A 55-year-old man on ICU develops cardiogenic shock after a large anterior STEMI. He undergoes primary PCI. Post-procedure, he is on noradrenaline 0.2 mcg/kg/min and dobutamine 10 mcg/kg/min. An IABP is in situ. Repeat echocardiography 3 days later shows EF 15% with LV mural thrombus. He develops acute ischaemia of the right leg with absent pedal pulses. What is the most likely cause?