Supraventricular Tachycardia (SVT) is a common type of abnormally fast heart rhythm, where the heart beats rapidly, often starting and stopping suddenly. This condition arises from irregular electrical signals within the upper chambers of the heart. The goal of “converting to sinus rhythm” is to restore the heart’s normal, regular beat, which originates from its natural pacemaker.
Understanding SVT and Normal Heart Rhythm
SVT is characterized by a rapid heart rate that originates above the heart’s lower chambers, or ventricles. During an SVT episode, the heart can beat between 150 to 220 times per minute, significantly faster than the typical resting rate of 60 to 100 beats per minute. This rapid beating reduces the time available for the heart’s chambers to fill with blood, potentially affecting the amount of blood pumped to the body.
Common symptoms during an SVT episode include:
- Palpitations (a pounding or fluttering sensation in the chest)
- Lightheadedness
- Dizziness
- Shortness of breath
- Chest pain
- Sweating
- Weakness or extreme tiredness
In contrast, a normal sinus rhythm represents the heart’s natural electrical activity, where impulses begin in the sinoatrial (SA) node and travel in an organized pattern to ensure efficient blood pumping.
Methods for Converting SVT
Various methods are employed to convert SVT back to a normal sinus rhythm, ranging from simple physical maneuvers to medical interventions. These approaches aim to interrupt the abnormal electrical pathways causing the rapid heart rate.
Vagal maneuvers are often the initial step for stable SVT episodes, working by stimulating the vagus nerve, which helps slow electrical conduction through the AV node. Common techniques include:
- Valsalva maneuver (bearing down as if having a bowel movement or blowing into a closed glottis)
- Coughing
- Gagging
- Applying an ice-cold, wet towel to the face (which can activate a “diving reflex”)
While vagal maneuvers can be effective, medical supervision is advised for certain techniques like carotid sinus massage.
When vagal maneuvers are not successful, medications are used to restore a normal rhythm. Adenosine is a first-line medication administered intravenously, known for its rapid action. It works by temporarily blocking electrical signals in the AV node, effectively interrupting the rapid rhythm. Calcium channel blockers, such as verapamil or diltiazem, and beta-blockers like metoprolol, are alternative intravenous medications that can also slow AV nodal conduction and terminate acute SVT episodes.
In urgent or resistant cases, electrical cardioversion may be employed. This procedure involves delivering a controlled electrical shock to the chest to reset the heart’s rhythm. Unlike defibrillation, which uses a stronger shock for cardiac arrest, synchronized cardioversion is performed on patients who still have a pulse but are experiencing unstable symptoms. The electrical current temporarily depolarizes heart cells, allowing the heart to resume normal control.
When to Seek Medical Help
Recognizing when to seek medical attention for SVT symptoms is important. While SVT is often not life-threatening, certain symptoms warrant immediate medical evaluation.
Individuals should seek immediate medical help by calling emergency services if a very fast heartbeat lasts for more than a few minutes, or if it occurs alongside severe symptoms, including:
- Chest pain
- Severe shortness of breath
- Fainting or near-fainting spells
- Significant dizziness
These symptoms may indicate that the heart is not pumping enough blood to the body, potentially leading to complications. If vagal maneuvers have been attempted and are ineffective in slowing the heart rate, medical intervention becomes necessary. Consulting a doctor is also advisable if SVT episodes become more frequent, last longer than usual, or cause increasing concern, even if immediate severe symptoms are not present.
Managing SVT and Preventing Future Episodes
After an SVT episode is converted, ongoing management and preventive strategies can help reduce future occurrences. Lifestyle modifications play a significant role in this long-term approach.
Avoiding common triggers like excessive caffeine, alcohol, and nicotine can help prevent SVT episodes. Managing stress through techniques such as deep breathing exercises, meditation, or yoga can also reduce the frequency of episodes. Maintaining a heart-healthy diet, along with regular, moderate exercise, contributes to overall cardiovascular health and can stabilize heart rhythm. Staying well-hydrated and ensuring adequate sleep are also beneficial practices.
For individuals with recurrent SVT, ongoing medication may be prescribed to prevent future episodes. These can include oral beta-blockers, calcium channel blockers, or antiarrhythmic drugs. In cases where medication is not effective or causes undesirable side effects, a more permanent procedure called catheter ablation may be considered. During this procedure, thin tubes are guided into the heart to identify and destroy the small area of heart tissue responsible for the abnormal electrical signals.