Supraventricular Tachycardias

DiagnosisTop

Key points for electrocardiographic (ECG) identification of supraventricular tachycardias (SVTs):

1) The ventricular rate should be classified as regular or irregular. An irregular ventricular rate suggests atrial fibrillation, multifocal atrial tachycardia, or atrial flutter with variable conduction.

2) If the atrial rate exceeds the ventricular rate, then atrial flutter or atrial tachycardia are usually present.

3) If the SVT is regular, this may represent atrial tachycardia with 1:1 conduction or an SVT that involves the atrioventricular node (atrioventricular nodal reentrant tachycardia [AVNRT], atrioventricular reentrant tachycardia [AVRT]).

4) In atrial tachycardia ECG will typically show a P wave with a morphology that differs from a sinus morphology.

5) In a typical AVNRT the retrograde atrial activation is nearly simultaneous with the QRS complex (P wave will be invisible or will deform the last portion of QRS). In orthodromic AVRT a retrograde P wave (coming from the ventricle to the atrium through the accessory pathway) is usually seen in the early part of the ST segment but later than we would expect with AVNRT (see Manifest and Concealed Accessory Pathways). Both AVNRT and orthodromic AVRT are forms of short-RP tachycardias. A long-RP tachycardia is usually an atrial tachycardia or rarely an uncommon form of AVRT or atypical AVNRT.

TreatmentTop

Classification of antiarrhythmic drugs: see Table 1 in Cardiac Arrhythmias.

Antiarrhythmic agents: see Table 2 in Cardiac Arrhythmias.

Acute Management of SVT of Unknown Origin

1. Irregular SVT: Management as in atrial fibrillation.

2. Regular SVT:

1) Vagal maneuvers, adenosine, or both.

2) If these are ineffective or not feasible, proceed according to the patient’s hemodynamic situation:

a) Stable: IV beta-blockers; IV diltiazem or IV verapamil. We suggest not to mix IV beta-blockers with IV calcium antagonists, especially if cardiac function is unknown.

b) Unstable: Synchronized cardioversion.

Ongoing Management of SVT of Unknown Origin

1. Preexcitation present in sinus rhythm (short PR plus delta wave):

1) Consider electrophysiologic study (EPS) and ablation.

2) If ablation is unavailable or refused by the patient, consider:

a) Flecainide or propafenone in the absence of structural heart disease.

b) Amiodarone or sotalol in patients with structural heart disease.

2. Without preexcitation in sinus rhythm:

1) Consider EPS and ablation.

2) If ablation is unavailable or refused by the patient, consider treatment with oral beta-blockers, diltiazem, or verapamil.