Supraventricular Tachycardia (SVT) is a common type of abnormal heart rhythm, or arrhythmia, where the heart suddenly begins beating very rapidly. This fast heart rate originates in the upper chambers of the heart, the atria, a location “above the ventricles.” For many, the primary concern is whether this sudden acceleration poses a serious threat to life. While generally not considered life-threatening, the answer depends on the individual’s underlying health and the severity of the episode.
Understanding Supraventricular Tachycardia
SVT describes a heart rhythm disorder where the heart rate abruptly exceeds 100 beats per minute at rest, often reaching rates between 150 and 220 beats per minute during an episode. This rapid pace is caused by a malfunction in the heart’s electrical signaling, typically involving a short circuit or an extra electrical pathway in the upper chambers.
The experience of an SVT episode can be highly unsettling. Common physical symptoms include a pounding or fluttering sensation in the chest, known as palpitations, and feelings of lightheadedness or dizziness. Some individuals may also experience shortness of breath or weakness.
Episodes of SVT are usually episodic, meaning they start and stop suddenly, and are often self-limiting. They may last from a few minutes to several hours before the heart spontaneously reverts to a normal rhythm. During the rapid rhythm, the heart does not have sufficient time to fill completely with blood between beats, which temporarily reduces the amount pumped out to the body.
Assessing the Risk Level
For the majority of otherwise healthy individuals who experience SVT, the condition is considered benign and does not pose a direct threat to life. The heart itself is structurally normal, and the rapid rhythm, while uncomfortable, is typically well-tolerated. The primary issue is the temporary reduction in the heart’s pumping efficiency, which causes associated symptoms like dizziness.
However, SVT can become dangerous under specific circumstances, particularly when it occurs in people with pre-existing heart conditions. Individuals who have underlying structural heart disease, such as cardiomyopathy or severe coronary artery disease, are at a higher risk. In these cases, the stress of the rapid rate can lead to complications like heart failure.
A significantly prolonged SVT episode, lasting many hours, can also pose a risk. A sustained, rapid heart rate can lead to hemodynamic instability, characterized by a substantial drop in blood pressure and potential fainting. If the rapid rate is sustained and occurs frequently over a long period, it can potentially weaken the heart muscle, leading to a form of heart failure over time.
Immediate Steps During an Episode
When an SVT episode begins, there are immediate, simple techniques that can be attempted to stop the fast rhythm. These are known as vagal maneuvers, which work by stimulating the vagus nerve to slow the electrical impulses traveling through the heart.
One common technique involves bearing down, similar to straining during a bowel movement, which temporarily increases pressure in the abdomen and chest. Another maneuver is splashing ice-cold water on the face, which triggers the “diving reflex” and can slow the heart rate. These actions are often the first line of defense.
If the SVT does not stop quickly after attempting these maneuvers, or if the symptoms are severe, emergency medical attention is necessary. Clear guidelines dictate when to seek immediate professional help, such as calling emergency services.
This is required if the rapid heart rate is accompanied by severe symptoms:
- Chest pain.
- Profound shortness of breath.
- Loss of consciousness (fainting).
Any episode that lasts longer than a few minutes and does not revert to a normal rhythm should be evaluated in an emergency setting, where fast-acting intravenous medication or other procedures can be administered to restore a normal heart rhythm.