Supraventricular Tachycardia - Prevention

Prevention

Once an acute arrhythmia has been terminated, ongoing treatment may be indicated to prevent recurrence. However, those who have an isolated episode, or infrequent and minimally symptomatic episodes, usually do not warrant any treatment other than observation.

Patients with more frequent or disabling symptoms generally warrant some form of prevention. A variety of drugs including simple AV nodal blocking agents such as beta-blockers and verapamil, as well as anti-arrhythmics may be used, usually with good effect, although the risks of these therapies need to be weighed against potential benefits.

Radiofrequency ablation has revolutionized the treatment of tachycardia caused by a re-entrant pathway. This is a low risk procedure that uses a catheter inside the heart to deliver radio frequency energy to locate and destroy the abnormal electrical pathways. Ablation has been shown to be highly effective: around 90% in the case of AVNRT. Similar high rates of success are achieved with AVRT and typical Atrial Flutter.

There is a newer treatment for SVT involving the AV node directly. This treatment is called Cryoablation. SVT involving the AV node is often a contraindication for using radiofrequency ablation due to the small (1%) incidence of injuring the AV node requiring a permanent pacemaker. With Cryoablation, a supercooled catheter is used (cooled by nitrous oxide gas), and the tissue is frozen to -10 °C. This provides the same result as radiofrequency ablation but does not carry the same risk. If you freeze the tissue and then realize you are in a dangerous spot, you can halt freezing the tissue and allow the tissue to spontaneously rewarm and the tissue is the same as if you never touched it. If after freezing the tissue to -10 °C, you get the desired result, then you freeze the tissue down to a temperature of -73 °C and you permanently ablate the tissue.

This therapy has further improved the treatment options for people with AVNRT (and other SVTs with pathways close to the AV node), widening the application of curative ablation to young patients with relatively mild but still troublesome symptoms who would not have accepted the risk of requiring a pacemaker.