Neck and shoulder pain

An emergency department visit from a 60-year-old lady with a history of non-small cell lung cancer complaining of neck and shoulder pain for the past six hours. Atrial flutter-like sinus tachycardia is seen on the initial ECG. After receiving 20 mg of diltiazem intravenously, the patient starts experiencing repeated 2- to 4-second sinus pauses every minute. Her heart rate ranges from 90 to 120 beats per minute with intermittent P waves, and her blood pressure is 115/70 mm Hg. Her chest scan shows typical postoperative improvements.