Increased heart rate has several causes: hyperthyroidism (it's important to check thyroid hormones), anemia (decreased blood hemoglobin), structural heart diseases (small case of mitral valve prolapse doesn't cause problems, as usually it is congenital), GI problems (such as gastritis, gastro-esophageal reflux, esophagogastroduodenoscopy can be done to exclude this), ischemic heart diseases (angina, previous infarction, which is not case for your age). If you don't have any of the above mentione ...
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