RT Book, Section A1 Hongo, Richard H. A1 Goldschlager, Nora F. A2 Crawford, Michael H. SR Print(0) ID 1139744741 T1 Conduction Disorders & Cardiac Pacing T2 CURRENT Diagnosis & Treatment: Cardiology, 5e YR 2017 FD 2017 PB McGraw-Hill Education PP New York, NY SN 9781259641251 LK accessmedicine.mhmedical.com/content.aspx?aid=1139744741 RD 2024/03/29 AB ESSENTIALS OF DIAGNOSISSinus node dysfunction (“sick sinus syndrome”)Sinus bradycardia: sinus rate of less than 60 bpm.Sinoatrial exit block, type I: progressively shorter P-P intervals, followed by failure of occurrence of a P wave.Sinoatrial exit block, type II: pauses in sinus rhythm that are multiples of basic sinus rate.Sinus arrest, sinus pauses: failure of occurrence of P waves at expected times.Atrioventricular (AV) blockFirst degree: prolonged PR interval more than 200 ms.Second degreeType I: progressive increase in PR interval, followed by failure of atrioventricular (AV) conduction and nonoccurrence of a QRS complex.Type II: abrupt failure of AV conduction not preceded by increasing PR intervals.“2:1 block”: due to lack of consecutive PR intervals; unable to assign either type I or type II block.“Advanced”: AV conduction ratio ≥ 3:1.Third degree (“complete”): independent atrial and ventricular rhythms, with failure of AV conduction despite temporal opportunity for it to occur.