The main findings of this study are that PVCs arising from the left ventricular septum can be safely and effectively eliminated with RFCA, the localization of optimal ablation site of the PVCs is different with the typical location for ectopy originating from the classical fascicular sites. The distinguishing characteristic of this arrhythmia is that Purkinje potentials were not present at the site of successful ablation, suggesting a myocardial as opposed to fascicular substrate. This is the first report that demonstrated that RFCA eliminates PVCs originating from the left ventricular septum (not from classical fascicular sites) by pace mapping and activation mapping, not by searching for Purkinje potential in the left ventricular septum, and found that most cases with the PVCs arising from the left ventricular septum behaved with parasystolic activity.
In this study, we found that PVCs originating from the left ventricular septum have distinctive ECG characteristics. First, the electrocardiographic patterns are different at the different sites of origin of left septal PVC. For PVCs originating from left anterosuperior septum, their QRS complex morphology were qR or qRs in leads II, III, aVF, Rs (R/s > 1) in leads V5~V6, rs(S) in leadsI, aVL and Qr in lead aVR. For PVCs originating from left posteroinferior septum, their QRS complex morphology were rS in leads II, III, aVF, R(r)S (R/S < 1) in leads V5~V6, qR(s) in leadsI,aVL and qR in lead aVR. The QRS morphology of PVCs originating from the left ventricular septum is similar to that seen in fascicular tachycardia [12
]. Why are there the similarity of the morphology of the premature septal beats and fascicular beats? We suggest that the PVCs may originate from the septal myocardium near by the Purkinje network. Second, most of the PVCs originated from the left septum appear in the form of ventricular parasystole, which is different with fascicular PVCs. In the study, the incidence of ventricular parasystole was 70%. This suggests that the mechanism of the two types of PVCs may be different.
In this study, ventricular parasystole was often observed, sustained ventricular tachycardia was not inducible by electrical stimulation and isoproterenol infusion in all 20 patients, ablation at the site recording the earliest Purkinje potential was not effective in all 20 patients, and Purkinje potentials were not identified at successful sites during point mapping. These suggest enhanced antomaticity, but not reentry as the most likely mechanism of PVCs originating from the left ventricular septum in the study [13
]. The electrophysiologic characteristics of the PVCs originating from the left ventricular septum in the study were different with those from the classical fascicular sites. Therefore, the form of ectopy may occur from the myocardium of the septum, instead of the Purkinje network.
In this study, we demonstrated PVCs arising from the left ventricular anterosuperior and posteroinferior septum can be safely and effectively eliminated with catheter ablation techniques. The immediate ablation success rate was 85%, and the chronic success rate was 80% (16 of 20 patients) during a mean follow-up period of 20.2 months. One patients experienced significant recurrence of PVCs with associated symptoms. The overall success rate for ablation of PVCs originating from the left ventricular septum in the present study nearly corresponded with the results of previous reports for ablation of PVCs originating from RVOT and/or other sites of origin [4
]. The mapping techniques in our study were basically the same as those described in previous studies [4
], which included pace mapping and activation mapping. No significant complications were observed in our patient group confirming the safety of the procedure.
First, the mechanism of the PVCs arising from the left ventricular septum is thought to be due to enhanced antomaticity, but not reentry, but this remains speculative in the limited clinical study. Second, although the PVCs may occur from the myocardium of the septum, instead of the Purkinje network, it is unknown that how distributed were these septal sites. To increase the accuracy of our study, our results need to be confirmed in a larger prospective randomized patient population.