AV Nodal Reentrant Tachycardia (AVNRT)

Your heart normally beats 60 to 100 times per minute at rest, with electrical signals traveling smoothly through a relay station between the upper and lower chambers. But in AVNRT, a circular electrical pathway forms within this relay station, causing your heart to suddenly race at 150 to 250 beats per minute. One moment your heart beats normally, the next it’s pounding rapidly in your chest—this abrupt switch is the hallmark of AVNRT. The condition affects people of all ages, often appearing first in young adulthood, and episodes can last seconds to hours before stopping just as suddenly as they started.

Overview

AVNRT is the most common type of supraventricular tachycardia—rapid heartbeat originating above the heart’s lower chambers. It accounts for about 60% of all cases where the heart suddenly starts racing for no obvious reason.

The problem involves your AV node, the electrical relay station sitting between your heart’s upper and lower chambers. Normally, the AV node has one pathway for electrical signals to pass through. In AVNRT, you’re born with two pathways through or near the AV node instead of one—a fast pathway and a slow pathway. These pathways conduct electrical signals at different speeds.

Under certain circumstances, an electrical signal can travel down one pathway and back up the other, creating a circular loop. This circle of electricity spins continuously within or near the AV node, driving your heart to beat very rapidly. The circuit is self-sustaining once it starts—signals just keep going around and around until something breaks the loop.

The rhythm starts suddenly, typically triggered by a premature heartbeat that arrives at just the right moment to enter the circuit. Your heart rate jumps from normal—perhaps 70 beats per minute—to 150-250 beats per minute within one or two beats. Episodes last anywhere from a few seconds to several hours, then stop just as abruptly, returning to normal rhythm within a beat or two.

This sudden on-off pattern is characteristic and helps distinguish AVNRT from sinus tachycardia, where heart rate increases and decreases gradually in response to activity or stress.

AVNRT can occur at any age but most commonly first appears in the teens, 20s, or 30s. Women are affected about twice as often as men. Many people have their first episode during adolescence or young adulthood, though it can start in childhood or even appear for the first time in older adults.

Episode frequency varies enormously. Some people have one or two episodes in their entire lifetime. Others experience weekly or even daily episodes. There’s no way to predict how often episodes will occur—they can be completely random.

The good news is that AVNRT is rarely dangerous in people with otherwise normal hearts. It’s uncomfortable and disruptive but doesn’t damage the heart or increase risk for more serious rhythm problems. More importantly, it’s highly curable with a procedure that has success rates exceeding 95%.

Causes

AVNRT results from the anatomical presence of dual pathways in or near the AV node. You’re born with this electrical setup, though symptoms typically don’t appear until later in life.

• The two pathways have different properties. The fast pathway conducts signals quickly but takes longer to recover and be ready for the next signal. The slow pathway conducts signals more slowly but recovers quickly. Under normal circumstances, signals travel down the fast pathway and the slow pathway sits idle.
• For AVNRT to start, a premature beat must arrive at precisely the right moment—when the fast pathway is still recovering but the slow pathway is ready. The signal then travels down the slow pathway to the lower chambers. By the time it reaches the bottom, the fast pathway has recovered. Instead of stopping, the signal travels back up the fast pathway. When it reaches the top, the slow pathway is ready again, so it goes back down. This creates a continuous loop.
• The circuit exists because of your anatomy—the presence of dual pathways is congenital. However, various factors can trigger episodes. Stress and anxiety commonly precipitate AVNRT by releasing adrenaline that makes the heart more electrically excitable. Caffeine triggers episodes in some people, though sensitivity varies—many people with AVNRT tolerate caffeine without problems. Alcohol can provoke episodes in susceptible individuals. Dehydration lowers the threshold for triggering the circuit. Lack of sleep makes episodes more likely. Hormonal changes during menstrual periods trigger AVNRT in some women.
• Physical triggers include sudden position changes like bending over quickly or standing up suddenly. Exercise triggers episodes in some people, while others find that regular exercise actually reduces frequency. Deep breathing, particularly sudden deep breaths, can initiate episodes.
• Sometimes no trigger is identifiable—episodes occur completely randomly without any apparent cause, which is frustrating but common.

