Hello thanks for asking from HCM for your health related queries I can understand your concern. Sudden onset racing heart along with thumping beats can occur due to anxiety. But before making anxiety as diagnosis other medical causes should be ruled out. Hyperthyroid states may cause such symptoms and result in rapid heart rate. Get your thyroid hormone levels done to rule out these conditions. Also get your ECG done to rule out any cardiac condition and any arrhythmias. If everything comes normal then most likely cause for your symptoms is anxiety. Anxiety can cause sudden onset palpitations and may result in ectopic beats. Medicines like propranolol or atenolol when used on PRN basis can help to calm down the racing heart. Even low dose benzodiazepines can help in such symptoms. Please visit a psychiatrist for prescription for these medicines. Thanks, Hope this helps you. Take care Dr. Seikhoo Bishnoi, Psychiatrist.