Cardiac electrophysiology is a branch of cardiology and basic science focusing on the electrical activities of the heart. The term is usually used in clinical context, to describe studies of such phenomena by invasive (intracardiac) catheter recording of spontaneous activity as well as of cardiac responses to programmed electrical stimulation - clinical cardiac electrophysiology. However, cardiac electrophysiology also encompasses basic research and translational research components. Specialists studying cardiac electrophysiology, either clinically or solely through research, are known as cardiac electrophysiologists. Description Electrophysiological (EP) studies are performed to assess complex arrhythmias, elucidate symptoms, evaluate abnormal electrocardiograms, assess risk of developing arrhythmias in the future, and design treatment. These procedures include therapeutic methods (typically radiofrequency ablation, or cryoablation) in addition to diagnostic and prognostic procedures. Other therapeutic modalities used in this field include antiarrhythmic drug therapy and implantation of pacemakers, implantable cardioverter-defibrillators and cardiac resynchronisation therapy devices. Electrophysiological study The cardiac electrophysiology (EP) study typically measures the response of myocardium to programmed electrical stimulation (PES) on specific pharmacological regimens in order to assess the likelihood that the regimen will successfully prevent potentially fatal sustained ventricular tachycardia (VT) or ventricular fibrillation VF (VF) in the future. Sometimes a series of EP study drug trials must be conducted to enable the cardiologist to select the one regimen for long-term treatment that best prevents or slows the development of VT or VF following PES. Such studies may also be conducted in the presence of a newly implanted or newly replaced cardiac pacemaker or ICD. Physician specialists A specialist in cardiac electrophysiology is known as an electrophysiologist, or "heart electrician" in layman' terms. Cardiac electrophysiology is a subspecialty of cardiology in most countries and usually requires two or more years of EP fellowship training after a general cardiology residency. In early 2011, the Centers for Medicare and Medicaid Services promoted cardiac electrophysiology to its own specialty category in the United States. Cardiac electrophysiologists are trained to perform interventional cardiac electrophysiology studies and cardiac rhythm management device implantations. Research cardiac electrophysiologist Cardiac electrophysiologists specialize in a sub-area of electrophysiology, which in turn is a sub-area of physiology. This specialization usually requires education at the doctoral (PhD, DSc, or MD/DO) level to become a principal investigator for research projects. The area of research is often multi-disciplinary involving chemistry, bioelectrics, biology, and biomedical engineering. The flagship tools used by cardiac electrophysiologists overlap with the toolbox of the neuroscientist including