The anatomical substrate that allows AVNRT—the dual pathways—is present from birth. However, why symptoms first appear when they do isn’t fully understood. Changes in the heart’s electrical properties with age and hormonal changes during puberty might explain why AVNRT often first appears in adolescence or young adulthood.

Symptoms

The sudden nature of AVNRT makes symptoms quite distinctive.

• The episode starts abruptly. You’re going about your day with normal heart rhythm, and suddenly within one or two beats, your heart is racing. This sudden switch from normal to very fast is often described as your heart “taking off” or “flipping a switch.”
• Palpitations are universal—you feel your heart pounding rapidly in your chest. The sensation is often described as fluttering, racing, or your heart beating out of your chest. Despite the rapid rate, the rhythm remains regular—beats come at perfectly even intervals, just much faster than normal.
• A fluttering sensation in your neck or throat is common. Some people feel a pounding in their neck as the heart contracts against closed valves, creating pressure waves that pulse in neck vessels.
• Dizziness or lightheadedness occurs because the very rapid rate reduces the time for heart chambers to fill between beats, decreasing the amount of blood pumped with each contraction. Your brain receives less blood flow, causing lightheadedness. However, most people don’t faint from AVNRT—actual loss of consciousness is uncommon.
• Shortness of breath develops because your heart isn’t pumping as efficiently at such rapid rates. You might feel you can’t catch your breath or need to breathe deeply.
• Chest discomfort or pressure can occur, particularly if episodes last for extended periods. The heart is working much harder than normal, which can cause a sensation of pressure or tightness in the chest.
• Anxiety is both a trigger and a result. The sudden onset of rapid heartbeat is frightening, especially the first time it happens. This anxiety releases more adrenaline, potentially prolonging the episode and creating a difficult cycle.
• Fatigue during and after episodes is common. Your heart has been working very hard, which is exhausting. After longer episodes, you might feel tired for hours.
• The need to urinate shortly after episodes affects some people. The rapid heart rate triggers hormone release that increases urine production.
• Nausea sometimes accompanies episodes, particularly if you’re also feeling anxious or dizzy.
• The sudden termination is often as noticeable as the onset. You feel your heart abruptly return to normal, sometimes with a brief pause or strong beat as normal rhythm resumes. This on-off pattern—sudden start and sudden stop—is a key diagnostic clue.

Diagnosis

Diagnosing AVNRT requires capturing the rhythm during an episode and confirming its characteristics.

• Your description of symptoms provides crucial information. The sudden onset and termination are key features. If you can check your pulse during an episode, noting that it’s very fast but perfectly regular helps distinguish AVNRT from other rhythms.
• An electrocardiogram during an episode definitively diagnoses AVNRT. The tracing shows rapid, regular heartbeat with a specific pattern—the electrical activity from the lower chambers often obscures or distorts the normal waves from the upper chambers because signals are traveling through the circuit so quickly. However, capturing an episode on electrocardiogram is challenging since episodes are unpredictable and often brief.
• Extended monitoring helps capture intermittent episodes. Event monitors worn for weeks or months allow you to press a button when episodes occur, recording the rhythm. Some monitors automatically detect and record rapid rates. Smartphone apps that record single-lead electrocardiograms during episodes are increasingly useful for capturing the rhythm.
• If you’ve never had an episode captured but describe classic AVNRT symptoms, your doctor might diagnose presumed AVNRT based on your history, though confirmation during an episode is ideal.
• Testing to trigger AVNRT can be performed if the diagnosis needs confirmation before considering treatment. During an electrophysiology study, catheters inserted into your heart record electrical activity and can trigger AVNRT in a controlled environment. This allows precise identification of the circuit and can be performed immediately before ablation.
• Physical examination between episodes is usually completely normal. Blood tests check for conditions that might mimic or contribute to rapid heartbeat—thyroid function, electrolyte levels, and sometimes caffeine or drug levels.
• Echocardiography evaluates heart structure and function. In people with AVNRT and no other heart problems, this test is normal, which is reassuring. It rules out structural heart disease that might affect treatment decisions.

