[Preferential conduction to right ventricular outflow track leads to left bundle-branch block morphology in patient with premature ventricular contraction originating from the aortic sinus cusp].

OBJECTIVE: The purpose of this study was to explore the relationship between originate and breakout and radiofrequency catheter ablation strategy in patients undergoing radiofrequency ablation for premature ventricular contractions originating from the aortic sinus cusp (ASC) using 3-dimensional electro anatomic mapping.
METHODS: This study included 21 consecutive patients (10 male) underwent ablation for frequent PVCs originating from ASC in our hospital between May 2009 and February 2012. Electro anatomic mapping and ablation of right ventricular outflow track (RVOT) and left ventricular outflow track (LVOT) were performed with the 7F 4-mm-tip ablation catheter from right femoral vein and artery. Activation mapping and pacing mapping were performed in all patients.
RESULTS: Ablation was successful in all 21 patients successful ablation target in left coronary sinus cusp (LCC, n = 17), in right coronary sinus cusp (RCC, n = 2) and in noncoronary sinus cusp (NCC, n = 2). Seven patients showed a RBBB morphology (group A) and 14 patients showed a LBBB morphology (group B). In group A, earliest ventricular activation (EVA) was recorded 22 - 34 (27.4 ± 4.6) ms earlier before QRS at the site of catheter ablation in ASC. In group B, EVA was later in RVOT than that in ASC in 5 patients and EVA at the site of catheter ablation in RVOT and ASC was 22 - 28 (25.2 ± 2.7) ms and 26 - 40 (32.8 ± 5.2) ms, respectively (t = -3.6, P = 0.024) while EVA was earlier in the remaining 9 patients and EVA recorded in RVOT and ASC was 22 - 38 (28.7 ± 5.9) ms and 18 - 28 (22.7 ± 3.6) ms, respectively (t = 3.8, P = 0.005).
CONCLUSION: Patients with premature ventricular contractions originating from the ASC often show preferential conduction to the RVOT, which may explain the LBBB morphology of ECG in these patients.