Supraventricular tachycardia (SVT) is a term that comes from Latin words meaning “above the ventricles” and “fast heart rate”. It refers to a group of conditions that make your heartbeat faster than normal. SVT can be very uncomfortable, but it is usually not a serious medical problem. However, you should always see a doctor if you have SVT.
How Your Heart Works
Your heart is a muscle that pumps blood and oxygen to your body. It has four chambers: two upper chambers called atria and two lower chambers called ventricles. Your heart beats about 100,000 times a day.
Your heart has a natural pacemaker called the sinoatrial node (SA node), which is located at the top of your right atrium. The SA node sends electrical signals to the rest of your heart, telling it when to contract and relax. This creates a regular rhythm for your heartbeat.
What Happens During SVT
When you have SVT, something goes wrong with the electrical signals in your heart. The signals fire off too early or too fast, making your atria contract faster than normal. This interrupts the normal signal from the SA node and makes your heart beat faster than normal.
When you are resting, your heart normally beats 50 to 99 times a minute. When you have SVT, your heart can beat more than 100 times a minute.
There are different types of SVT, depending on where the abnormal electrical signals come from:
- Atrial tachycardia: This happens when there is a short circuit in your right or left atrium, causing a faulty electrical signal.
- Paroxysmal supraventricular tachycardia: This is a type of SVT that comes and goes suddenly and unpredictably.
- Atrioventricular nodal reentrant tachycardia: This happens when you have an extra pathway in your heart that connects your atria and ventricles, causing the electrical signal to loop around and around without moving down to the ventricles.
- Atrioventricular reciprocating tachycardia: This happens when you have an abnormal pathway that links your atria and ventricles, causing the electrical signal to loop around and around between them.
Symptoms of SVT
SVT can affect how much blood and oxygen your heart can pump to your body. This can cause symptoms such as:
- Dizziness and confusion;
- Shortness of breath;
- Chest pain;
Causes of SVT
The exact causes of SVT are not always clear. Some people are born with abnormal pathways or electrical circuits in their hearts that can trigger SVT. Others develop SVT later in life due to scar tissue from surgery or other heart problems.
Some factors that can increase your risk of having SVT or make it worse include:
- Certain medicines, such as asthma drugs or decongestants;
- Some herbal diet remedies;
- Excessive use of caffeine or alcohol;
- Illegal drugs, such as cocaine or methamphetamine.
Diagnosis of SVT
If you think you have SVT, you should see a doctor as soon as possible. Your doctor will ask you about your symptoms, such as:
- When did you first notice them?
- How do they start (for example, during exercise or at rest)?
- Do they have any connection to caffeine intake or stress level?
- Do they come on suddenly or gradually?
- How long do they last?
- Do you or anyone in your family have any history of heart problems or procedures?
Your doctor will also examine you and check your:
- Heart rate and rhythm;
- Blood pressure;
- Thyroid gland;
- Blood sample.
Tests and Treatments for SVT
If you have symptoms of SVT, your doctor may recommend some tests to diagnose your condition and find the best treatment for you. These tests may include:
- ECG or EKG: This is an electrocardiogram that records your heart rhythm over time and detects any abnormalities. It involves attaching six sticky patches (electrodes) on your chest and some others on your arms and legs. You will have to breathe normally and lie still while the test is done.
- Electrophysiology study: This is a test that allows doctors to study the electrical signal in your heart and how it travels through each part of your heart. You will be given a sedative to make you relaxed and sleepy during the test. The doctor will insert thin wires (catheters) through a vein in your groin or neck and guide them to your heart. The catheters will send electrical impulses to your heart and record its response.
- Holter monitor: This is a small portable EKG that records your heart’s activity for 24 to 48 hours. You will have to wear electrodes on your chest and carry a small device that records the signals. You can do your normal daily activities while wearing the monitor, except for showering or bathing.
- Event monitor: This is another type of portable EKG that can be worn for days or weeks, depending on how often your symptoms occur. You will have to activate the monitor when you feel an episode of SVT, so that it can record your heart rhythm at that moment.
The treatment for SVT depends on the cause, the frequency, and the severity of your symptoms, as well as how you respond to different medications. Some of the possible treatments are:
- Medicines: These are drugs that can slow down your heartbeat or prevent episodes of SVT. You may have to take them regularly or only when you have an attack. Some examples are beta blockers, calcium channel blockers, and antiarrhythmics.
- Ablation: This is a procedure that destroys the pathway or circuit that causes the abnormal electrical signal in your heart. You will be given a sedative and a local anesthetic before the procedure. The doctor will insert catheters through a vein in your groin or neck and guide them to your heart. The catheters will deliver heat, cold, or radiofrequency energy to the target area, creating a scar tissue that blocks the signal.
It is important that you see a doctor if you experience any of the symptoms of SVT. SVT can affect your quality of life and increase your risk of complications, such as stroke or heart failure.