Supraventricular tachycardia (SVT) is a heart rhythm disorder that originates in the heart’s upper chambers, called the atria. The primary symptom of SVT is a rapid heartbeat.
There are several types of SVT. The most common type of SVT is atrioventricular node reentrant tachycardia (AVNRT), affecting
SVT can cause the heart to beat so quickly that it does not have enough time to fill with blood between beats. This can reduce blood flow to the body and, in severe cases, lead to fainting or a heart attack.
Often, people with SVT may experience discomfort and require treatment.
Keep reading to learn more about how SVT can affect the heart, the symptoms it can cause, and how doctors might treat the condition.
SVT is a heart rhythm disorder or arrhythmia affecting the atria, the top chambers of the heart. The condition can cause people to have episodes of a very fast heart rate.
The typical adult heart rate is 60–100 beats per minute (bpm). In an
How does the heart beat?
The heart has four chambers. The two upper ones are the atria and the two lower ones are the ventricles. People refer to the sinoatrial (SA) node, which is in the right atrium, as the pacemaker.
In a typical heartbeat, the electrical signal that controls heart rate begins in the SA node. The signal travels through the atria to the atrioventricular (AV) node in the lower right atrium. From there, it passes into the ventricles, allowing them to contract and pump blood.
In people with SVT, the electrical signal that initiates the heartbeat comes from somewhere above the ventricle other than the SA node. As a result, the heart rate accelerates, shortening the time the ventricles have to fill with blood. This prevents the heart from pumping blood efficiently to the body.
These episodes of abnormal heart rhythm may last for just a few seconds or go on for several hours. They can also occur often or only once in a while.
- AVNRT: This is the most common type of SVT, accounting for around two-thirds of cases. It happens when the electrical signal travels in a circle, passing through the AV node twice.
- Atrioventricular reciprocating tachycardia: This is another common type of SVT that occurs when a second connection between the upper and lower chambers exists. The electrical impulses then move more quickly.
- Atrial fibrillation (A-fib): The most common type of heart arrhythmia, A-fib will affect more than
12 million people in the United States by 2030, according to estimates. In A-fib, the beating in the atria is irregular, the heart can race, and there can be a higher risk of clots leading to stroke. - Atrial flutter (AFL): With AFL, the atria beat abnormally fast, up to 300 bpm, but the ventricle usually has a regular pattern and conducts at half or another fraction of the rate of the atria. AFL creates a distinct “saw tooth” pattern on an electrocardiogram (ECG), a test doctors use to diagnose arrhythmias.
- Paroxysmal SVT: These are SVT episodes that occur intermittently and usually self-terminate.
- Atrial tachycardia: With this kind of SVT, the electrical signal originates from somewhere other than the SA node.
There is often no specific cause of SVT.
Some people have atypical electrical pathways in their hearts from birth. Other times, SVT can develop later in life because of certain triggers,
- stress
- stimulant medications
- caffeine
- thyroid disease
- alcohol
- cigarette smoking
- electrolyte abnormalities
- a pulmonary embolism
- infection
The symptoms a person with SVT may experience can depend on how quickly their heart is beating.
They may include:
Doctors begin by taking a medical history to help diagnose SVT heart problems. They may ask about symptoms and any family history of heart conditions. They may also check for a pulse in the neck arteries.
Next, they will perform a physical exam, listen to the heart with a stethoscope, and check for abnormal heart sounds. They may also check the thyroid gland in the neck.
Imaging tests, such as a chest X-ray or echocardiogram, can be useful to detect the cause of heart problems. A doctor may also use cardiac MRI in rare cases.
ECG
If doctors suspect SVT, they will likely order an ECG test.
During an ECG, the doctor places sticky electrodes on the chest. The electrodes connect to an ECG machine, which measures the heart’s electrical activity and produces a readout on paper.
A doctor may also provide an ECG device for the person to wear at home. This may be a small Holter monitor to record the heart’s electrical activity for 24 hours or up to 2 weeks.
Alternatively, it may be a wearable event monitor that the individual wears for as long as needed until an episode of SVT happens. An implantable loop recorder is a small monitor that a doctor will fit under a person’s skin to record their heart rhythm for up to 3 years.
If the ECG shows SVT, a doctor may recommend an electrophysiology study to determine the type and cause. This test takes place in the hospital and requires sedation. During the study, doctors insert catheters through the veins in the leg and thread them to the heart. Then, they use electrical signals to stimulate the heart and record the electrical activity on an ECG.
The goal of treatment for SVT is to slow the heart rate and restore a normal heart rhythm. Treatment options may include medications and surgery. The treatment course may depend on:
- the type of SVT
- the frequency of SVT episodes
- the severity and duration of symptoms — people often require no treatment if their symptoms are mild
Brief episodes of SVT
A person can use vagal maneuvers, such as bearing or squeezing down, coughing, or holding their breath, to slow the electrical impulses in the heart.
A doctor may prescribe medications, such as beta-blockers, for a person to take as needed for SVT episodes. These drugs also slow the electrical impulses in the heart.
If the SVT does not resolve, people should visit the emergency room. A doctor may recommend a medication called adenosine or another called verapamil to help the heart beat correctly.
In rare cases, an individual may need an electrical shock to return the heart to a typical rhythm.
Long-term treatment
If someone experiences SVT episodes often, a doctor may prescribe daily medication to prevent them. Beta-blockers and verapamil are common choices. These drugs help slow down the heart’s electrical impulses. Antiarrhythmic medications that are more effective than beta-blockers include flecainide and sotalol.
Doctors may recommend ablation therapy if medications do not work or are unsuitable. With ablation, a doctor uses heat, cold, or radiofrequency waves to destroy the electrical pathway in the heart that is causing SVT.
Ablation is usually successful in treating specific forms of SVT. However, it has some rare but serious risks.
SVT can be unpredictable and can occur without warning. One way to help manage the condition is to avoid triggers. These may include:
- alcohol
- cigarettes
- caffeine
- drugs such as cocaine and methamphetamine
- herbal supplements
It is also important for people to get regular sleep and share any new symptoms with their doctor.
They should consider attending regular checkups and should not use any new medications or supplements without talking with a doctor first.
Generally, SVT is not life threatening, and most people have good outcomes with treatment. The outlook is excellent in healthy people with no structural defects of the heart.
However, in some cases, SVT may lead to complications,
- hematoma
- bleeding
- heart attack
- heart block and the need for a pacemaker
- stroke
In some instances, the condition can even be fatal.
SVT is a type of abnormal heart rhythm that happens when electrical signals make the heart beat too fast. It can cause a racing heart, chest pain, and shortness of breath.
SVT is not typically life threatening, but it can sometimes cause complications. Prompt treatment with medications and surgery can help alleviate the symptoms. People who notice any changes in their heart health should talk with their doctors about any issues they are experiencing.