Rapid Heartbeats from the Upper Chambers: Understanding Supraventricular Tachycardia
Supraventricular Tachycardia (SVT)
What is SVT?
Supraventricular tachycardia (SVT) is an abnormally fast heart rhythm that originates in the atria, the top chambers of the heart, or in the electrical connection between the atria and ventricles (the AV node). SVT is a broad term that covers several specific types of rapid heart rhythms. These may occur sporadically or be sustained for longer periods. Understanding SVT helps you recognize symptoms, identify triggers, and explore treatment options.
How the normal heart beats
Your heart relies on a finely tuned electrical system to pump blood efficiently. The impulse starts in the sinoatrial (SA) node, your heart’s natural pacemaker, and travels through the atria to the atrioventricular (AV) node. The AV node then directs the signal to the ventricles, ensuring coordinated contraction of the heart chambers. This precise timing keeps blood flowing effectively throughout your body.
Causes of SVT
SVT occurs when part of the atria or the AV node overrides the SA node, triggering rapid heartbeats. The main types of SVT include:
Atrial tachycardia: A portion of the atria fires electrical signals independently of the SA node, causing a rapid rhythm.
Atrioventricular nodal reentrant tachycardia (AVNRT): A short circuit forms within the AV node, producing fast, repeated heartbeats.
Atrioventricular reentrant tachycardia (AVRT): An extra electrical pathway between the atria and ventricles allows a looping signal, often associated with Wolff-Parkinson-White (WPW) syndrome.
Symptoms of SVT
SVT episodes usually start and stop suddenly. Common signs include:
Palpitations or a rapid fluttering heartbeat
Awareness of your heartbeat in your throat or chest
Shortness of breath or reduced exercise capacity
Dizziness, lightheadedness, or fainting
Chest discomfort or pressure
Some people experience frequent episodes for years and may have been misdiagnosed with anxiety or panic attacks.
Is SVT dangerous?
For most people with a structurally normal heart, SVT is not life-threatening. However, certain types, such as those associated with WPW, can rarely cause serious complications.
Diagnosing SVT
Because SVT can appear intermittently, capturing an episode is crucial for diagnosis. Methods include:
Electrocardiogram (ECG): Records heart rhythm when symptoms occur.
Holter or ambulatory monitor: Continuous ECG recording over 24–48 hours, or up to a week, while you carry on daily activities.
Implantable loop recorder: A small device placed under the skin that can monitor your heart rhythm for up to three years.
Echocardiogram: Ultrasound of the heart to assess structure and function.
Blood tests: Check for electrolyte or hormone imbalances that can trigger arrhythmias.
Triggers
Common triggers include caffeine, alcohol, stress, and sleep deprivation. However, SVT can also occur spontaneously, without an identifiable trigger.
Treatment of SVT
Management depends on the type of SVT, frequency of episodes, and impact on your life. Approaches include:
Conservative measures
Vagal manoeuvres: Techniques like breath-holding, bearing down, or splashing cold water on your face can sometimes stop an episode.
Medications
On-demand therapy: Medications such as adenosine or beta-blockers can terminate an SVT episode.
Preventive therapy: Beta-blockers or calcium channel blockers may reduce episode frequency, though they often do not cure SVT.
Catheter ablation
Curative approach: A minimally invasive procedure that destroys the abnormal electrical pathway responsible for SVT.
Success rate: Over 90%, with low risk of complications.
Procedure: Thin wires are guided to the heart via veins in the leg. Electrical signals are mapped, and the abnormal tissue is ablated to prevent further episodes.
Tips for living with SVT
Keep a record of ECGs or mobile ECG recordings from episodes.
Learn and practice vagal manoeuvres to terminate palpitations.
Track triggers, lifestyle factors, and symptoms to share with your cardiologist.
Outlook
Most people with SVT can live full, active lives with proper diagnosis and management. Catheter ablation offers a potential cure, while medications and lifestyle adjustments help manage symptoms when ablation is not suitable.