Your public profile offers very little information about where you are. I'm only 3-4 months ahead of you in this process; I just passed the CPC test and earned my CPC-A two weeks ago. So, I'll pass along advice that I've found helpful.
First, join your local AAPC Chapter, attend its meetings, and become acquainted with its members. Network with three goals in mind: (1) finding job opportunities, (2) meeting members who do cardiology coding, and (3) finding a mentor to advise and guide you. Be willing to look a coding jobs that are not specifically in cardiology so you can gain experience that will help remove the -A.
Focus, for the time being, on preparing for the CPC exam. I found it very helpful to buy and use the CPC Exam Prep and Review book, and I bought and used the 3 online practice tests (each is 50 questions). Since the exam is 5 hour and 40 min, set a goal for completing each practice test in 1 hr 53 min or 2-1/4 min/question. These questions are very much like those on the actual test.
For more information on preparing for the exam, see the Student Forum in the Education section:
https://www.aapc.com/memberarea/forums/forumdisplay.php?f=449
Once you have your CPC-A in hand, you'll need to start earning CEUs. AAPC offers several ways for getting them; one is a program called Code-a-Round. Included in that are 10 sets of cardiology cases, each set consisting of 5 cases. You can use these to hone your knowledge of the specifics of cardiology coding. Here's a link to the Code-a-Round page:
https://www.aapc.com/medical-coding-education/code-a-round.aspx
In the meantime, read the questions posted, here, in Cardiology and work them out as best you can, subscribe to the thread, then, read and study the answers posted to glean knowledge about cardiology coding.
Good Luck!