This diagram demonstrates the conduction system of the normal heart. The impulse from the SA node spreads through atrial muscle to the AV node and then the impulse proceeds through the His-Purkinje system to activate the ventricles.
The conduction defect producing heart block in patients with inferior infarction is usually located in the area of the AV node rather than the bundle of His or the bundle branches. The high incidence of heart block in this setting is due to the fact that inferoposterior wall ischemia initiates a reflex increase in vagal tone. In addition, in ninety percent of patient the right coronary artery supplies the AV node as well as the inferior wall.
The following animation illustrates what we have just described.
2nd degree block - treatment
If the patient remains clinically stable, no treatment of type I second degree AV block is indicated. This type of heart block is usually transient. The patient should be carefully monitored and an external pacemaker should be readily available. If the patient becomes symptomatic due to the AV block, an external pacer or intravenous atropine can be used to stabilize the patient until a temporary transvenous pacemaker can be inserted. The pacemaker should be kept until the AV block resolves.
Our patient
Our patient’s vital signs remain stable and this arrhythmia was transient. He received no treatment.