Supraventricular Tachycardia (SVT) describes an abnormally fast heart rhythm that begins in the upper chambers of the heart, above the ventricles. During an SVT episode, the heart rate can suddenly increase, often beating between 150 to 220 times per minute, making it challenging for the heart to fill adequately with blood between beats. This article provides information on immediate steps individuals might take to potentially interrupt an SVT episode, along with details on when medical intervention is necessary. This information is for general understanding and does not replace professional medical guidance for diagnosis or treatment.
Immediate Self-Help Techniques
Vagal maneuvers are physical actions that stimulate the vagus nerve, which helps regulate heart rate, potentially slowing down a rapid heart rhythm like SVT. The Valsalva maneuver involves exhaling forcefully against a closed airway. To perform this, sit or lie down, take a deep breath, and then bear down as if having a bowel movement for approximately 10 to 15 seconds. This action increases pressure within the chest and abdomen, stimulating the vagus nerve, which can help revert the heart to a normal rhythm.
After straining, release the breath and wait at least a minute before attempting the maneuver again if needed. A modified Valsalva maneuver, which involves lying flat and raising the legs to a 45-degree angle immediately after the strain, can also be effective.
Another technique involves stimulating the “diving reflex” by applying a cold stimulus to the face. This can be done by splashing cold water on the face or immersing the face in a bowl of ice water for about 10 seconds. This reflex triggers a slowing of the heart rate.
Strong, sustained coughing can also generate pressure in the chest and stimulate the vagus nerve, similar to the Valsalva maneuver. The cough must be forceful and sustained for it to have an effect on the heart rhythm. Carotid sinus massage is another vagal maneuver, but it carries risks, such as stroke, and should only be performed by a healthcare professional. These self-help techniques are not always effective; stop if symptoms worsen or if the episode does not resolve.
When to Seek Emergency Medical Care
Recognize when an SVT episode requires immediate medical attention, even if self-help techniques have been attempted. If the rapid heart rate does not subside after a few minutes, seeking emergency care is advised. Persistent symptoms indicate that the episode may not resolve on its own.
Certain severe symptoms accompanying an SVT episode warrant calling emergency services. These include chest pain or pressure, severe shortness of breath, dizziness, lightheadedness, fainting, or extreme weakness. These symptoms suggest that the heart may not be effectively pumping blood, leading to insufficient oxygen supply to organs and tissues.
Individuals with pre-existing heart conditions, such as coronary artery disease or valvular heart disease, should seek immediate medical care even for milder or shorter episodes of SVT. Their underlying health status can make them more susceptible to complications. If there is any doubt about the severity of an SVT episode or if significant distress is present, contacting emergency services is the safest course of action.
Medical Treatments for SVT Episodes
When self-help measures are ineffective, healthcare professionals have several interventions to restore a normal heart rhythm. Intravenous medications are commonly used to terminate SVT. Adenosine is often a first-line medication, administered as a rapid intravenous push. It works by temporarily blocking electrical conduction through the atrioventricular (AV) node, interrupting the reentrant circuit that causes the rapid heartbeat. Adenosine has a very short half-life, typically less than 10 seconds, meaning its effects are rapid and brief.
Other medications that may be administered intravenously include beta-blockers or calcium channel blockers. These drugs work to slow the heart rate and reduce the excitability of heart cells. The choice of medication depends on the patient’s specific condition and the type of SVT.
If medications are ineffective or if the patient is hemodynamically unstable, electrical cardioversion may be employed. This procedure involves delivering a controlled electric shock to the chest through paddles or adhesive pads. The shock is synchronized with the heart’s electrical activity to reset the heart’s rhythm, allowing the normal pacemaker (the sinus node) to resume control. Electrical cardioversion is effective for many types of irregular heartbeats.
For individuals experiencing recurrent SVT episodes, long-term management options might be discussed. These could include daily oral medications to prevent episodes or a procedure called catheter ablation. Catheter ablation involves using thin, flexible tubes threaded through blood vessels to the heart, where targeted energy is used to destroy the small area of heart tissue responsible for the abnormal electrical signals causing SVT. These long-term treatments are considered after careful evaluation by a cardiologist.