Aortic Valve Calcification – Complementary parameter for Aortic Stenosis severity estimation

• In around 40% of aortic stenosis (AS) cases assessment of severity is discordant – area-gradient mismatch: area is smaller but pressure gradient is low or reverse area-gradient mismatch where the gradient is higher and area stenosis is less severe.^1,2
• Measurement of aortic valve calcium (AVC) is an emerging parameter in cases with discordant echocardiographic findings.
• Discordant findings are common in the elderly because they have concomitant coronary artery disease, left ventricle dysfunction and other valve lesions. This is a compelling reason to perform a multi-modality imaging for to accurately assess severity of AS who could definitely be benefitted from Transcatheter Aortic Valve Replacement (TAVR).
• AVC is obtained on non contrast, non ECG gated CT scan using the Agatston method.
• Assessment of AVC is a useful tool for identifying patients who may benefit from TAVR.
• Calcification of the mitral annulus, left ventricular outflow tract and coronaries should be carefully excluded from AVC measurement.
• AVC score of more than 1300 in women and 2000 in men is considered as severe AS.
• Sensitivity and specificity of this parameter are 82 and 78% respectively.
• AVC has a strong prognostic value with a hazard ratio for mortality 2.11.
• Indexation of AVC to body surface area did not add incremental prognostic value.
• CT based AVC estimation has been recommended in the latest 2017 ESC guidelines on valvular heart disease as a complementary method to estimate the severity of AS.
• The gold standard for estimation of AS severity is echocardiography and AVC is a complementary modality only.
• In patients with area:gradient mismatch AVC has an excellent diagnostic value.
• Compared to dobutamine stress echo this is a simple, faster tool. Also the risk of radiation is low.
• Patients with less severe but significant CT AVC, frequent close monitoring of AS progression is needed.
• Limitations of AVC:
  1. At times the AS pathology is predominantly fibrotic rather than calcific – eg. women with bicuspid aortic valve.
  2. Fibrotic leaflet thickening can also lead to hemodynamic obstruction that can’t be identified by AVC.

Conclusion:

Aortic valve calcification as measured by CT is an accurate, reproducible, and well-validated marker of stenosis severity, progression of disease, and a powerful predictor of adverse events.

In patients with discordant echo findings and are symptomatic estimation of AVC is a simple tool for those who benefit from TAVR or TAVI.

Key words:

TAVR, Aortic stenosis, TAVI, Transcatheter Aortic valve Replacement

References:

1. Pawade T, Sheth T, Guzzetti E, Dweck MR, Clavel MA. Why and how to measure aortic valve calcification in patients with aortic stenosis. JACC Cardiovascular Imaging. 2019;12: 1835-48.
2. Abbas AE, Franey LM, Goldstein J , Lester S. Aortic valve stenosis: to the gradient and beyond. The mismatch between area and gradient severity. J Interv Cardiol; 2013:26: 183-94.
3. Wang TKM, Flamm SD,  Schoenhagen P, Griffin BP,  Rodriguez LL, Grimm RA, Xu B. Diagnostic and Prognostic Performance of Aortic Valve Calcium Score with Cardiac CT for Aortic Stenosis: A Meta-Analysis. Radiology: Cardiothoracic Imaging 2021 3:4.