The diagnostic accuracy of aortic valve calcium score in patients with low gradient and high gradient aortic stenosis
Authors: Nagy A I , Juhasz D , Jermendy A , Szilveszter B , Manouras A , Apor A , Merkely B , Suhai F , Panajotu A , Maurovich-Horvat P , Molnar L , David D , Herczeg S Z , Czimbalmos C S , Vacsey-Nagy M 
Published: October 2024

Abstract

Introduction
The standard imaging modality for diagnosing aortic stenosis (AS) is echocardiography (echo), by which the definition of severe AS is based on the transvalvular mean gradient (AMG) (&gt;40 mmHg) and aortic valve area (AVA) (&lt;1 cm2). However, in around one quarter of the cases, echo provides discordant findings (AVA&lt;1 cm2, despite of an AMG &lt;40 mmHg), complicating clinical decision making. Computed tomography aortic valve calcium scoring (CT- AVCS) offers an alternative diagnostic method. In cases with discordant echo measurements current guidelines recommend the use CT-AVCS to decide on severity.

Purpose
Our aim was to validate the sensitivity of the recommended AVCS thresholds within our patient population, as well as to identify any factors associated with below cut-off AVCS values despite confirmed severe AS (low AVCS).

Methods
Our retrospective study included 332 consecutive patients with severe AS (AVA ≤1 cm2), who underwent CT angiography (CTA) for transcatheter aortic valve implantation (TAVI) planning. Based on the AMG the patients were classified into high gradient (HG: AMG ≥ 40 mmHg) and low gradient (LG: AMG &lt;40 mmHg) groups. In the LG group AS severity was assessed by a multiparametric algorithm. To specify the predictors of low AVCS among patients with HG-AS, logistic regression analysis was used. The patients were followed for 50 months. Cox proportional hazard model was used to assess the risk of death from any cause.

Results
The HG-AS group consisted of 244 and the LG-AS cohort of 88 patients. In the HG-AS population the sensitivity of AVCS to diagnose severe AS was 89%.
Within the HG severe AS group, logistic regression analysis revealed an association between low AVCS and the AMG (OR 0.89, CI 0.83 – 0.95, p &lt;0,001), whereas none of the other tested factors (age, sex, hypertension, diabetes, left ventricle function, renal function) showed any association. In the LG-AS group, contrary to the HG- AS patients, the sensitivity of AVCS to define severe LG AS was limited (53% in males and 67% in females).
Over a median follow-up of 50 months, the prognosis of HG AS patients with low AVCS was more favourable than that of the high AVCS patient population (HR 0.41; CI 017 – 097; p=0.04), however, in the LG AS group, the prognosis was not different when stratifying the patients according to high or low AVCS (p=0.21).

Conclusions
Our results confirmed that among patients with HG AS, the recommended AVCS thresholds provide a good diagnostic sensitivity for severe AS. Nonetheless, the number of severe AS patients with low AVCS is not negligible, especially within the LG-AS population, where the diagnosis is the most challenging. Our findings underline that in patients with discordant echocardiographic findings, a personalized, multiparametric diagnostic approach is needed, instead basing the final diagnosis exclusively on AVCS.