MRCP2-3658
A 53-year-old male presents to the emergency department with sudden onset palpitations and shortness of breath which began whilst he was watching television a few hours previously. He describes an odd fluttering sensation in his chest with mild dyspnoea but no chest pain. He denies having experienced this before. On systems review, he also complains of severe muscle cramps and a slight tremor in his hands over the last few days.
His past medical history includes hypertension and gout for which he takes amlodipine and allopurinol. He denies any history of exertional dyspnoea but does occasionally get central chest pain on exertion for which he has not sought help. He has recently been diagnosed with small cell lung cancer and underwent his first round of chemotherapy last week; although he is unsure which drugs are being used. He used to smoke a pipe until his recent diagnosis of cancer and drinks a few measures of whisky most evenings.
On examination, his respiratory rate is 22 breaths/min and his oxygen saturations are 96% breathing two litres of oxygen. His heart rate is irregularly irregular and approximately 130 beats/min, his blood pressure is 152/78 mmHg. An ECG shows atrial fibrillation with no ischaemic changes.
What is the most likely cause for his new atrial fibrillation?