Hello and Welcome to ‘Ask A Doctor’ service.
I have reviewed your query and here are my thoughts.
Chantix is
Varenicline and a prescription medications to stop smoking.
Your symptoms are surely suggestive of
heart attack as you have mentioned like
chest pain, palpitations and difficulty in breathing.
But since the cardiac check up is normal we have to look for other causes too.
Chantix can cause such symptoms.
Withdrawal also can cause same.
Stress and
anxiety are among other reasons and since your Doctor has already said cardiac to be normal.
But told you about
pleurisy, You need a proper CT scan of chest and other investigations to know the cause and get treated accordingly.
Hope I have answered your query.
Let me know if I can assist you further.