TY - CHAP M1 - Book, Section TI - Cardiologic Principles I: Electrophysiologic and Electrocardiographic Principles A1 - Clancy, Cathleen A2 - Nelson, Lewis S. A2 - Howland, Mary Ann A2 - Lewin, Neal A. A2 - Smith, Silas W. A2 - Goldfrank, Lewis R. A2 - Hoffman, Robert S. Y1 - 2019 N1 - T2 - Goldfrank's Toxicologic Emergencies, 11e 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 identify the functional types of membrane receptors and ion channels. Molecular genetic studies identify the gene coding for the key cardiac ion channels and elucidate 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 - 2024/03/28 UR - accesspharmacy.mhmedical.com/content.aspx?aid=1163017659 ER -