IST - Information and Support

tachy@hotmail.co.uk

IST FAQ

What is IST?

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. See what is IST?

What is 'Tachycardia' ?

Tachycardia is a heart rhythm that has a rate of greater than 90 beats per minute (older medical text books will say greater than 100 beats per minute).

Is IST dangerous?

IST can produce many unpleasant and disabling symptoms, it is not life-threatening.

Can IST be cured?

The 'Sinus Node Modification' / Ablation procedure, potentially offers a cure, the success rates for this procedure are lower than for most other types of arrhythmia. If the SA node Modification / Ablation is initially succesful (i.e. cures the IST), unfotunately the IST sometimes returns within a few months.

Can IST be treated?

IST can be treated with medications - some tried by cardiologists and other doctors include: Beta-blockers, Calcium channel Blockers, Anti-arrhythmics, Serotonin-reuptake inhibitors (e.g. Prozac), Florinef and Midodrine. For more information see treatments.
Non-drug treatment is very much last resort and is not reversible, the complications associated with these non-drug treatments are not insignificant. The treatments include
Sinus Node Modification, Sinus Node Ablation (with implantation of a pacemaker to take over the function of the Sinus Node) or Complete AV Node Ablation (producing complete heart block - with implantation of a pacemaker to pace the ventricles - the lower chambers of the heart). In the past Surgical Excision (removal) of the Sinus Node has been used but is not generally considered now with the ablation techniques available. See treatments.

Do I have to be treated for my IST?

No, the only reason to treat IST is to relieve symptoms. Being treated will not increase your lifespan (IST itself does not shorten lifespan). If you can live with the symptoms then there is no reason to have treatment. If the (drug) treatment makes you feel worse - you should discuss alternatives with your cardiologist / electrophysiologist.

In the rare individual where the persistent tachycardia has caused some changes in the heart muscle (this is known as Tachycardiomyopathy or Tachycardia Induced Cardiomyopathy); then some drug treatment or ablation treatment may be needed to lower the heart rate. This has been reported for other types of supraventricular tachycardia (tachycardia originating in the top chambers of the heart, or at the AV Node junction).
These changes in the heart muscle can be seen in an echocardiogram (heart ultrasound) and in anyone presenting to a cardiologist with an abnormal sinus tachycardia - an echocardiogram should be performed. The heart muscle generally returns to normal once the tachycardia is controlled. It usually only occurs when the heart rate is constantly very fast (more rapid than the usual resting heart rates of IST, please see references at the bottom of this page).

What is an Ablation?

An ablation is a catheter (a thin flexible tube) based, invasive treatment that happens as part of an EP Study. After an ablation the area of the heart treated will now be unable to initiate a rapid heartbeat. For more information see treatments.

What is an EPS / EP Study / Electrophysiology Study ?

An EP study is a type of cardiac catheterisation where the heart's electrical system is studied from inside the heart. During this test, one or more catheters (thin flexible tubes) are inserted into a vein in your groin or sometimes in other places (under collar bone or neck). X-rays are used to gently guide the catheters into the right positions in the heart. The catheters sense the electrical activity in the heart and also stimulate different areas of your heart. The areas of the heart generating abnormal heart rhythms can be located. An Ablation can also be performed as part of the EP Study. For more information see tests & diagnosis.

How did I get IST?

In general scientists and cardiologists do not know why someone develops IST.
IST has been reported in some patients following their having an ablation for another type of heart arrhythmia called AVNRT (AV Node Re-entry Tachycardia). Again, the reason for this is not fully known. One proposed reason is that some nerve control of the Sinus Node might have been damaged during the ablation for AVNRT. In some people this recovers.

Web Hosting by Yahoo!