Third degree AV block diagnostic study of choice
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Soroush Seifirad, M.D.[2]
Overview
A 12-lead Electrocardiography (ECG) is the gold standard test for the diagnosis of third degree AV block. Nevertheless, it might be normal in patients with transient AV block. A Holter monitoring and/or telemetry must be performed when the patient presents with sign and symptoms which raising concern for complete heart block in the presence of a normal ECG. Diagnostic electrophysiologic studies might be used in certain complicated cases
Diagnostic Study of Choice
Study of choice
A 12-lead Electrocardiography (ECG) is the gold standard test for the diagnosis of third degree AV block.
Nevertheless, it might be normal in patients with transient AV block.
A Holter monitoring and/or telemetry must be performed when:
- The patient presents with sign and symptoms which raising concern for complete heart block such as:
- Syncope
- History of Heart disease
- Risk factors of Heart disease
- Elderly
- History of AV blocking agents in heir manuscript
- History of heart surgery
Investigations:
- Among the patients who present with clinical signs of third degree AV block, the electrophysiologic studies and cardiac catheterization is the most specific test for the diagnosis.
- Among the patients who present with clinical signs of third degree AV block, the ECG is the most sensitive test for diagnosis.
- Among the patients who present with clinical signs of third degree AV block, the ECG is the most efficient test for diagnosis.
Name of Diagnostic Criteria
The diagnosis of third degree AV block is generally based on the 12-lead ECG findings which is characterized by complete lack of conduction, and no P -QRS relationship. Nevertheless, this should not mistaken by AV dissociation. Additionally, we may diagnose the location of the block as follows:
- Look at the QRS and see if it is is narrow (< 120 msec) during conducted beats and narrow with the same morphology during escape beats
- If yes, this is a junctional AV block.
- If no and the conducted QRS is wide during the escape rhythm then this is probably a distal block located somewhere in the His bundle or in both right and left bundles.
- Nevertheless, only diagnostic electrophysiologic studies during cardiac catheterisation can accurately and certainly demonstrate the exact level of block in the system.