Europace Advance Access originally published online on December 3, 2008
Europace 2009 11(1):35-41; doi:10.1093/europace/eun311
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Ablation: Imaging
A new approach for contrast-enhanced X-ray imaging of the left atrium and pulmonary veins for atrial fibrillation ablation: rotational angiography during adenosine-induced asystole
1 Department of Internal Medicine/Cardiology, German Heart Institute Berlin, Augustenburger Platz 1, 13353 Berlin, Germany; 2 Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, China
Manuscript submitted 15 July 2008. Accepted after revision 22 October 2008.
* Corresponding author. Tel: +49 30 4593 2436; fax: +49 30 4593 2438. E-mail address: kriatselis{at}dhzb.de
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Abstract |
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Aims: Atrial fibrillation ablation is a complex procedure that requires detailed anatomic information about left atrium (LA) and pulmonary veins (PVs). The goal of this study was to test rotational angiography of the LA during adenosine-induced asystole as an imaging tool in patients undergoing atrial fibrillation ablation.
Methods and results: Seventy patients with paroxysmal or persistent atrial fibrillation undergoing PV isolation were included. After transseptal puncture, adenosine (30 mg) was given intravenously, and during atrioventricular block, contrast medium was directly injected in the LA; a rotational angiography was performed (right anterior oblique 55° to left anterior oblique 55°). Rotational angiography images were assessed qualitatively in all patients and quantitatively in 45 patients in comparison with computed tomography (CT) images. The majority of rotational angiography imaging data (94%) were deemed at least ‘useful’ in delineating the LA–PV anatomy. The so-called ‘ridge’ between left superior PV and left atrial appendage was delineated in 90% of the patients. All accessory PVs were independently identified by rotational angiography and CT. A blinded quantitative comparison of PV ostial diameters showed an excellent correlation between rotational angiography and CT measurements (r > 0.90 for all PVs). No serious adverse effects occurred in association with adenosine.
Conclusion: Intra-procedural contrast-enhanced rotational angiography of the LA–PV during adenosine-induced asystole is feasible and provides anatomical information of high diagnostic value for atrial fibrillation ablation.
Key Words: Atrial fibrillation ablation, Rotational angiography, Adenosine, Pulmonary vein ostia
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Introduction |
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TopAbstractIntroductionMethodsResultsDiscussionConclusionFundingAcknowledgementsReferences |
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Interventional treatment of atrial fibrillation by means of radio frequency ablation has proven effective for the treatment of both paroxysmal and persistent atrial fibrillation.1
–4 Because of the complexity and variability of left atrial–pulmonary venous (LA–PV) anatomy, PV isolation is technically very challenging even for experienced electrophysiologists. For that reason, anatomical information gained from pre-procedural volumetric imaging techniques such as computed tomography (CT) and magnetic resonance tomography (MRT) is mandatory. Integration of CT/MRT data sets with electroanatomical mapping systems is used to guide real-time catheter mapping and ablation of atrial fibrillation.5,6 However, there are a number of limiting factors concerning the use of these systems: CT/MRT data sets are gained most of the time at least 1 day before the ablation procedure. Consequently, the volume status of the patient during the procedure can be different from that at the day of CT/MRT data acquisition. Computed tomography/magnetic resonance tomography scanning of the heart at deep inspiration may convey anatomical information that differs significantly from that during normal respiration, mainly because of the inferior displacement of the PV ostia during inspiration.7 Pre-procedural CT/MRT imaging also increases both the administrative burden of scheduling these additional imaging exams and the financial burden of these expensive imaging studies. Contrast-enhanced rotational X-ray angiography of LA and PVs can be performed immediately before the ablation procedure and if necessary repeated during or after that. This study assessed the feasibility and accuracy of rotational angiography during adenosine-induced ventricular asystole as well as possible implications for catheter ablation of atrial fibrillation.
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Methods |
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A total of 70 patients scheduled to undergo catheter ablation for paroxysmal or persistent atrial fibrillation were included in this study. All patients underwent a cardiac CT and a transoesophageal echocardiography 1 day before the ablation procedure and gave informed consent for the atrial fibrillation ablation procedure. Patients with severe bronchial asthma were excluded.
