TY - CHAP M1 - Book, Section TI - The Bradyarrhythmias: Disorders of the Sinoatrial Node A1 - Sauer, William H. A1 - Koplan, Bruce A. A2 - Loscalzo, Joseph A2 - Fauci, Anthony A2 - Kasper, Dennis A2 - Hauser, Stephen A2 - Longo, Dan A2 - Jameson, J. Larry PY - 2022 T2 - Harrison's Principles of Internal Medicine, 21e AB - The sinoatrial (SA) node serves as the natural pacemaker of the heart and has variable rates in response to parasympathetic and sympathetic stimulation. If the sinus node is dysfunctional or suppressed a subsidiary pacemaker in the atrioventricular node or specialized conduction system will take over leading to a slower junctional or ventricular rhythm. Symptoms of sinus node dysfunction can vary but typically present as fatigue, exercise intolerance, or dyspnea. The diagnostic evaluation includes an investigation into reversible causes of sinus bradycardia, confirmation of sinus node dysfunction with outpatient telemetry monitoring or exercise testing, and possibly cardiac imaging if structural heart disease is suspected. Once irreversible sinus node dysfunction is confirmed, permanent pacemaker implantation is the only reliable therapy for symptomatic bradycardia. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/19 UR - accessmedicine.mhmedical.com/content.aspx?aid=1198226886 ER -