An extension cannula and in-line connector for use with a conventional ECMO return cannula is provided. The extension cannula includes a self-expanding conduit transitionable between a collapsed insertion state and an expanded, deployed state via a retractable sheath. The extension cannula may be inserted through a conventional ECMO return cannula such that the proximal end of the self-expanding conduit is disposed within and proximal to the end of the conventional ECMO cannula, while the distal end of the self-expanding conduit is disposed in a patient's thoracic aorta to improve cerebral oxygenation, maintain systemic arterial pulsatility, and reduce the potential for end-organ injury. The extension cannula and/or in-line connector may be used to permit delivery of additional interventional or vascular equipment using a single port of access, thereby avoiding complications associated with contemporary VA-ECMO.