It puts the ‘A’ in ‘A-fib’

noun

1. The central room of a Roman house
2. A rectangular open patio around which a house is built
3. A many-storied court in a building (such as a hotel) usually with a skylight
4. An anatomical cavity or passage

noun

1. A peptide hormone secreted by the cardiac atria that in pharmacological doses promotes salt and water excretion and lowers blood pressure

idiom

1. For a short period of time in order to try something out

   "I'm using the product on a trial basis."