Patients with complete AV-block accompanying an acute myocardial infarction often have ischemic symptoms of chest pain or dyspnea. The patient's status at the time of presentation can vary depending on the concurrent disease and the rate of the escape rhythm. They may have significant hemodynamic instability and can be obtunded. Usually, they may present with generalized fatigue, tiredness, chest pain, shortness of breath, presyncope, or syncope. Patients with third-degree blocks can have varying clinical presentations. This rhythm is unresponsive to atropine and exercise. The heart rate will typically be less than 45 to 50 beats/min, and most patients will be hemodynamically unstable. The SA node continues its activity at a set rhythm, but the ventricles activate through an escape rhythm that can be mediated by either the AV node (junctional escape), one of the fascicles (fascicular escape), or by ventricular myocytes themselves (ventricular escape rhythm). As the name implies, no impulses from the SA node get conducted to the ventricles, leading to a complete atrioventricular dissociation. The third-degree block is also known as complete heart block. These delays present in the form of AV blocks, which are of first, second, and third-degree. When there is a pathological delay in the AV nodal conduction, it is visualized on an electrocardiogram as an alteration in the PR interval. From the AV node, the electrical impulse passes through the His-Purkinje system to activate ventricular contraction. That impulse gets delayed in the AV node, assuring the contraction cycle in the atria is complete before a contraction begins in the ventricles.

Under its regular function, the AV node receives an impulse from the SA node.

Liftl junctional escape rhythm