Treatment

Treatment approaches depend on episode frequency, duration, severity, and how much AVNRT affects your life.

• For stopping acute episodes, vagal maneuvers are simple techniques that stimulate the vagus nerve, potentially breaking the electrical circuit. The Valsalva maneuver—bearing down forcefully as if having a bowel movement while holding your breath for 10-15 seconds—works for many people. The modified version, where you lie down and elevate your legs immediately after bearing down, is even more effective. Immersing your face in ice-cold water triggers a reflex that can terminate AVNRT. These techniques work by temporarily slowing conduction through the AV node, breaking the circuit.
• If vagal maneuvers don’t work, medications given through an IV in emergency or clinic settings can stop episodes. Adenosine is most commonly used, causing a very brief pause in AV node conduction that interrupts the circuit. The medication works within seconds but can cause temporary chest discomfort and flushing. Other medications including beta-blockers or calcium channel blockers also terminate AVNRT.
• For prevention, if episodes are infrequent and brief, you might not need any preventive treatment beyond learning vagal maneuvers. Many people manage occasional episodes this way without medications or procedures.
• Daily medications prevent episodes in people with frequent or prolonged AVNRT. Beta-blockers reduce episode frequency and sometimes make episodes easier to terminate. Calcium channel blockers also prevent AVNRT. These medications don’t cure the condition but reduce how often episodes occur.
• Catheter ablation offers potential cure and is increasingly considered first-line treatment, even for people who’ve had only a few episodes. The procedure destroys one of the two pathways—usually the slow pathway—so the circuit can no longer form. Success rates exceed 95%, and most people never have AVNRT again after successful ablation.
• The procedure involves threading catheters through blood vessels to your heart, mapping the electrical system to locate the pathways, then using heat or cold energy to destroy the slow pathway tissue. It takes several hours, requires overnight hospital stay, and has relatively low complication rates. Recovery is quick—most people return to normal activities within a week.
• The main risk of ablation is damage to the AV node itself, which sits very close to the slow pathway being ablated. This occurs in less than 1% of procedures but would require permanent pacemaker implantation. Despite this small risk, many people choose ablation because success rates are so high and the alternative is either living with unpredictable episodes or taking daily medications indefinitely.

What Happens If Left Untreated

For most people with AVNRT and otherwise normal hearts, leaving the condition untreated isn’t medically dangerous but significantly impacts quality of life.

• AVNRT doesn’t damage your heart or lead to more serious rhythm problems. Brief episodes, even if frequent, don’t harm heart muscle or increase risk for dangerous rhythms. This is reassuring—the condition is more of a nuisance than a medical threat in people with structurally normal hearts.
• However, quality of life can suffer considerably. The unpredictability is extremely frustrating—never knowing when your heart might suddenly start racing creates constant anxiety. This affects work, driving, exercise, social activities, and daily life.
• Some people restrict activities unnecessarily, avoiding exercise, caffeine, or situations where they’ve experienced episodes. This self-imposed limitation reduces quality of life more than the AVNRT itself might.
• Frequent emergency room visits create stress, inconvenience, and expense. Each episode might feel like an emergency, leading to repeated urgent care visits for episodes that could be prevented with treatment.
• Very prolonged episodes lasting many hours can occasionally cause temporary heart muscle fatigue, though this is uncommon and usually reversible with rate control.
• The psychological impact can be profound. Constant worry about when the next episode will occur, fear that something is seriously wrong, and anxiety about experiencing episodes in embarrassing or dangerous situations all reduce wellbeing.
• Some people develop panic disorder or health anxiety after experiencing AVNRT, sometimes having difficulty distinguishing between panic attacks and actual rhythm episodes.

What to Watch For

Most AVNRT episodes don’t require emergency care, particularly once you’ve been diagnosed and know what you’re experiencing.

