Low-Gradient TAVR

Hemodynamic aspects

Aortic stenosis is classified as important when it has a valve area less than 1.0 cm2 with a mean systolic gradient greater than 40 mmHg. When we find patients with an area smaller than 1.0 cm2, but with a gradient below 40 mmHg, we are facing low gradient aortic stenosis.

In this context, we found three subtypes of aortic stenosis, the “low-flow low-gradient” with reduced ejection fraction (stage D2); the “paradoxical low-flow low-gradient” with preserved ejection fraction (stage D3) and the recently described “normal-flow low-gradient” (stage D4).

According to recent studies, up to 40% of patients with major aortic stenosis can be classified as “low-gradient”, but the treatment for these subtypes is not as clear as for stage D1 patients. Often the question remains whether they are patients with moderate stenosis and several other imaging methods are necessary to better stratify the valve disease.

We draw special attention to patients classified as stage D3, they have preserved ejection fraction, although they may have some degree of systolic deficit displayed by strain analysis, leading to a reduction in stroke volume. It has high afterload, both due to valve obstruction and high peripheral vascular resistance. Stage D2 shows more exuberant LV systolic dysfunction with increased systemic and pulmonary vascular resistance. Stage D4, on the other hand, manifests itself with more stable hemodynamics and apparently can benefit less from aortic valve replacement when compared to similar subtypes, of all, the best medium-term survival is in subtype D4, followed by paradoxical and lastly stage D2, largely due to the drop in the ejection fraction, which alone increases mortality.

Stage D4 is perhaps still the most challenging for adequate stratification and selection for treatment with valve replacement, whether conventional or by TAVR. In the literature, only those who are symptomatic, with high BNP levels and very high calcium score would be eligible for valve replacement treatment. Some studies report that stage D4 would be between Genereaux stages 1 and 2 and that treatment would improve symptoms, with little impact on hemodynamic aspects.

Stage D3 could represent an expression of aortic stenosis with advanced diastolic dysfunction, manifesting itself as heart failure with preserved ejection fraction. Some more detailed analyzes of systolic function show some degree of dysfunction, but the calculation of the ejection fraction is preserved. In Genereaux classification, they would be in groups 2 or 3. Valve replacement may have a positive impact on reverse remodeling, including improvement in longitudinal strain.

A recent article published in Eurointervention states that stage D4 would be the most prevalent of all, manifesting itself as an early stage of the development of severe low gradient aortic stenosis that can progress to stages D3 or D2, with D2 being the final stage, more advanced with greater hemodynamic repercussions and worse survival. In any case, interventional treatment in all subtypes seems to benefit both symptomatology and survival.

Suggested literature:

1 – Schewel J, Schlüter M, Schmidt T, et al. Early haemodynamic changes and long-term outcome of patients with severe low-gradient aortic stenosis after transcatheter aortic valve replacement. EuroIntervention. 2020 Jan 17;15(13):1181-1189.

 

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