Supraventricular Tachycardia (SVT): Causes, and Symptoms

Supraventricular tachycardia (SVT) is a condition where your heart beats suddenly accelerate. While normal heart rate is between 60-100 beats per minute, during SVT this number can rise to 150-250. This condition can usually last from a few minutes to several hours and often resolves spontaneously. If you don’t have another heart disease, SVT is not a serious life-threatening condition, but it can significantly reduce your quality of life. It is possible to completely get rid of SVT attacks, especially with ablation treatment.

What Is Supraventricular Tachycardia?

Supraventricular tachycardia (SVT) is a rapidly occurring heart rhythm that originates from the atria or areas between the atria and ventricles, starting suddenly. It generally occurs due to extra pathways in the heart’s electrical system. Your pulse can suddenly rise to 150-250 beats. SVT is common in young adults and can often occur even without structural heart disease.

The word “supraventricular” refers to areas above the ventricles, which are the lower chambers of the heart. The upper chambers are the atria. The term “tachycardia” describes the heart beating faster than normal.

During supraventricular tachycardia, a short circuit occurs in your heart’s electrical signals. This condition causes your heart muscle to beat much faster than normal. When the heart beats this fast, the chambers may not have time to fill completely with blood, and the amount of blood sent to your body may decrease.

What Are the Types of Supraventricular Tachycardia?

There are three main types of supraventricular tachycardia:

Atrioventricular Nodal Reentrant Tachycardia (AVNRT)

AVNRT is a type of palpitation that starts and ends suddenly, originating from two different electrical pathways within the AV node in your heart. Your pulse usually rises in the 140-240 range, and the palpitation appears and disappears suddenly.

AVNRT is an abbreviation for “atrioventricular nodal reentrant tachycardia.” Within the AV node (atrioventricular node), which is one of the heart’s electrical centers, there can be both a slow and a fast conduction pathway. With this dual pathway, the stimulus begins to move cyclically. This causes unnecessary repeated stimulation in the heart and sudden increase in heart rate. AVNRT is especially common in young adults and often develops without structural heart disease.

Atrioventricular Reentrant Tachycardia (AVRT)

AVRT is a type of tachycardia that occurs as a result of the heart’s electrical system working cyclically through a pathway outside the normal. Your pulse can suddenly accelerate to 180-250 beats and usually starts and ends abruptly.

AVRT is an abbreviation for “atrioventricular reentrant tachycardia.” Due to an additional conduction pathway that exists congenitally between the atrium and ventricle in the heart, electrical stimuli circulate in a pathway outside the normal. This cycle causes your heart to beat very fast. The most well-known subtype is Wolff-Parkinson-White (WPW) syndrome.

Atrial Tachycardia

Atrial tachycardia is a regular but excessively fast heart rhythm originating from the atrial region of the heart. During this rhythm disorder, your pulse can rise to 100-200 beats/minute levels.

In atrial tachycardia, electrical stimulation comes from a focus other than the SA node, which is the normal heart pacemaker, and this focus causes the atria to contract excessively fast. It usually originates from a specific point (focal tachycardia), but sometimes it can come from multiple foci. It can sometimes develop after heart surgeries, hypertension, heart muscle diseases, or age-related structural changes.

What Are the Symptoms of Supraventricular Tachycardia?

When an SVT attack begins, your heart beats very fast. This condition can last from a few seconds to several hours. Symptoms can be mild or you may feel them at a disturbing level.

Supraventricular tachycardia symptoms include:

• Sudden onset rapid heart palpitations (150-250 beats per minute)
• Chest pain or pressure sensation
• Shortness of breath
• Dizziness
• Palpitations in neck vessels
• Sweating
• Hot flashes
• Anxiety and fear
• Weakness
• Fainting (rare)
• Nausea
• Sudden stopping of palpitations

What Causes Supraventricular Tachycardia?