Pre-procedural cardiac computed tomography
Pre-procedural multi-slice cardiac CT imaging was performed using a dual source multi-slice scanner (Somatom Definition, Siemens Inc., Germany). Imaging parameters included 120 kV, 850 mA s, 64 x 0.6 mm collimation, and 0.32 s rotation time. Images were reconstructed with 0.76 mm slice thickness and a 20 cm field-of-view. Electrocardiogram-gated reconstruction was performed on a 512 x 512 pixel matrix using a medium smooth cardiac reconstruction filter kernel. Following a timing bolus-chase injection (20 mL at 5 mL/s), an intravenous iodinated contrast injection (Imeron 400, Altana Pharma, Germany) of 100 mL at 5 mL/s, an end-inspiratory breath-hold of 
20 s was required.
Intra-procedural rotational X-ray angiography
In all patients, imaging was performed using an X-ray FD10 flat-detector system (Allura Xper, Philips Medical Systems Inc., Best, The Netherlands). After obtaining vascular access from the femoral vein, a quadrapolar catheter (Josephson-type, Bard, Lowell, MA, USA) was placed at the right ventricular apex. A stable catheter position and a pacing threshold 
1.5 mA/1.0 ms had to be achieved. A sedation with propofole was started intravenously.
An 8-pole (Supra-CS, Bard) or a 10-pole catheter (Inquiry, St Jude Medical, St Paul, MN, USA) was introduced in the coronary sinus through the left subclavian vein or the left femoral vein, respectively. After performance of two transseptal punctures, three SL1 sheaths (St Jude Medical) were introduced in the LA (two for Lasso catheters according to the double Lasso technique and one for the ablation catheter). A 6 Fr ‘pigtail’ catheter was placed in the LA and connected to a power injector.
Left atrial–pulmonary venous chamber isocentering was achieved as follows: the fluoroscopic image was divided in four quadrants. The examination table was adjusted in a way that the distal end of the pigtail catheter was at the upper right quadrant but close to the centre of the image (about one-third of the distance between centre and right superior angle of the fluoroscopy screen) in three projections: right oblique 55° and anterio-posterior and left oblique 55°. A bolus injection of 30 mg adenosine was given intravenously. Upon occurrence of complete atrioventricular block, 60 mL contrast medium (Ultravist, Shering, Germany) was injected in the LA through the pigtail catheter at 20 mL/s. After a delay of 1 s, rotational X-ray image acquisition was started using a 110° rotation (from 55° right oblique to 55° left oblique) over 4 s at a sampling rate of 30 frames/s. After the end of rotation, ventricular pacing at 80 bpm was performed until spontaneous atrioventricular conduction recovered (Figure 1).
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Ablation procedure
Anatomical reconstruction of the LA was performed with the use of an electroanatomic mapping system (CARTO, Biosense Webster, Inc., Diamond Bar, CA, USA). The ostium of the PVs was delineated by using rotational angiography in at least one right anterior oblique (RAO) and one left anterior oblique (LAO) projection and was annotated in the electroanatomic mapping system. A 3.5 mm irrigated-tip catheter was used for radio frequency ablation (Navistar, Biosense Webster, 30 W energy, flow 17 mL/min). The endpoint of the procedure was complete electrical isolation of all four PVs, as verified by complete disappearance of all PV potentials at a decapolar diagnostic catheter placed at the PV ostium.
Qualitative image analysis
The rotational angiography image results were assessed independently by two expert physicians. For each patient, rotational angiography was assessed in 23 projections (RAO 55° to LAO 55° in steps of 5°). The classification of the data sets was based on a scale of 1–3 using the following criteria: (i) ‘not diagnostic’, no identification of the junction between LA–PV junction in at least one RAO or one LAO projection; (ii) ‘useful’, identification of the LA–PV junction in at least one RAO or one LAO projection; and (iii) ‘optimal’, identification of the PV–LA junction in at least one RAO and one LAO projection. For left atrial appendage (LAA), the classification was as follows: (i) ‘not diagnostic’, LAA not visible in any projection; (ii) ‘useful’, LAA can be seen in at least one RAO or one LAO projection, but there is no complete filling with contrast, the so-called ‘ridge’ between LAA and left superior PV cannot be clearly identified; and (iii) ‘optimal’, complete filling of LAA with contrast and clear identification of ‘ridge’.
If there was any discrepancy in the ‘grading’ of the angiograms between the two reviewers, the images were re-assessed by both and a consensus had to be reached.
