An expandable atherectomy device (50, 70, 80, 90, 300) comprising: a flexible catheter tube (17)； a guide wire (10) on which the atherectomy device can be advanced and which can be inserted into a blood vessel until its distal end is adjacent to an area of atheromatous material, said guide wire being able to be introduced through said tube catheter； a flexible hollow stem (13, 313) rotatably driven by a motor that can slide on said guide wire and is coaxial to the longitudinal axis of said guide wire； an expandable cutting unit having two longitudinally spaced ends, wherein said cutting unit, when expanded, is eccentrically rotatable about the longitudinal axis to cut and remove atheromatous material from said blood vessel； an actuator (9) that is operable to induce selective expansion of said cutting unit； and said hollow stem comprising internal (16, 16A； 314) and external (14, 14A； 94； 316； 1014) tubular portions that can be rotated simultaneously by means of the motor (11) while one of said internal and external tubular portions it slides over the other in a direction substantially parallel to the longitudinal axis in response to a driving action of said actuator, wherein said cutting unit (19, 79, 89, 99, 1019) can expand in response to said pulling action. actuation while causing said two separate ends (20, 21； 81, 83) of said cutting unit to come close to each other, where a first of said two ends is connected to a distal end of said internal tubular portion and a second of said two ends are connected to said external tubular portion, characterized in that said internal and external tubular portions are radially interconnected while simultaneously rotating by means of a pin (7) holding to said inner tubular portion and by means of a widthwise edge of a window (31) formed with said outer tubular portion (14) having a width only slightly greater than said pin.Un dispositivo de aterectomía expandible (50, 70, 80, 90, 300) que comprende: un tubo (17) de catéter f
