It’s easy to confuse atrial fibrillation (AFib) with what’s called supraventricular tachycardia (SVT). After all, both have to do with your heart rate and both start in the upper chambers of your heart. But they’re actually quite different. AFib is a heart rhythm problem where your heart’s upper chambers (the atria) beat irregularly. But SVT is a fast heart rate that begins in your atria due to abnormal electrical connections in your heart.
There are effective treatments for both so that you can live a full and productive life. Here are some important differences (and similarities) between the two.
What Causes Atrial Fibrillation?
AFib is quite common. It affects about 2.7 million American adults. The biggest risk factor is age. Most people who get AFib are over the age of 65. In AFib, your atria don’t work correctly because of abnormal electrical activity. Your heart can’t move blood out of your heart’s upper chambers (atria) as quickly, which raises your risk for blood clots that can lead to a stroke.
Besides age, there are other risk factors for AFib:
- Heart disease
- Previous heart attack
- Heart failure
- Alcohol and binge drinking
- Hyperthyroidism or an overactive thyroid gland.
- Certain medications – Drugs that stimulate the heart, like the asthma medication theophylline, can trigger AFib.
- Sleep apnea
- Chronic kidney disease
What Causes Supraventricular Tachycardia?
SVT is also caused by abnormal electrical activity, which triggers a fast heart rate. When your heart beats too fast, it can’t fill with blood between beats. This makes it hard to get enough blood to the rest of your body.
Women are more at risk for SVT than men. You are also more likely to develop SVT if you:
- Have anxiety
- Use alcohol heavily
- Drink a lot of caffeine
Types of AFib and Supraventricular Tachycardia
Types of AFib
The three main types of AFib are:
Paroxysmal AFib. This kind of AFib lasts less than 1 week. It usually goes away without treatment.
Persistent AFib. This is AFib that lasts longer than 1 week and requires treatment.
Long-standing persistent AFib. This form of AFib can go on for more than a year. It's often difficult to treat.
Types of SVT
The three main types of SVT are:
Atrial tachycardia (AT). Your sinoatrial (SA) node is the only place that can create a new electrical impulse to cause a heartbeat. But if you have AT, an extra area in your atria is sparking electrical impulses. If you have more than one site sending out these pulses, it’s called multifocal atrial tachycardia (MAT). Most often, MAT is diagnosed only in people who have a major illness of the heart and lungs. It goes away once the other problem is treated.
Atrioventricular reciprocating tachycardia (AVRT). This happens when cells in your heart send electrical impulses in an extra circle. Normally, each signal your SA node sends out stops once it travels through all the chambers and causes a single heartbeat. This node must start a new electrical pulse to get the next heartbeat going. But with this kind of tachycardia, the signal loops back to the atrioventricular (AV) node after it’s traveled through the ventricles instead of moving along as it should. That’s what ends up causing the extra heartbeats.
Atrioventricular nodal reentrant tachycardia (AVNRT). This is the most common kind of SVT. You may also hear it called AV nodal reentrant tachycardia. If you have this type, the cells near your AV node don’t send electrical impulses through your heart the way they should. The cells create a circular signal around the node instead of simply passing them along. The signal, which spurs each chamber of your heart to beat, is moving in a small circle like a car around a race track. That is what causes the extra beats.
There are other forms of SVT, including:
Premature atrial contractions (PACs)
Paroxysmal supraventricular tachycardia (PSVT)
Accessory pathway tachycardias (like Wolff-Parkinson-White syndrome)
What Are the Symptoms of AFib vs. SVT?
AFib and SVT can have similar symptoms, which include:
- Heart palpitations
- Chest tightness or mild pain
- A feeling that your heart is racing
- Mild shortness of breath, especially when you work out
More severe symptoms include trouble breathing, especially during exercise, fainting, chest pain, and severe fatigue.
If you have SVT, you are more likely to notice that your heart is racing. Many people have a fast heartbeat that’s more than 100 beats per minute, even when they are at rest. This can last for hours. Serious SVT can cause you to pass out or go into cardiac arrest.
How Are AFib and SVT Diagnosed?
Both conditions are usually diagnosed via an electrocardiogram (EKG). This is a test that measures your heart’s electrical activity. Your doctor may want you to wear a Holter monitor for a couple of days. It’s an EKG device that monitors your heart activity. Some smartwatches may also be able to monitor your heart rhythm.
Your doctor may also run the following tests if you have AFib to see if you have another medical condition that’s causing symptoms:
- Echocardiogram, a heart ultrasound, to look for heart failure or heart valve problems
- Blood tests to screen for thyroid disorders
- Sleep studies and lung function tests to look for sleep apnea or lung disease
How Is AFib Treated vs. SVT?
Most people with SVT do not need treatment. But if they do, there is some overlap in how doctors treat both conditions. For both AFib and SVT, your doctor may prescribe medications to bring down your heart rate. They include:
- Beta-blockers like carvedilol (Coreg) and metoprolol (Lopressor, Toprol XL)
- Calcium channel blockers like diltiazem (Cardizem) or verapamil (Cala SR, Verelan, Verelan PM)
- Digoxin (Digitek, Lanoxin)
Many people with AFib also take an anticoagulant medicine to help prevent a stroke, where a blood clot travels from the heart to the brain. Anticoagulant medication can prevent about 60% of strokes due to AFib. They do carry a very small risk of bleeding.
There are other, nondrug treatments that are sometimes used to treat either AFib or SVT. They include:
- Cardioversion. An electrical current is applied to the heart to fix its rhythm.
- Ablation. It uses heat or cold to destroy the small part of the heart that sends abnormal electrical signals.
- Pacemaker. This is a device implanted in your body that sends electrical signals to your heart to control your heartbeat.
There are also some techniques your doctor may also recommend for SVT that generally aren’t used for AFib.
Carotid sinus artery massage. Your doctor will apply gentle pressure on your neck, where your carotid artery splits into two branches. This causes your body to release chemicals that slow the heart rate. Always have a medical professional do this. Don’t try it on your own.
Physical maneuvers on your vagus nerve. Your doctor may ask you to do one of these actions while you have an episode of SVT:
- Bear down as if you are having a bowel movement
- Put an ice pack on your face
These all affect your vagus nerve, which helps control your heartbeat.
Can You Prevent AFib or SVT?
You can reduce your chances of getting either AFib or SVT, or make them less severe, if you do the following:
- Control your blood pressure.
- Limit alcohol.
- Cut down on caffeine.
- Get treatment for thyroid disease.
- Get regular exercise.
- Lose weight if you are overweight.
- Reduce stress.
What's the Outlook for AFib or SVT?
You can live a long and healthy life with either condition. AFib does increase your risk of stroke: About 5% of people with AFib have a stroke each year, which is anywhere from two to seven times the rate of stroke in people without AFib. Age plays a big role, though: While the rate is only 1.5% if you’re in your 50s, it goes up to 30% in your 80s. You can reduce much of this risk by following the treatment your doctor recommends. This includes regular use of blood thinners.
Most people with SVT are able to manage their symptoms through lifestyle. If you can’t, your doctor may recommend medication or possibly an ablation. This has a cure rate among people with SVT of about 95%.