PVCs with multiple exits and single site of origin in the outflow tract: What is the mechanism?

Fig. 1. 12 Lead ECG with Activation and Pace Mapping of PVC 2 in the RVOT. A: Twelve lead electrocardiogram recorded during the procedure showing sinus rhythm (SR) and premature ventricular contractions (PVC) 1 and 2. B: Intracardiac electrograms recorded during activation mapping of PVC2 at the RVOT posterior septum. The black arrow indicates the local ventricular potential preceding the QRS onset by 20 ms. The unipolar electrogram showed a QS pattern. C: Pace mapping at the RVOT posterior septum revealed a pace map score of 10/12 for PVC 2. The pacing stimulus to QRS interval was 8ms (arrowhead). MAPD, MAPP (the distal and proximal electrode pairs of the mapping catheter); UNI (the distal unipolar electrode of the mapping catheter).

Fig. 2. Activation and Pace Mapping of PVC 1 and PVC 2 in the Aortic Cusp. A: Intracardiac electrograms recorded during activation mapping of PVC 1 and PVC 2 at the junction of the left coronary and right coronary cusp (LCC/NCC junction). The black arrow indicates the local ventricular potential preceding the QRS onset by 30 and 28 ms for PVC 1 and PVC 2, respectively. B: Pacing at a 6mA output at the LCC/NCC junction revealed a 10/12 pace-map for PVC 1. C: Pacing at 9mA at the same site revealed QRS complexes with morphology similar to PVC 1 (5th QRS complex, pace map 10/12) and PVC 2 (4th QRS complex, pace map 10/12). The first three paced complexes represent fusion complexes. The pacing stimulus to QRS (S-QRS, black arrowhead) for PVC2 was 28ms. D: Pacing at 15mA at the same site revealed QRS morphology similar to only PVC 2. Pace-map score was 11/12 with a S-QRS interval of 38, 50 and 56 ms, suggestive of decremental conduction. Refer to Fig. 1 for other abbreviations.

Fig. 3. Three-dimensional electroanatomical CARTO map of the LV and RV outflow tracts are shown as a mesh in RAO 30 (A) and LAO 30 (B). The non (NCC), left (LCC), and right (RCC) coronary cusps are labelled. The yellow tags represent the His and red tags represent the ablation points. The earliest activation site of PVC1 and PVC2(shown in Fig. 2) was at the NCC/LCC junction (C and D). This was the site of successful radiofrequency ablation and is shown in LAO (A and C).

Fig. 4. Diagram showing the origin and presumed preferential conduction paths of PVC 1 and PVC 2. With regards to PVC2, we hypothesized that preferential conduction occurred via an insulated myocardial fiber from the origin in the aortic cusp and the exit in the RVOT septum.