- Introduction: Pulmonary vein isolation (PVI) using the irrigated multi-electrode ablation system (nMARQ™) remains challenging in complex atrial anatomy cases and when CARTOMERGE™ technology is not available, due to absence of a leading guide-wire. Objectives: Our objective was to assess feasibility and safety of PVI using nMARQ™ catheter with intra-procedural contrast injections through the deflectable sheath compared to nMARQ™ alone. Methods: This is a prospective non-randomized observational study of 78 consecutive patients who underwent PVI only with nMARQ™. The first group (n=37, 64±10.5 years, 62% male, 13.5% persistent AF) underwent the procedure with the guidance of signal mapping, fluoroscopy, and electro-anatomical mapping (EAM) alone. Since 12/2013 an automatic closed-loop contrast media injector was added to improve catheter location (n=41, 62.5±11 years, 71% male, 34% persistent AF). Results: Total procedure time was 78±19 and 85.5±18.5 minutes, and mean fluoroscopy time was 30±9 and 29.5±8.7 minutes for the first and second groups, respectively (NS); acute success rate was 97% and 97.5%, with a mean of 14.7±5 and 17.6±5.4 RF applications, respectively (p=0.02); and mean total burning time of 10.3±3.6 and 12±4 minutes, respectively (p=0.08). Mean contrast used was 60±18 mL versus 203±65 mL, with no effect on renal function or major complications. One year freedom from AF was 77% and 83%, respectively (p=0.5). Conclusions: Addition of contrast injections to standard nMARQ™ procedure is feasible and safe. It has no benefit in routine use but further studies may confirm its potential added value to EAM in catheter localization by newly trained operators and in selective cases of large/common PV anatomy.