It is either connected to reflux, or to pancreatic insulinoma which cause a rapid rise
and then rapid fall of
blood glucose resulting in rapid heart rate. Apart from this it can even be due to anemia, low blood pressure, hypoglycemia, anxiety, hyperthyroidism etc.
Please consult your PCP for primary examination (blood sugar, thyroid levels, hemoglobin, BP monitoring etc) followed by proper referral.
Take care!