The main cause leading to SVT is extra pathways or abnormal foci that generate stimulation in the heart’s electrical system. These pathways can be congenital or develop later.

Conditions that can cause supraventricular tachycardia include:

• Congenital conduction pathway anomalies (e.g., WPW)
• Genetic predisposition
• Isolated foci after heart surgeries
• Heart muscle diseases
• Hypertension and age-related structural changes
• Excessive stress, caffeine, alcohol, or stimulant substance use
• Thyroid hormone excess

In some patients, no clear cause can be found. In this case, SVT is called “idiopathic,” meaning tachycardia of unknown cause.

Who Can Experience Supraventricular Tachycardia?

SVT can occur in any age group. However, it is frequently seen in young adults, women, and individuals without structural heart disease.

• Age groups: Young adults and middle-aged groups are more frequently affected. The first attack usually occurs between ages 20-40. It can also be seen in children, but its frequency may decrease or increase with age.
• Gender factor: SVT is seen approximately 2-3 times more frequently in women than men. Hormonal changes can trigger SVT attacks especially during pregnancy, menstrual periods, and menopause.
• Family history: Risk is higher in people with a family history of SVT. Genetic factors can affect the structure of the heart’s electrical system.
• Other health conditions: Risk of SVT may increase in people with heart disease, hypertension, diabetes, and thyroid diseases. Sleep apnea is also among the risk factors.

How Is Supraventricular Tachycardia Diagnosed?

Diagnosis is mostly made with ECG taken during an attack. However, since palpitation attacks usually start suddenly and last for a short time, ECG recording may not always be possible.

• History taking and physical examination: Your doctor asks about your symptoms in detail. When attacks started, how long they lasted, triggering factors, and family history are important information. During physical examination, heart sounds are listened to and pulse is checked.
• Electrocardiogram (ECG): Shows the heart’s electrical activity and is the most important test in SVT diagnosis. ECG taken during an attack provides definitive diagnosis. However, ECG may appear normal between attacks.
• Holter monitor: A small device worn for 24-48 hours. It continuously records your heart rhythm during daily activities. This test helps capture ECG changes during attacks.
• Event monitor: A recording device that you activate when you feel symptoms. It can be carried for several weeks and records your heart rhythm when an attack begins.
• Electrophysiologic study: A special test performed in some cases. This test definitively determines the type of SVT and can also provide treatment with ablation at the same time.

How Is Supraventricular Tachycardia Treated?

Treatment aims to both reduce the number and duration of attacks and normalize rhythm during attacks. Applied treatment options may include vagal maneuvers and medications according to the severity, type, and frequency of the disease. Catheter ablation provides permanent treatment in many patients with SVT. Success rate varies between 95-98%.

Methods Applied During Attack

When the heart beats very fast during an SVT attack, rhythm can be returned to normal with some simple maneuvers. These maneuvers are called vagal maneuvers. For example, straining (Valsalva), washing face with cold water, or holding breath can slow the heart. These techniques affect the heart’s electrical system by stimulating the vagus nerve. The vagus nerve is part of the parasympathetic system that slows heart rhythm.

If these maneuvers are not effective, some rhythm-regulating medications given intravenously (such as adenosine) can return heart rhythm to normal. In emergency situations, these medications are effective in a short time and are usually applied in the hospital.

Cardioversion

If the attack is very severe, serious symptoms such as low blood pressure, fainting, chest pain have developed, or there is no response to medications, electrical cardioversion can be applied. With this method, a short-term, controlled electrical stimulus is given to the heart and rhythm is returned to normal. The procedure is usually performed under sedation, quickly and safely.

Long-term Treatment

If attacks are recurrent or affecting quality of life, a long-term treatment plan is needed. Rhythm-regulating medications (antiarrhythmics) can reduce the frequency and severity of attacks. However, these medications require regular monitoring.

