Cardiac Electrophysiology. Using computer simulations, FDA investigators study the electrical activity of the heart as it relates to medical devices such as cardiac pacemakers and defibrillators. Both approaches involve studies of single and multiple cells, and the whole heart. Optical mapping of membrane potential is used to record the electrical activity and intracellular calcium dynamics as well as wave propagation. FDA is studying the effect of defibrillation waveforms on the ability to stop fibrillation, the dangerous and potentially fatal rapid, irregular, and unsynchronized contraction of the heart. The United States is the global leader in medical device innovation and the Food and Drug Administration's (FDA) Center for Devices and Radiological Health (CDRH) is committed to assuring that American patients have timely access to important new technologies and next-generation products without compromising their safety. Each year, millions of American patients benefit from innovative medical devices that reduce suffering, treat previously untreatable conditions, extend lives, and improve public health. CDRH is responsible for advancing public health and facilitating innovation to help bring novel technologies to market and make the medical devices that are already on the market safer and more effective. February, 2011.