what is supraventricular tachycardia

3 min read 08-03-2025

Supraventricular tachycardia (SVT) is a heart rhythm disorder characterized by a rapid heartbeat originating above the ventricles (the lower chambers of the heart). This means the abnormal electrical signals causing the rapid heart rate start somewhere in the atria (the upper chambers) or in the atrioventricular (AV) node, a cluster of cells that acts as a gatekeeper between the atria and ventricles. Understanding SVT is crucial for effective diagnosis and treatment.

Understanding the Heart's Electrical System

To grasp SVT, it's helpful to understand the heart's electrical conduction system. This system controls the heart's rhythm and ensures coordinated contractions. Electrical impulses originate in the sinoatrial (SA) node, the heart's natural pacemaker, located in the right atrium. These impulses travel through the atria, causing them to contract, then pass through the AV node to the ventricles, triggering their contraction.

In SVT, this orderly process is disrupted. The rapid heartbeat isn't controlled by the SA node; instead, an abnormal electrical pathway or circuit takes over. This causes the heart to beat much faster than normal, often exceeding 100 beats per minute.

Types of Supraventricular Tachycardia

Several types of SVT exist, each with its own cause and characteristics:

1. Atrial Flutter

Atrial flutter involves a rapid, repetitive electrical signal in the atria, resulting in a very fast atrial rate (often 250-350 beats per minute). Not all of these impulses reach the ventricles, but the ventricular rate can still be significantly elevated.

2. Atrial Fibrillation

Atrial fibrillation (AFib) is a common type of SVT where the atria beat chaotically and irregularly, rather than in a coordinated fashion. This can lead to an irregular and often rapid ventricular rate. AFib increases the risk of stroke.

3. AV Nodal Reentrant Tachycardia (AVNRT)

AVNRT is caused by an abnormal electrical pathway in the AV node. The electrical impulse circulates within the node, creating a rapid heartbeat.

4. Atrioventricular Reciprocating Tachycardia (AVRT)

AVRT involves an extra electrical pathway connecting the atria and ventricles, causing a re-entrant circuit and a rapid heart rate. This pathway is usually present from birth (congenital).

Symptoms of Supraventricular Tachycardia

SVT symptoms vary depending on the individual and the severity of the rapid heartbeat. Some people experience only mild symptoms, while others may have more severe effects. Common symptoms include:

Rapid or fluttering heartbeat (palpitations)
Shortness of breath
Lightheadedness or dizziness
Chest pain or pressure
Fainting (syncope)
Fatigue

Diagnosing Supraventricular Tachycardia

Diagnosing SVT usually involves:

Physical examination: Listening to the heart with a stethoscope can reveal a rapid heartbeat.
Electrocardiogram (ECG or EKG): This test measures the heart's electrical activity and is essential for diagnosing SVT and identifying the specific type. An ECG during an episode of SVT shows a characteristic pattern.
Holter monitor: This portable device continuously records the heart's electrical activity for 24-48 hours, helping to detect episodes of SVT that may not occur during a standard ECG.
Event recorder: Similar to a Holter monitor, but it only records when activated by the patient when symptoms occur. This is useful for infrequent episodes.

Treating Supraventricular Tachycardia

Treatment for SVT depends on the severity of symptoms, the type of SVT, and the patient's overall health. Options include:

Vagal maneuvers: These maneuvers stimulate the vagus nerve, which can slow the heart rate. Examples include bearing down as if having a bowel movement (Valsalva maneuver) or immersing the face in ice water.
Medication: Several medications can be used to control the heart rate or convert the rhythm back to normal.
Cardioversion: This involves delivering a controlled electrical shock to the heart to restore a normal rhythm. It's usually done if medication is ineffective.
Catheter ablation: This procedure uses catheters to destroy the abnormal electrical pathways causing SVT. It's a minimally invasive procedure often considered for recurrent SVT.

Living with Supraventricular Tachycardia

Many people with SVT can lead active and healthy lives with appropriate management. Regular follow-up appointments with a cardiologist are essential to monitor the condition and adjust treatment as needed. Understanding your triggers (stress, caffeine, alcohol) and learning coping mechanisms can help prevent episodes.

Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with a healthcare professional for diagnosis and treatment of any medical condition.