| At | acidity, total; astatine; atrium, atrial |
|---|---|
| ATB | at the time of the bomb [A-bomb in Japan]; atrial tachycardia with block |
| At fib | atrial fibrillation |
| Atr | fib atrial fibrillation |
| BAS | balloon atrial septostomy; benzyl anti-serotinin; beta-adrenergic stimulation; boric acid solution |