TY - CHAP M1 - Book, Section TI - Cardiac Conduction A1 - Prystowsky, Eric N. A2 - Prystowsky, Eric N. A2 - Klein, George J. A2 - Daubert, James P. PY - 2020 T2 - Cardiac Arrhythmias: Interpretation, Diagnosis, and Treatment, 2e AB - The normal cardiac impulse originates in the sinus node, a crescent-shaped structure approximately 9 to 15 mm long that is located at the juncture of the superior vena cava and right atrium (Figure 1-1).1 After the electrical impulse exits the sinus node, it proceeds to activate the right and left atria. Activation of the atria is responsible for the P wave recorded on the electrocardiogram (ECG) (Figure 1-1, orange color). Activation of the normal human atria takes approximately 90 to 100 ms, the right atrium being activated within approximately 65 ms.2 The last area to be activated is the left atrial appendage, although atrial tissue near the left inferior pulmonary vein can also be activated very late. It should be noted that as the spread of atrial activation occurs, some sections of the right and left atria are activated at the same time.2 SN - PB - McGraw Hill CY - New York, NY Y2 - 2024/04/20 UR - accesscardiology.mhmedical.com/content.aspx?aid=1176521913 ER -