Third degree AV block laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Zand, M.D.[2] Soroush Seifirad, M.D.[3] Raviteja Guddeti, M.B.B.S. [4]

Overview

There is not any recommendation about routine laboratory tests in patients presented with bradycardia or conduction disorder. However, in suspicion of the underlying causes of bradycardia including sepsis, rheumatologic disorder, or thyroid disease specific tests are warranted.

Laboratory tests in patients with bradycardia or conduction disorder based on the underlying cause may include:
Thyroid function test in suspicion of hypothyroidism
Lyme titer in acute Lyme carditis in a young person who develops atrioventricular block in an endemic area
Potassium level, PH in patients with renal insufficiency
Blood digoxin level in patients suspected digoxin overdose

Class IIa
“1 Thyroid function tests, Lyme titer, potassium, pH) based on clinical suspicion for a potential underlying cause is recommended in patients with bradycardia (Level of Evidence C)”

↑ Kusumoto, Fred M.; Schoenfeld, Mark H.; Barrett, Coletta; Edgerton, James R.; Ellenbogen, Kenneth A.; Gold, Michael R.; Goldschlager, Nora F.; Hamilton, Robert M.; Joglar, José A.; Kim, Robert J.; Lee, Richard; Marine, Joseph E.; McLeod, Christopher J.; Oken, Keith R.; Patton, Kristen K.; Pellegrini, Cara N.; Selzman, Kimberly A.; Thompson, Annemarie; Varosy, Paul D. (2019). “2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society”. Circulation. 140 (8). doi:10.1161/CIR.0000000000000628. ISSN 0009-7322.