Aortic root abscess - Corner Case -2​ : April 2021

Contributed by
Dr Richita V Pandit
Dr. Ashita Barthur
Department of Radiology
Sri Jayadeva Institute of Cardiovascular Sciences & Research
Bangalore

A 32-year-old gentleman presented with fever and chest pain for five days.  Transthoracic echocardiogram revealed a bicuspid, thickened and densely calcific aortic valve with severe aortic regurgitation.  Asymmetrical septal hypertrophy was noted with normal left ventricular systolic function. There was suspicion of aortic arch dissection.

An ECG-gated computed tomography ruled out aortic dissection and showed calcification confined to the aortic valve. Trans-oesophagal echocardiography did not add to these findings.

Cardiac magnetic resonance imaging (CMR) was requested to assess the aortic root and myocardium. See the representative cardiac MRI images below. What is your diagnosis?

Findings:

Answer: Aortic root abscess

CMR revealed a bicuspid aortic valve (Fig 1e) with moderate aortic stenosis and severe aortic regurgitation (Fig 1c). The aortic root was dilated with an irregular peripherally enhancing (Fig 1i) T1 isointense and STIR hyperintense (Fig 1d) collection extending from the level of the aortic valve at the posterior commissure opposite the interatrial septum (Fig 1a, b, e), along the length of the aortic root for a distance of 4cm from the annulus (Fig 1j), consistent with an aortic root abscess. The left ventricle was dilated with normal systolic function (left ventricular ejection fraction 60%). Mild burden of LV non-ischemic scar was also noted (Fig 1f, g, h) MRI results were crucial and expedited further management of the patient. The patient then underwent surgery with debridement of the abscess.

Aortic root abscesses, although rare, warrant a prompt diagnosis. Echocardiography is the primary imaging modality for paravalvular abscesses with sensitivity being higher for trans-esophageal approach1. Accurate diagnosis is difficult through a trans-thoracic approach, and trans-esophageal approach has had limited usage in the wake of the COVID pandemic. An ECG-gated CT fares better in the visualization of a paravalvular collection but comes at a price of limited ascertainment of extent due to motion and decreased spatial resolution and additionally, risks associated with radiation exposure.2 As depicted in our current case, Gadolinium-enhanced MRI, with excellent spatial resolution, plays a pivotal role in the diagnosis of presence and extent of abscess and its differentiation from debris and tumours.3 

Figure 1: 1(a, b and c): Still images of a steady state free precision (SSFP) sequence in 3 chamber (a, b) and left ventricular out flow tract view (c). The yellow arrows point to the thickened aortic valve leaflets and the annular plane, the red arrows point towards the doming of the bicuspid aortic valve leaflets and the blue arrows illustrate the aortic regurgitation jet. The blue stars demonstrates the periaortic hypointense soft tissue. 1(d): STIR sequence showing the hyperintense periaortic soft tissue.1(e): Still images of an SSFP sequence in the aortic short axis view showing the location of the periaortic hypointense soft tissue opposite the posterior commissure. 1(f, g, h, i): Late gadolinium enhanced PSIR sequence showing mild burden of patchy non ischemic scar (white arrows) in left ventricle and peripherally enhancing aortic root abscess (yellow star). 1(j): ECG and respiratory gated 3D whole heart DIXON imaging showing an oblique coronal image demonstrating the extent of the aortic root abscess (white stars).

References

  1. Sverdlov AL, Taylor K, Elkington AG, Zeitz CJ, Beltrame JF. Images in cardiovascular medicine. Cardiac magnetic resonance imaging identifies the elusive perivalvular abscess. Circulation. 2008;118(1):e1–3.
  2. Murphy, DJ, Keraliya, AR, Agrawal, MD, Aghayev, A, Steigner, ML. Cross-sectional imaging of aortic infections. Insights Imaging. 2016; 7(6): 801–818.
  3. Liu H., Juan Y. H., Wang Q. et al. Aortic root ring sign: multimodality imaging of aortic root abscess. QJM. 2016 Jan;109(1):53-4.  doi: 10.1093/qjmed/hcv073. Epub 2015 Apr 7.