Supraventricular Tachycardia (SVT)
What is SVT?
Supraventricular tachycardia is a general term for rapid rhythms arising above the ventricles, the lower chambers of the heart. In everyday practice, SVT often refers to regular episodes that begin and end suddenly. The precise mechanism needs to be identified because different rhythms require different treatment.
What symptoms can occur?
- Sudden rapid palpitations.
- A pounding sensation in the chest or neck.
- Dizziness or feeling faint.
- Breathlessness.
- Chest discomfort, weakness or anxiety during an episode.
- Less commonly, fainting or low blood pressure.
Episodes may last seconds, minutes or longer. Some patients are entirely well between episodes. A normal resting ECG between attacks does not exclude SVT.
What are the common types?
AV nodal re-entrant tachycardia (AVNRT)
An electrical circuit in or around the atrioventricular node sustains the rapid rhythm. This is a common cause of sudden regular palpitations.
AV re-entrant tachycardia (AVRT)
The circuit uses an additional electrical connection between the atria and ventricles. Some people have a visible accessory-pathway pattern on their resting ECG, as in Wolff–Parkinson–White syndrome; others do not.
Atrial tachycardia
A rapid rhythm arises from an atrial focus or circuit outside the normal sinus node. Further assessment helps distinguish it from other atrial arrhythmias.
What can trigger an episode?
Stress, sleep deprivation, alcohol, stimulants and excess caffeine may contribute in some people. An episode can also begin without an obvious trigger. Thyroid disease and other medical problems may need assessment, but many SVTs are related to the heart's electrical pathways rather than structural damage.
How is it diagnosed?
An ECG during symptoms is particularly useful. If it is safe to do so, seek medical assessment during an episode rather than relying only on pulse readings. Holter or longer monitoring can record intermittent events. A suitable wearable ECG may provide additional information, but its tracing requires medical interpretation.
Echocardiography evaluates cardiac structure and function. Blood tests may assess thyroid function and electrolytes. An electrophysiological study can identify the mechanism and may be combined with catheter ablation.
How is an episode treated?
Treatment depends on the recorded rhythm and the patient's stability. In selected stable, regular SVTs, clinician-taught vagal manoeuvres may help. Do not perform carotid massage yourself. Medicines such as adenosine may be administered under monitoring for appropriate rhythms.
Electrical cardioversion may be needed when a tachycardia causes significant circulatory instability. An irregular rapid rhythm or suspected accessory-pathway problem requires particular care; medicines suitable for one rhythm may be unsafe for another.
Can SVT be prevented?
Long-term options include observation for infrequent, well-tolerated episodes, appropriate medication or catheter ablation. Treatment is selected according to the mechanism, frequency, symptoms, other conditions and patient preference.
Catheter ablation
Thin catheters are advanced through blood vessels to locate the responsible electrical pathway or focus. Ablation aims to interrupt the abnormal circuit. It can provide lasting control for many common re-entrant SVTs. Success and procedural risks vary with the mechanism and location.
Is SVT dangerous?
Many common SVTs in an otherwise healthy heart are treatable and do not usually cause life-threatening complications. However, a very fast or prolonged episode can impair circulation, and risk differs with the rhythm and underlying disease. Symptoms should not be dismissed without an ECG-based diagnosis.
When is it an emergency?
Palpitations with fainting, severe chest pain, marked breathlessness, confusion or serious weakness require immediate medical assessment. Call 112. Do not drive yourself if you feel faint or unwell.
Assoc. Prof. Sezen Bağlan Uzunget, MD — Cardiologist
This information is educational. Diagnosis and treatment require individual rhythm assessment.
Türkçe: Supraventriküler Taşikardi (SVT)