Conduction properties of the preferential pathway in a patient with idiopathic outflow ventricular arrhythmia

Figures

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  Fig. 1. A: A 12-lead electrocardiogram showed regular sinus rhythm and frequent PVCs. The PVC showed right bundle branch block (RBBB) morphology, inferior axis, and the maximum deflection index (MDI) in the inferior lead of 0.57. Fig. 1B: The local ventricular activation time recorded at the great cardiac vein (GCV) preceded the onset of the QRS complex by 28 ms, and pace mapping at this site was a good match for the QRS complex of the clinical PVC. Discrete potentials preceding the QRS onset during PVC and non-conducted potential were recorded at the HD mapping catheter located at the LVOT. Fig. 1C: At the earliest site of the pre-potential during the PVC, late potentials were recorded during sinus rhythm (indicated by blue arrow and red circle).

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  Fig. 2. The discrete potentials preceding the QRS were recorded by the HD mapping catheter (Advisor™ HD Grid Mapping Catheter, Abbott, St. Paul, MN). These prepotentials were recorded to conduct longitudinally from the distal to the basal side of the LVOT. The earliest activation site (Site 1) is shown by a white star, and the VA exit site is shown by a yellow star. The impulse is conducted through the preferential pathway indicated by black allows. The conduction velocity of the preferential pathway was calculated by using a 3D mapping system and found to be extremely slow, 0.11 m/s. The pace map at site1, the PVC origin site, show extremely short stimulus-QRS interval in contrast to 167 ms EGM to QRS of native PVC. Although the pace map from the catheter located in the GCV indicated by the yellow star shows a perfect pace map (12/12) with the clinical PVCs, all the other pace maps from the endocardial site, including the earliest activation site (indicated by a white star) during the PVCs did not match.

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  Fig. 3. A: An 8F, 4 mm flexible irrigated-tip catheter (TactiCath™ Ablation Catheter, Abbott, St. Paul, MN) was positioned at the earliest activation site of prepotentials. The radiofrequency energy application between the VA origin and the VA exit immediately terminated the PVCs. Fig. 3B and C: The discrete potentials indicated by the red allow recordings by both the ablation and HD mapping catheter. Fig. 3D: The discrete potential was dependent on the RV pacing cycle (Pacing cycle length = 500 ms), which suggested that this potential was not completely isolated or bidirectionally blocked. Furthermore, the discrete potential exhibited Wenckebach-like behavior.