Atrioventricular Nodal Reentrant Tachycardia (AVNRT)
Disease Description
Atrioventricular nodal reentrant tachycardia (AVNRT) is a type of supraventricular tachycardia (SVT) characterized by sudden episodes of rapid heart rhythm originating within or near the atrioventricular (AV) node.
Causes of the Disease
The cause of AVNRT is a congenital dual-pathway physiology of the AV node, in which two conduction pathways share a common entry and exit but differ in their electrophysiological properties.
As in Wolff–Parkinson–White (WPW) syndrome, the key mechanism in AVNRT is re-entry, whereby an electrical impulse begins to circulate in a closed loop, resulting in tachycardia.
Symptoms
Patients with AVNRT experience episodes of sudden-onset rapid palpitations, lasting from several minutes to several hours (less commonly). These episodes also end abruptly.
Attacks may be accompanied by dizziness, shortness of breath, near-fainting sensations, and chest discomfort.
Diagnosis
There are typically no specific ECG changes at rest. The diagnosis is established based on an ECG recorded during an episode of tachycardia and is confirmed by an electrophysiological study (EPS).
Treatment
Drug therapy for AVNRT is generally ineffective as a long-term solution. To terminate acute episodes, patients may use vagal maneuvers, such as breath-holding with abdominal strain (Valsalva maneuver), facial immersion in cold water, or gentle pressure on the eyeballs.
The only effective and definitive treatment for AVNRT is radiofrequency catheter ablation (RFA), during which the abnormal conduction pathway responsible for the arrhythmia is eliminated.
Treatment Prognosis
Up to 50% of patients with AVNRT may also experience atrial fibrillation. In most cases, atrial fibrillation resolves after successful catheter ablation of AVNRT.
Radiofrequency catheter ablation has a very high success rate and typically provides a permanent cure, allowing patients to return to a normal quality of life without recurrent tachycardia.