TY - CHAP M1 - Book, Section TI - Conduction Disorders & Cardiac Pacing A1 - Hongo, Richard H. A1 - Goldschlager, Nora F. A2 - Crawford, Michael H. Y1 - 2023 N1 - T2 - Current Diagnosis & Treatment: Cardiology, 6e AB - ESSENTIALS OF DIAGNOSISSinus node dysfunction (“sick sinus syndrome”)Sinus bradycardia: sinus rate less than 50 bpm.Sinoatrial (SA) exit block.Type I: P wave nonoccurrence preceded by decreasing P-P intervals.Type II: abruptly longer P-P intervals that are multiples of sinus interval.Sinus pauses: P wave nonoccurrence more than 3 seconds.Sinus arrest: no evidence of P waves.Atrioventricular (AV) blockFirst degree: 1:1 AV conduction ratio and PR interval more than 200 ms.Second degreeType I: failure of AV conduction and QRS complex nonoccurrence preceded by increasing PR intervals.Type II: failure of AV conduction not preceded by increasing PR intervals.“2:1”: without consecutive PR intervals, unable to define as either type I or type II block.Advanced (“high-grade” or “high-degree”): ≥ 3:1 AV conduction ratio.Third degree (“complete”): independent atrial and ventricular rhythms with failure of AV conduction despite temporal opportunity to occur SN - PB - McGraw Hill Education CY - New York, NY Y2 - 2024/03/29 UR - accesscardiology.mhmedical.com/content.aspx?aid=1198112568 ER -