Electrophysiology Fellow Queen's University Kingston, Ontario, Canada
Case background: A 61-year-old man with a high burden of symptomatic Premature Ventricular Contraction (PVC) was referred for catheter ablation. He has a history of Paroxysmal Atrial Fibrillation with a successful PVI in 2017 with no evidence of recurrence.
The 12-lead electrocardiogram showed a PVC with left bundle block pattern with transition in V3 and right inferior axis. His last Holter monitor showed a 59% PVC burden with recurrent NSVT. A recent echocardiogram estimated a left ventricular ejection fraction of 63%.
The patient presented to the electrophysiology laboratory with sinus rhythm and frequent PVCs. The procedure was conducted under conscious sedation. Mapping and ablation were aided by the EnSite Precision System (Abbott, St Paul, MN). A 9 French phased array intracardiac echocardiography (ICE) catheter (ViewFlex Xtra, Abbott, St Paul, MN) was advanced into the right ventricle to guide mapping, catheter contact, lesion formation, and monitoring for complications.
Right Ventricular (RV) Mapping demonstrated the earliest activation in the anteroseptal aspect of the Right Ventricular Outflow Tract (RVOT) by 0 ms. The pace map was 66%.
Using a 4 Fr Gidecath catheter with a 2 Fr multipolar catheter (EpStar, Boston Scientific), the Coronary Sinus, Great Cardiac Vein, Anterior Interventricular Vein and Septal Perforators veins were mapped. The earliest activation was in the first septal vein by 6 ms. The pace map was 85%.
Aortic Root and Left Ventricular Outflow Tract (LVOT) mapping showed an early activation just below the Left Coronary Cusp (LCC) – Right Coronary Cusp (RCC) commissure by 8 ms. The pace map was 80%.
Radiofrequency energy at 30-35 W for 60-120 sec was applied below the RCC-LCC commissure and anatomically close to the earliest epicardial site, as well as from the earliest site in the RVOT, using normal saline and half saline, achieving temporary suppression of PVC in both cases.
Given the failure of RF ablation, bipolar ablation was attempted. A Tactiflex catheter (Abbott, St Paul, NM) with contact force was placed on the anteroseptal aspect of the RVOT, and a FlexAbility catheter (Abbott, St Paul, NM) was positioned just below the RCC-LCC commissure, with an intercatheter tip distance of 16 mm. A T connection was used to allow simultaneous electrogram recording and visualization of the ground catheter on the electroanatomic map. True bipolar ablation was attempted using half normal saline from the RVOT to the LVOT (30-40 W, 90-120 sec lesion, 15-20 Ohm impedance drop) under ICE monitoring, achieving permanent PVC suppression without steam pops. Two consolidation lesions were applied, and no recurrence was observed after a 30-minute waiting period (Figure 1).
At 3 months follow-up, a 24-hour Holter monitor showed no recurrence of the clinical PVC ( < 1% PVC burden)
Management Challenges: Radiofrequency ablation (RF) has been widely studied and proven to be highly effective and safe for treating atrial and ventricular arrhythmias.
However, certain cases, such as PVCs of intramural origin, can be refractory to traditional RF ablation due to its limited ability to create deep intramural lesions.
In challenging scenarios involving deep intramural arrhythmias, non-conventional strategies such as half-normal saline infusion, impedance modulation, bipolar ablation, simultaneous unipolar ablation, ablation with a needle catheter, and transcoronary alcohol ablation may be necessary to effectively target deep intramural arrhythmias. These approaches often require the use of "off-label" equipment.
In the present clinical case, we demonstrate how bipolar ablation—utilizing a pre-existing, non-custom Abbott T-connector and a custom cable to connect the T connector to the impedance port of the Abbott generator (Figure 2)—combined with half-normal saline represents a viable and safe alternative for addressing intramural substrates, achieving deeper and transmural lesions.
