Original title: Invasive Hemodynamic Characteristics of Low Gradient Severe Aortic Stenosis Despite Preserved Ejection Fraction. Reference: Juliane Lauten et al. J Am Coll Cardiol 2013;61:1799–808.
Although the pathophysiology, clinical features, and natural course of severe aortic stenosis have been extensively described, management recommendations are still evolving. The current European and American guidelines recommend a valve area cutoff of 1 cm2, or indexed for body surface area of 0.6 cm2/m2, and a ≥40 mm Hg mean pressure gradient, to identify severe aortic stenosis in the presence of normal cardiac output and preserved ejection fraction. However, in a considerable number of patients with normal cardiac output that present aortic stenosis, these appear to be severe judging by their valve orifice area, but moderate (or even mild) judging by their transvalvular gradients.) Because both values usually derived from echocardiography, these cases with low gradients with 40 mm Hg mean gradient and ≥50% ejection fraction were analyzed by echo; they routinely underwent invasive hemodynamic evaluation with retrograde passage of the aortic valve and calculation of aortic orifice area by the Gorlin formula (stroke volume was measured both by oxymetry or by thermodilution in all patients).
Stroke volumes measured by thermodilution were higher than stroke volumes measured by oxymetry (p < 0.0001). Given this difference, results were compared against echo measurements. In this population, the echo area (0.8 ± 0.15 cm²) correlated modestly compared to the invasive measurement of stroke volumes with oxymetry , (0.69 ± 0.16 cm2, bias 0.14 ± 0.17 cm2) or using thermodilution (0.85 ± 0.19 cm2, bias 0.03 ± 0.19 cm2) Mean gradients were very similar by echo and catheterization, with nonsignificant differences. Reclassification to moderate stenosis by hemodynamics occurred in one patient using oxymetry and in 6 patients using thermodilution.
Conclusion:
Low gradient severe aortic stenosis despite preserved ejection fraction was confirmed by invasive hemodynamics and was not the result of a systematic bias in echo calculation of the aortic orifice area.
Editorial Comment:
Although both methods present limitations and the area calculation correlates modestly, patient reclassification, that would eventually change therapeutics, is not frequent, especially when oxymetry is used to calcualte stroke volumen.
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