What is Supraventricular Tachycardia?
Supraventricular tachycardia (SVT) is a type of arrhythmia characterized by an abnormally fast heartbeat originating from the upper chambers of the heart. It can result in a heart rate that exceeds 100 beats per minute, often reaching between 150 to 220 beats per minute. This condition, sometimes referred to as paroxysmal supraventricular tachycardia, can lead to various symptoms but is typically not life-threatening in individuals without pre-existing heart conditions.
Types of SVT
SVT encompasses several specific types, including:
Atrioventricular Nodal Reentrant Tachycardia (AVNRT): This is the most common form of SVT, often characterized by rapid heart rhythms due to a reentrant circuit involving the AV node.
Atrioventricular Reciprocating Tachycardia (AVRT): Frequently observed in younger individuals, this type involves an accessory pathway between the atria and ventricles.
Atrial Tachycardia: This variant does not involve the AV node and is more commonly seen in individuals with existing heart disease.
Other types of SVT include sinus nodal reentrant tachycardia (SNRT), inappropriate sinus tachycardia (IST), multifocal atrial tachycardia (MAT), junctional ectopic tachycardia (JET), and nonparoxysmal junctional tachycardia (NPJT).
Symptoms of SVT
The hallmark symptom of SVT is a noticeably rapid heartbeat that can last from a few minutes to several days. Common symptoms include:
- Palpitations or a fluttering sensation in the chest
- A pounding feeling in the neck
- Chest pain or discomfort
- Lightheadedness or dizziness
- Shortness of breath
- Sweating
- Fatigue
In infants and young children, symptoms may be less distinct and can include sweating, poor feeding, changes in skin color, and a rapid pulse.
Causes of SVT
SVT is primarily caused by faulty electrical signaling within the heart. In a healthy heart, electrical signals from the sinus node dictate the heartbeat. In SVT, abnormal signals cause the upper chambers (atria) to contract prematurely, leading to a rapid heartbeat that prevents proper filling of the heart with blood.
Heart Structure and Function
The heart consists of four chambers: two atria (upper chambers) and two ventricles (lower chambers). The sinus node initiates the heartbeat, and signals normally travel through the AV node to the ventricles. When this signaling process is disrupted, the heart beats too quickly.
Risk Factors
SVT is particularly common in infants and children and is more prevalent in women, especially during pregnancy. Various health conditions and lifestyle factors can increase the risk, including:
- Coronary artery disease and heart valve disorders
- Heart failure or congenital heart defects
- Previous heart surgeries
- Obstructive sleep apnea
- Thyroid disorders and uncontrolled diabetes
- Emotional stress and excessive caffeine intake
- Smoking and the use of stimulant drugs
Complications
If left untreated, frequent SVT episodes can weaken the heart over time and may lead to heart failure. In severe cases, an SVT episode can result in fainting or even sudden cardiac arrest.
Diagnosis
Diagnosis of SVT typically involves a thorough examination, including:
Medical History: The healthcare provider will inquire about symptoms, health habits, and any relevant medical history.
Electrocardiogram (ECG): This test records the heart’s electrical activity and can identify the presence of arrhythmias.
Holter Monitor: A portable ECG device that records heart activity over one to two days during regular activities.
Echocardiogram: This ultrasound test provides images of the heart’s structure and blood flow.
Other diagnostic tests may include an exercise stress test, tilt table test, or electrophysiological study to assess the heart’s electrical signals.
Treatment Options
Most individuals with SVT do not require treatment. However, if episodes are frequent or prolonged, various treatment options may be considered:
Vagal Maneuvers: Techniques such as coughing or bearing down can sometimes help slow the heart rate.
Cardioversion: This procedure uses electrical shocks to reset the heart rhythm and is typically employed in emergency situations.
Catheter Ablation: Involves inserting catheters to target and disrupt the faulty electrical pathways causing the rapid heartbeats.
Pacemaker: In rare cases, a pacemaker may be implanted to help regulate the heart’s rhythm.
Prevention
To help manage and potentially prevent SVT, individuals can adopt a heart-healthy lifestyle, which includes:
- Eating a nutritious diet
- Engaging in regular physical activity
- Avoiding tobacco products
- Limiting caffeine and alcohol intake
- Managing stress effectively
Keeping a diary of symptoms and identifying potential triggers can also be beneficial in managing the condition.