Which Low-Flow, Low-Gradient Patients Benefit from Valve Replacement?

A mean gradient ≥40 mmHg, an aortic valve area ≤1 cm², or a combination of both, during dobutamine stress echocardiography, correctly qualifies as severe aortic stenosis in about half of all patients. The other half consists in cases of pseudo-severe aortic stenosis.

In turn, a projected aortic valve area ≤1 cm² is a much better indicator than the aforementioned markers, correctly diagnosing 70% of all patients (a statistic that is still far from being perfect).

The American College of Cardiology/American Heart Association (ACC/AHA) guidelines consider that patients have true-severe stenosis when the mean gradient is ≥40 mmHg and an aortic valve area ≤1 cm² during dobutamine stress echocardiography. However, these criteria have not been previously validated, and nowadays we face the more pressing need to correctly classify patients according to their eligibility for percutaneous replacement.

Read also: TAVR in Low-Flow Low-Gradient Aortic Stenosis and Severe Impairment of Systolic Function.

Before transcatheter aortic valve replacement (TAVR), the correct diagnosis of low-flow, low-gradient patients was an academic issue, since most of them could not afford the risks of conventional surgery, anyways.

The aim of this study was to assess the value of these criteria to predict the presence of true-severe aortic stenosis in low-flow, low-gradient patients, and to assess their prognosis.

One hundred eighty-six patients with impaired ventricular function and low-flow, low-gradient ventricular severe aortic stenosis were prospectively enrolled and assessed through dobutamine stress echocardiography. Researchers conducted measurements of the mean gradient, the aortic valve area, and the projected aortic valve area, which is an estimate of the aortic valve area at a standardized normal flow rate. True severity of stenosis was independently corroborated by macroscopic evaluation at the time of valve replacement in 54 patients, by multislice computed tomography in 25 patients, and by both methods in 8 patients. According to these last parameters, only 50 of 87 (57%) patients had true-severe aortic stenosis.

Read also: Low Gradient Aortic Stenosis Won’t Improve with TAVR.

A mean gradient ≥40 mmHg, an aortic valve area ≤1 cm², or a combination of both, during dobutamine stress echocardiography, correctly classified 48%, 60%, and 47% of patients, respectively. On the other hand, projected aortic valve area ≤1 cm² correctly classified 70% of the population, thus being more precise than all other parameters (p < 0.007).

Among the population, 47% (88 patients) of all cases were managed conservatively. In this subset, 52 patients died during a follow-up of 2.8 ± 2.5 years.

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After adjustment for age, sex, functional capacity, chronic kidney failure, etc., dobutamine stress mean gradient and aortic valve area were not predictors of mortality in this subset. In contrast, projected aortic valve area was a strong predictor of mortality for conservatively managed patients (hazard ratio [HR]: 3.65; p = 0.0003).

Conclusion

Parameters proposed in the guidelines to identify patients with low-flow low-gradient true-severe aortic stenosis have limited value to correctly identify actual aortic stenosis and to predict its outcomes.

Projected valve area better distinguishes true-severe aortic stenosis from pseudo-severe aortic stenosis and is strongly associated with mortality in patients under conservative management.

Original title: Dobutamine Stress Echocardiography for Management of Low-Flow, Low-Gradient Aortic Stenosis.

Reference: Mohamed-Salah Annabi et al. J Am Coll Cardiol 2018;71:475-85.

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