Workup and Management of Patients With Paradoxical Low-Flow, Low-Gradient Aortic Stenosis

About 60% of patients with paradoxical low-flow, low-gradient (PLF-LG) aortic stenosis (AS) have a severe disease that justifies aortic valve replacement (AVR). The first step in patients with symptomatic PLF AS should be to rule out measurement errors and treat hypertension. The second step is to distinguish pseudo-severe from true severe AS (TSAS). The third step is to select the optimal treatment modality at the right time. Regarding the second step, projected aortic valve area calculated using stress echocardiography is superior to traditional severity criteria (AVA < 1.0 cm² and mean gradient ≥ 40 mmHg) to unmask TSAS and predict outcomes. Aortic valve calcification score quantitated by computed tomography is helpful to identify TSAS by applying thresholds of 2000 and 1200 AU, respectively, for men and women. This modality should be considered, particularly if stress echocardiography is either not feasible or inconclusive. Once AS severity is confirmed, a risk stratification based on symptomatic status and the importance of left ventricular (LV) systolic impairment will guide therapeutic decision. Symptomatic assessment should not solely rely on patient-reported symptom status, but rather include an objective exercise test. The presence of symptomatic PLF-LG TSAS is a class IIa indication for AVR in the guidelines. In asymptomatic patients, a markedly reduced stroke volume, the presence of myocardial fibrosis by cardiac magnetic resonance imaging, a poor longitudinal LV function as assessed by speckle tracking echocardiography, and/or a moderate to severe LV diastolic dysfunction are predictors of poor outcome in PLF-LG patients and may indicate the need of early AVR. The type of AVR should be discussed within a multidisciplinary team, bearing in mind that transcatheter AVR (TAVR) is superior to medical treatment in inoperable patients. Furthermore, TAVR may be a useful alternative to surgical AVR (SAVR) in high-risk patients. Nevertheless, the potential benefits of TAVR, including the lower risk of severe patient-prosthesis mismatch, should be weighed against the risk of paravalvular regurgitation, which is likely poorly tolerated by patients with PLF-LG who often harbor a small and non-compliant LV cavity.