Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ 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... Your Access profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Password? Forgot Username? Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free a profile for additional features.