Quantitative image analysis
For quantitative analysis of the rotational angiography, the reviewers selected these projections in which LA–PV junction could be clearly visualized. Both sagittal and frontal projections of the PV ostia were analysed if appropriate visible. In frontal projections, the LA–PV junction was identified according to the higher contrast density compared with the LA, and in these projections, horizontal and vertical diameters of the PV ostium were measured (Figure 2A). In the sagittal projections, the LA–PV junction was defined as the point of inflection between the PV wall and the LA wall, and only the vertical PV ostium diameter was measured (Figure 2B). Pulmonary vein ostia classified as ‘not diagnostic’ were excluded from the quantitative analysis. Imaging data sets from CT were manually pre-segmented in order to show only LA–PV anatomy. Computed tomography measurements were performed separately and independent of the quantitative analysis of rotational angiography. The LA–PV junction was defined as the point of inflection between the PV wall and the LA wall. The reviewers were free to manually reorient the cutting plain of CT to obtain the maximal dimensions of the PVs. If it was difficult to define the transition from the PV orifice to the left atrial antrum (especially at the superior border of the left superior PV), this was arbitrarily defined as the point of intersection with a line that is perpendicular to the long-axis of the PV and runs through the opposite orifice site.
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The number of first-order branches in the four PVs was calculated independently of rotational angiography and CT.
Statistical analysis
Results are expressed as mean ± standard deviation for continuous data. A Pearson correlation coefficient was calculated to examine the correlation between CT and rotational angiography measurements, and a two-tailed paired-samples t-test was performed to compare the differences. P-values less than 0.05 were considered statistically significant. Statistical analysis was performed using SPSS version 13.0 (SPSS Inc., Chicago, IL, USA).
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Results |
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Patients' characteristics
Patient' characteristics are summarized in Table 1. Most of the patients were males and had persistent atrial fibrillation, preserved systolic left ventricular function (ejection fraction 68%), and a mean LA size of 48 mm. At the time of ablation procedure, 38 patients were in sinus rhythm. Fifty-four patients were on anti-arrhythmic drugs, which were continued for at least 4 weeks after catheter ablation.
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Rotational angiography image acquisition
The mean heart rate before performing rotational angiography was 62 ± 16 and 66 ± 16 bpm for patients in sinus rhythm and atrial fibrillation, respectively (P: 0.76). The time required to perform rotational angiography (last transseptal puncture till removal of the pigtail catheter from LA after angiography, including testing of the right ventricular pacing threshold) was 7 ± 3 min. After i.v. injection of 30 mg adenosine, atrioventricular block with a duration of >6 s was induced in 35 of 38 patients in sinus rhythm and in 28 of 32 patients in atrial fibrillation.
Two patients with paroxysmal atrial fibrillation who were in sinus rhythm at the beginning of the procedure developed atrial fibrillation shortly after adenosine infusion. In both of them, atrial fibrillation terminated spontaneously in 3 and 8 min, respectively.
Two patients showed a significant increase in right ventricular pacing threshold from 1.2 mA/1.0 ms before adenosine infusion to 10 mA/1.0 ms during ventricular asystole; effective ventricular pacing could be immediately performed after stimulation energy was adjusted to 12 mA/1.0 ms. No other reactions to adenosine occurred.
Qualitative image assessment
Complete contrast-filling of the LA, all PVs, and LAA during rotational angiography were achieved in all 63 patients, with asystole >6 s. In seven patients with asystole <6 s, complete contrast-filling occurred up to the first ventricular contraction (mean duration of asystole 2.8 ± 1 s). Ventricular contraction led to a rapid draining of LA contrast medium into the left ventricle and ascending aorta, rendering all imaging data from that moment till the end of rotation ‘not diagnostic’.
Imaging of the PV ostia was classified as ‘optimal’ in 63 (100%) right superior pulmonary veins (RSPVs), in 62 (98%) right inferior pulmonary veins (RIPVs), in 63 (100%) left superior pulmonary veins (LSPVs), and in 61 (97%) left inferior pulmonary veins (LIPVs), in 63 patients with asystole >6 s. As ‘useful’ were classified one (1.6%) RIPV and two (3%) LIPVs. No PV was classified as ‘not diagnostic’ in these 63 patients.
In the seven patients with a short asystole (<6 s), no PV was classified as ‘optimal’. As ‘useful’ were classified four (57%) RSPVs, four (57%) RIPVs, three (43%) LSPVs, and two (29%) LIPVs. As ‘not diagnostic’ were classified three (43%) RSPVs, three (43%) RIPVs, four (57%) LSPVs, and five (71%) LIPVs.
In five patients, a common ostium of the LSPV and LIPV was identified and was classified as ‘optimal’ in all cases (Figure 3A). Using CT data, six patients were identified with a common ostium of LSPV and LIPV (Figure 3B). Among them were all five patients identified also by rotational angiography and an additional patient in whom asystole lasted for only 3 s, and all imaging data after ventricular contraction were classified as ‘not diagnostic’.
