Atrioventricular reentry tachycardia
Clinical presentation is variable, with most patients reporting episodes of abrupt onset palpitations, lightheadedness, dizziness, diaphoresis, shortness of breath, chest pain, syncope, and/or presyncope. The symptom manifestation depends largely on the heart rate.
The arrhythmia generally initiates with a perfectly timed, premature atrial, ventricular, or junctional beat due to a difference in conduction speed and refractoriness of the normal conduction system and the accessory pathway.
The arrhythmia may be conducted through the AV node in an anterograde fashion and back to the atria via the accessory pathway (orthodromic AVRT), or it may conduct from the atria to the ventricle through the accessory pathway and back to the atria via the AV node in a retrograde fashion (antidromic AVRT). Ninety to ninety-five percent of AVRTs are orthodromic.
Accessory pathways may be capable of conducting in antegrade direction (atria to ventricles), retrograde direction (ventricles to atria), or both. Pathways are termed "manifest" pathways if they can conduct in an antegrade direction or both directions. These pathways result in pre-excitation of the ventricle during sinus rhythm, resulting in the appearance of a "delta wave" on a resting ECG. Manifest pathways comprise 0.1%-0.3% of AVRT cases. Accessory pathways are defined as "concealed" when they conduct only in the retrograde fashion. Concealed pathways do not cause pre-excitation and thus do not demonstrate a delta wave.
Wolff-Parkinson-White (WPW) syndrome is defined by ventricular pre-excitation, manifesting as a delta wave on a resting ECG, as well as a history of arrhythmia. By conducting in an antegrade fashion down the accessory pathway, thus bypassing the AV node, atrial fibrillation may be associated with extremely rapid ventricular rates in patients with WPW, which can decompensate to ventricular fibrillation and sudden cardiac death (SCD). The 10-year risk of SCD in patients with WPW is approximately 0.15%-0.24%.
I49.8 – Other specified cardiac arrhythmias
233897008 – Re-entrant atrioventricular tachycardia
Differential Diagnosis & Pitfalls