In several heart conditions, particularly long QT syndrome and Brugada syndrome, certain medicines or drugs can cause problems and trigger dangerous heart rhythms. These should therefore be avoided. Unfortunately, sale there is a rather long list of these! However a compressive list is available on-line, which is regularly updated:
For long QT syndrome: http://www.sads.org.uk/drugs-to-avoid
For Brugada syndrome: http://www.brugadadrugs.org/
It is very important that you tell anyone that prescribes you a new medicine that you have a heart condition, so that they can check it is safe for you to use!
If you buy over-the counter medications, make sure you tell the pharmacist as well.
Remember – if you have any doubts about what you are taking, seek medical advice!