Contributor: Nick Hatch, MD Educational Pearls: Complete heart block or 3rd degree atrioventricular (AV) block is diagnosed via EKG and occurs when electrical signals from the sinoatrial (SA) node are blocked from reaching the ventricles via the AV node and AV bundles P waves and QRS complexes are independent Often QRS rate is around 40 The rate is slow because the ventricular purkinje fibers have an intrinsic rate of 20-40 bpm, whereas the SA node has an intrinsic rate of 60-100 bpm Treatment is usually with pacemaker, unless there is an identifiable etiology causing the heart block that can be reversed References Knabben V, Chhabra L, Slane M. Third-Degree Atrioventricular Block. [Updated 2020 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK545199/   The Emergency Medical Minute is excited to announce that we are now offering AMA PRA Category 1 credits™ via online course modules. To access these and for more information, visit our website at www.emergencymedicalminute.org/cme-courses/ and create an account.  Donate to EMM today!