The Contact (St Jude Medical) System uses a novel impedance- based measure of Electrical Coupling Index (ECI) to assess the quality of catheter tip to endocardium contact. We sought to establish average ECI measurements during pulmonary vein (PV) isolation procedures.

Forty-five patients undergoing PV isolation for atrial fibrillation (AF) were studied. ‘Non-contact’ and upper range ‘in-contact’ catheter positioning was performed for system calibration. ECI measurements were recorded pre-ablation at 14 standardized locations around the PV antra.

The mean ECI non-contact value was 77 ± 11 (range 63–107); the mean upper range in-contact value was 111 ± 16 (range 81–145). Mean ECI values pre-ablation around the PV antra ranged from 85 ± 18 to 107 ± 19. A trend towards higher mean ECI values was noted with increasing body mass index (BMI). Pre-ablation mean ECI values were 92 ± 10 (BMI 20-25), 95 ± 12 (BMI 26-30) and 104 ± 11 (BMI >30)(p< 0.01 for 20-25 vs. >30). A positive correlation was noted for mean pre-ablation ECI values and BMI (r=0.50).

An expected range of ECI values during PV isolation has been documented in this study. Observed ECI values correlate with patient BMI. The potential limitations of the current generation Contact System are discussed.