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).
For more information see
what is IST?.

What is the Sinus Node?

The heart beat (electrical impulse) originates in the Sinus (SA) Node. The Sinus Node is a collection of specialised heart cells. The SA Node is located in the upper part of the right atrium (one of the 2 upper heart chambers) and the impulse spreads from here across to
the other heart chambers in an organised manner, making the heart muscle contract.


What is a pacemaker?

The Sinus Node is the 'natural' pacemaker of the heart. When the Sinus Node or AV Node fail(s), then an artificial Pacemaker can be implanted to generate impulses and stimulate the heart to contract. When most people hear the word pacemaker - they think of the artifical kind.


Why do most doctors not know about IST?
D
octors in general do not know a great deal about IST. This became very clear to me over a number of years. To see an account of my experiences visit the stories page. Physicians have many different aspects of cardiac disease to focus on; whilst this may not be a reasonable excuse for them to not know about IST - it is realistic. IST is rare.

What sort of doctor do I need to see?

The best doctor/physician to see is a Cardiac Electrophysiologist. An EP (electrophysiologist) is a cardiologist who specialises in the study and treatment of cardiac arrhythmias (heart rhythm disturbances). EP's are experts in all kinds of heart rhythm problems including IST. This is very important - because IST can be confused with other more common kinds of arrhythmia. For anyone with any kind of arrhythmia - it is reasonable to ask to see an EP.


Is IST caused by being unfit or lazy or is it a psychological condition?

No, IST is not caused by lazyness or by being physically de-conditioned or unfit.
It is not a psychological or psychiatric condition.
A severely deconditioned individual may have a raised heart rate, but a cardiologist will be able to evaluate this possibility when examining the individual.


How does the Heart work?

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.

Will I have to take medication for the rest of my life?

Maybe - but there is no general answer to this. Cardiologists do not know what the natural course of IST is. Does it 'get better' over time and disappear? Certainly some elderly people do get IST (this is documented but much more uncommon). If you choose to never have ablation treatment and you find that medication controls the IST symptoms then you may need to take medication for many years.

Is there any research going on into IST?

Yes. Have a look at the technical links section, where you can view abstracts from many papers on IST and relevant issues. This should give you a little bit of an idea of the research into IST via the combined efforts of electrophysiologists, cardiologists, researchers, clinical scientists, pathologists and other scientists and healthcare professionals.
It is early days into the study of IST (most, but not all, of the earliest work done on IST is within the last 10 years). The whole study and treatment of heart rhythm problems in general - called cardiac electrophysiology is a very new branch of cardiology (most of the EP catheter based treatments are only 15 - 20 years old) and therefore, much of the research is very new and many of the treatments under investigation.


                                                        
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If you have any links you would like to see here on IST or related conditions; then please send them to me via email.

I cannot guarantee all submissions will be posted, some may be editied if necessary.
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by Fran Horne
The content of this page was last modified at  16:51 GMT Wednesday 26th March 2008
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PLEASE READ
References:

Inappropriate sinus tachycardia; Richard N. Fogoros, M.D., November 2003

Radiofrequency catheter modification of the sinus node for "inappropriate" sinus tachycardia.
Lee RJ. Kalman JM. Fitzpatrick AP. Epstein LM. Fisher WG. Olgin JE. Lesh MD. Scheinman MM.
Circulation. 92(10):2919-28, 1995.


What Is a Pacemaker? National Heart Lung and Blood Institute; Diseases and Conditions Index (DCI)

Prevalence, characteristics and natural course of inappropriate sinus tachycardia
Aino-Maija Stilla,*, Pekka Raatikainena, Antti Ylitalob, Heikki Kaumac, Markku Ik�heimoa, Y. Antero Kes�niemic and Heikki V. Huikuria; Europace 2005


Inappropriate sinus tachycardia: an update; Morillo CA, Guzm�n JC. Rev Esp Cardiol. 2007 Oct
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