Supraventicular tachycardias

Supraventicular tachycardias

Supraventricular tachycardias (SVT) are rapid arrhythmias that originate from above the ventricles. Although this including atrial flutter and fibrillation, the term is generally used to describe arrhythmias caused by an abnormal piece of wiring within the heart or accessory pathway. The presence of a second, abnormal connection, from the atrium to ventricle, forms the requirement for loop like "reentry" circuits, allowing signals to go down one connection, revolve around the chamber then up the other connection to the second chamber in a self perpetuating loop like process (Figure 7).

Wolff Parkinson White Syndrome cannot only cause symptoms, but is a type of accessory pathway that can cause life threatening arrhythmias. It is reported that there is a 0.2% annual risk of sudden cardiac death but recent reports suggest this can be as high as 1-2% even in patients with no symptoms.

 These arrhythmias occur in 1% of the population and often beginnings early in life. SVTs are not life threatening except for a condition called Wolff Parkinson White Syndrome. The difficulty of SVTs is the unpredictable nature of how they behave, when they occur, how long an attack may persist and when it would end.

Drugs are often effective in complete control of the arrhythmia in half of all cases and the drugs are effective only for the duration that they are taken. This means that young patients may face the prospect of several decades of take drugs therapy with potential long-term side effects from medication.

Because these arrhythmias arise from abnormal focal strands of wiring and their behaviour has been well categorised and understood, catheter ablation techniques can now locate these abnormal strands of muscle acting as bridging pieces of electrical wiring and focal delivery of high frequency radiowaves (Figure 8) can completely cure these arrhythmias (Figure 9). Even left sided pathways can be easily treated with procedural risk of up to 1%.