Atrioventricular nodal reentrant tachycardia (AVNRT) is a type of supraventricular tachycardia characterized by an abnormal heart rhythm caused by a reentrant circuit within the atrioventricular (AV) node. This results in a rapid heart rate, typically between 150 and 250 beats per minute, and can lead to symptoms such as palpitations, shortness of breath, and dizziness.