Pacing site and bradycardia dependent retrograde conduction block over an atrioventricular accessory pathway

Abstract

Intermittent retrograde conduction over an accessory pathway (AP) is an uncommon phenomenon. We report a case of Wolff-Parkinson-White syndrome in which retrograde conduction of the bypass tract was present only during right ventricular (RV) outflow tract and left ventricular pacing or during RV inflow tract pacing with a fast pacing rate (pacing site and bradycardia dependent conduction block). The interaction between different branches/fibres of the bypass tract might explain the mechanism of this phenomenon. The AP was successfully ablated at the lateral aspect of mitral valve annulus. It is suggested that careful evaluation by decremental ventricular stimulation should be applied from multiple sites both during baseline study and after apparent AP ablation in order to detect such uncommon cases of intermittent conduction.

Catheter Ablation of Accessory Pathway in the Treatment of Pacemaker‐Mediated Tachycardia

“…Multiple cases have been reported with PMT but only some, like the present 10–12 . In this case, the patient received a dual‐chamber pacemaker after ablation of the atrioventricular node and in the electrophysiologic study, a left lateral accessory pathway was found.…”

“…Multiple cases have been reported with PMT but only some, like the present. [10][11][12] In this case, the patient received a dual-chamber pacemaker after ablation of the atrioventricular node and in the electrophysiologic study, a left lateral accessory pathway was found. During the tachycardia, the left lateral accessory pathway was the retrograde limb and not the atrioventricular node.…”

What is the diagnosis of palpitations? A case report of rate-dependent retrograde conduction over an accessory pathway

“…Bradycardia dependent block of retrograde conduction over the concealed accessory pathway is very rare with few isolated cases reported. [1][2][3] Differently, due to the absence of antegrade ventricular pre-excitation and arrhythmias recorded by ECG, it is difficult to make right diagnosis. Super normal conduction over AP might be an reasoned explanation in our case, usually characterized by a 'conduct-block-conduct' pattern of retrograde atrial activation during decremental ventricular pacing.…”