Supraventricular Tachycardia: What It Is, Types, and Causes

The heart suddenly speeds up: 150, 180, 200 beats per minute — and just as suddenly returns to normal. This is often what supraventricular tachycardia looks like: the first episodes often appear at age 25–40, although SVT is possible at any age. We explain the terms from an ECG report — without panic and without unnecessary words.

What supraventricular tachycardia is

Supraventricular tachycardia (SVT) is a condition in which the heart suddenly beats noticeably faster than normal and then sharply slows down. The cause is a malfunction in the electrical system that controls the rhythm. A normal resting pulse is 60–100 beats per minute; with SVT it jumps above 100. An episode can occur at rest or during exercise.

An episode usually lasts several minutes, sometimes hours. Frequency varies: several times a day or once a year. Age offers no protection, but in many people the first symptoms appear between ages 25 and 40. The sensations may be as follows:

• palpitations that you can clearly feel;
• pain or discomfort in the chest;
• shortness of breath, weakness, dizziness, sweating;
• anxiety or panic during the episode;
• sometimes — fainting.

There may be no other symptoms at all.

Paroxysmal and non-paroxysmal tachycardia: what the difference is

Paroxysmal tachycardia refers to episodes with a sudden onset and an equally sudden end. In paroxysmal supraventricular tachycardia (PSVT), the rhythm is fast but regular: 150–240 beats per minute, and episodes last from seconds to several hours. Prevalence is about 2.3 per 1000 people, and women are affected more often than men.

The paroxysmal form is distinguished precisely by the sudden onset and equally sudden end of the episode: this is the word in the report that indicates a paroxysmal course. Details about the non-paroxysmal form are best clarified with a cardiologist.

Myth: if an episode has passed on its own, no examination is needed. Fact: recurring rapid heartbeat is a reason to have an ECG and understand exactly what is happening with the rhythm.

Atrial tachycardia and other types

Behind the abbreviation SVT are several mechanisms. The most common is atrioventricular nodal reentrant tachycardia, 56% of cases: a reentry loop of the impulse appears in the AV node. Next is atrioventricular reentrant tachycardia — 27%: an additional electrical pathway between the atria and ventricles is at work, sometimes in association with Wolff-Parkinson-White syndrome. Atrial tachycardia accounts for 17%: signals originate in the atria, the upper chambers of the heart. A rare junctional tachycardia arising from the area where the atria and ventricles meet is also distinguished separately.

Causes of paroxysmal tachycardia

The exact cause is often unknown. The mechanism is usually the same: an extra pathway for impulse conduction and reentry of the signal. Risk factors: alcohol, psychostimulants (caffeine, nicotine, amphetamines), psychological stress, Wolff-Parkinson-White syndrome, which is often inherited. Triggers include caffeine, alcohol, and certain substances — but often there is no obvious trigger.

The risk picture for arrhythmias is broader: a previous heart attack, smoking, congenital heart defects, stress, a family history of arrhythmias, diseases of the heart and lungs, kidneys, obesity, sleep apnea, older age, surgery on the heart, lungs, or throat, certain medications, and illicit substances.

How supraventricular tachycardia is diagnosed

The main tool is an ECG: in PSVT, narrow QRS complexes and a rhythm above 150 beats per minute are seen. The doctor asks about symptoms and habits, performs an examination, listens to the rhythm and pulse, checks the legs and feet for swelling, and looks for signs of other conditions, such as thyroid disease. Blood tests and other heart tests are ordered; cardiac ultrasound helps rule out structural problems.

Why it is dangerous and when to see a doctor

SVT rarely threatens life, and the prognosis is usually favorable if the heart is otherwise normal. The longer and more frequent the episodes, the higher the chance that hospital care will be needed. Uncontrolled arrhythmias in general can damage the heart, brain, and other organs. With recurring rapid heartbeat, go to a general practitioner or cardiologist: a conversation, examination, and ECG provide the first answer.

Supraventricular tachycardia by itself is not a reason to call 103 or 112. Call an ambulance if a diagnosed SVT lasts longer than usual, and also for a rapid pulse with shortness of breath, chest pain, a presyncopal state, or fainting. Do not drive in such a situation.

This material is for reference: it helps you understand the terms and formulate questions for your doctor, but it does not replace a cardiologist's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer