- Aortic aneurysm
- Aortic dissection
- Aortic valve disease
- Aortic valve regurgitation
- Aortic valve stenosis
- Aplastic anemia
- Appendicitis
- ARDS – Acute respiratory distress syndrome
- Arteriovenous fistula
- Arteriovenous malformation
- Arthritis
- Arthrodesis of the dorsal vertebrae
- Arthrodesis of the lumbar vertebrae
- Arthrosis
- Asthma
- Asthma attack
- Astigmatism
- Atelectasis
- Atherosclerosis
- Athletic Foot
