i had the same balance problems with inclines and sometimes still do on bad days.
i also sometimes get the heart rate problems on bad days as well.
i like to think it is just part of the migraine-type neurological symptom set playing around with the autonomic system and making everything go a bit wrong.
it could also be the meds though, or if the meds have lowered your blood pressure, your heart has to work harder to pump it around, or if the meds have lowered/slowed your cardio response, your heart has to go into override to 'wake up' to higher activity.
that's my non-medical opinion!