If attacks continue despite medications or if medication use is not desired, catheter ablation permanently treats SVT in most cases. The ablation procedure has a high success rate (95-98%) for most SVT types and usually one session is sufficient. In this method, the focus causing rhythm disorder is determined by electrophysiologic study (EPS) and is disabled using heat or freezing energy.

What Are the Risks of Supraventricular Tachycardia?

SVT is generally a benign rhythm disorder. However, if left untreated, some risks may occur:

• Heart fatigue and decreased quality of life due to palpitations may occur
• When pulse rises very high, you may experience low blood pressure and fainting
• Continuous attacks may result in heart muscle weakness (tachycardia-induced cardiomyopathy)
• Long-standing uncontrolled SVT may rarely lead to heart failure development

How to Continue Daily Life with Supraventricular Tachycardia?

It is possible to maintain normal life with SVT:

• Try to recognize which situations trigger SVT attacks. Stress, fatigue, caffeine, or certain activities can be triggers. Keep these factors under your control as much as possible.
• Regular sleep hours and adequate rest can reduce SVT attacks. Take care to get 7-8 hours of quality sleep per day. Find activities that will help you manage your stress.
• Use the medications prescribed by your doctor regularly. Do not adjust medication doses yourself and do not stop without medical supervision. Monitor side effects and share them with your doctor.
• Plan in advance what to do when an SVT attack begins. Learn and apply the Valsalva maneuver. Know when you need to go to the emergency room.

How Should Nutrition and Exercise Be?

• Limit caffeine consumption. 1-2 cups of coffee per day is usually safe, but adjust according to your personal tolerance. Reduce alcohol consumption as it can trigger SVT attacks.
• Drink plenty of water; dehydration can cause heart rhythm disorders. Take care to consume at least 8-10 glasses of water per day. Limit salty and processed foods.
• Consume foods rich in magnesium and potassium. Green leafy vegetables, bananas, avocado, nuts, and whole grains support heart health.
• Regular light exercise is beneficial for SVT control. Aerobic exercises such as walking, swimming, and light jogging improve heart health. However, avoid excessively intense exercise.
• Start exercise slowly and increase gradually. Monitor your heart rate during exercise and rest if symptoms begin. Share your exercise program with your physician.

When Should You Consult a Doctor?

• Situations requiring emergency consultation: If you experience severe chest pain, inability to breathe, fainting, or feeling of fainting along with heart palpitations, immediately go to the emergency room. If SVT attack lasts longer than 20-30 minutes and Valsalva maneuvers are not effective, emergency intervention is needed.
• Situations requiring routine control: If the frequency of SVT attacks is increasing, new symptoms are occurring, or the effectiveness of your current treatment is decreasing, consult your physician. If you are experiencing medication side effects or your quality of life is seriously affected, evaluation is also needed.
• Follow-up appointments: Go to regular doctor controls after diagnosis. Treatment effectiveness, side effects, and your quality of life are evaluated. Controls after catheter ablation are also very important.

Frequently Asked Questions

What should be done during an SVT attack?

When an SVT attack begins, first stay calm. Valsalva maneuver can be tried. Face can be washed with cold water. If the attack lasts long or there are severe symptoms, go to the hospital.

Does SVT threaten life?

SVT usually does not threaten life. It is harmless for most patients. However, it can be risky in people with heart disease. Long-lasting attacks can rarely cause serious problems.

Is SVT dangerous during pregnancy?

SVT may be seen more frequently during pregnancy. It usually does not pose serious risk to mother and baby. Contact your gynecologist during an attack. Treatment is adjusted according to pregnancy status.

How often do SVT attacks occur?

SVT attack frequency varies from person to person. Some patients may experience it a few times a year. Some may have several attacks per month. Frequency may increase or decrease over time.

Is ablation treatment safe?

Ablation treatment is a safe procedure. Complication risk is between 1-2%. Success rate is very high. Most patients recover completely after the procedure. It should be performed in experienced centers.

Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5135523/