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Original research
Inconsistency in aortic stenosis severity between CT and echocardiography: prevalence and insights into mechanistic differences using computational fluid dynamics
  1. Tarun Kumar Mittal1,2,
  2. Luise Reichmuth1,
  3. Sanjeev Bhattacharyya1,
  4. Manish Jain1,
  5. Aigul Baltabaeva3,
  6. Shelley Rahman Haley1,
  7. Saeed Mirsadraee1,2,
  8. Vasileios Panoulas2,3,
  9. Tito Kabir3,
  10. Edward David Nicol1,2,
  11. Miles Dalby2,3 and
  12. Quan Long4
  1. 1 Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK
  2. 2 Faculty of Medicine, NHLI, Imperial College London, London, United Kingdom
  3. 3 Cardiology, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom
  4. 4 Institute of Bioengineering, Brunel University, Uxbridge, Middlesex, UK
  1. Correspondence to Dr Tarun Kumar Mittal; t.mittal{at}outlook.com

Abstract

Objectives The aims of this study were to evaluate the inconsistency of aortic stenosis (AS) severity between CT aortic valve area (CT-AVA) and echocardiographic Doppler parameters, and to investigate potential underlying mechanisms using computational fluid dynamics (CFD).

Methods A total of 450 consecutive eligible patients undergoing transcatheter AV implantation assessment underwent CT cardiac angiography (CTCA) following echocardiography. CT-AVA derived by direct planimetry and echocardiographic parameters were used to assess severity. CFD simulation was performed in 46 CTCA cases to evaluate velocity profiles.

Results A CT-AVA>1 cm2 was present in 23% of patients with echocardiographic peak velocity≥4 m/s (r=−0.33) and in 15% patients with mean Doppler gradient≥40 mm Hg (r=−0.39). Patients with inconsistent severity grading between CT and echocardiography had higher stroke volume index (43 vs 38 mL/m2, p<0.003) and left ventricular outflow tract (LVOT) flow rate (235 vs 192 cm3/s, p<0.001). CFD simulation revealed high flow, either in isolation (p=0.01), or when associated with a skewed velocity profile (p=0.007), as the main cause for inconsistency between CT and echocardiography.

Conclusion Severe AS by Doppler criteria may be associated with a CT-AVA>1 cm2 in up to a quarter of patients. CFD demonstrates that haemodynamic severity may be exaggerated on Doppler analysis due to high LVOT flow rates, with or without skewed velocity profiles, across the valve orifice. These factors should be considered before making a firm diagnosis of severe AS and evaluation with CT can be helpful.

  • aortic valve
  • valve stenosis
  • CT
  • echocardiography
  • computational fluid dynamics

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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Footnotes

  • Contributors TKM developed the hypothesis and design the study. LR, SB, MJ and TKM collected the clinical, echocardiographic and CT data. SM was involved in the study of interobserver variability. QL was responsible for the computational fluid dynamics. TM, SB, AB, SRH, VP, TK, EDN, MD and QL assisted in study drafts and final version.

  • Funding This research has received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests No, there are no competing interests for any author.

  • Patient consent for publication Not required.

  • Ethics approval NHS (National Health Service) research ethics approval was obtained (IRAS Project ID: 2014HS002H).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request.

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