• Seek emergency care if you experience AVNRT with severe chest pain, especially if pain is crushing or radiating to your arm or jaw. While AVNRT doesn’t cause heart attacks, you could be having one coincidentally.
• Call emergency services if you faint during an episode. Brief lightheadedness is common and not concerning, but actual loss of consciousness warrants urgent evaluation.
• Head to the emergency room if an episode lasts much longer than your typical pattern. If your episodes usually last minutes but one continues for hours despite your usual techniques to stop it, seek medical care.
• Contact your doctor if you’re having your first episode ever. While likely not an emergency, new onset AVNRT warrants evaluation to confirm the diagnosis and discuss treatment options.
• Report to your doctor if episode frequency increases significantly. If you typically have AVNRT once every few months but suddenly experience daily episodes, this change needs evaluation.
• Notify your doctor if episodes are interfering significantly with daily life, work, or causing significant anxiety, even if they’re not medically dangerous.

Living with AVNRT

Managing AVNRT involves learning to stop episodes and deciding whether preventive treatment is worthwhile.

• Learn and practice vagal maneuvers when you’re not having an episode. Knowing how to perform these techniques effectively helps you stop episodes quickly, reducing their impact. The modified Valsalva with leg elevation is particularly effective—practice the movements so you know exactly what to do when an episode starts.
• Identify your personal triggers by paying attention to circumstances when episodes occur. Common triggers include stress, caffeine, alcohol, lack of sleep, or dehydration. Once you know your triggers, you can moderate or avoid them.
• Stay well-hydrated. Dehydration lowers the threshold for triggering episodes in many people.
• Get adequate sleep. Sleep deprivation makes AVNRT more likely.
• Manage stress through techniques that work for you—regular exercise, meditation, counseling, or other methods.
• If you choose to live with AVNRT rather than undergo ablation, understand that this is a reasonable option if episodes are infrequent and easily managed. Not everyone needs aggressive treatment.
• However, don’t hesitate to discuss ablation with your cardiologist if episodes are frequent or significantly affecting your life. The procedure’s high success rate makes it an attractive option for many people.
• If you’ve had successful ablation and episodes recur, contact your cardiologist. While recurrence is uncommon, the pathway can occasionally recover or a different circuit might become active, requiring repeat procedure.

Key Points

• AVNRT is the most common type of supraventricular tachycardia, accounting for about 60% of cases where the heart suddenly races without obvious cause.
• The condition results from dual pathways in or near the AV node that create a circular electrical circuit, causing your heart to suddenly race at 150-250 beats per minute.
• The sudden onset and termination—your heart switches from normal to very fast within one or two beats, then back again just as abruptly—is the key diagnostic clue.
• Vagal maneuvers, particularly the modified Valsalva with leg elevation, successfully terminate many episodes without needing medications or emergency care.
• AVNRT is rarely dangerous in people with structurally normal hearts. It’s uncomfortable and disruptive but doesn’t damage the heart or lead to more serious problems.
• Catheter ablation offers cure rates exceeding 95%, making it an attractive option even for people with infrequent episodes. Many people choose ablation to avoid unpredictable episodes and lifelong medication.
• The procedure is safe with serious complications occurring in less than 1% of cases. The main risk is requiring a pacemaker if the normal AV node pathway is inadvertently damaged during ablation.
• Episode frequency varies enormously and unpredictably. Some people have one or two episodes in their lifetime, while others experience them weekly or daily.
• Women are affected about twice as often as men, and symptoms typically first appear in teens, 20s, or 30s, though AVNRT can start at any age.
• Work with a cardiologist, preferably one specializing in heart rhythm disorders, to determine the best treatment approach for your situation. Factors including symptom frequency, episode duration, how episodes affect your life, and your preferences all influence whether you should pursue ablation, take daily medications, or simply manage episodes as they occur with vagal maneuvers. The goal is finding an approach that allows you to live without constant worry about your heart while minimizing treatment burden. For many people, AVNRT ablation is transformative—eliminating a rhythm problem that significantly impacted quality of life with a single, highly successful procedure.

Reference: AVNRT