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| 2. |
- Vahedi, Farzad, et al.
(författare)
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Effect of heart rate on ventricular repolarization in healthy individuals applying vectorcardiographic T vector and T vector loop analysis.
- 2011
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Ingår i: Annals of Noninvasive Electrocardiology. - : John Wiley & Sons. - 1542-474X .- 1082-720X. ; 16:3, s. 287-294
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Tidskriftsartikel (refereegranskat)abstract
- Background: Ventricular repolarization (VR) is strongly influenced by heart rate (HR) and autonomic nervous activity, both of which also are important for arrhythmogenesis. Their relative influence on VR is difficult to separate, but might be crucial for understanding while some but not other individuals are at risk for life-threatening arrhythmias at a certain HR. This study was therefore designed to assess the “pure” effect of HR increase by atrial pacing on the ventricular gradient (VG) and other vectorcardiographically (VCG) derived VR parameters during an otherwise unchanged condition. Methods: In 19 patients with structurally normal hearts, a protocol with stepwise increased atrial pacing was performed after successful arrhythmia ablation. Conduction intervals were measured on averaged three-dimensional (3D) QRST complexes. In addition, various VCG parameters were measured from the QRS and T vectors as well as from the T loop. All measurements were performed after at least 3 minutes of rate adaptation of VR. Results: VR changes at HR from 80 to 120 bpm were assessed. The QRS and QT intervals, VG, QRSarea, Tarea, and Tamplitude were markedly rate dependent. In contrast, the Tp-e/QT ratio was rate independent as well as the T-loop morphology parameters Tavplan and Teigenvalue describing the bulginess and circularity of the loop. Conclusions: In healthy individuals, the response to increased HR within the specified range suggests a decreased heterogeneity of depolarization instants, action potential morphology, and consequently of the global VR.
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| 3. |
- Axelsson, Karl-Jonas, et al.
(författare)
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Adaptation of ventricular repolarization duration and dispersion during changes in heart rate induced by atrial stimulation.
- 2020
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Ingår i: Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc. - : Wiley. - 1542-474X. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- The duration of ventricular repolarization (VR) and its spatial and temporal heterogeneity are central elements in arrhythmogenesis. We studied the adaptation of VR duration and dispersion and their relationship in healthy human subjects during atrial pacing.Patients 20-50 years of age who were scheduled for ablation of supraventricular tachycardia without preexcitation but otherwise healthy were eligible. Vectorcardiography recordings with Frank leads were used for data collection. Incremental atrial pacing from a coronary sinus electrode was performed by decrements of 10ms/cycle from just above sinus rate, and then kept at a fixed heart rate (HR) just below the Wenckebach rate for ≥5min and then stopped. VR duration was measured as QT and VR dispersion as T area, T amplitude and ventricular gradient. The primary measure (T90 End) was the time to reach 90% change from baseline to the steady state value during and after pacing.A complete study protocol was accomplished in 9 individuals (6 women). VR duration displayed a monophasic adaptation during HR acceleration lasting on average 20s. The median (Q1-Q3) T90 End for QT was 85s (51-104), a delay by a factor >4. All dispersion measures displayed a tri-phasic response pattern during HR acceleration and T90 End was 3-5 times shorter than for VR duration.Even during close to "physiological" conditions, complex and differing response patterns in VR duration and dispersion measures followed changes in HR. Extended knowledge about these responses in disease conditions might assist in risk evaluation and finding therapeutic alternatives.
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| 4. |
- Bacharova, Ljuba, et al.
(författare)
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ISE/ISHNE expert consensus statement on the ECG diagnosis of left ventricular hypertrophy : The change of the paradigm
- 2023
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Ingår i: Annals of Noninvasive Electrocardiology. - 1082-720X. ; 29:1, s. e13097-
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Tidskriftsartikel (refereegranskat)abstract
- The ECG diagnosis of LVH is predominantly based on the QRS voltage criteria. The classical paradigm postulates that the increased left ventricular mass generates a stronger electrical field, increasing the leftward and posterior QRS forces, reflected in the augmented QRS amplitude. However, the low sensitivity of voltage criteria has been repeatedly documented. We discuss possible reasons for this shortcoming and proposal of a new paradigm. The theoretical background for voltage measured at the body surface is defined by the solid angle theorem, which relates the measured voltage to spatial and non-spatial determinants. The spatial determinants are represented by the extent of the activation front and the distance of the recording electrodes. The non-spatial determinants comprise electrical characteristics of the myocardium, which are comparatively neglected in the interpretation of the QRS patterns. Various clinical conditions are associated with LVH. These conditions produce considerable diversity of electrical properties alterations thereby modifying the resultant QRS patterns. The spectrum of QRS patterns observed in LVH patients is quite broad, including also left axis deviation, left anterior fascicular block, incomplete and complete left bundle branch blocks, Q waves, and fragmented QRS. Importantly, the QRS complex can be within normal limits. The new paradigm stresses the electrophysiological background in interpreting QRS changes, i.e., the effect of the non-spatial determinants. This postulates that the role of ECG is not to estimate LV size in LVH, but to understand and decode the underlying electrical processes, which are crucial in relation to cardiovascular risk assessment.
