A 58-year-old man from Delhi presents to the emergency department with acute-onset chest pain radiating to the left arm for 2 hours. On examination, blood pressure is 95/60 mmHg, heart rate 110 bpm, and JVP is elevated at 8 cm H₂O. Auscultation reveals a new pansystolic murmur best heard at the apex. Chest X-ray shows pulmonary edema. Echocardiography confirms acute mitral regurgitation secondary to papillary muscle rupture. During the cardiac cycle, at which point does the regurgitant jet occur?