| 1. |
- Holm, Magnus, et al.
(author)
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Non-Invasive Assessment of the Atrial Cycle Length during Atrial Fibrillation in Man: Introducing, Validating and Illustrating a New ECG Method
- 1998
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In: Cardiovascular Research. - 1755-3245. ; 38:1, s. 69-81
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Journal article (peer-reviewed)abstract
- OBJECTIVES: Atrial fibrillation (AF) in man has previously been shown to include a wide variety of atrial activity. Assessment of the characteristics of this arrhythmia with a commonly applicable tool may therefore be important in the choice and evaluation of different therapeutic strategies. As the AF cycle length has been shown to correlate locally with atrial refractoriness and globally with the degree of atrial organization, with, in general, shorter cycle length during apparently random AF compared to more organized AF, we have developed a new method for non-invasive assessment of the AF cycle length using the surface and the esophagus (ESO) ECG. METHODS AND RESULTS: From the frequency spectrum of the residual ECG, created by suppression of the QRST complexes, the dominant atrial cycle length (DACL) was derived. By comparison with multiple intracardiac simultaneously acquired right and left AF cycle lengths in patients with paroxysmal AF, we found that the DACL in lead V1, ranging from 130 to 185 ms, well represented a spatial average of the right AF cycle lengths, whereas the DACL in the ESO ECG, ranging from 140 to 185 ms, reflected both the right and the left AF cycle length, where the influence from each structure depended on the atrial anatomy of the individual, as determined by MRI. In patients with chronic AF, the method was capable of following changes in the AF cycle length due to administration of D,L-sotalol and 5 min of ECG recording was sufficient for the DACL to be reproducible. CONCLUSIONS: We conclude that this new non-invasive method, named 'Frequency Analysis of Fibrillatory ECG' (FAF-ECG), is capable of assessing both the magnitude and the dynamics of the atrial fibrillation cycle length in man.
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| 2. |
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| 3. |
- Pehrson, Steen, et al.
(author)
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Improvement of Echocardiographic M-Mode Detection of Ventricular Precontraction in the Wolff-Parkinson-White Syndrome by Transesophageal Atrial Pacing
- 1998
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In: Echocardiography. - : Wiley. - 0742-2822 .- 1540-8175. ; 15:5, s. 479-488
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Journal article (peer-reviewed)abstract
- BACKGROUND: The purpose of this study was to evaluate the accuracy of conventional M-mode echocardiography in localizing the site of the accessory pathway in 21 patients with overt Wolff-Parkinson-White (W-P-W) syndrome during sinus rhythm (SR) and during transesophageal atrial stimulation (TAS). METHODS: The invasive electrophysiological study was used as a reference, and the results were compared with the pathway localization obtained through algorithmic interpretation of the 12-lead electrocardiogram during SR. Echocardiographic left parasternal short-axis recordings were performed during SR and TAS (100-120 beats/min). The shortest electromechanical interval measured at six different sites of the atrioventricular valve plane from the onset of the delta wave to the peak of the precontraction defined the pathway localization. RESULTS: Correct localization of the accessory pathway with echocardiography could be attained in 14 patients during SR (14 of 21, or 66%). With the aid of TAS, correct pathway localization was achieved for an additional 2 patients, making a total of 16 patients (76%). During TAS, precontraction was enhanced in 63% of the patients. With the algorithmic electrocardiographic interpretation, the localization of the accessory pathway was correct in 13 of the 21 patients (62%). The differences were not significant. CONCLUSION: M-mode echocardiography is a simple and readily available method for the identification of precontraction. The method is comparable to pathway localization through algorithmic ECG interpretation during SR. Transesophageal left atrial pacing during echocardiography can amplify the precontraction and thereby facilitate the interpretation of the wall motions.
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| 4. |
- Pehrson, Steen, et al.
(author)
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Non-invasive assessment of magnitude and dispersion of atrial cycle length during chronic atrial fibrillation in man
- 1998
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In: European Heart Journal. - : Oxford University Press (OUP). - 1522-9645 .- 0195-668X. ; 19:12, s. 1836-1844
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Journal article (peer-reviewed)abstract
- AIMS: Atrial fibrillation cycle lengths can be assessed from right precordial ECG leads and the unipolar oesophageal ECG using a non-invasive method called Frequency Analysis of Fibrillatory ECG. The purpose of this report is to present the results from application of this method in a large group of patients with long-term atrial fibrillation and to examine the differences between patients with 'coarse' and 'fine' atrial fibrillation. METHODS AND RESULTS: Simultaneous 15 min recordings from V1, V2 and an oesophageal lead at a position behind the posterior atrium were obtained in 28 patients, aged 41 to 78 years, with long-term (> 1 month) atrial fibrillation. In each lead, using the time averaging technique, the QRST complexes were suppressed. Thereafter, the frequency distribution of the residual ECG was estimated by means of Fast Fourier Transform. In the 3-12 Hz range of each lead, the dominant atrial cycle length, the power maximum and the spectral width were calculated. In 26 patients (93%), frequency spectra in the 3-12 Hz range could be obtained. The dominant atrial cycle length ranged from 120 to 175 ms, mean 150+/-16 (SD) ms in V1, and from 120 to 190 ms, mean 150+/-16 in an oesophageal lead (ns). The absolute difference in the dominant atrial cycle length between V1 and the oesophageal lead was 10.4+/-7.7 ms. There was no significant difference in the dominant atrial cycle length in V1 between patients with coarse and fine atrial fibrillation. The power maximum in V1 was significantly greater in patients with coarse compared to fine atrial fibrillation (P=0.01). The spectral widths ranged from 10 to 55 ms and demonstrated significantly higher mean values in lead V2 compared to V1 (P=0.001). Compared to V1, the mean values tended to be smaller in the oesophageal lead (P=0.05). CONCLUSIONS: Using the Frequency Analysis of Fibrillatory ECG method, the dominant atrial cycle length, power maximum and spectral width can be estimated from the frequency spectra in the majority of patients with atrial fibrillation. Spatial dispersion of the dominant atrial cycle length occurs in some patients and may be an important proarrhythmic marker. The distinction between coarse and fine atrial fibrillation cannot be used as a marker of the atrial cycle length.
