Symptoms of postural orthostatic tachycardia syndrome include lightheadedness, dizziness, heart palpitations, weakness and feelings of anxiety, according to About.com. Other possible symptoms include blurred vision and shakiness, and approximately 40 percent of patients experience one or more episodes of passing out. Postural orthostatic tachycardia syndrome causes an increased heart rate upon standing.
Due to the occasional occurrence of postural orthostatic tachycardia syndrome with other nervous system disorders, some sufferers may experience diarrhea, constipation, abdominal cramps, bloating and similar symptoms, states About.com. Some individuals may also experience extreme fatigue as well as aches and pains. Even after successful treatment of the accelerated heart rate, these symptoms may remain.
To diagnose postural orthostatic tachycardia syndrome, a health care professional uses a tilt-table test or other method to check for an elevated heart rate when the patient is standing. It can take several minutes for this symptom to manifest. While an average person's heart rate may increase by around 10 beats per minute when standing up, the heart rate of someone with postural orthostatic tachycardia syndrome often increases by more than 30 beats per minute. Before concluding the diagnosis, the doctor must rule out other potential conditions such as dehydration and diabetic neuropathy.