Vagal maneuvers cause increase in vagal tone, which has been shown to slow many types supraventricular tachycardia, such as atrial fibrillation (AF).
The mechanism for the effects of the rectal exam on the AF is likely due to the increase in parasympathetic activity through cranial nerve X (Vagus nerve), which also dampens the sympathetic stimulation to the heart.
The parasympathetic branch of the Autonomic nervous system has several effects on the heart.
- First, increased parasympathetic activity slows the rate of impulse formation of the sinus atrial (SA) node.
- Second, increased parasympathetic activity slows conduction and increases refractory through the atrioventriuclar (AV) node.