Supraventricular Tachycarida (SVT)
What is supraventricular tachycardia?
Supraventricular tachycardia or SVT is an abnormal heart rhythm. SVT causes the heart to beat very rapidly. The normal resting heart rate is about 70 beats-per-minute. The heart rate during SVT is usually between 120-240 beats-per-minute. SVT can last for a few seconds or may last for several days.
What causes SVT?
SVT is caused by an electrical short circuit in the heart. In most cases the patient is born with this short circuit but the short circuit may be a result of other heart disease. However, in most cases the heart is completely normal apart for the electrical short circuit. The short circuit is usually very small, about the thickness of a human hair and only 2-3 mm long.
How does the short circuit cause SVT?
The heart is composed of millions of heart cells. The heart uses electrical currents to tell the heart cells when to contract so that they contract in a coordinated fashion. When this orderly flow of electricity is disrupted by a short circuit, abnormal heart rhythms result.
What symptoms does SVT cause?
Most people with SVT notice a rapid pulsation from the heart beating quickly in the chest. Other symptoms may include: dizziness, fainting, chest tightness or chest pain, difficulty breathing and tiredness. Some patients feel the need to pass water during an attack of SVT or soon afterwards.
Is SVT dangerous?
SVT is rarely fatal. However, it can significantly interfere with a person’s ability to go about their daily activities. If SVT causes dizziness or fainting it can be dangerous, particularly if a patient is in a situation where losing consciousness could be dangerous such as up a ladder or driving.
What brings on attacks of SVT?
In most cases SVT simply occurs randomly and can not be predicted. In some patients attacks are brought on by exercise, emotion or stimulants such as caffeine or cold tablets.
How often will SVT occur?
The time between attacks of SVT varies amongst patients. Some patients have attacks several times per day whereas others have an attack only every few years. In general attacks tend to occur more frequently as the patient gets older.
Will SVT get better without treatment?
SVT does not usually cure itself. However, sometimes the attacks occur very frequently and at other times less frequently. However, the tendency is for attacks to occur more frequently as the patient gets older.
What are the treatment options for SVT?
If attacks do not cause severe symptoms, are short lived and not very frequent, no treatment may be required. However, if attacks are starting to interfere with the activities of daily life treatment should be considered. The two main types of treatment are medication and catheter ablation (see below)
What do I do if I have an attack of SVT – do I need to go to hospital?
It is important not to panic if you have an attack of SVT. If possible sit down and try to relax. Taking deep breaths and holding them may stop the attack of SVT. Sometimes, a gentle massage of the carotid artery, just below the angle of the jaw, will stop an attack. You doctor will show you how to do this. If you feel unwell during an attack you should see your doctor or attend the emergency department of your closest hospital.
Can SVT be cured with medication?
Medications do not cure SVT. However, taking regular medications may decrease the number of attacks of SVT. To prevent attacks of SVT medications usually need to be taken every day. Some medications cause side effects but these side effects are not always severe. Medications usually need to be taken for life which can cause some difficultly, particularly in women who may be considering pregnancy.
What is catheter ablation?
Catheter ablation is a technique for curing SVT. The aim of catheter ablation is to destroy the short circuit which causes SVT. Catheter ablation is always performed in a hospital and usually takes 1 ½ – 2 hours. The procedure is usually performed under general anaesthetic or heavy sedation. Most patients stay in hospital overnight following catheter ablation. Small wires are placed in the veins at the top of the thigh and passed up these veins into the heart. The electrical short circuit is located and then an electric current is passed down one of the wires (catheter) to destroy the short circuit. The electric current produces a small burn about the size of a pea. Usually this burn does not cause ill effects. Following the procedure, the doctor removes the wires (catheters). The patient is left with several small wounds in the groin just a few millimetres across. These are not usually painful. Sutures (stitches) are not usually inserted in the wounds, which heal by themselves.
What are the chances that catheter ablation will cure SVT?
Catheter ablation cures SVT in 95-98% of cases. In the 2-5% of cases where the ablation is not successful, a repeat procedure is usually successful.
What are the risks of catheter ablation of SVT?
The risks of the procedure are generally small. The risk of death, heart attack or a stroke are <1% (approximately 1 in 2000). The risk of needing a pacemaker following catheter ablation is <1% (about 1 in 400). Other risks include bleeding, infection, blood clots in the leg or minor damage to the nerve or blood vessel in the leg, this risk is approximately 1-2% (1-2 in 100).
When can I return to work or school?
Many people feel well enough to return to work or school 2-3 days after the procedure. However, many patients feel tired for a few days afterwards and it is recommended that the patient usually takes a week off work or school.
Will I feel unwell after catheter ablation?
Following catheter ablation patients usually do not feel unwell. You may have a sore throat from the breathing tube inserted by the anaesthetist. Their may be minor discomfort in the groin. Occasionally patients feel some minor chest tightness.
When do I get out of bed following catheter ablation?
It is recommended patients remain in bed for approximately four hours after catheter ablation. It is important you do not move your legs for these first few hours to decrease the risk of bleeding or bruising.
Can I have catheter ablation if I am pregnant?
No. Because x-rays are used to guide the catheters, catheter ablation should not be performed on pregnant women except in an emergency. If you think you might be pregnant it is important to inform the doctor before undergoing catheter ablation.
Do I need to stop my medications before catheter ablation?
You should discuss this with your doctor. Anti-arrhythmic medications (medications used to control SVT) should be stopped prior to catheter ablation.
Eastern Heart Clinic
Prince of Wales Hospital
Barker Street Randwick
Medication: Last dose before procedure
© Dr Mark McGuire 18/8/15 (version 1.3)