I will try to help you the best I can with my under two years experience on a step-down telemetry/cardiothoracic unit. This is my first and only nursing position so I do not have experience on a general med-surg floor.
I think you will make the transition just fine but that doesn't mean there won't be a learning curve for you. I'm not sure what your patient ratio is, or what it will be, but you probably already have your time management fine tuned. We typically have 4 patients on daylight and 5-6 on nightshift unfortunately. I would dive into studying all your cardiac drips. When are they used, the facility's protocol on titration, and most importantly, what you need to assess for and how often. On my unit, we most often see cardizem, nitro, amiodarone, and heparin gtts. We rarely ever have dopamine or epi unless they are started during a code and the patient will eventually be transferred to our ICU.
Telemetry monitoring and EKG interpretation is also very important. You want to be able to quickly determine what's going on with your patient so that you can call the doc for orders if needed. Brush up on the electrophysiology of the heart. The MOA of drugs like tikosyn and fleccanide. Different treatments for rhythm issues like ablations, cardioversions, watchmen procedures, permanent/temporary pacemakers. Study the settings and what they mean on temporary pacers.
Study and learn about cardiac caths and open heart surgeries. After open heart, your patients will have chest tubes in place. If you didn't work a lot with chest tubes on your med surg floor, I'd definitely go back and study that. Know how to identify an air leak, how to properly hook your patient up to suction etc.
It's important to study the anatomy of the heart, the vessels, NSTEMI vs STEMI, cardiac stents, how to wean TR bands, and post cath site checks. And you definitely want to understand the pathophysiology of CHF, cardiomyopathy, cor pulmonale & left sided HF. We also deal a lot with valvular disease and receive patients s/p TAVR or valve replacements.
If you already have the basic understanding of these subjects, the rest you will learn with experience and by asking a ton of questions. As you already know, you just need to know enough to be safe when starting a new speciality, you will certainly learn in time. I'm not sure if I answered your questions in the way you were hoping, but I hope this will help you somewhat. I just think it's important to show your potential manager that you have a genuine interest for cardiac nursing and your eager to learn along the way. Keep us updated & goodluck!