SVT, or supraventricular tachycardia, is a type of abnormally fast heart rhythm that originates above the heart’s lower chambers (the ventricles). During an episode, the heart typically beats between 150 and 220 times per minute, compared to a normal resting rate of 60 to 100. Episodes start and stop suddenly, can last anywhere from a few minutes to a few days, and often feel like a fluttering or pounding sensation in the chest.
What Happens Inside the Heart
Your heart’s rhythm is controlled by electrical signals that follow a specific path. In SVT, something goes wrong with that signaling above or within the junction between the upper and lower chambers. The result is a rapid-fire loop of electrical activity that forces the heart to beat much faster than it should. Because the heart can’t fill with blood properly at those speeds, you may feel dizzy, lightheaded, or short of breath until the episode breaks.
There are a few distinct types, each involving a different electrical glitch:
- AVNRT (AV nodal reentrant tachycardia): The most common form. Two electrical pathways exist within the heart’s natural relay station (the AV node), and signals get caught in a loop between them.
- AVRT (AV reentrant tachycardia): An extra electrical connection, called an accessory pathway, exists between the upper and lower chambers. Signals travel down the normal route and back up through the extra one, creating a circular circuit.
- Atrial tachycardia: A spot in one of the upper chambers fires electrical impulses too quickly, driving the heart rate up without involving a reentrant loop through the AV node.
How Common SVT Is
About 0.17% of U.S. adults have symptomatic SVT, which translates to roughly 140 to 168 people per 100,000. The incidence of new episodes between 2010 and 2015 was estimated at 73 per 100,000. It’s not rare, but many people go years between episodes or have episodes so brief they never seek medical attention.
Symptoms During an Episode
The hallmark of SVT is a sudden pounding or fluttering in the chest. Most people also notice a pulsing sensation in the neck. Other common symptoms include chest pain, lightheadedness, dizziness, shortness of breath, and anxiety. The onset is typically abrupt, sometimes described as a “switch flipping on,” and termination is equally sudden. Some episodes resolve in seconds; others persist for hours or, rarely, days.
The severity depends partly on heart rate and partly on how long the episode lasts. A brief run at 150 beats per minute might feel uncomfortable but tolerable. A sustained episode at 200 or higher can cause near-fainting or actual fainting because the heart isn’t pumping blood efficiently.
Common Triggers
Episodes are often set off by physical exertion or emotional stress. Alcohol is a well-established trigger. Nicotine and stimulant drugs can also provoke episodes. Caffeine has long been blamed, but the evidence is surprisingly weak. One study gave caffeine to SVT patients before electrophysiology testing and found no measurable effect on the heart’s electrical properties or the ability to trigger SVT. That said, individual sensitivity varies, so some people do notice a personal link between coffee and episodes.
Other triggers include dehydration, sleep deprivation, and sudden position changes. Some people identify very specific patterns over time, like bending over after a meal or standing up too quickly.
How SVT Is Diagnosed
The primary tool is a 12-lead electrocardiogram (ECG), which records the heart’s electrical activity. Doctors look for a fast, narrow-complex rhythm and compare it with recordings taken during a normal heartbeat. When SVT is suspected but hasn’t been captured on a standard ECG, you may wear a portable heart monitor for days or weeks to catch an episode as it happens.
In some cases, a medication called adenosine is given intravenously as both a treatment and a diagnostic test. How the heart responds, whether the rhythm stops, slows, or doesn’t change, helps pinpoint which type of SVT is involved. For AVRT specifically, certain signature patterns on the ECG (a short interval before the main electrical spike and a slurred onset of the heartbeat signal) can point to an accessory pathway even when the heart is in a normal rhythm.
Stopping an Episode at Home
The first-line technique for breaking an SVT episode is a vagal maneuver, which stimulates the nerve that slows heart rate. The most widely used version is the Valsalva maneuver: sit or lie down, take a breath, then bear down as if you’re trying to have a bowel movement while keeping your mouth and nose closed. Hold for 15 to 20 seconds, then release and breathe out.
A modified version, where someone raises your legs immediately after you stop straining, tends to work better. If three attempts don’t break the rhythm, medical treatment is the next step. Other simple techniques include splashing ice-cold water on your face or briefly immersing your face in cold water, both of which activate the same nerve response.
Medical Treatment Options
When vagal maneuvers fail in an acute episode, doctors typically use a fast-acting intravenous medication that briefly interrupts electrical conduction through the AV node, resetting the rhythm. The effect is almost immediate, though many people describe a brief, intense sensation of chest pressure or flushing that passes within seconds.
For people who have frequent or bothersome episodes, long-term options include daily oral medications (beta blockers or calcium channel blockers) that slow conduction through the AV node and make episodes less likely. These don’t cure SVT but can reduce how often episodes happen and how fast the heart goes when they do.
Catheter ablation is the closest thing to a cure. A thin wire is threaded through a blood vessel to the heart, and the small area of tissue responsible for the abnormal electrical circuit is destroyed using heat or cold. Success rates are 90% to 95% for most types of SVT. Recurrence happens in 2% to 11% of cases, and a second procedure can usually address it. Many people choose ablation to avoid taking daily medication indefinitely.
Long-Term Risks
Most people with occasional SVT episodes face no serious long-term consequences. The condition is not typically life-threatening. However, when SVT is frequent, prolonged, or poorly controlled over months to years, the sustained rapid heart rate can weaken the heart muscle, a condition called tachycardia-induced cardiomyopathy. This has been documented across several types of fast rhythms, including SVT.
The good news is that this type of heart muscle weakening is largely reversible. Once the arrhythmia is controlled through medication or ablation, heart function tends to improve substantially. Research following patients for a median of about six years found that overall survival was similar to other forms of heart muscle disease, but people with tachycardia-induced cardiomyopathy were more likely to be rehospitalized, usually because the arrhythmia came back. This makes reliable rhythm control especially important for anyone who has developed signs of heart weakening from SVT.