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| IST (inappropriate sinus tachycardia) For a quick view to familiarise yourself with the normal conduction system of the heart and heart rhythms please check out these links: how your heart works by Dr. Carl Bianco, M.D. the cardiac electrical system by Dr Rich Fogoros, M.D. Inappropriate sinus tachycardia (IST) is a type of cardiac arrhythmia (an abnormal heart rhythm) in which a person's resting heart rate is usually greater than 90 - 100 beats per minute (or rapidly accelerates to greater than 90 - 100bpm very frequently), the heart rate increases dramatically with small amounts of exercise, emotional or physical stress. People with IST often find that their fast heart rate causes them to experience symptoms including palpitations, shortness of breath and other symptoms and an inability to engage in exercise and physically demanding activities. The symptoms can be very frightening, especially when an individual first becomes aware of them. People with IST often find their lives made a misery, not only by the symptoms and effects of the condition - but by the apparent lack of knowledge amongst healthcare professionals. Many doctors/physicians and even some cardiologists do not appear to know a great deal about IST. To see an account of my own and others experiences visit the stories page. Cardiologists have many different aspects of cardiac disease to focus on, and whilst this may not be a reasonable excuse for them to not know about IST - it is realistic. IST is rare. My greatest wishes are for cardiologist and medics to become educated about IST, so that more people do not feel like they are being brushed off as being 'anxious' or 'crazy' and they can get appropriate care from professionals. A doctor who will have the greatest knowledge about IST is a Cardiac Electrophysiologist (or 'EP' for short). Click here to find out more. What is IST? IST is a type of tachycardia (a fast heart beat). 1st to explain the 'Inappropriate' in Inappropriate Sinus Tachycardia……. Sinus tachycardia ('Appropriate' Sinus tachycardia) is a normal heart rhythm. Sinus Rhythm is the name given to the normal heart rhythm, with the heart rate in the range of 50 - 90 bpm (beats per minute). Older textbooks will say 60 - 100 bpm. But no-one would consider a resting heart rate of 100bpm to be normal or desirable. Sinus Tachycardia is described as a sinus rhythm over 100 bpm. An 'Appropriate' Sinus Tachycardia can develop as a desirable response to pregnancy, physical exertion and emotion. Sinus tachycardia can also develop as a 'compensatory response' by the circulatory system in response to various conditions including low blood pressure, low blood volume (including via blood loss), anaemia, structural heart disease, pain, cancer, endocrine disorders, also in response to some prescription and non-prescription drugs and can result from drug toxicity. When there is no known cause and all possible known causes of Sinus Tachycardia have been excluded, the heart rhythm is called 'Inappropriate' Sinus Tachycardia. There are 2 main types of abnormal rapid heart rate that also need to be excluded before IST is considered - SVT (Supraventricular Tachycardia), and VT / V-Tach (Ventricular Tachycardia). These fast rhythms are generated in parts of the heart that do not normally initiate the heart beat. IST is generated in the Sinus Node (where normal sinus rhythm is generated). So, on an ECG - IST looks exactly the same as a 'normal' sinus tachycardia. 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 17:05 GMT Wednesday 26th March 2008 |
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