pacemaker The center of electrical activity in the heart that regulates the heartbeat. The term is also used for an artificial device implanted in the heart to provide an adequate heart rate.
palliative therapy Treatment that is aimed at relieving the symptoms rather than curing the ailment.
palpitations A feeling that the heart is pounding against the chest, caused by an irregular, strong, or rapid heartbeat.
parietal lobes The top middle part of the brain.
paroxysmal nocturnal dyspnea Difficulty in breathing that comes on intermittently and suddenly when the affected person is lying down, often waking him or her from sleep.
paroxysmal tachycardia A sudden increase in heart rate up to 130 to 260 beats per minute from the normal 60 to 80 beats per minute. This condition may last for from a few minutes to several days.
patent ductus arteriosus A heart defect in which the fetal opening between the aorta and puhnonary artery fails to close at birth. As a result, oxygenated blood from the aorta goes into the lungs, through the left side of the heart, and then out through the aorta.
percutaneous transluminal coronary angioplasty (PTCA) The technical name for balloon angioplasty of the coronary arteries.
perfusion imaging A test using radionuclide scanning that shows the pattern of the flow of blood in the heart.
pericarditis An inflammation of the sac around the heart (pericardium).
pericardium The membranous sac around the heart.
peripheral vascular disease (PVD) Disease that affects the outlying blood vessels (arteries) such as those in the limbs.
phlebitis Inflammation of a vein or veins, occurring most often in the legs.
plaque Fatty deposits that form raised patches in the inner lining of the arteries. Denotes atherosclerosis.
plasma The pale yellow fluid portion of the blood.
platelets The smallest of the blood cells, also called thrombocytes; responsible for clotting.
platelet scintigraphy A radionuclide scan studying the behavior of the platelets, the prime components in the blood-clotting process.
pleural effusion Accumulation of excessive fluid between the layers of the membrane (pleura) that lines the lungs and chest cavity.
polyunsaturated fats Fatty acids that carry the least amount of hydrogen. They are soft at room temperature and can produce a lowering of blood cholesterol. Sources include canola, corn, safflower, and sunflower oils.
positron emission tomography (PET) scanning A nuclear diagnostic test that employs special radioisotopes that emit positrons and produce unique three dimensional isotope pictures (scans) of heart blood flow and metabolism.
potassium A mineral (electrolyte) that is essential in maintaining the body’s proper biochemical balance.
pre-eclampsia A condition that can occur during the last three months of pregnancy. Also called toxemia, its symptoms include high blood pressure, fluid buildup, and headaches.
prophylactic antibiotics (prophylaxis) Antibiotics administered to prevent infection, usually for patients with endocarditis or rheumatic heart disease.
prostaglandins Hormone-like chemicals that are secreted by many body tissues and are instrumental in many body functions, including blood clotting, control of blood vessel size, and muscle function.
pulmonary embolism A blocking of the pulmonary artery or one of its branches by a blood clot (embolus).
pulmonary hypertension Abnormally high blood pressure in the arteries that supply the lungs.
pulmonary regurgitation (insufficiency) A defect in the pulmonary valve, allowing a backflow of blood into the right ventricle.
pulmonary stenosis A narrowing or obstruction of the pulmonary valve or artery, impeding the flow of blood to the lungs.
pulmonary valve The valve between the right ventricle and the pulmonary artery.
pulse The expansion and contraction of a blood vessel, especially an artery, that corresponds to the beating of the heart.
Purkinje fibers Conduction fibers that form a network in the lower chambers of the heart and that carry electrical impulses to the walls of the ventricles.