Just making it through orientation will be an accomplishment, especially on a cardiac floor. Trust me on that.
If you or your preceptors are noticing any issues, ADDRESS THEM RIGHT AWAY. Ask for honest feedback right away. The LAST thing you want is to find out, towards the end of orientation, your preceptors were concerned all along, and now it is too late to improve upon any issues. Ask for feedback from both your preceptor and your manager. Trust me, preceptors report things to managers all the time that they don't necessarily address with their orientees. Although it is probably not true, it does seem that some preceptors are more interested in looking good, looking superior, getting rid of someone they don't care for, or have other negative motives and these motives keep them in constant with the nurse manager.
You probably will have to study outside of work. Although some of your coworkers and supervisors may recommend you take the night off to relax, that is probably not the best advice. STUDY as much as you need to in order to prove to them you have a basic idea of what you are doing and that you are trying to improve.
It may not be possible to have only one preceptor, but try and keep the number of preceptors to a limit. It is difficult to make progress when you have numerous preceptors who have different expectations. If one preceptor's style of coaching doesn't fit yours, ask if it is possible to switch to another. If there is another coworker that you feel that you would learn more from, ask if they could possibly be your preceptor.
Make sure your communication with your preceptors is up to par. Come to them with a plan of what you want to address that day, and see if your priorities coincide with yours. Although you may have different ways of organizing your workload, they're going to want to see that you are critically thinking. They will want to understand your reasoning for performing the way you have. Ask them how they want to be addressed. Do they want you to tell them everything before you make a move? Or would they rather that you perform what needs to be done, come back and report what you have done, and then discuss what else needs to be covered?
Lastly, if you get the inkling at all that the position may not be for you, which I really hope you do NOT experience, address them with your managers/supervisors and preceptors. See what their feedback is. If they have positive feedback, take that into account, and relax so you are more comfortable with your new role. But, if they are having any doubt about you being a fit as well, discuss the possibility of transferring to a different unit. Be proactive and take as much control over the situation again. There would be nothing wrong with deciding that you need a different unit, as long as it is a decision you are a part of. However, when the managers take the leap to decide the position is not the right fit before you do, you may find yourself without a position not only within that department, but within that facility itself. You may end up leaving to go to a nursing position that is not in your desired specialty. Not trying to scare you, just saying take as much control as you can. It is the absolute worst feeling in the world to be told that despite your efforts, the unit has decided you are no longer an asset.
With that said, good luck and best wishes to you!