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Background: The evaluation of the QT interval in the presence of left bundle branch block (LBBB) is associated with the challenge to discriminate native QT interval from the prolongation due to the increase in QRS duration. The newest formula to evaluate QT interval in the presence of LBBB suggests: modified QT during LBBB = measured QT interval minus 50% of LBBB duration. The purpose of this study is therefore to validate the abovementioned formula in the clinical setting., Methods: Validation in two separate groups of patients: Patients who alternated between narrow QRS and intermittent LBBB and patients with narrow QRS who developed LBBB after transcatheter aortic valve implantation (TAVI)., Results: The acquired mean native QTc intervals and those calculated by the presented formula displayed no significant differences (p > .99 and p > .75)., Conclusions: In this study we proved for the first time the validity and applicability of the experimentally acquired formula for the evaluation of the QT interval in the presence of LBBB in a clinical setting., (© 2016 Wiley Periodicals, Inc.)

Q waves can regularly be observed in the 12-lead electrocardiogram either due to heart axis underlying pathology such as subacute myocardial infarction, myocardial scar, or accessory pathways. Rarely, other entities such as circumscribed hypertrophy can induce significant Q wave and represent an important differential diagnosis especially in younger patients. In the setting of atypical chest pain determination of the correct diagnosis can be challenging. Therefore, circumscribed hypertrophy should be taken into account to avoid unnecessary invasive procedures., (© 2015 Wiley Periodicals, Inc.)

The main tool for the differentiation of supraventricular tachycardia is the 12-lead electrocardiogram (ECG). Especially differentiating the atrioventricular nodal reentrant tachycardia (AVNRT) from the atrioventricular reentrant tachycardia (AVRT) due to concealed accessory pathway or from an atrial tachycardia (AT) is very important for catheter setting and ablation approach in an electrophysiological study. In our case we saw the occurrence of a U wave during tachycardia-simulating a pseudo P wave. This mimicked a long RP-tachycardia, although it was a common type AVNRT., (© 2014 Wiley Periodicals, Inc.)

Background: Left bundle branch block (LBBB) and QT prolongation both are associated with a worse prognosis. LBBB lengthens the QT interval. To date it is not known whether QT prolongation during LBBB differs in repolarization from QT prolongation during narrow QRS., Objective: The purpose of the present proof-of-concept-study was to develop a formula that allows comparison of the adjusted QT interval during LBBB with reference values and thereby allows interpretation of the QT interval irrespective of QRS widening., Methods: Sixty consecutive patients with sinus rhythm (SR) and narrow QRS underwent electrophysiologic study for ablation. In all patients, the intrinsic QRS ,QT, and JT times were measured during SR, and ventricular pacing from both the right ventricular apex (RVA) and the right ventricular outflow tract (RVOT) caused LBBB. We determined prolongation of the QT during as compared to SR (ΔQT). ΔQT was then divided by the QRS length during pacing QRS (QRSb). This describes the percentage of the QRS duration at LBBB, which must be subtracted from the measured QT (QTb) to determine the modified QT interval (QTm)., Results: The ratio of ΔQT to paced QRS was calculated as 48.3% (RVA) and 48.8% (RVOT) (mean 48.5%). The ratio intrinsic of JTi to paced JT was 1.0055 (RVA) and 1.0087 (RVOT). There was no significant difference in intrinsic JT vs paced JT (P = .2)., Conclusion: Right ventricular pacing causes prolongation of the QT due to a paced LBBB without prolongation of the JT time. In our study, we showed that QT prolongation caused by LBBB constitutes 48.5% of the QRS width. This is the value that must be subtracted from the measured QT in LBBB in order to estimate the modified QT. Thus, the resulting formula for "modified QT" estimation in LBBB is QTm = QTb - 48.5% * (QRSb)., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Interatrial block (IAB: P wave > or = 110 ms) is highly prevalent in people > or =65 years old living in a community., Methods: We investigated 720 consecutive people age > or =65 years old, from the general population, with the intention of evaluating the prevalence of IAB in their electrocardiogram. After excluding 42 people with atrial fibrillation and atrial flutter (5%) or having a permanent pacemaker (0,83%), we evaluated the electrocardiograms of the remaining 678 people with sinus rhythm., Results: We identified 400 (59%) persons with IAB with a similar distribution between men (58.5%) and women (59.4%). IAB was also identified in 347 from a total of 570 hypertensive people (60,9%) and only in 53 out of 108 (49.1%) nonhypertensive people (P = 0.015)., Conclusions: The surprisingly large prevalence of the IAB in the general older population emphasizes the importance of the early recognition of this abnormality from the surface 12-lead electrocardiogram.