Supraventricular Tachycardia (SVT) refers to a medical condition characterised by an irregularly fast and erratic heartbeat (arrhythmia) that arises from the heart's upper chambers.
In other words, in SVT, the heart suddenly beats much faster than the normal rate. A person's heart typically beats about 60 to 100 times per minute. A heart rate of more than 100 beats per minute is called tachycardia. During an attack of SVT, the patient's heart rate can range between 150 and 220 beats per minute.
SVT arises from the atria or the atrioventricular node in the heart. In this condition, electrical signals in the atria fire on early and hence the atria contracts too soon. This interrupts the main electrical signal coming from the SA node, and as a result, the heart beats quickly, causing the abnormality.
There are four main types of SVT:
- Atrial Fibrillation
- Atrial Flutter
- Paroxysmal Supraventricular Tachycardia (PSVT)
- Wolff-Parkinson-White syndrome
SVT Causes
In some cases, Supraventricular Tachycardia patients are born with abnormal pathways or electrical circuits in the heart. However, in some cases, SVT can also be caused due to the following reasons:
- Consumption of caffeine or alcohol
- Smoking, tobacco in any form
- Physical or emotional stress
- Any kind of heart disease
- Diabetes
- Chronic lung disease
- Thyroid disease
- Side effects of certain medications such as asthma drugs, decongestants, and some herbal diet remedies
- Consumption of chemical drugs such as cocaine or meth, etc.
- Pregnancy
- Excessive exercise
Signs Or Symptoms of SVT
The main symptom of supraventricular tachycardia is a very fast heartbeat that may last for a few minutes to a few days. Some people with SVT have no signs or symptoms. In some cases, SVT symptoms may arise and get resolved suddenly without any kind of treatment.
Symptoms of SVT include:
- Rapid heartbeat (more than 100 beats per minute)
- Pounding in the chest, i.e. palpitations
- Pounding sensation in the neck
- Fatigue or tiredness
- Chest pain
- Shortness of breath
- Dizziness or Lightheadedness
- Sweating
- Fainting
In infants and very young children, signs and symptoms of SVT may also include pale skin, sweating, poor feeding and a rapid pulse.
Risk Factors of SVT
Supraventricular tachycardia is very common in infants and children. It also occurs in pregnant women. Other risk factors for SVT are:
SVT is more common in middle-aged or older people.
Patients who have a medical history of narrowed heart arteries, heart failure, damage to the heart or heart valves, cardiomyopathy, or any previous heart surgery have increased risks of SVT.
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Nicotine and illegal drug use
Excessive use of nicotine and drugs, such as amphetamines and cocaine, can trigger SVT.
Chances of SVT are higher in patients who have an overactive or underactive thyroid gland.
Diabetes increases the risk of developing heart disease and high blood pressure and arrythmia.
In obstructive sleep apnea, breathing is interrupted during sleep. This increases the risk of SVT in patients.
SVT is common in people born with a congenital heart defect.
Diagnosis and Test for SVT
Diagnosis starts with a physical exam and medical history. After the physical examination, a few tests can be prescribed by the healthcare provider. These tests may include:
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Electrocardiogram (ECG)and holter
ECG analyses the abnormal heart rhythm. ECG helps to watch heart rhythm over a long period continuously(holter).
Blood work is done to test for various underlying medical conditions such as hyperthyroidism or electrolyte abnormalities.
X-ray is done to check for lung problems and examine the size of the heart.
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Treadmill test (TMT)/ Stress test
TMT is done to check how the heart works during physical exercise.
Echocardiography is done to check the heart structure and function.
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Electrophysiologic study (EPS)
EPS is done to evaluate the electrical activity and detect abnormal pathways in the heart and these are ablated if found.
Treatment and Care for SVT
Supraventricular tachycardia is rarely a life-threatening condition. But some patients require treatment. Treatment of SVT includes procedures like:
Thin tubes are placed through a vein or artery into the heart to deliver radiofrequency waves to locate and destroy the abnormal electrical pathways. This is an invasive but low-risk procedure that permanently cures most patients' problems.
This treatment involves the AV node. It uses extreme cold to destroy those tissues in the brain that triggers SVT.
A small electric shock is given to the heart to help it get back to a normal rhythm.
Medication is given in the form of tablets or intravenously. An acute attack of Supraventricular Tachycardia is treated with Esmolol. A severe attack of SVT is treated with a variety of drugs, including simple AV nodal blocking agents such as beta-blockers, verapamil and sometimes, antiarrhythmic drugs.
Prevention of SVT
- Maintaining a healthy lifestyle is an important step in preventing SVT. These include steps like eating a heart-healthy diet, not smoking, getting regular exercise and managing stress.
- Large amounts of caffeine intake should be avoided.
- To prevent an episode of Supraventricular tachycardia, it is crucial to identify the triggers and try to avoid them.
- Medications, which the patient regularly uses for treating any kind of medical condition, should be consumed with utmost care and caution. Some medicines may contain stimulants that trigger SVT. Most important thing to remember is that the medications may not be discontinued abruptly.
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