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:
At times the AS pathology is predominantly fibrotic rather than calcific – eg. women with bicuspid aortic valve.
Fibrotic leaflet thickening can also lead to hemodynamic obstruction that can’t be identified by AVC.
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.