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Three accessory PVs could be clearly identified in three patients (one right superior and two right middle PVs) by both rotational angiography and CT (Figure 4A and B). There were no accessory PVs that could be identified in CT, but not in rotational angiography.
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Classification of the LAA was ‘optimal’ in all 63 (100%) patients with a long asystole (Figure 5A) and four of seven (57%) patients with a short asystole. In three (43%) patients with a short asystole, LAA was classified as ‘useful’.
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Clear identification of the first-order branches of the PVs was possible in many RAO and LAO projections in all patients with a long asystole (Figure 5B).
The mean time for qualitative image assessment per patient was 2 ± 1 min (range 1–3).
Quantitative image assessment
Measurement of pulmonary vein ostia diameters
In 45 of 63 (71%) patients with an asystole longer than 6 s after adenosine injection, quantitative analysis of rotational angiography and CT data were performed. A clear identification of the PV ostium at a sagittal projection was possible for each PV in all patients, so that the vertical PV ostial diameter could be measured. A clear identification of the PV ostium at a frontal plane was possible in 29 of 45 (65%) RIPVs and in 27 of 45 (60%) LIPVs, enabling measurement of both vertical and horizontal diameters. Identification of the PV ostium at a frontal plane was not possible in any projection between RAO 55° and LAO 55° for the superior PVs. For that reason, no measurement of the horizontal diameter of RSPV or LSPV could be performed.
Table 2 summarizes the measurements of the PV ostial diameters and shows the correlation between rotational angiography and CT-derived values.
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The number of first-order branches as identified by rotational angiography/CT in 45 patients was as follows: 102/102 RSPV, 119/119 RIPV, 125/125 LSPV, and 95/95 LIPV branches.
The mean time for quantitative image assesment per patient was 17 ± 14 min (range 10–30), including CT imaging data analysis.
Table 3 shows the comparison of performance time and estimated effective doses of rotational angiography and cardiac CT.
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Inter-observer variability
Inter-observer correlations for the diameters of the ostia of RSPV, RIPV, LSPV, and LIPV were excellent, with correlation coefficients (r) being 0.96, 0.97, 0.98, and 0.94, respectively.
Acute and late complications
One patient developed a severe pericardial effusion 6 h after the ablation procedure. Because of signs of right ventricular tamponade, the effusion was acutely drained (500 mL blood) with immediate improvement of the haemodynamic status. The patient was discharged 2 days later without any further incidents. Four patients developed a significant groin haematoma within 24 h after the ablation procedure, requiring blood transfusion in two of them.
At 3 months of follow-up, 66 of 70 (94%) patients underwent an MRT (two patients refused examination and two patients were lost to follow-up). There was no PV stenosis (defined as a reduction of luminal diameter of at least 20%) or occlusion.
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Discussion |
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The major findings of this study are that contrast-enhanced rotational X-ray angiography of the LA and PVs can be safely performed during adenosine-induced ventricular asystole, and it provides detailed and exact anatomical information about the size of the PV ostia, peripheral branches, and the presence of additional PVs.
To the best of our knowledge, this is the first study to evaluate X-ray rotational angiography of the LA and PVs during adenosine-induced asystole. Adenosine is a naturally occurring nucleoside that activates acetyl-choline-sensitive K+ current in the atrium and sinus and AV nodes by interaction with specific G protein-coupled receptors. This results in the depression of sinus node automaticity, slowing of AV conduction, shortening of atrial myocyte action potential duration, and refractory period and in the suppression of catecholamine-induced triggered activity.8–10 Because of its negative dromotropic effects, it is clinically useful for the termination of supraventricular tachycardias.11,12 The usual dose of adenosine is 6–12 mg as bolus intravenously, but use of a much higher dose (up to 90 mg) has been reported.13 The incidence of adenosine-induced atrial fibrillation ranges from 1%14 up to 12%15 in patients treated with adenosine for the acute termination of supraventricular tachycardia. In contrast, in patients who are in sinus rhythm, adenosine-induced atrial fibrillation is rare (2%), even if high doses of adenosine are administered.13 In our study, 2 of 38 patients (5,2%) who were in sinus rhythm developed atrial fibrillation after adenosine administration. In both patients, atrial fibrillation terminated spontaneously in <8 min. No patient developed any ventricular arrhythmia. Polymorphic ventricular tachycardias or even ventricular fibrillation has been reported after adenosine administration, but they occurred at the setting of either severe myocardial ischaemia16 or at the presence of a pre-excitation syndrome.17 In our patients, no ventricular arrhythmia occurred, probably because of the absence of these predisposing factors. The dramatic increase in right ventricular pacing threshold that occurred in two patients after the administration of adenosine has not been reported earlier. Nevertheless, effective ventricular stimulation has been possible at the maximum output in both patients, and taking into account the very short half-life of adenosine (a few seconds), it is improbable that any safety issues will arise due to inappropriate long ventricular asystole.
