An extracorporeal life support system comprising: a blood pump and an oxygenator configured to be disposed outside a patient's body; a drainage cannula assembly (22; 30; 40) configured to be disposed in the superior vena cava or inferior vena cava to receive deoxygenated blood, said drainage cannula assembly comprising a drainage balloon (208; 311; 415), a drainage occluder and a drainage reservoir, wherein the drainage balloon is configured to be inflated or deflated to control venous return blood flow, the drainage occluder is configured to be compressed or relaxed to control blood drainage into the extracorporeal life support system and the drainage reservoir is configured to be actuated together with the drainage occluder to result in a continuous blood pump flow; and an infusion cannula assembly configured to be disposed opposite to the drainage cannula assembly (22; 30; 40) in either the superior vena cava or the inferior vena cava, the infusion cannula assembly comprising an infusion balloon and an infusion occluder that are employed to deliver oxygenated blood flow back to the patient's circulation; wherein said drainage balloon (208; 311; 415), drainage occluder, infusion balloon and infusion occluder are configured to be activated using an electrocardiographic signal as the triggering reference signal to control inflation and deflation of the balloons and opening and closure of the occluders so as to maximize during heart systole the oxygenated blood volume stored in the right atrium before the tricuspid valve opens and the withdrawal of deoxygenated blood from the right atrium when the tricuspid valve is closed. a blood pump and an oxygenator configured to be disposed outside a patient's body; a drainage cannula assembly (22; 30; 40) configured to be disposed in the superior vena cava or inferior vena cava to receive deoxygenated blood, said drainage cannula assembly comprising a drainage balloon (208; 311; 415), a drainage occluder and a drainage reservoir, wherein the drainage balloon is configured to be inflated or deflated to control venous return blood flow, the drainage occluder is configured to be compressed or relaxed to control blood drainage into the extracorporeal life support system and the drainage reservoir is configured to be actuated together with the drainage occluder to result in a continuous blood pump flow; and an infusion cannula assembly configured to be disposed opposite to the drainage cannula assembly (22; 30; 40) in either the superior vena cava or the inferior vena cava, the infusion cannula assembly comprising an infusion balloon and an infusion occluder that are employed to deliver oxygenated blood flow back to the patient's circulation; wherein said drainage balloon (208; 311; 415), drainage occluder, infusion balloon and infusion occluder are configured to be activated using an electrocardiographic signal as the triggering reference signal to control inflation and deflation of the balloons and opening and closure of the occluders so as to maximize during heart systole the oxygenated blood volume stored in the right atrium before the tricuspid valve opens and the withdrawal of deoxygenated blood from the right atrium when the tricuspid valve is closed.