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Re. “Contrast Enhanced Ultrasound Can Replace Computed Tomography Angiography for Surveillance After Endovascular Aortic Aneurysm Repair”
Eur J Vasc Endovasc Surg (2017) 53, 446e447
CORRESPONDENCE Re. “Contrast Enhanced Ultrasound Can Replace Computed Tomography Angiography for Surveillance After Endovascular Aortic Aneurysm Repair” We read with interest the paper by Bredahl et al. comparing the use of contrast enhanced ultrasound (CEUS) with duplex ultrasound (DUS) in the detection of post-EVAR leak, with the outcomes from those two groups benchmarked against computed tomography angiography (CTA).1 The authors concluded that CEUS can potentially replace CTA for postoperative EVAR surveillance programmes based on similar detection rates of leaks that required re-intervention. Although a well-written paper, there are certain weaknesses with the methodology, implying that the conclusion should be taken with caution. The study lacked any mention of the cost in time, expenses, and personnel required to complete each scanning modality, although that was not the objective of the study. Based on our own observation, CEUS can have a learning curve and be time-consuming. Another limitation to external validity of this study is the need for referring all patients to a central unit staffed by individuals well-trained in performing the CEUS scans, unlike CTAs which can be performed in satellite hospitals and the images linked to be reported by the vascular radiology consultants based in the main tertiary unit. Also, we feel that one operator performing both ultrasound modalities in the same session, in the same sequence every time, would undoubtedly bias the results in favour of CEUS. In addition, with one individual performing all ultrasound scans the risk of an intra-observer error is not stratified, although we accept this has probably limited the risk of inter-observer error. On page 4, “In 278 patients, McNemar’s chi-square test rejected the hypothesis that CEUS and CTA were diagnostically equivalent (p ¼ .002.), as opposed to CEUS compared with CTA (p ¼ .827).” The authors need to clarify which two tests are compared as they have CEUS and CTA in both. Lastly, the study lacked any form of power calculations, and therefore it is not fully clear if the sample size was adequate for analysis, or indeed to draw any conclusions. We feel that this study certainly generated some interesting hypotheses with regards to post-EVAR surveillance protocols; however, more evidence should be sought before recommending any change in practice. REFERENCE 1 Bredahl KK, Taudorf M, Lönn L, Vogt KC, Sillesen H, Eiberg JP. Contrast enhanced ultrasound can replace computed tomography angiography for surveillance after endovascular aortic aneurysm repair. Eur J Vasc Endovasc Surg 2016;52(6):729e34.
K. Bashar*, T. Jaipersad, J. Asquith, S. Rajagopalan Dept. of Vascular Surgery and Interventional Radiology, Royal Stoke University Hospital, Stoke on Trent, UK *Corresponding author. Ward 110, Lyme Building, Royal Stoke University Hospital, Stoke on Trent ST46QG, UK. Email-address: [email protected] (K. Bashar) Available online 31 January 2017 Ó 2016 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ejvs.2016.12.028 DOI of original article: http://dx.doi.org/10.1016/ j.ejvs.2016.07.007
Response to commentary on “Re: Contrast Enhanced Ultrasound can Replace Computed Tomography Angiography for Surveillance After Endovascular Aortic Aneurysm Repair” We would like to express our gratitude for Mr Khalid Bashar et al.’s comments on the above paper.1 We agree with Bashar et al. that ultrasound surveillance of EVAR treated patients requires experienced sonographers but would also draw attention to the fact that little research has been undertaken to identify and overcome the challenges associated with the implementation of vascular ultrasound. The minimum number of supervised investigations required to obtain proficiency in EVAR surveillance using duplex or contrast enhanced ultrasound is an interesting topic which remains unresolved. We recognise that the use of a second or even third operator in our study would have been of great benefit for settling external validity. Therefore, until learning curves, reproducibility assessment, and validated educational modules have been established, we agree that the results of this study should be implemented by other institutions with caution. As discussed in the article, the study design highly favours contrast enhanced ultrasound compared with duplex ultrasound. Nevertheless, the setup is very similar to daily practice. The study demonstrates the concept of replacing computed tomography angiography with ultrasound and highlights the potential benefit of adding a subsequent contrast enhanced ultrasound investigation performed by the same operator. More endoleaks requiring intervention were detected with contrast enhanced ultrasound, and type II endoleaks associated with sac growth were identified. A minor error occurred on p. 4, for which we apologise. It
