predicting changes in flow category in patients with severe aortic stenosis and preserved left ventricular ejection fraction on medical therapy backgroundobjectives controversy surrounds the prognosis and management of patients with paradoxical lowflow severe aortic stenosis as with preserved left ventricular ejection fraction lvef it was not certain if patients in a particular flow category remained in the same category as disease progressed we investigated whether there were switches in categories and if so their predictorsmethods consecutive subjects n 203 with isolated severe as and paired echocardiography 180 days apart were studied they were divided into 4 groups based on their flow categories and if they progressed on subsequent echocardiography to switch or remain in the same flow category univariate analyses of clinical and echocardiographic parameters identified predictors of these changes in flow categoryresults one hundred eighteen were normal flow svi 35 mlm2 while 85 were low flow on index echocardiography in the patients with normal flow 33 switched to low flow this was associated with higher valvuloarterial impedance zva p 477 mm hgmlm2 auc 081 95 ci075087 p 001 in patients with low flow 25 switched to normal flow which was associated with lower zva and higher sac and the switch was predicted by a higher initial mean transaortic pressure gradientconclusions a significant number of patients switched flow categories in severe as with preserved lvef on subsequent echocardiography changes in flow were reflected by respective changes in zva and sac identifying echocardiographic predictors of a switch in category may guide prognostication and management of such patients