From the Guidelines
A vagal block, also known as a vagal maneuver, is a non-invasive medical procedure that involves stimulating the vagus nerve to terminate supraventricular tachycardia (SVT), specifically atrioventricular nodal reentrant tachycardia (AVNRT) 1.
Definition and Purpose
A vagal block is used to interrupt the abnormal electrical pathways in the heart that cause AVNRT, restoring a normal heart rhythm. The goal of a vagal block is to increase vagal tone, which can help to slow down the heart rate and convert AVNRT to a normal sinus rhythm.
Types of Vagal Maneuvers
There are several types of vagal maneuvers that can be used to perform a vagal block, including:
- Valsalva maneuver: involves bearing down against a closed glottis for 10 to 30 seconds to increase intrathoracic pressure 1
- Carotid sinus massage: involves applying steady pressure over the right or left carotid sinus for 5 to 10 seconds 1
- Facial immersion in cold water: involves immersing the face in cold water to stimulate the vagus nerve 1
Effectiveness and Safety
Vagal maneuvers are a safe and effective way to terminate AVNRT, with a success rate of approximately 27.7% 1. They are recommended as a first-line treatment for AVNRT, and can be performed quickly and easily in a clinical setting. However, if vagal maneuvers are unsuccessful, other treatments such as adenosine or synchronized cardioversion may be necessary 1.
From the Research
Definition and Mechanism of Vagal Block
- A vagal block, also known as anodal block, is a technique used in selective vagus nerve stimulation (VNS) to mitigate side effects and produce functionally specific effects 2.
- The exact mechanism of vagal block is not fully understood, but it is believed to involve the targeting of specific fiber types within the vagus nerve to produce desired effects 2.
Applications and Benefits of Vagal Block
- Vagal block has been shown to reduce the severity of side effects associated with VNS, such as hoarseness, throat pain, and coughing 2.
- It has also been demonstrated to increase the efficacy of VNS in some cases, particularly in the treatment of refractory epilepsy and depression 2, 3.
- The use of vagal block and other selective VNS techniques has the potential to provide crucial information about vagal nerve physiology and to achieve greater specificity in treatment 2.
Comparison with Other Techniques
- Vagal block is one of several paradigms of selective VNS, including spatially selective, fiber-selective, and kilohertz electrical stimulation block 2.
- While vagal block can achieve strong side-effect mitigation, it is less specific than fiber- and spatially selective paradigms 2.
- The choice of technique depends on the specific application and the desired outcome, as well as the individual patient's response to treatment 2, 4.