Aortic Stenosis, Severe or Moderate, Intervention?

In the scheme there are certainties and questions, defined by question marks.

Among the former, the presence of a mean LV-Ao gradient > 40 mm Hg implies  severe AS, not requiring other measurements.

With an average gradient of 20-40 mmHg the dilemma is: Severe or moderate AD?

The problem could be solved with flow estimation: if it is compromised, ( "low flow") the AD is severe ; Otherwise it will be moderate .

The calculation of the aortic area should clarify the issue, but there may be technical difficulties (estimation of the sub-aortic area) that determine the certainty of the measurement.

Low flow is inferred if the ejection fraction (EF) is < 50%. If with dobutamine infusion the mean gradient is > 40 mm Hg, AS is severe. But there is another condition that implies low flow: decreased stroke volume (< 35 mL/m 2 ) due to a reduced ventricular chamber in the absence of LV dysfunction. This condition, “ paradoxical low flow/low gradient ” is the most common in elderly patients with an incidence that will increase in the coming years. However, estimating stroke volume poses the same problems as calculating valve area.

In this situation, the Ca score by CT is the best method to define the severity: (men > 2000; women > 1200) This Ca score range implies not only severity of AD, but also greater speed of progression.

A second type of question refers to the decision to intervene, with surgical valve replacement or endovascular implantation (TAVI).

With mean gradient > 50 mm Hg, the indications for intervention are illustrated in the diagram.

With an average gradient of 20-40 mm Hg, decision making offers different scenarios.

Without symptoms (condition not illustrated in the graph), for some authors, intervention is justified if the EF is < 50% and with dobutamine the mean gradient is > 40 mm Hg. To prevent progression of myocardial damage. (Questionable decision)

With symptoms, the first question is whether they are due to AD or another co-morbidity, common in elderly patients. There is no diagnostic procedure (PEG / O2 consumption that allows us to confidently assign that the symptoms are motivated by AD.

The biggest question when it comes to intervening is: Low flow/low gradient AD or moderate AD? With EF < 50%, dobutamine can clarify the situation, as analyzed.

The issue will be resolved, from another perspective, with ongoing clinical trials (TAVR UNLOAD trial in moderate AD and EF < 50%): If the result is favorable, the “moderate – severe” difference will lose validity. Meanwhile, in the case of TAVI, the intervention is a firm option even with the uncertainty about its severity.

In the absence of dysfunction, EF > 50%, the “moderate-severe difference” takes on greater significance. (Ca as the best diagnostic option).

With symptoms and in the case of TAVI, some cardiologists (shared decision with the patient) will suggest intervention, hoping to alleviate the symptoms and improve the prognosis.