Supraventricular tachycardia

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Template:DiseaseDisorder infobox | }} A supraventricular tachycardia (SVT) is a rapid rhythm of the heart in which the origin of the electrical signal is either the atria or the AV node. These rhythms require the atria or the AV node for either initiation or maintenance. This is in contrast to ventricular tachycardias, which are tachycardias that are not dependent on the atria or AV node.

1 Types of SVTs
2 Diagnosis
3 Treatment
4 References
5 See also
6 External links

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Types of SVTs

Supraventricular tachycardia is a general term that describes a number of different arrhythmias of the heart, each with a different mechanism of impulse maintenance. While some treatment modalities can be applied to all SVTs with impunity, there are specific therapies available that can cure many of the arrhythmias that require intimate knowledge of how the arrhythmia is propagated.

The SVTs can be separated into two groups, based on whether they involve the AV node for impulse maintenance or not. Those that involve the AV node can be terminated by maneuvers that decrease conduction through the AV node, whereas those that do not involve the AV node may be unmasked by the transient AV block caused by the decreased conduction through the AV node.

SVTs that require the AV node for impulse maintenance include:

AV nodal reentrant tachycardia (AVNRT)
AV reentrant tachycardia (AVRT)
Permanent junctional reciprocating tachycardia (PJRT)
Junctional tachycardia.

SVTs that do not require the AV node for impulse maintenance include:

Sinoatrial node reentrant tachycardia (SANRT)
Multifocal atrial tachycardia (MAT)
(Unifocal) Atrial tachycardia (AT)
Inappropriate sinus tachycardia.

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Diagnosis

In the clinical setting, it is important to determine whether a wide-complex tachycardia is an SVT or a ventricular tachycardia, since they are treated differently. Ventricular tachycardia has to be treated appropriately, since it can quickly degenerate to ventricular fibrillation and death.

A number of different algorithms have been devised to determine whether a wide complex tachycardia is supraventricular or ventricular in origin.Template:Fn In general, a history of structural heart disease dramatically increases the likelihood that the tachycardia is ventricular in origin.

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Treatment

SVT can be treated through several modalities, the simplest of which is the vagal or valsalva maneuver, wherein a patient is asked to bear down as if having a bowel movement. This puts pressure on the vagus nerve and, under normal circumstances, slows the patient's heart rate by stimulating the parasympathetic nervous system. Another modality involves treatment with medications. Prehospital care providers and hospital clinicians might administer Adenosine, Cardizem, Toprol, or Verapamil. If none of the above works, or if the patient is extremely unstable, synchronized cardioversion may also be used.

Another form of treatment is Radiofrequency ablation, a surgical procedure that uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue and has shown great promise eliminating SVT.

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References

Template:Fnb Lau EW, Ng GA. Comparison of the performance of three diagnostic algorithms for regular broad complex tachycardia in practical application. Pacing Clin Electrophysiol. 2002 May;25(5):822-7. (Medline abstract)

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