Hello, Acid reflux or exercise can increase increase heart rate slightly, but 155 persisting for 7 hours is less likely. This can be a cardiac arrhythmia like psvt or atrial fibrillation, in which heart rate suddenly goes up. Blood pressure may fall during these episodes and one has dizziness, fainting, blackouts, sometimes syncope. Usually ecg is normal as it is usually done in between the episodes. ECG done during episodes will show abnormality. You will need 24 hour holter monitoring or get ecg done during high heart rate. Also, hemoglobin and thyroid test should be done. ln order to abort such episodes you should try to cough hard. Is there any stress or anxiety associated. Till the time your evaluation is complete, you can ask your local doctor for tab ciplar LA 20 mg once a day. If none of the above is successful then last option is of electrophysiological studies which is invasive test which can diagnose and treat the arrhythmia permanently in most of the cases. Hope this helps you and get back if you have any doubts.