Dobutamine Stress Echocardiography in Low-Gradient Aortic Stenosis

Background Dobutamine stress echocardiography (DSE) is recommended by guidelines to distinguish between true-severe and pseudo-severe aortic stenosis (AS) in patients with low-gradients and left ventricular ejection fraction (LVEF) <50%. However, DSE has mostly been tested in the setting of LVEF<35% and determination of AS severity has mostly been based on outcome data and surgeon’s evaluation. The purpose of this study was to examine the diagnostic accuracy of guideline recommendations for DSE, in patents with low-gradient severe AS with a wide range of LVEF and to examine the interaction between the diagnostic accuracy of DSE and LVEF. Furthermore, we wanted to study the safety and feasibility of DSE in patients with LVEF>50%. Methods Patients with aortic mean gradient <40 mmHg, AVA <1.0 cm 2 , and stroke volume index ≤35 mL/m 2 undergoing DSE and Cardiac Computer Tomography (C-CT) were identified from three prospectively collected patient cohorts, and stratified according to LVEF; LVEF <35%, LVEF 35-50% & LVEF >50%. Severe AS was defined as AVC score ≥2000 AU among men, and ≥1200 AU for women on C-CT. Results Two hundred twenty-one patients were included in the study. Seventy-eight (35%) presented with LVEF <35%, 67 (30%) with LVEF 35-50%, and 76 (34%) with LVEF >50%. DSE was performed without adverse symptoms or significant arrhythmias in 215 (96%) patients and stroke volume increased uniformly with no significant differences between groups (p=0.28). Mean gradient and V max during DSE showed significantly diagnostic heterogeneity between LVEF groups, being most precise when LVEF <35% (both AUC=0.90), albeit with optimal thresholds of 30 mmHg & 377 cm/s, and a limited diagnostic yield in patients with LVEF≥35% (AUC=0.67 in LVEF 35-50% and AUC 0.65 in LVEF≥35%). Using guideline thresholds led to a sensitivity and specificity of 49%/84% for all patients with LVEF <50%. Conclusion While DSE is safe and leads to a uniform increase in stroke volume in patients with low gradient AS regardless of baseline LVEF, the association between DSE gradients and AS severity assessed by C-CT demonstrates important heterogeneity depending on LVEF, with highest accuracy in patients with LVEF <35%. Clinical perspective What is new? Dobutamine stress echocardiography (DSE) is safe in patients with low-gradient AS with LVEF >50%, and leads to similar increase in stroke volume as in patients with LVEF <50%. The diagnostic accuracy of DSE, compared to AVC as the reference for severe AS, depends on LVEF with highest accuracy in patients with LVEF <35%. Suggested reference thresholds for DSE may not be the most accurate for AS severity, when compared to AVC. What are the clinical implications? Based on our study, we suggest that DSE should primarily be used for determining AS severity in patients with LVEF <35%.