be established whether this is an extreme right or extreme left axis. An indeterminate axis is not seen with conduction through the normal His-Purkinje system. With a …

Purpose: To compare the new "Seattle Criteria" for ECG interpretation in athletes, with former recommendations from ESC. Methods: In 2008, 574 professional football players (mean age 25, range 18-38 years) in Norway underwent preparticipation ECG-screening (CARDIOLINE, RealClick version 3.5.4., Milan, Italy). ECGs were read manually by one investigator, measuring the global QRST complex with calipers. Analyzes were performed according to the definitions of Corrado et al. 2010, as "updated" by Uberoi et al. 2011, and the new "Seattle criteria" by Drezner et al. 2013, and the results were compared. Results: Main differences are presented in Table 1. Altogether 111 (19%) players had abnormal ECG-findings according to the "Seattle Criteria", compared to 292 (51%) applying the former ESC recommendations (p

Despite overdrive pacing leads to the same increase in Ap in both groups, the pAF burden is only reduced in Group I. Conclusion: Atrio-ventricular sequence may be an important parameter in AF prevention pacing efficacy. Preserved AV conduction may be a relevant factor when selecting candidates to such therapy. Further prospective investigations focusing on AV conduction are on the way to wniirm these observations.