medical_specialty premature atrial contraction
A subclinical ___MASK66___ ( sometimes called a preinfection ) is an ___MASK66___ that , being subclinical , is nearly or completely asymptomatic ( no signs or symptoms ). A subclinically infected person is thus an asymptomatic carrier of a microbe , intestinal parasite , or virus that usually is a pathogen causing illness , at least in some individuals . Many pathogens spread by being silently carried in this way by some of their host population . Such infections occur both in humans and nonhuman animals . An example of an asymptomatic ___MASK66___ is a mild common cold that is not noticed by the infected individual . Since subclinical infections often occur without eventual overt sign , their existence is only identified by microbiological culture or DNA techniques such as polymerase chain reaction . Premature atrial contractions ( PACs ) , also known as atrial premature complexes ( APC ) or atrial premature beats ( APB ) , are a common cardiac dysrhythmia characterized by premature heartbeats originating in the atria . While the sinoatrial node typically regulates the heartbeat during normal sinus rhythm , PACs occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat . The exact cause of PACs is unclear ; while several predisposing conditions exist , PACs commonly occur in healthy young and elderly people without heart disease , and by themselves are not considered an abnormal finding . PACs are often completely asymptomatic and may be noted only with Holter monitoring , but occasionally they can be perceived as a skipped beat or a jolt in the chest . In most cases , no treatment other than reassurance is needed for PACs , although medications such as beta blockers can reduce the frequency of symptomatic PACs . Medicine ( British English ; American English ) is the science and practice of the diagnosis , treatment , and prevention of disease . The word " medicine " is derived from Latin " medicus ", meaning " a physician ". Medicine encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness . Contemporary medicine applies biomedical sciences , biomedical research , ___MASK32___ , and medical technology to diagnose , treat , and prevent injury and disease , typically through pharmaceuticals or ___MASK96___ , but also through therapies as diverse as psychotherapy , external splints and traction , medical devices , biologics , and ionizing radiation , amongst others . Electrocardiography ( ECG or EKG *) is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin . These electrodes detect the tiny electrical changes on the skin that arise from the heart muscle ' s electrophysiologic pattern of depolarizing during each heartbeat . It is a very commonly performed ___MASK64___ test . In medicine , a Holter monitor ( often simply " Holter " or occasionally ambulatory electrocardiography device ) is a portable device for continuously monitoring various electrical activity of the cardiovascular system for at least 24 hours ( often for two weeks at a time ). A disease is a particular abnormal condition , a disorder of a structure or function , that affects part or all of an organism . The study of disease is called ___MASK97___ which includes the causal study of etiology . Disease is often construed as a medical condition associated with specific symptoms and signs . It may be caused by external factors such as pathogens , or it may be caused by internal dysfunctions particularly of the immune system such as an immunodeficiency , or a hypersensitivity including allergies and autoimmunity . In medicine , a disease is considered asymptomatic if a patient is a carrier for a disease or ___MASK66___ but experiences no symptoms . A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated . Asymptomatic infections are also called subclinical infections . Other diseases ( such as mental illnesses ) might be considered subclinical if they present some but not all of the symptoms required for a clinical diagnosis . The term clinically silent is also used .