Background: Scar tissue can be identified by a low voltage of bipolar electrograms as recorded by catheters contacting with the left atrial (LA) endocardium. However, lack of contact can also result in low voltage. Purpose: to evaluate the extent to which low voltage areas as identified by standard catheters persist when explored assuring good contact. Methods: We prospectively obtained an electroanatomic map of the left atrium (LA) in 11 consecutive patients undergoing atrial fibrillation (AF) ablation (5 with persistent AF; 6 paroxysmal AF; 72% men, mean crossectional LA area measured by CT-scan 27.8 + 8.2 cm2). A first LA map (Map-A) was created with a circular duodecapolar catheter. The identified low voltage areas were subsequently explored with a contact force sensing catheter creating a second LA map (Map-B). Low voltage was defined as ,0.5 mV and "dense scar" as ,0.2 mV. Surface of the low voltage areas was measured off-line. Both maps were performed after PV isolation, and the encircled PV were excluded from the measured low voltage areas.