I have supra ventricular tachycardia or racing heart. I take a half tab of 25 mg atenolol and the Dr. prescribed .125mg Digoxin. I have been taking atenolol for about 20 years for the racing heart. The Digoxin was prescribed because my pulse was so low. I have been taking the Digoxin for 1 month. I have a biomointor implant for EKG monitoring. A 3rd degree AV block showed up. Could this be from the Digoxin?