When will you request TEE in Ischemic Stroke?

The main reason for getting a TEE in a patient with ischemic stroke is to find out if that patient has an indication for warfarin anticoagulation. You can begin the selection process by excluding patients who already have an obvious indication for warfarin (e.g. atrial fibrillation) and those who have a contraindication for warfarin.

Among the remaining patients only those with cryptogenic stroke are likely to need a TEE. This is an old paper demonstrating a high yield for TEE in finding an indication for warfarin in such patients. Here is a new study documenting similar findings:
The TOAST classification may be helpful in the determination of cryptogenic stroke.