it is always hard to figure out what problems may be caused by a medicine, but if none have been started/changed recently it is hard to attribute new symptoms to it

Cervical problems can definitely mess with the autonomic nervous system (which controls HR)--I was diagnosed with autonomic dysfunction a couple of years ago---my heart rate would randomly go from the 140's to 40bpm with exciting changes in blood pressure

The docs had no idea what specifically caused it, IVIG helped get rid of it for me

Be careful flying as the cabins are generally underpresurized---one long flights I often get short of breath and majorly fatigued

Take care