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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

MEDICATIONS

  • For regular narrow QRS tachycardia, adenosine 6–12 mg is useful to ...

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