A device for electrically isolating pulmonary veins in atrial fibrillation for treatment thereof by ablation of a circumferential zone of tissue. The device includes a catheter (with terminal and distal parts) and comprising a first tubular element； a second tubular element concentric with the first tubular element and an axial rod-like element which extends beyond the distal end of the first and second tubular elements； and a first tubular toroidal element supported by tubular arms extending from the distal end towards the toroidal element, forming a cage which can be opened in umbrella fashion around the distal end of the catheter. The tubular arms and the toroidal element are in fluid communication with each other and with the tubular element of the catheter. The device also includes a second toroidal tubular element in fluid communication by means of the radial arms with the first tubular element of the catheter.
