Supraventricular Tachycardia- SVT
Supraventricular tachycardia (SVT) is a rapid heart rhythm of the upper heart chambers. In supraventricular tachycardia electrical signals travel from the upper chambers of the heart to the lower chambers of the heart.In normal rhythm, the electrical impulse starts in the upper heart chambers and then travels through the A-V node, which is like a staircase connecting the top and bottom floors of a building.The electrical signal in supraventricular tachycardia starts in the upper chamber and then travels down the A-V node connecting the top and bottom chambers. When the lower heart chamber is activated by the electrical signal reaching it, the lower chamber beats and pumps blood to the rest of the body. The heart rate during the supraventricular tachycardia is the rate that the lower heart chamber beats.
Supraventrical Tachycardia Symptoms
SVTs are usually 150-250 beats per minute but can be both slower or faster. Commonly, supraventricular tachycardia results in symptoms such as rapid heart beating, dizziness, shortness of breath, or chest discomfort.
SVTs are not felt to be life-threatening themselves. Patients with SVTs may have a wide range of symptoms. Particularly when SVTs are brief or not too rapid patients may not be aware that they have an SVT. Most commonly patients describe a rapid heart sensation, often as if their hearts are pounding out of their chests. Patients also describe shortness of breath, chest discomfort, or dizziness or lightheadedness.
For many patients, most or all episodes of SVT stop on their own. The duration ranges widely from seconds to minutes and occasionally hours.
Treatment for Supraventricular Tachycardia
In some patients, an intervention is required to stop the SVT. Patients are frequently taught to bear down as if they are having a bowel movement in order to increase the pressure within the chest cavity to try to stop the SVT episode. This action called a vagal maneuver works by causing the body’s control system called the autonomic nervous system to put the breaks on conduction through the A-V node, the staircase described above connecting the upper and lower heart chambers. Other techniques such as placing one’s head in cold water is not used frequently any longer. In some patients, the SVT does not stop on its own and the patient seeks emergency care by calling 911.
The patient may be given a medication through an intravenous (IV) called adenosine, which causes a strong flushing sensation that lasts about 30 seconds. In some cases the medication is given more than once. Patients frequently ask about the potential consequences of staying in the tachycardia for prolonged periods of time, for example, many hours. For many patients, there may be a significant decrease in the ability of the heart to pump blood throughout the body during the episode of SVT. The consequences of decreased blood being pumped through the body will vary based on the patient’s overall condition, their degree of hydration, and specific medical conditions such as heart disease.
Some patients may experience impairment of kidney function. Patients with artery problems of the heart could have a heart attack. Patients should discuss their physician an appropriate time to call 911 if the SVT does not stop on its own. Frequently, 30 minutes is a reasonable time period but in some patients with other heart problems, it may be a shorter period of time.
Most patients with SVT do not have any other significant problems of the heart. However, there are a number of heart conditions and medical conditions that are associated with SVTs particularly the ones called atrial tachycardias. Patients who are born with specific heart conditions, called congenital heart disease, prior heart surgery, or with heart valve problems are more likely to have these arrhythmias.
Other treatments of supraventricular tachycardias:
- Catheter ablation
Most patients with supraventricular tachycardia that are felt to require daily treatment with medications are given the option of either having a catheter ablation or receiving daily medications. For patients previously not treated with medications, either option is reasonable as a first choice. The choice is largely left to patient preference. Some patients may prefer to be treated with medications while other patients may prefer a procedure. For patients for whom one or more medications have been tried but supraventricular tachycardias still recur, options include increasing the dose of the medications, trying a different medication, combining two or more medications, or proceeding with catheter ablation.