An influential physician-administrator once complained to me that whenever he asked potential new faculty hires where they saw themselves in a decade they always said they were interested in global health or teaching. "It sounds sexy," he remarked. "But many of them have nothing in their C.V.s to bolster their interest in either pursuit."
When asked where you see yourself in ten years, consider how your accomplishments thus far might demonstrate an evolution. The idea is to have a trajectory that you can back up, defend, and easily justify. This doesn't mean you're stuck with what you've done even if you didn't like it, though. You could point out that having tried myocardial bench research, you realize that your real interest is in clinical investigations of new cardiac markers.
Many medical school applicants say they don't know what field they want to go into. That's okay! And many residency applicants don't know if they want to do a fellowship. That's also to be expected. The point is to focus on your previous strengths and achievements and leverage them to demonstrate a logical path, going forward.
