Atoms can join together to form molecules, which in turn form most of the objects around you. Atoms are composed of particles called protons, electrons and neutrons. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons 'orbit' the nucleus.
Practice Essentials. Percutaneous coronary intervention (PCI), also known as coronary angioplasty, is a nonsurgical technique for treating obstructive coronary artery disease, including unstable angina, acute myocardial infarction (MI), and multivessel coronary artery disease (CAD). See the image below.
patient-controlled analgesia (PCA), a drug-delivery system that dispenses a preset intravascular dose of a narcotic analgesic when the patient pushes a switch on an electric cord. The device consists of a computerized pump with a chamber containing the drug. The patient administers a dose of narcotic when the need for pain relief arises. A lockout interval automatically inactivates the system if a patient tries to increase the amount of narcotic within a preset period.