Are there instances when you would recommend against pursuing adrenal vein sampling in a patient with primary hyperaldosteronism and normal adrenal imaging?  

Yes, it is not uncommon for patients to choose not to pursue an adrenalectomy. I do not get the adrenal vein sampling (AVS) until I've had a discussion about the risk/benefits of adrenalectomy. Sometimes, I'll have them visit the surgeon before attempting an AVS to get a full picture of the surgery ...