For angiographic imaging of the PVs, different methods are used. The most common is selective angiography of each individual PV at two standard fluoroscopic projections (one RAO and one LAO).2,18 At a variation of this approach, the two ipsilateral PVs are intubated selectively, and contrast-medium is injected simultaneously in both.19 Finally, injection of contrast-medium in the pulmonary artery and rotational angiography during the late phase can provide adequate contrasting of the PVs and LA to enable three-dimensional reconstruction of these structures.20
Selective angiography of all four PVs is used in most atrial fibrillation ablation procedures for fluoroscopic imaging of the PV–LA junction. However, there are many disadvantages adherent to this approach: (i) all PVs have to be intubated selectively and sequentially; (ii) fluoroscopic projections (usually one RAO and one LAO projection) are predetermined and not chosen according to the individual spatial orientation of the PVs and the LA–PV junction; (iii) special regions of interest such as intersection between the left superior PV and LAA (the so-called ‘ridge’) cannot be visualized; (iv) accessory PVs may be either completely missed or unsuitable for intubation with the angiography catheter; and (v) selective angiography does not allow for visualization of the peripheral branches of the PVs.
Rotational angiography during adenosine-induced ventricular asystole may have significant advantages over selective angiography: (i) it does not require selective intubation of the PVs; (ii) optimal projections of the LA–PV junction in rotational angiography can be selected for each patient to guide the ablation procedure; (iii) the so-called ‘ridge’ between the left superior PV and LAA is clearly visualized in the majority of patients (90%); and (iv) all accessory PVs and the peripheral branches of the PVs are clearly visualized in many fluoroscopic projections. Underdetection of supernumerary PVs may influence the success rate of catheter ablation if the variant veins are inadequately treated. Angiographic imaging of the peripheral branches of the PVs might be helpful in balloon-based ablation procedures (such as cryoablation), in which placement of the guiding wire in different branches of the PVs is required to achieve ostial adaptation of balloon at different angles, if multiple energy applications become necessary.
The high correlation of pulmonary ostial diameters between rotational angiography and CT shows that the quantitative analysis of the PV ostia can be performed from the angiographic data, thus facilitating some steps of the procedure (i.e. selection of the diameter of the circular diagnostic catheter for registration of the PV potentials or of the balloon size for balloon-based ablation procedures).
Finally, rotational angiography during adenosine-induced asystole can be performed with any conventional fluoroscopy system and does not require any additional specialized software for qualitative and quantitative assessment.
Limitations
There are several limitations in our approach. First, high doses of adenosine are not tolerated by a conscious patient, because of the induced flush and dyspnoea. For that reason, rotational angiography was always performed under sedation in this study. Secondly, the occurrence of a ventricular contraction during rotational angiography leads to a significant deterioration of the quality of imaging data, rendering them ‘not-diagnostic’. This was the case in seven (10%) of the 70 patients who use 30 mg adenosine. Use of higher doses of adenosine (i.e. 40 or 50 mg) would be expected to further reduce the number of patients with short asystole and has been shown to be safe.13 Finally, measurement of the horizontal diameters of the superior PVs was not possible in any fluoroscopic projection between RAO 55° and LAO 55°. Extension of the rotation to RAO 110°–LAO 110° could possibly allow for visualization of the superior PVs at a frontal plane.
Another limitation is that our study was not designed to show improved outcomes and safety of atrial fibrillation procedures performed with rotational angiography compared with other angiographic imaging techniques (i.e. selective angiography of the PVs).
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Conclusion |
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TopAbstractIntroductionMethodsResultsDiscussionConclusionFundingAcknowledgementsReferences |
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Contrast-enhanced rotational X-ray angiography of the LA and PVs during adenosine-induced asystole is feasible, and it provides detailed and accurate anatomical information about anatomic sites that play a key role in atrial fibrillation ablation.
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Funding |
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M.T. received a grant from ‘Kaiserin-Friedrich-Stiftung’.
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Acknowledgements |
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The authors would like to thank Rini Maas (Philips, The Netherlands) for his technical support.
Conflict of interest: none declared.
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Footnotes |
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The first two authors contributed equally to this work. 
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References |
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