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treatment of IST |
| < back to Medication Therapy for IST < back to Invasive (non-medication) Therapy More detailed information on Ablation treatments for IST (contains quite detailed information and reference sources) Specifically, in IST - ablation is technically very difficult. The success rates are not as high as for other arrhythmias treated with ablation. In addition, the complication rates are much higher (usually this refers specifically to the need for an artificial pacemaker to be implanted due to too much damage caused to the sinus node - the heart's natural pacemaker). Unfortunately, it has been shown that the IST can reccur within a few months following ablation. Repeat EP Studies in these patients show that another part of the right atrium is acting like the sinus node and unfortunately in some patients, means that IST can be generated by these cells. Electrophysiologists have discovered that the Sinus Node is much larger than previously thought and that much of the right atrium (one of the upper chambers of the heart) can act as 'Sinus Node' - i.e. initiate the heart beat. In addition - certain parts of the sinus node produce faster heart rates than others. This allows the electrophysiologist to ablate (destoy) the parts producing the fastest rates (usually at the top, central part of the sinus node), leaving the other parts of the node intact; which, in theory, should mean the patient won't need a pacemaker; (this is called a Sinus Node Modification). The Sinus Node Ablation / Modification does work in some patients! and for the severely symptomatic person - they may decide that despite the risk of a pacemaker and the chance of the IST returning even after the ablation - it is worth an attempt. Electrophysiologists have learnt a great deal about the Sinus Node whilst studying IST during EP Studies and studies (post-mortem) of normal hearts and hearts of people who had IST. Researchers, Scientists, Pathologists and Electrophysiologists have collectively learnt that the Sinus Node is not exactly the same in everyone, women have naturally faster intrinsic heart rates than men and that sometimes the Sinus Node is located more towards the 'outside' (epicardium) of the heart muscle than towards the 'inside' (endocardium). This latter fact maybe sheds some light on the problem of ablation not always working , or adding to the technical difficulty in ablating IST (as the RF ablation catheters used to ablate IST can usually only cause fairly small lesions. Often in EP Studies and ablations done for IST - special types of 'mapping' are done to locate where the fastest rates are generated in the sinus node (and also to check that the rhythm is actually being generated by the sinus node and not in 'normal' heart muscle cells in the atria - this would be called an Atrial Tachycardia. Sometimes, but not often - the EP Study is needed to tell IST appart from an Atrial Tachycardia). Echo (ultrasound) is also used inside the heart to help position the catheter in the right place. Newer ablation catheters are being investigated for various arrhythmias and hopefully these will come into use for IST as well. One of interest is called a 'cold tip' or 'cryo' ablation catheter and looks very exciting as it allows the Electrophysiologist to 'cool down' an area inside the heart to see if that stops the arrhythmia. The beauty of this approach is that if 'cooling' this area of the heart gives an undesirable result - i.e. it does not 'cure' the arrhythmia or worse still - causes heart block (a condition that would usually require a pacemaker be implanted)....... then the catheter can be re-warmed and the 'damage' is reversible! If a good result is acheived then the catheter can be cooled even further and a permanent ablation caused. These types of catheters are also able to generate deeper 'lesions' than RF (radiofrequency), which may also be a useful aid to the Electrophysiologist when attempting to modify the sinus node. For more information on specialised 'mapping techniques' , ablation catheters and intracardiac echocardiography used in the EP Study check out : Endocardial Solutions (for patients) CARTO EP Navigation Procedure (for patients) Cryocath Intracardiac Echo - from theeplab.com (for healthcare professionals) References: (for healthcare professionals & other interested Individuals) 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. Inappropriate Sinus Tachycardia Michael D. Lesh M.D., Franz X. Roithinger M.D. Atrial Tachycardia ( Clinical Approaches to Tachyarrhythmias, V. 11) chapter VII. 1999. Inappropriate sinus tachycardia (IST): management by radiofrequency modification of sinus node. Jayaprakash S. Sparks PB. Vohra J. Australian & New Zealand Journal of Medicine. 27(4):391-7, 1997. Surgical excision of the sinus node in a patient with inappropriate sinus tachycardia. Esmailzadeh B. Bernat R. Winkler K. Meybehm M. Pfeiffer D. Kirchhoff PG. Journal of Thoracic & Cardiovascular Surgery. 114(5):861-4, 1997. For more technical papers, links and book referrences, check out the links section |
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| The content of this page was last modified at 02:46 GMT Wednesday 20th July 200 |
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