Nocturnal heart flutters

An 85-year-old lady who enjoys generally good health and looks after herself in her own home presents with a three-week history of intermittent palpitations and dyspnoea. The palpitations have mostly woken her at night or been present while resting in bed but have only lasted a few moments at a time.

Past health has been excellent and she is on no medications at the present time. She has minimal intake of alcohol and caffeine.

The examination demonstrates a somewhat irregular pulse, although it seems mostly regular at a rate of about 76