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| 5. |
- Pehrson, Steen
(author)
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The oesophageal route in clinical electrocardiology
- 1998
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Doctoral thesis (other academic/artistic)abstract
- The subject of this thesis is the clinical use of the oesophageal electrode in electrocardiology. The three areas covered are oesophageal electro- cardiography, the biophysics of transoesophageal atrial stimulation (TAS) and the clinical utility of TAS. The literature is reviewed with respect to these areas. TAS was performed in 64 patients with documented supraventricular tachycardia (SVT) or a clinical history suggesting this disease. A subgroup of the patients underwent an invasive electrophysiological study (EPS) as well. It is concluded that the inducibility of SVT by TAS is high and comparable with that obtained by EPS. The accuracy of conventional M-mode echocardio- graphy in locating the site of accessory pathways was assessed in 21 patients with overt WPW (Wolff-Parkinson-White) syndrome during sinus rhythm and during TAS and compared with the correspon- ding accuracy of a 12-lead ECG algorithm. Correct location of the accessory pathway during sinus rhythm could be attained in the majority of patients by both methods. TAS applied during echocardiography could amplify the precontraction but gave only limited diagnostic information. The influence of body position, interelectrode spacing, electrode surface area and stimulation waveform on pacing thresholds during TAS was assessed. Further, the effect of intra- oesophageal local anaesthesia and pacing waveform on the discomfort experienced during TAS was studied. Neither the interelectrode pole distance, the pole surface area nor the body position had any significant influence on pacing thresholds. Intra-oesophageal lidocaine did not affect the pacing discomfort. The peak pacing thresholds using the triangular waveform were significantly higher compared to thresholds using a square waveform. A new non-invasive method called "Frequency Analysis of Fibrillatory ECG" (FAF-ECG) for the assessment of the dominant atrial cycle length (DACL) during atrial fibrillation is introduced. The DACLs were derived from lead V1, the oesophageal lead and right and left atrial invasive recordings. The DACL may be useful as an index of atrial refractoriness. Spatial dispersion in DACL occurs in some patients.
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| 6. |
- Pehrson, Steen, et al.
(author)
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The optimal oesophageal pacing technique--the importance of body position, interelectrode spacing, electrode surface area, pacing waveform and intra-oesophageal local anaesthesia
- 1999
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In: Scandinavian Cardiovascular Journal. - : Informa UK Limited. - 1651-2006 .- 1401-7431. ; 33:2, s. 103-109
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Journal article (peer-reviewed)abstract
- In order to improve the technique of transoesophageal atrial stimulation (TAS), the effects of body position, interelectrode spacing and electrode surface area on pacing threshold were assessed in two substudies. The effects of intra-oesophageal local anaesthesia and of two different pacing wave configurations on pacing threshold and discomfort were also assessed. Substudy I comprised 16 subjects (3 patients with a history of paroxysmal supraventricular tachycardia and 13 healthy volunteers) and substudy II comprised 16 healthy volunteers. TAS was performed using a hexapolar luminal prototype oesophageal electrode catheter. In substudy I bipolar pacing was performed in the semi-supine and left decubitus body positions for different pulse durations (20, 10, 6 and 2 ms), interelectrode pole distances (10 to 24 mm) and electrode pole surface areas (0.22 to 0.66 cm2). In substudy II TAS was performed with square wave and triangular waveform pulses after intra-oesophageal saline and lidocaine 20 mg/ml. These solutions were given in random order. Neither the interelectrode distance nor electrode surface areas had any significant influence on pacing thresholds. Stimulation thresholds were not affected by body position. Intraoesophageal lidocaine did not affect the discomfort experienced. Peak pacing thresholds using a triangular waveform were significantly higher than thresholds using a square waveformn (p < 0.001). The optimal pacing technique for TAS remains to be defined. The TAS-induced pain is probably not generated from the oesophageal mucous membrane. There is a significant difference in pacing thresholds between triangular and square waveforms.
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