When is it safe to take daily 10 mg zyrtec (cetirizine) after cardiac rf ablation? is there a safer antihistamine for arrhythmia patients?

Fexofenadine: There is nothing which is a 100% safe but fexofenadine would be my choice in your situation. On the other hand, why not try a nasal spray (cortisone or antihistamine) instead if the problem is mainly nasal. This will have no effect on the arrhythmia and is more effective.

Ablation: zyrtec (cetirizine) is considered relatively safe following cardiac ablation.