A 62-year-old male patient complains of intense pain in the left leg that suddenly arose three hours before, leg numbness and coldness. During the year there has been pain in the leg while walking, hypersensitivity to cooling. Objectively: the left foot and shin have marbled skin, subcutaneous veins are collapsed. The foot is cold, active movements of the foot and toes are preserved. Pulse is present only on the femoral artery. There is rough systolic murmur above the artery. Make a provisional diagnosis: