Supraventricular Tachycardia: Sensitivity and Specificity
Introduction: Supraventricular tachycardia is any tachyarrhythmia that requires atrial or atrioventricular junctional tissue for its initiation and maintenance. It is usually manifested by a narrow complex tachycardia (unless there is aberrancy). The different types are: sinus tachycardia, atrial tachycardia, atrial fibrillation or flutter, AV reentrant tachycardia, AV nodal reentrant tachycardia, multifocal atrial tachycardia, and junctional tachycardia.
**Distinguishing a wide-complex tachycardia as SVT with aberrancy versus VT is covered in the Ventricular Tachycardia entry.**
Often these can be distinguished on the basis of ECG during the tachcardia, but giving atropine to slow the rhythm can help.
Various ECG features are helpful in distinguishing the mechanisms:
For atrial fibrillation, the ventricular rate is irregular.
For atrial flutter, flutter waves are seen and the rate is usually an integer fraction of ~300-320bpm.
From [J Am Coll Cardiol. 1993 Jan;21(1):85-9. PMID 8417081]
Presence of P waves suggests (sinus,) atrial, or AVRT. Usually, the P wave follows the QRS in AVRT or AVNRT and is inverted; indeed, this paper found that RP/PR >= 1 suggested atrial tachcardia. In this paper, P waves were not necessarily seen in AVNRT.
Presence of pseudo-R' in V1 or pseudo-S in II/III/aVF suggests AVNRT.
QRS alternans suggests AVRT
While the patient is in sinus, pre-excitation (WPW pattern) suggests AVRT, though this was only seen in 45% of the cases. (Certainly, an accessory pathway is required for AVRT, but it is not always evident on ECG.)
Even using all of these criteria, 19% of tachycardias were misassigned.
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Differential Diagnoses include:
The sensitivity and specificity
of findings for Supraventricular Tachycardia are listed below.
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