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.