A 44 year old woman has lost weight over 12 months. She has also noticed episodes where her heart beats rapidly and strongly. She has a regular pulse rate of 90bpm. Her ECG shows sinus rhythm. What is the most appropriate investigation to be done?

The key is B. TFT. [This is a probable case of thyrotoxicosis. The patient has paroxysmal atrial fibrillation. That is why there is no arrhythmia in between attacks. From the given option TFT is the appropriate test as thyrotoxycosis is a leading cause of paroxysmal atrial fibrillation and thyrotoxicosis is the probable cause of weight loss of this lady].