Out of all existing ECG rhythms, atrioventricular (AV) blocks are among the most challenging to interpret correctly. A form of heart block known as an AV block happens when electrical impulses traveling from the heart’s upper chambers (atria) to the lower chambers (ventricles) fail to reach their destination (Tanaka & Fujimura, 2019). The sinoatrial node typically generates electrical impulses to regulate heart rate, whereas the AV node serves as the conduit through which the signal travels to the ventricles. In the context of an AV block, these impulses are either delayed or entirely stopped.
Based on the nature of the delay, AV blocks can be categorized into three groups: first-degree, second-degree, and third-degree AV blocks. The former is characterized by a delay in the PR interval of approximately 200 ms, without dropped or skipped heartbeats (Ho et al., 2022). The second-degree blocks can be of two subtypes, Mobitz I and II; Mobitz I refers to a progressive PR interval prolongation resulting in a skipped beat, whereas Mobitz II results in randomly skipped beats (Ho et al., 2022). Finally, a third-degree AV block represents a complete stop in electrical communication between the atria and ventricles.
The problems with AV blocks’ interpretation arise due to the occurrence of a significant number of similar rhythms that are not connected to pathological or abnormal cases. For instance, second-degree Mobitz I supertype and first-degree AV blocks are considered benign and can occur spontaneously without any underlying causes (Ho et al., 2022). Consequently, treating these symptoms seriously might do more harm than good to the patient.
However, when it comes to registering a Mobitz II subtype or a third-degree AV block, the NP must act accordingly. To improve their ability to distinguish between dangerous and non-dangerous heart rhythms, NPs can seek guidance in an NIH publication or read the latest articles on the topic to inform their evidence-based practice (Ho et al., 2022; NIH, n.d.). This, combined with constant practice during clinical hours, can significantly improve ECG interpretation skills.
References
Ho, R., Ruskin, J., & Ng, C. Y. (2022). Concealed His extrasystoles: A masquerader of atrioventricular block. HeartRhythm Case Reports, 8(11), 727-729.
NIH. (n.d.). National library of medicine.
Tanaka, K., & Fujimura, O. (2019). Analysis of variable conduction ratios into the atrioventricular node during atrial flutter: Multilevel block theory. HeartRhythm Case Reports, 5(5), 274-276.