Each antiarrhythmic drug has a predominant use for certain types of arrhythmias. You need to be able to determine which antiarrhythmic is suitable for certain arrhythmias. Yes, this is more important for Step 2, however it is knowledge you are required to have some familiarity with for Step 1, especially since often the stem of the question may reveal the type of arrhythmia and ask you about the unkown drug being used. Unfortunately, in Kaplan and First Aid this information is scattered in a difficult to study manner.
THE SOLUTION: If you have Lippincott's Pharmacology, go to page 174 (figure 17.2). This is a full page sized reader-friendly figure showing the different arrhythmias and the anti-arrhythmics that can be used. It is very organized and I highly recommend you refer to this. If you don't have the book, email me and I will scan this page for you.