Which clinical and echocardiographic parameters (i.e. LVEF, AVA) do you use when determining patient candidacy for LV device-assisted percutaneous balloon aortic valvuloplasty in patients with cardiogenic shock and severe AS?  

This is a tough one and there is no one best answer. The entire clinical picture must be taken into account. Typically, use of an RHC can help guide a patient in cardiogenic shock the best. Historically, patients with mean gradients over 40 mmHg with AVA < 1.0 cm sq by echo or by invasive testing...