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Electroanatomic Mapping of Focal Atrial Tachycardia: Reproducibility ofActivation Time Measurement and Focus Localization
Linköping University, Department of Medicine and Health Sciences, Cardiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
Linköping University, Department of Medicine and Health Sciences, Cardiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
Linköping University, Department of Medicine and Health Sciences, Cardiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.ORCID iD: 0000-0003-3059-4404
2010 (English)Article in journal (Other academic) Submitted
Abstract [en]

Background: Different algorithms of estimating local activation time (LAT) can be usedduring the mapping of focal atrial tachycardia (FAT).

Objective: The impact of these algorithms on the reproducibility of LAT measurementand the location of the focus.

Methods: Fifteen patients (48 ± 17 yrs) with FAT were studied. Three independentobservers reviewed 1438 bipolar electrograms and successively assigned the LAT on thepeak amplitude (Bi-peak), the steepest downslope (Bi-dslope), and the onset (Bi-on) ofthe electrograms. The reproducibility of LAT measurement was estimated.

Results: The mean interobserver absolute differences in LAT for the three algorithmswere 1.47 ± 2.75 ms (Bi-peak) vs. 2.15 ± 3.89 ms (Bi-dslope) vs. 2.87 ± 3.47 (Bi-on) (p <0.0001). The corresponding intraobserver differences were 2.29 ± 3.74 ms (Bi-peak) vs2.47 ± 4.17 ms (Bi-dslope) vs 3.16 ± 4.49 ms (Bi-on) (p < 0.0001). The interobserverdifferences in the location of the focus were 3.57 ± 3.81 mm (Bi-peak) vs 5.47 ± 4.98mm (Bi-dslope) vs 6.57 ± 6.94 mm (Bi-on) (p = 0.03), with differences of up to 13 mm(Bi-peak), 16 mm (Bi-dslope), and 25 mm (Bi-on). However, regardless of the method ofLAT determination, the foci computed by the three observers clustered within regions oflow-amplitude fractionated electrograms.

Conclusions: Significant observer variability exists among the three algorithms, whichtend to compute different LAT and foci with different locations. However, the foci aresituated in regions of low voltage fractionated electrograms.

Place, publisher, year, edition, pages
2010.
Keyword [en]
Ectopic atrial tachycardia; catheter ablation; atrial electrogram
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-20460OAI: oai:DiVA.org:liu-20460DiVA: diva2:234577
Available from: 2009-09-09 Created: 2009-09-09 Last updated: 2013-12-17Bibliographically approved
In thesis
1. Focal atrial tachycardia: Insights concerning the arrhythmogenic substrate based on analysis of intracardiac electrograms and inflammatory markers
Open this publication in new window or tab >>Focal atrial tachycardia: Insights concerning the arrhythmogenic substrate based on analysis of intracardiac electrograms and inflammatory markers
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Focal atrial tachycardias are tachycardias characterized by a radial spread of activation from a discrete area of the atrial myocardium. They account for 10-15% of supraventricular tachycardias and are generally poorly responsive to pharmacological treatment. The pathophysiologic substrate of these arrhythmias remains poorly understood. Computational studies suggest that a certain degree of intercellular uncoupling and anisotropy are important prerequisites for the development of focal arrhythmias. The anisotropy and intercellular uncoupling could promote focal arrhythmias by minimizing the suppressive effect of the surrounding atrial muscle on the pacemaking process in the focus. This hypothesis would be in agreement with the fact that fractionated electrograms, a marker of anisotropy and reduced intercellular coupling, are often recorded at the site of earliest activated site. Reduced intercellular coupling could be induced by factors enhancing the amount of intracardiac connective tissue, such as advancing age or cardiac disease states. Indeed, focal inflammatory processes have been reported in atrial specimens resected from patients with focal tachycardia undergoing arrhythmia surgery.

Methods: In a group of patients with paroxysmal and permanent atrial fibrillation we sought to assess whether there is a link between inflammation and the occurrence of atrial arrhythmia. We therefore analyzed different inflammatory markers (C-reactive protein and interleukin-6 and 8) in the systemic and pulmonary circulation as well as in the heart in these patients. In addition, we assessed the extent of intercellular uncoupling in the vicinity of tachycardia origin in patients with focal atrial tachycardia. We also assessed the impact of electrogram fractionation on the method of activation time determination, by comparing different methods for estimating activation time with regard to the appearance of the resultant activation maps and the location of the foci. We also assessed the observer variability in the estimation of activation time during mapping of these tachycardias.

Results: There was no evidence of elevated circulatory levels of inflammatory markers in patients with paroxysmal atrial fibrillation. However, patients with permanent atrial fibrillation had increased levels of inflammatory markers (interleukin-8) in the systemic circulation but not in the pulmonary circulation or in the heart. In patients with focal atrial tachycardia, a higher degree of electrogram fractionation existed in the region surrounding the earliest activation site and activated within the first 15 ms as compared with the remaining atrium. Moreover, within this region, from the periphery towards the earliest activated site, there was a gradual increase in electrogram fractionation as well as a gradual decrease in the peak-to-peak voltage. When comparing different methods for estimating local activation time we found that different methods can generate activation maps with different appearances and foci with different locations. However, regardless of the method of activation time determination, the foci tend to cluster within relatively large areas of low-amplitude fractionated electrograms. In addition we found significant observer variability in the estimation of the local activation time.

Conclusion: Patients with paroxysmal atrial fibrillation (and probably focal atrial tachycardia) do not have elevated levels of inflammatory markers. The increased levels of interleukin-8 in the systemic circulation suggest a link between long-lasting arrhythmia and inflammation. A relatively wide area of increased electrogram fractionation exists around the site of origin of focal atrial tachycardia. These findings suggest a sizeable atrial region with particular electrophysiological proprieties and raise the possibility of an anatomical substrate of the tachycardia. Increased electrogram fractionation can impact the process of activation determination, as suggested by the fact that different methods compute foci with different locations. In addition, there is significant observer variability in the estimation of local activation time in these patient.

Place, publisher, year, edition, pages
Linköp: Linköping University Electronic Press, 2009. 96 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1148
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-20461 (URN)978-91-7393-556-2 (ISBN)
Public defence
2009-09-04, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings Universitet, Linköping, 13:00 (English)
Opponent
Note
Article II and III are the same article while article III is linked to the corrected article and article II to the original article.Available from: 2009-09-09 Created: 2009-09-09 Last updated: 2010-02-25Bibliographically approved

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