[Calcified aortic stenosis with left ventricular dysfunction and low transvalvular gradients. Must one reject surgery in certain cases?].

The natural history of severe aortic stenosis (aortic valve area < 1 cm2 or < 0.6 cm2/m2) with left ventricular systolic dysfunction and low transvalvular gradients (mean gradient < 40 mmHg) is mediocre in the short term and the operative risk is high. Dobutamine echocardiography provides a reliable evaluation of the aortic obstacle by diagnosing the rare cases of relative aortic stenosis in which the valve surface area has been underestimated because of a low cardiac output (aortic surface area > 1.2 cm2 with a mean gradient < 30 mmHg with dobutamine): in this case, the limited available data suggests that medical therapy with strict follow-up of its efficacy is the best management. The other use of dobutamine echocardiography is to assess left ventricular contractile reserve, defined as a increase > or = 20% in stroke volume under dobutamine. Cases with a contractile reserve have an operative risk of 5 to 10% and the medium-term benefits of valve replacement have been demonstrated. In the absence of contractile reserve, the operative risk is much grater, 30 to 60%, and also depends on other parameters such as the mean basal transaortic pressure gradient (risk five times greater in cases with a mean gradient < 20 mmHg), the need for coronary bypass surgery and associated co-morbid conditions. The surgical contraindications are in fact relatively few and concern patients with several risk factors: absence of contractile reserve itself is not a definitive surgical contraindication.