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USEFULNESS OF AORTIC VALVE RESISTANCE IN ASSESSMENT OF HEMODYNAMIC SEVERITY IN AORTIC STENOSIS

Purpose: This prospective study was designed to determine the usefulness of aortic valve resistance for the evaluation of aortic stenosis (AS) and separation of patients with severe aortic stenosis from those with milder disease. Methods: In 193 patients aortic valve area (AVA), mean pressure gradient (Δpmean), valve resistance (VR), left ventricular function (LVF) and cardiac output (CO) were determined by transthoracic echocardiography at rest. A threshold value of valve resistance was identified to seperate patients with truly critical (AVA < 0.7 cm2) from those with truly noncritical aortic stenosis (AVA > 0.8 cm2 and Δpmean < 50 mm Hg). The usefulness of this threshold value for assessing the hemodynamic severity of aortic stenosis was investigated in the subgroup of patients with aortic valve area ranging from 0.7 to 0.8 cm2. Results: When severe AS was diagnosed in patients (AVA < 0.7 cm2) valve resistance was determined ≥ 250 dyn·s·cm−5 (n = 93, mean: 455.8 ± 169.1 dyn·s·cm−5) in all but one patient with severe LV dysfunction and low CO. In all patients with AS classified as mild to moderate (AVA > 0.8 cm2 and Δpmean < 50 mm Hg) calculated VR was < 250 dyn·s·cm−5 (n = 43, mean: 158.5 ± 48.2 dyn·s·cm−5). Conclusion: The identified threshold value of VR = 250 dyn·s·cm−5 may help to identify patients with critical aortic stenosis even if aortic valve area is in moderate range.