TY - CHAP M1 - Book, Section TI - Electrophysiologic and Electrocardiographic Principles A1 - Clancy, Cathleen A2 - Hoffman, Robert S. A2 - Howland, Mary Ann A2 - Lewin, Neal A. A2 - Nelson, Lewis S. A2 - Goldfrank, Lewis R. PY - 2015 T2 - Goldfrank's Toxicologic Emergencies, 10e AB - The clinical tool most commonly used to assess cardiac function is the surface electrocardiogram (ECG). The ECG records the sum of the electrical changes occurring within the myocardium. The electrophysiologic basis of cardiac function and the ECG are complex and are subject to alteration by numerous xenobiotics. Ion currents flowing through various ion channels are responsible for cardiac function. Electrophysiologic studies have identified the functional types of membrane receptors and ion channels. Molecular genetic studies have identified the gene coding for the key cardiac ion channels and have elucidated the structural and physiologic relationships that lead to the toxic effects of many xenobiotics. These channels are critical for maintenance of the intracellular ion concentrations necessary for action potential development, impulse conduction throughout the heart, and myocyte contraction. This chapter will first review the individual ion channels and their currents, and then summarize their contribution and effects on the ECG. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/19 UR - accessemergencymedicine.mhmedical.com/content.aspx?aid=1108425515 ER -