A guide catheter (30) is described for introduction into a patient's vasculature, to provide a substantially continuous guide lumen (28) within the vasculature to the ascending aorta (34), through which one or more other functional catheters (44) may be introduced and removed during the procedure. The guide catheter includes an aligner (70) at its distal region for aligning the position and/or inclination of the distal region of the guide catheter with respect to the ascending aorta. The aligner includes an embolic protection filter (88). The guide catheter is made of material collapsible/distensible in cross section to adopt a small shape when no catheter is present inside, and to distend to a large shape to accommodate passage of functional catheter therethrough. The cross - section shape collapses/distends by folding/unfolding of material without elastic stretching of the material.
