Atrioventricular Reciprocating Tachycardia: Preexcitation

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Wolff-Parkinson-White syndrome

  • – Short P-R interval (< 120 ms)

  • – Wide QRS complex caused by a delta wave due to preexcitation over an atrioventricular (AV) bypass tract

  • – Supraventricular tachycardia with heart rates of 140–250 bpm

• Atrioventricular reciprocating tachycardia (AVRT) with a narrow QRS is the most common arrhythmia

GENERAL CONSIDERATIONS

• AV bypass tracts or accessory pathways have a 2:1 male-to-female predominance and may be familial

• Left ventricular free wall is the most common location for accessory pathways

• Right-sided bypass tracts are commonly associated with structural heart disease

• 5–10% have structural heart disease (Ebstein’s anomaly is the most common)

• Fewer than half of those with documented bypass tracts sustain a clinical arrhythmia

• When the bypass tract conducts retrograde (antegrade conduction over the AV node), AVRT results

• Orthodromic AVRT (antegrade over AV node) accounts for 90–95%, and antidromic AVRT (retrograde over AV node) accounts for < 10%

• Orthodromic tachycardia has a narrow QRS complex, and antidromic tachycardia has a wide QRS complex

• Atrial fibrillation with antegrade conduction over the bypass tract can lead to ventricular fibrillation (1:1 AV conduction) and sudden death

• Concealed bypass tracts conduct retrograde only and cause orthodromic AVRT, but cannot be detected during sinus rhythm

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Palpitations, chest pain, and dyspnea

• Dizziness

• Syncope

• Sudden death

• Asymptomatic

PHYSICAL EXAM FINDINGS

• Normal clinical exam in most patients

• If associated with Ebstein’s anomaly, physical exam may be positive for tricuspid regurgitation and associated anomalies

• Midsystolic click and murmur are present if there is associated mitral valve prolapse (MVP)

DIFFERENTIAL DIAGNOSIS

• AV nodal reentrant tachycardia

• Supraventricular tachycardia with aberrancy

• Ventricular tachycardia (for antidromic tachycardia)

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Serum thyroid-stimulating hormone in atrial fibrillation patients

ELECTROCARDIOGRAPHY

• ECG during sinus rhythm (SR) or narrow QRS tachycardia

  • – If there is preexcitation during SR, then antegrade conduction is present; otherwise concealed bypass tract

  • – Antidromic tachycardia usually has a wider QRS complex

• Holter monitoring or event recorder to document arrhythmia

IMAGING STUDIES

• Echocardiogram

  • – If Ebstein’s or MVP suspected

  • – Recommended in patients with a presenting arrhythmia of atrial fibrillation

DIAGNOSTIC PROCEDURES

• Electrophysiologic study to define mechanism of the tachycardia

TREATMENT

CARDIOLOGY REFERRAL

• All patients should be evaluated by a cardiologist

• Referral to electrophysiology decided by a cardiologist

HOSPITALIZATION CRITERIA

• Patients presenting with syncope

• Sudden death survivors

• Atrial fibrillation in a patient with known antegrade conduction

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