Complex sentence: She was in a relationship with Dr. Gregory House (Hugh Laurie), when a clotted aneurysm in his right thigh led to an infarction during a game of golf, causing his quadriceps muscle to become necrotic.
Split into simpler sentences: She was in a relationship with Dr. Gregory House (Hugh Laurie), when he suffered an infarction in his right leg during a game of golf. This was caused by a clotted aneurysm in his thigh, which had led to an infarction that caused his quadriceps muscle to become necrotic.