Supraventricular tachycardia: causes and treatments

Supraventricular tachycardia (SVT) – from Latin “above the ventricles” and “fast heart rate”, respectively – is a group of conditions that occur when our heartbeat is faster than normal. Despite being very unpleasant, SVT often does not represent a serious medical condition, but a medical examination is always required.

Normally, your heart pumps about 100,000 times a day to send oxygen and blood out to your body using four pumping chambers. In order for it to contract and keep beating, there is a sinoatrial node (SA node), also called natural pacemaker, located at the top of the heart. It is fueled by electrical signals that do not occur normally during SVT.

If you are at rest, your heart beats 50 to 99 times a minute. People with SVT can register more than 100 beats a minute, because the electrical signals fire off early, causing the atria, the top chamber of the heart, to contract sooner. As a result, the main electrical signal coming from the SA node is interrupted and your heart beats faster than normal.

There are three types of supraventricular tachycardia:

• Atrial tachycardia, a faulty electrical signal caused by a short circuit in the right or left atrium;
• Paroxysmal supraventricular tachycardia, a type of SVT that only occurs occasionally;
• Atrioventricular nodal reentrant tachycardia, occurring when you have an extra pathway in your heart, causing the electrical signal to circle around and around in a loop, without moving to down to the ventricles;
• Atrioventricular reciprocating tachycardia, occurring when the ventricles and the atria are linked by an abnormal pathway that causes the electrical signal to circle around and around in a loop.

Symptoms

Since the heart cannot send enough blood to the body, SVT causes the following symptoms:

• Dizziness and confusion;
• Shortness of breath;
• Chest pain;
• Fatigue.

Causes

It is not always clear what causes SVT. Symptoms usually start in teenage years or early 20s and are often due to:

• Abnormal pathways or electrical circuits you were born with;
• Scar tissue left behind after surgery.

In more general terms, tachycardia can be caused by:

• Smoke;
• Stress;
• Certain medicines, such as asthma drugs, decongestants;
• Some herbal diet remedies;
• Abuse of caffeine and/or alcohol;
• Drugs such as cocaine or methamphetamine.

Diagnosis

The first step to get a diagnosis of SVT is to go to the doctor, that will probably ask you:

• When you first noticed your symptoms;
• How your symptoms begin (during exercise, for example);
• Whether you have noticed a link between the use of caffeine and your symptoms;
• Whether you are stressed and how stress affects your symptoms;
• Whether the symptoms came on suddenly or slowly;
• How long your symptoms tend to last;
• Whether you or anyone in your family has had heart problems or procedures.

After listening to your heart and lungs, your doctor might want to:

• Measure your blood pressure;
• Feel your thyroid gland;
• Get your temperature;
• Take a small sample of your blood.

Test

After asking about your symptoms, your doctor might prescribe the following tests:

• ECG, or EKG, is an electrocardiogram that allows you to record your heart rhythm over time and detect anomalies. It only requires six sticky patches (electrodes) on your chest and some others on your arms and legs. You will be asked to breathe normally and lie still;
• Electrophysiology study, that allows doctors to study the electrical signal in your heart and how it is sent by each section while you are sedated;
• Holter monitor, a small portable EKG that allows you to record your heart’s activity for 24-48 hours. You will only need to put its electrodes on your chest and carry on with your normal daily activities, making sure you only remove it to shower or bathe.
• Event monitor, another type of portable ECG that can be worn for days or weeks, according to how often your symptoms occur.

Treatments

The treatment strictly depends on the cause, the frequency of the symptoms and how your body responds to each medication. These include:

• Medicines to slow your heartbeat;
• Ablation, a procedure to burn the pathway that causes the anomaly.

Make sure you get an appointment with your doctor if you experience any of the symptoms mentioned above.