CORRESPONDENCE Re. “Contrast Enhanced Ultrasound Can Replace Computed Tomography Angiography for Surveillance After Endovascular Aortic Aneurysm Repair” We read with interest the paper by Bredahl et al. comparing the use of contrast enhanced ultrasound (CEUS) with duplex ultrasound (DUS) in the detection of post-EVAR leak, with the outcomes from those two groups benchmarked against computed tomography angiography (CTA).1 The authors concluded that CEUS can potentially replace CTA for postoperative EVAR surveillance programmes based on similar detection rates of leaks that required re-intervention. Although a well-written paper, there are certain weaknesses with the methodology, implying that the conclusion should be taken with caution. The study lacked any mention of the cost in time, expenses, and personnel required to complete each scanning modality, although that was not the objective of the study. Based on our own observation, CEUS can have a learning curve and be time-consuming. Another limitation to external validity of this study is the need for referring all patients to a central unit staffed by individuals well-trained in performing the CEUS scans, unlike CTAs which can be performed in satellite hospitals and the images linked to be reported by the vascular radiology consultants based in the main tertiary unit. Also, we feel that one operator performing both ultrasound modalities in the same session, in the same sequence every time, would undoubtedly bias the results in favour of CEUS. In addition, with one individual performing all ultrasound scans the risk of an intra-observer error is not stratified, although we accept this has probably limited the risk of inter-observer error. On page 4, “In 278 patients, McNemar’s chi-square test rejected the hypothesis that CEUS and CTA were diagnostically equivalent (p ¼ .002.), as opposed to CEUS compared with CTA (p ¼ .827).” The authors need to clarify which two tests are compared as they have CEUS and CTA in both. Lastly, the study lacked any form of power calculations, and therefore it is not fully clear if the sample size was adequate for analysis, or indeed to draw any conclusions. We feel that this study certainly generated some interesting hypotheses with regards to post-EVAR surveillance protocols; however, more evidence should be sought before recommending any change in practice. REFERENCE 1 Bredahl KK, Taudorf M, Lönn L, Vogt KC, Sillesen H, Eiberg JP. Contrast enhanced ultrasound can replace computed tomography angiography for surveillance after endovascular aortic aneurysm repair. Eur J Vasc Endovasc Surg 2016;52(6):729e34.
K. Bashar*, T. Jaipersad, J. Asquith, S. Rajagopalan Dept. of Vascular Surgery and Interventional Radiology, Royal Stoke University Hospital, Stoke on Trent, UK *Corresponding author. Ward 110, Lyme Building, Royal Stoke University Hospital, Stoke on Trent ST46QG, UK. Email-address: [email protected] (K. Bashar) Available online 31 January 2017 Ó 2016 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ejvs.2016.12.028 DOI of original article: http://dx.doi.org/10.1016/ j.ejvs.2016.07.007
Response to commentary on “Re: Contrast Enhanced Ultrasound can Replace Computed Tomography Angiography for Surveillance After Endovascular Aortic Aneurysm Repair” We would like to express our gratitude for Mr Khalid Bashar et al.’s comments on the above paper.1 We agree with Bashar et al. that ultrasound surveillance of EVAR treated patients requires experienced sonographers but would also draw attention to the fact that little research has been undertaken to identify and overcome the challenges associated with the implementation of vascular ultrasound. The minimum number of supervised investigations required to obtain proficiency in EVAR surveillance using duplex or contrast enhanced ultrasound is an interesting topic which remains unresolved. We recognise that the use of a second or even third operator in our study would have been of great benefit for settling external validity. Therefore, until learning curves, reproducibility assessment, and validated educational modules have been established, we agree that the results of this study should be implemented by other institutions with caution. As discussed in the article, the study design highly favours contrast enhanced ultrasound compared with duplex ultrasound. Nevertheless, the setup is very similar to daily practice. The study demonstrates the concept of replacing computed tomography angiography with ultrasound and highlights the potential benefit of adding a subsequent contrast enhanced ultrasound investigation performed by the same operator. More endoleaks requiring intervention were detected with contrast enhanced ultrasound, and type II endoleaks associated with sac growth were identified. A minor error occurred on p. 4, for which we apologise. It