Supraventricular Tachycardia (SVT) is an abnormally fast heart rhythm, or arrhythmia, that originates in the heart’s upper chambers (atria) or the atrioventricular (AV) node. During an SVT episode, the heart rate suddenly increases, often reaching 150 to 220 beats per minute, significantly faster than the normal resting rate of 60 to 100 beats per minute. This rapid rate is typically caused by a faulty electrical circuit in the upper heart structure. While SVT is often not life-threatening, an attack can be frightening and cause symptoms like heart fluttering, dizziness, and shortness of breath. This information provides a general understanding of managing an SVT episode.
Vagal Maneuvers for Self-Correction
The immediate goal during a stable SVT episode is to stimulate the vagus nerve, which releases chemicals that slow electrical impulses passing through the AV node. These physical actions, known as vagal maneuvers, are the first self-management technique recommended by healthcare providers. The most commonly effective self-applied method is the Valsalva maneuver, involving forceful exhalation against a closed airway. To perform this, sit or lie down comfortably, take a deep breath, and then bear down strongly for about 10 to 15 seconds, similar to the effort involved in a bowel movement.
The modified Valsalva maneuver is substantially more effective than the standard version, with success rates roughly doubling to around 43% in clinical studies. This modification involves lying supine immediately after the 15-second strain phase, and then raising the legs to a 45-degree angle for an additional 15 to 60 seconds. This postural change increases blood return to the heart, enhancing the vagal nerve stimulation required to revert the rhythm to normal sinus rhythm.
Other techniques can be attempted if the Valsalva maneuver is unsuccessful. Forceful, sustained coughing generates enough pressure in the chest cavity to stimulate the vagus nerve and potentially break the abnormal rhythm. Another method involves the diving reflex, triggered by submerging the face in ice-cold water or applying an ice pack to the face or neck for a few seconds. Note that carotid sinus massage, which involves gentle pressure on the neck, should only be performed by a medical professional due to the potential for serious complications.
Identifying Symptoms Requiring Emergency Care
Although many SVT attacks resolve spontaneously or with vagal maneuvers, certain symptoms indicate a medical emergency requiring immediate attention. Patients experiencing an SVT episode with associated chest pain, especially if it is severe or radiates, should seek emergency medical care without delay. The rapid heartbeat prevents the heart chambers from filling properly, which reduces blood flow and can lead to insufficient oxygen supply to the heart muscle.
A persistent feeling of lightheadedness, severe dizziness, or syncope (temporary loss of consciousness) are urgent signs that the body’s organs, particularly the brain, are not receiving adequate blood flow. The onset of profound shortness of breath or extreme weakness suggests hemodynamic instability and warrants an immediate call to emergency services. If a previously diagnosed SVT episode lasts longer than 20 to 30 minutes and does not respond to self-management techniques, proceed to the Emergency Room for professional intervention.
Clinical Treatments for Persistent SVT
When self-administered vagal maneuvers fail to convert the rhythm, or if the patient presents with unstable symptoms, medical interventions become necessary. In a hospital setting, the first-line pharmacological treatment is often an intravenous injection of Adenosine. This drug temporarily blocks electrical conduction through the AV node, effectively resetting the heart rhythm. Adenosine is highly effective, but its use is limited to the hospital setting due to its very short half-life and the need for continuous cardiac monitoring.
If Adenosine is contraindicated or unsuccessful, other intravenous medications, such as beta-blockers or calcium channel blockers, may be used to slow the heart rate. These drugs work by blocking the effects of hormones that accelerate the heart rate or by slowing the electrical signal flow within the heart. For clinically unstable patients—showing symptoms like extremely low blood pressure or signs of shock—synchronized electrical cardioversion may be employed to deliver a controlled electrical shock to the chest wall to immediately reset the rhythm.
For individuals who experience frequent, recurrent SVT episodes, catheter ablation is often the recommended definitive treatment. This minimally invasive procedure involves threading thin, flexible tubes through a blood vessel, usually in the groin, to reach the heart. Radiofrequency energy or cryotherapy is then used to destroy the tiny, abnormal electrical pathway responsible for the rapid rhythm, offering a high success rate that can exceed 95%.
Lifestyle Changes for Long-Term Management
Long-term management of SVT focuses on minimizing the frequency of episodes by identifying and avoiding common triggers. These often include excessive consumption of caffeine, which acts as a stimulant, and alcohol. Nicotine from smoking is also a known trigger that constricts blood vessels and increases heart rate.
Maintaining a heart-healthy lifestyle is foundational for reducing the risk of recurrence. This involves adopting a balanced diet rich in whole grains, fruits, and vegetables, while limiting high-sodium and processed foods. Stress and anxiety are significant non-physical triggers, making stress management techniques, such as meditation or deep breathing exercises, beneficial for maintaining a calmer baseline heart rhythm. Ensuring adequate sleep, typically seven to nine hours for adults, and avoiding dehydration are effective strategies to support overall cardiovascular health.