Conduction from the atria to the ventricles normally occurs via the atrioventricular node–His–Purkinje system. Accessory pathways (APs) directly connect the atrium and ventricle and bypass the atrioventricular node, bridging the mitral or, less commonly, the tricuspid annulus. Concealed APs conduct electrical impulses retrogradely from the ventricles to the atria, but not antegradely from the atria to the ventricles. Approximately 40% of all APs are concealed, and orthodromic atrioventricular reentrant tachycardia due to concealed APs is present in up to 15% of patients with supraventricular tachycardias referred for catheter ablation. Most concealed APs are left-sided, exhibiting non-decremental retrograde conduction. Tachyarrhythmias due to concealed APs are managed similarly to those supraventricular tachycardias associated with manifest APs, and symptomatic tachyarrhythmias are successfully treated by radiofrequency catheter ablation in the majority of patients.
Idiopathic premature ventricular contractions and ventricular tachycardias originating from the vicinity of tricuspid annulus: Results of radiofrequency catheter ablation in thirty-five patients