الفهرس 
Aortic valve stenosisOnly 14 pages are availabe for public view
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Abstract
Low-flow, low-gradient (LF-LG) aortic stenosis may occur with depressed (classical LF-LG) or preserved (paradoxical LF-LG) left ventricular ejection fraction, and both situations are amongst the most challenging encountered in patients with valvular heart disease. In both cases, the decrease in transvalvular pressure gradient relative to stenotic severity is due to a reduction in transvalvular flow. In patients with low left ventricular ejection fraction, LF-LG aortic stenosis, dobutamine stress echocardiography (DSE) was useful to distinguish between true-severe versus pseudo-severe aortic stenosis and to assess the severity of myocardial impairment. Patients with pseudo-AS showed an increase in valve area and relatively little increase in gradient in response to increasing flow,whereas true-severe aortic stenosis was characterised by little or no increase in valve area and marked increase in gradient, which was congruent with the relative increase in flow. Therefore, DSE clearly could help to differentiate truesevere from pseudo-severe AS. Another indication of dobutamine stress echocardiography (DSE) in patients with low left ventricular ejection fraction, LF-LG aortic stenosis, was to distinguish the presence or absence of LV contractile reserve. Patients with no left ventricular contractile reserve were defined by a percent increase in stroke volume <20% during DSE.