| Some info on IST : Most people who have IST are women (not all, but most). This is reported in data collected for study. It has also been reported that many of these patients are young, usually under the age of 30. There are also said to be cases of patients who are elderly women who have IST. It is not unusual for patients to first present to cardiologists and other doctors with arrhythmias when they are in their teens and twenties. IST appears to be similar in this respect. Many patients with IST find that they have to be very persistent when seeking diagnosis and treatment. IST can also be confused with other conditions, notably one called POTS (Postural Orthostatic Tachycardia Syndrome) - notably a drop in blood pressure upon standing, with a sudden rise in heart rate and sometimes accompanyied by blurred vision, dizziness and pre-syncope (a feeling that you are about to faint) and syncope (fainting). For information on POTS please check out these links : POTS Place: A Guide to Postural Orthostatic Tachycardia Syndrome Postural Orthostatic Tachycardia Syndrome Patient's report on causes, symptoms, and treatment IST Symptoms Most patients with IST have a resting heart rate of greater than 90 - 100bpm. During sleep the heart rate usually falls to 70 - 90 bpm. With tiny amounts of exertion, the heart rate can quickly rise to over 150 bpm. The main symptom experienced by IST sufferers is usually palpitations (being aware of your heart beat) and can be very distressing and exhausting. Please visit the symptoms page. What causes IST? The cause of IST isn't known at present. There are several possibilities (and certainly it could result from one or a combination of these or from another mechanism not yet discovered). Some scientists and/or cardiologists especially electrophysiologists (cardiologists specialising in the diagnosis and treatment of heart rhythm disorders) think that IST is caused by the sinus node itself having an abnormal structure or function, some believe it is part of a problem called dysautonomia (a disturbance with the autonomic nervous system). For information on dysautonomia please check out these links : Dysautonomia by Dr Rich Fogoros M.D. National Dysautonomia Research Foundation Other Dysautonomic Syndromes What needs to be excluded before IST is diagnosed? Other abnormal heart rhythm disorders - various types of SVT - can sometimes be confused with sinus tachycardia. Abnormal SVT needs to be excluded, they can often be diagnosed and cured. There are lots of treatable medical disorders that can be confused with IST (but often aren't as IST is very much a 'last resort' consideration). If someone has a persistent, frequent, sinus tachycardia other causes need to be considered and investigated. These can include hyperthyroidism, a type of benign tumor (called a phaeochromocytoma) that produces substances that behave like adrenaline in the body, diabetic autonomic dysfunction, and prescibed and non-prescription drugs. From The Cleveland Clinic at webMD : Abnormal Heart Rhythm page 1 page 2 |
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what is IST ? by Fran Horne |
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| The content of this page was last modified at 17:25 GMT Wednesday 26th March 2008 |