It is perfectly safe to take Claritin with your medications despite your arrhythmia problems. However, I recommend that you consult an allergist to see if you could try other treatments that might be more useful for you (nasal spray, eye drops, desensitization). In addition, in some people, long-term use of allergy medications such as Claritin can sometimes make them less effective. It would therefore be interesting for you not to take Claritin all year round and to try desensitization or to stay as far away as possible from the identified allergens.
