What Is SVT?
Supraventricular Tachycardia (SVT) is a group of abnormal heart rhythms that start in the upper chambers of the heart (the atria). In SVT, the heart beats faster than normal-often between 150 and 250 beats per minute. While not usually life-threatening, SVT can cause uncomfortable symptoms and affect one’s quality of life.
The term “supraventricular” means the abnormal rhythm begins above the ventricles, in the atria or the AV node (the connection between the atria and ventricles).
Common Types of SVT
- AV Nodal Reentrant Tachycardia (AVNRT): Most common type; involves a re-entry circuit within or near the AV node.
- AV Reentrant Tachycardia (AVRT): Often seen in people with Wolff-Parkinson-White (WPW) syndrome, involving an extra pathway.
- Atrial Tachycardia: A less common form where the rhythm originates from a single site in the atria.
Symptoms of SVT
SVT can come and go suddenly, lasting for seconds, minutes, or even hours. Symptoms include:
- Rapid heartbeat or palpitations
- Chest discomfort
- Dizziness or lightheadedness
- Shortness of breath
- Fatigue
- Anxiety
- Fainting (less common)
What Triggers SVT?
SVT can occur in healthy hearts or be triggered by:
- Caffeine or alcohol
- Stress or anxiety
- Lack of sleep
- Certain medications e.g., decongestants
- Hormonal changes
- Underlying heart conditions (in some cases)
Is SVT Dangerous?
SVT is usually not dangerous, especially in people with otherwise normal hearts. However, frequent or prolonged episodes can:
- Interfere with daily life
- Lead to fainting or near-fainting episodes
- Occasionally cause heart strain if left untreated over time
Diagnosing SVT
If your doctor suspects SVT, they may order:
- Electrocardiogram (ECG): To capture the rhythm if you’re in SVT during the test
- Holter monitor (ambulatory ECG): an extended ECG monitor used to track your heart rhythm
- Event monitor or loop recorder
- Electrophysiology (EP) study: A specialised test to map the source of the rhythm
Treatment Options for SVT
Treatment depends on the type, frequency, and severity of your episodes.
- Lifestyle Measures & Vagal Maneuvers
- Techniques like bearing down, coughing, or applying cold to the face may stop some episodes.
- Medications
- Medications such as beta-blockers or calcium channel blockers may help control or prevent episodes.
- Cardioversion
- In urgent cases, a brief electrical shock may be used to restore normal rhythm.
- Catheter Ablation
- A minimally invasive procedure which uses techniques including heat (radiofrequency), or Pulsed Field Ablation (PFA) using electroporation (pulses of electric fields) to destroy cardiac cells, thus destroying the abnormal circuit causing SVT. Ablation is often curative, with success rates over 95% in many types of SVT.
When to See a Cardiologist
You should seek specialist care if:
- You experience frequent or prolonged palpitations
- Episodes interfere with daily activities or cause fainting
- You are concerned about your risk or diagnosis
SVT is a manageable condition—and in many cases, it can be completely cured.