If you want to be a heart nurse, work in a busy CVICU if that is really your passion. Neuro is very interesting though and is a wonderful speciality to have. You will become familiar with all the vasoactive drips you will see on any cardiac unit (most of them anyway). I surely wouldn't expect you to see much balloon pumps though. If it's a strictly neuro icu and not a mix (like a sicu, etc..), then I don't think you'll see a balloon pump. Swans, we have a lot of them, but that depends where you are, as many docs are not using them so much anymore.
You can always transfer within your hospital. As a new grad, good luck. You will be getting the basics down that first year anyway.
You will be spending your time doing neuro exams, going for stat ct scans, helping with putting in evds, and more importantly managing them. It's a great knowledge to have, taking care & understanding neuro pts, as it can be complicated and serious. Good luck.