Diagnostic value of low dose dobutamine stress echocardiography in paradoxical low flow low gradient aortic stenosis
Authors: Nowack T , Sveric K , Mierke J , Ueberschaer F , Rochor N , Heitmann C , Friedrich J , Woitek F , Winzer E , Fischer J , Jellinghaus S , Mangner N , Linke A , Heidrich F 
Published: October 2024

Abstract

Background
In aortic stenosis with low-gradient scenarios distinguishing between fixed and pseudo-severe stenosis becomes challenging. Low-dose dobutamine stress echocardiography (DSE) is recommended for classical low-flow low- gradient stenosis with reduced ejection fraction. Doubts of DSE's utility in paradoxical low-flow low-gradient (PLFLG) stenosis when ejection fraction is preserved are partially reasoned by proposed inefficiency in generating a contractile reserve 1. Guidelines advocate an integrated approach, combining various clinical and imaging aspects 2.

Purpose
This study aimed to investigate usefulness of DSE in PLFLG stenosis, identifying specific features to predict the possibility of generating significant stroke volume augmentation and distinguishing fixed aortic stenosis.

Methods
We identified patients with aortic stenosis who underwent DSE and multi-modality imaging at our centre between 2020 and 2023. Among them, those with PLFLG situations were used for detailed analysis. Multiple linear regression analysis was performed to identify parameters predictive of significant contractile reserve, defined as 20% stroke volume increase from baseline. For patients demonstrating contractile reserve we assessed predefined parameters by receiver operating characteristics (ROC) analysis to predict fixed stenosis defined as final aortic valve area &lt; 1cm² and valve area change &lt;0.2cm² or final mean pressure gradient &gt;40mmHg. For predictive value of Agatston score we conducted post-hoc analysis.

Results
Among 256 DSE cases, 67 were conducted for PLFLG stenosis. Patients were 82 years of median age and mostly female (63%). Symptoms included dyspnea in 90% and angina in 40% of cases. Baseline echo showed median aortic valve area (indexed to body surface area) of 0.8cm² (0.44cm²/m²) with mean pressure gradient of 20mmHg. Contractile reserve was inducible in 70% of patients, of which 74% showed criteria of fixed stenosis. Higher left ventricular end-diastolic diameter (LVESD) and lower baseline systolic flow-rate were predictive for contractile reserve (p&lt;0.05). Among patients with contractile reserve ROC for baseline mean pressure gradient, acceleration time (median 0.08s; range 0.04-0.11s) and acceleration time to ejection time index (0.28; range: 0.148-0.458) revealed good prediction of fixed stenosis in DSE meanwhile Agatston calcium score (median 1076; range: 301-8821) did not (figure 1). No correlation was found between Agatston score probability of severe stenosis and aortic valve pressure gradient behavior with increased stroke volume (figure 2).

Conclusion
DSE proves to be a useful a method in the differentiation between fixed and pseudo-severe stenosis in PLFLG situation. Our findings question the predictive value of Agatston score for aortic valve behavior with increase of stroke volume and warrant further investigations regarding value of acceleration time and acceleration time to ejection time index in those patients.Receiver operating characteristicsPost-hoc analysis of Agatston score