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Which patient should be referred to an electrophysiologist: supraventricular tachycardia
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  1. Richard J Schilling
  1. Correspondence to:
    Dr Richard Schilling, Cardiology Department, St Barts Hospital, West Smithfield. London EC1 7BE, UK;
    richard.schilling{at}bartsandthelondon.nhs.uk

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The management of supraventricular tachycardia (SVT) has changed considerably over the last 10 years, and some of the techniques that interventional electrophysiologists were using last year are now outdated. This rapid evolution means that many cardiologists who do not specialise in this field find it difficult to keep up to date with the optimum strategies for the investigation and treatment of arrhythmia. This review aims to give an update on the available treatment options and their outcomes, and provide a guide to appropriate referral to specialist interventional cardiac electrophysiologists.

CLASSIFICATION AND AETIOLOGY OF SUPRAVENTRICULAR ARRHYTHMIAS

Most tachycardia has a re-entry mechanism (fig 1) and the classification of most arrhythmias is based on the location of this re-entry circuit. Tachycardia can be categorised as ventricular (involving the ventricle ± the His-Purkinje system only) and supraventricular (involving the supra-hisian structures with or without ventricular tissue). They can then be subdivided into regular or irregular tachycardia. Irregular SVTs—that is, atrial fibrillation (AF)—are less amenable to catheter ablation than regular SVT, but catheter ablation may be possible in selected patients. Regular SVTs can be cured by catheter ablation with high success rates (95–99%) and low complication rates (< 1%). Regular SVTs take the form of:

  • atrioventricular re-entry tachycardias (AVRT), using the ventricle as part of the circuit; these tachycardias are dependent on the presence of an accessory atrioventricular (AV) pathway (fig 2)

  • atrioventricular nodal re-entry tachycardia (AVNRT), where the re-entry circuit is within the AV node and the ventricle plays no part in maintaining the arrhythmia (fig 3)

  • atrial tachycardia, where the re-entry circuit does not involve any part of the AV junction. Examples are atrial flutter (fig 4) or ectopic atrial tachycardia (AT) (fig 5).

Figure 1

Diagrammatic representation of the mechanisms of re-entry. (1) A wavefront (arrows), initiated in a normal fashion in the sinus node, passes around an obstacle …

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