Echocardiography examination
All patients had well-controlled heart rate and underwent transthoracic and transoesophageal echocardiography prior to the ablation using a Vivid E9 ultrasound system (GE Vingmed Ultrasound AS). The following variables were prospectively measured during AF as an average of five cardiac cycles and indexed to the body surface area: LA anteroposterior diameter, RA and LA maximum and minimum length (long axis) and planimetered area and volume. All measurements were performed by a single experienced physician using well established criteria [3]. RA and LA contractile and reservoir functions were analysed calculating the following indices and expressed as percentage where appropriate: (1) emptying fraction (EF), by dividing the difference between maximum and minimum volume by maximum volume (2) stroke volume (SV), as the difference between maximum and minimum volume (3) expansion index (EI), by dividing the difference between maximum and minimum volume by minimum volume. The right to left atrial ratio of all determined parameters was then calculated and expressed as percentage. Moreover a biatarial volume index expressed as the sum of the right and left atrial indexed maximum and minimum volume and biatarial area index expressed as the sum of the right and left atrial indexed maximum and minimum planimetered area were calculated. Enlargement of the LA was defined with maximum indexed LA volume >34ml/m2 whereas enlarged RA with maximum indexed RA volume >25ml/m2 in men and > 21ml/m2 in women. Left ventricular hypertrophy (LVH) was defined on the basis of indexed ventricular mass calculated by system software > 115g/m2in men and >95g/m2 in women [3]. Mitral (MR) and tricuspid (TR) regurgitation was assessed according to guidelines [4].