How do I explain supraventricular tachycardia (SVT) to a patient?

How to Explain SVT to a Patient

Supraventricular tachycardia (SVT) is an electrical short-circuit in your heart that causes sudden episodes of very rapid, regular heartbeats—typically 150-300 beats per minute—that start and stop abruptly, like flipping a light switch on and off. 1

What SVT Is in Simple Terms

• SVT is an abnormal heart rhythm that originates in the upper chambers of your heart (the atria) or in the electrical wiring between the upper and lower chambers 1, 2
• The condition involves an extra electrical pathway or a loop in the heart's wiring system that allows electrical signals to circle around repeatedly, causing your heart to beat very fast 1
• Most people with SVT have structurally normal hearts—there's nothing wrong with the heart muscle itself, just the electrical system 1, 3

What Episodes Feel Like

Patients typically experience: 1

• Sudden onset of rapid, regular palpitations—your heart feels like it's racing or pounding
• Lightheadedness or dizziness
• Chest discomfort or pressure (not typically severe pain)
• Shortness of breath
• Fatigue or weakness
• Anxiety from the sensation
• Rarely, fainting (occurs in about 15% of patients, usually right when the episode starts) 1

The hallmark feature is that episodes start suddenly—like someone flipped a switch—and stop just as abruptly, rather than gradually speeding up or slowing down like normal exercise-related heart rate changes 1

Why It Happens

• SVT occurs because of an extra electrical pathway in your heart or abnormal properties in the heart's natural pacemaker system that create a circular electrical loop 1, 3
• This is usually something you're born with, though episodes may not start until later in life 1
• Episodes can be triggered by caffeine, alcohol, stress, lack of sleep, or sometimes occur without any identifiable trigger 1
• The condition most commonly affects younger individuals without other heart disease, though it can occur at any age 1

What Makes It Different from Normal Fast Heart Rate

Unlike normal sinus tachycardia (when your heart speeds up gradually with exercise or stress), SVT has these distinct features: 4

• SVT starts and stops suddenly, not gradually 1, 4
• Heart rates are typically much faster (150-300 bpm) compared to normal exercise-related increases (rarely over 180 bpm in adults) 4
• The rhythm is extremely regular—like a metronome—after the first few beats 1, 4
• Episodes occur without an obvious reason like exercise, fever, or stress 4

Is It Dangerous?

• SVT is usually not life-threatening, but it can significantly impact your quality of life and cause considerable anxiety 5
• The unpredictable nature of episodes causes many patients to limit their activities out of fear 5
• If episodes are prolonged (lasting weeks to months with persistent fast rates), SVT can rarely weaken the heart muscle, a condition called tachycardia-mediated cardiomyopathy 1
• About 15% of patients may experience fainting, particularly when episodes first start 1

What Happens Next

Your doctor will want to capture the rhythm on an ECG (heart tracing) during an episode to confirm the diagnosis and determine the specific type of SVT 1

• You may need to wear a heart monitor (Holter monitor or event recorder) to catch an episode 2, 3
• An echocardiogram (ultrasound of your heart) may be done to ensure there's no underlying structural heart problem 1
• Blood tests may be ordered to rule out thyroid problems or other conditions that can cause fast heart rates 2

Treatment Options Available

For acute episodes: 1, 2

• Vagal maneuvers (bearing down, holding your breath, or putting your face in ice water) can sometimes stop episodes
• Medications given in the emergency department (like adenosine) can terminate episodes immediately
• Cardioversion (electrical shock) is used only if you're unstable

For long-term management, you have two main options: 2, 3

• Catheter ablation: A minimally invasive procedure that fixes the electrical short-circuit permanently, with a 95% success rate and less than 5% recurrence rate 3, 6
• Daily medications (beta-blockers or calcium channel blockers) to prevent episodes, though these don't cure the problem 2, 3

Catheter ablation is now recommended as first-line treatment for recurrent, symptomatic SVT because of its high success rate and low risk 2, 6

Common Pitfalls to Avoid

• Don't dismiss episodes as "just anxiety"—sudden-onset, rapid, regular palpitations are characteristic of SVT and warrant proper evaluation 5
• Episodes often terminate before you reach medical care, but this doesn't mean they're not real or don't need treatment 5
• If you have SVT with certain ECG patterns (called pre-excitation or Wolff-Parkinson-White syndrome), you need prompt evaluation by a heart rhythm specialist due to potential risks 1