Application of the European Society of Cardiology (ESC) 2017 Guidelines for the Classification of Aortic Stenosis Severity: The Low Frequency of Low-Gradient Aortic Stenosis

Background and Objectives: The updated ESC guidelines for the diagnosis of aortic stenosis (AS) severity present a simplified approach based on trans-aortic pressure gradients (PG), calculated aortic valve area (AVA), trans-valvular flow (indexed stroke volume; SVi), and left ventricular ejection fraction (LVEF). We examined the performance of these guidelines in clinical practice.

Methods: Consecutive patients with moderate or severe AS (AVA calculated by the continuity equation ≤1.5 cm²) who were examined at our institution during a 20 months period were identified via the echocardiography laboratory computerized database and the ESC algorithm was applied for the classification of AS severity.

Results: Among 561 patients with moderate or severe AS – mean PG (mPG) ≥40 mmHg, indicating severe AS, was evident in 242 patients. Of these, the large majority had a small AVA (≤1.0 cm²; n=206, 85.1%), normal SVi (>35 ml/m²; n=236, 97.5%), and preserved LVEF (≥50%; n=215; 88.8%). Of the 319 patients with mPG <40 mmHg – AVA was >1.0 cm², indicating moderate AS, in 202 patients (63.3%), and ≤1.0 cm², suggestive of severe AS, in 117 patients (36.7%). When trans-aortic flow was incorporated in the algorithm (SVi ≤35 ml/m² defining low-flow) – flow was normal in most patients with a small calculated AVA and low gradients (n=91; 77.8%), consistent with the diagnosis of non-severe AS, whereas low-flow low-gradient severe AS (LFLG-SAS) was evident in only 26 patients (22.2%). Of the patients with LFLG-SAS – 13 patients (50%) had reduced LVEF (<50%) and 13 (50%) had preserved LVEF, necessitating confirmation of AS severity by an LVEF-specific integrated approach. Assuming confirmation of severe AS in all patients with LFLG-SAS – a total of 268 patients were eventually diagnosed as having severe AS, with LFLG-SAS observed in only a small minority (n=26; 9.7%).

Conclusions: The 2017ESC guidelines present a practical approach for the diagnosis of severe AS. Application of these guidelines results in a low frequency of true LFLG-SAS (<10%). Adherence to these guidelines may prevent unnecessary valve interventions in patients with non-severe AS.