The supraventricular tachycardia av node reentry
The supraventricular tachycardia av node reentry Supraventricular tachycardia (SVT) is a rapid heartbeat that originates above the ventricles, often causing episodes of palpitations, dizziness, or shortness of breath. Among the various types of SVT, one of the most common is atrioventricular (AV) node reentrant tachycardia (AVNRT). Understanding AVNRT involves exploring the intricate electrical pathways of the heart and the mechanisms that lead to abnormal rapid rhythms.
The supraventricular tachycardia av node reentry The heart’s electrical system is responsible for maintaining a regular heartbeat. It begins with the sinoatrial (SA) node, which acts as the natural pacemaker. The electrical impulse travels through the atria to the atrioventricular (AV) node, then down the bundle of His and Purkinje fibers to stimulate ventricular contraction. In AVNRT, an abnormal circuit forms within or near the AV node, causing a reentrant loop that results in rapid heartbeats. This loop involves two pathways with different conduction velocities and refractory periods, often labeled as “fast” and “slow” pathways.
In typical AVNRT, the slow pathway conducts the impulse first, which then travels back through the fast pathway, setting up a continuous loop. When this reentry occurs, the heart beats very rapidly—often between 150 and 250 beats per minute—leading to the characteristic episodes of SVT. Patients may experience sudden onset and termination of symptoms, which can be frightening but are usually not life-threatening in healthy individuals. The supraventricular tachycardia av node reentry
The supraventricular tachycardia av node reentry Diagnosing AVNRT typically involves an electrocardiogram (ECG) during an episode, which reveals a narrow QRS complex tachycardia with a rapid rate. Sometimes, the P waves are hidden within the QRS complex or are inverted, making the diagnosis subtle. In certain cases, electrophysiological studies may be performed to map the electrical pathways and confirm the diagnosis, especially if the episodes are frequent or resistant to initial treatments.
Management of AVNRT can vary based on symptom severity and frequency. Acute episodes are often terminated with vagal maneuvers—such as coughing or bearing down—that stimulate the vagus nerve and slow conduction through the AV node. If these are ineffective, medications like adenosine are administered intravenously; adenosine temporarily blocks conduction through the AV node, often restoring normal rhythm swiftly. Other drugs, including beta-blockers or calcium channel blockers, may be prescribed for prevention. The supraventricular tachycardia av node reentry
For patients with recurrent AVNRT or those who do not tolerate medications well, catheter ablation offers a potential cure. During ablation, a catheter is threaded to the area near the AV node, where radiofrequency energy destroys the abnormal conduction pathway. This procedure has high success rates and a low risk of complications, making it a preferred treatment for many.
In summary, AVNRT is a common and usually manageable form of SVT caused by reentrant circuits within or near the AV node. Advances in electrophysiology and minimally invasive procedures have significantly improved outcomes, allowing many patients to lead normal lives without episodes of tachycardia. Understanding the underlying mechanisms not only helps in effective management but also provides reassurance to those affected. The supraventricular tachycardia av node reentry
