When would you consider initiating patients with CAD and aortic stenosis on PCSK9 inhibitors (as an adjunct to statin therapy), given favorable findings in the FOURIER trial?  

There are limited data to support PCSK9 inhibitors in the treatment of aortic stenosis, and in fact, most is theoretical. Elevation of lipoprotein (a) levels independently increases the risk of in early-onset CAD and calcific aortic stenosis. Lp(a) levels are lowered by PCSK9 inhibitors by ~20-30%, ...

Only if they have a guideline indication for non-statin therapy due to LDL being above goal. 

We shall see if lowering Lp(a) helps slow the progression of aortic stenosis with the new Lp(a) antisense med Pelacarsen. [Lp(a)FRONTIERS CAVS] trial is currently recruiting.