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| 6. |
- Chaudhry, Uzma, et al.
(författare)
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Evaluation of the ECG based Selvester scoring method to estimate myocardial scar burden and predict clinical outcome in patients with left bundle branch block, with comparison to late gadolinium enhancement CMR imaging
- 2017
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Ingår i: Annals of Noninvasive Electrocardiology. - : Wiley. - 1082-720X. ; 22:5
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Tidskriftsartikel (refereegranskat)abstract
- Background: Myocardial scar burden quantification is an emerging clinical parameter for risk stratification of sudden cardiac death and prediction of ventricular arrhythmias in patients with left ventricular dysfunction. We investigated the relationships among semiautomated Selvester score burden and late gadolinium enhancement-cardiovascular magnetic resonance (LGE-CMR) assessed scar burden and clinical outcome in patients with underlying heart failure, left bundle branch block (LBBB) and implantable cardioverter-defibrillator (ICD) treatment. Methods: Selvester QRS scoring was performed on all subjects with ischemic and nonischemic dilated cardiomyopathy at Skåne University Hospital Lund (2002-2013) who had undergone LGE-CMR and 12-lead ECG with strict LBBB pre-ICD implantation. Results: Sixty patients were included; 57% nonischemic dilated cardiomyopathy and 43% ischemic cardiomyopathy with mean left ventricular ejection fraction of 27.6% ± 11.7. All patients had scar by Selvester scoring. Sixty-two percent had scar by LGE-CMR (n = 37). The Spearman correlation coefficient for LGE-CMR and Selvester score derived scar was r = .35 (p = .007). In scar negative LGE-CMR, there was evidence of scar by Selvester scoring in all patients (range 3%-33%, median 15%). Fourteen patients (23%) had an event during the follow-up period; 11 (18%) deaths and six adequate therapies (10%). There was a moderate trend indicating that presence of scar increased the risk of clinical endpoints in the LGE-CMR analysis (p = .045). Conclusion: There is a modest correlation between LGE-CMR and Selvester scoring verified myocardial scar. CMR based scar burden is correlated to clinical outcome, but Selvester scoring is not. The Selvester scoring algorithm needs to be further refined in order to be clinically relevant and reliable for detailed scar evaluation in patients with LBBB.
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| 7. |
- Dahlberg, Pia, et al.
(författare)
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QT correction using Bazett's formula remains preferable in long QT syndrome type 1 and 2
- 2021
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Ingår i: Annals of Noninvasive Electrocardiology. - : John Wiley & Sons. - 1082-720X .- 1542-474X. ; 26:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: The heart rate (HR) corrected QT interval (QTc) is crucial for diagnosis and risk stratification in the long QT syndrome (LQTS). Although its use has been questioned in some contexts, Bazett's formula has been applied in most diagnostic and prognostic studies in LQTS patients. However, studies on which formula eliminates the inverse relation between QT and HR are lacking in LQTS patients. We therefore determined which QT correction formula is most appropriate in LQTS patients including the effect of beta blocker therapy and an evaluation of the agreement of the formulae when applying specific QTc limits for diagnostic and prognostic purposes.Methods: Automated measurements from routine 12-lead ECGs from 200 genetically confirmed LQTS patients from two Swedish regions were included (167 LQT1, 33 LQT2). QT correction was performed using the Bazett, Framingham, Fridericia, and Hodges formulae. Linear regression was used to compare the formulae in all patients, and before and after the initiation of beta blocking therapy in a subgroup (n = 44). Concordance analysis was performed for QTc >= 480 ms (diagnosis) and >= 500 ms (prognosis).Results: The median age was 32 years (range 0.1-78), 123 (62%) were female and 52 (26%) were children <= 16 years. Bazett's formula was the only method resulting in a QTc without relation with HR. Initiation of beta blocking therapy did not alter the result. Concordance analyses showed clinically significant differences (Cohen's kappa 0.629-0.469) for diagnosis and prognosis in individual patients.Conclusion: Bazett's formula remains preferable for diagnosis and prognosis in LQT1 and 2 patients.
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