Q. A 43-year-old woman comes to the emergency department due to chest palpitations. The patient's medical history is significant for fibroadenoma. She has a remote history of intravenous drug abuse but is currently in long-term remission. She has smoked 20 cigarettes/day for the last 20 years. The patient's vital signs show BP: 135/90, HR: 110 bpm, respiratory rate: 12/min, temperature:36.8 degrees Celsius. Her ECG shows irregular QRS complexes with absent P waves. Regarding the above patient, which of the following waves is expected to be absent in the jugular venous pressure curve?