Supraventricular Tachycardia (SVT)

Table Of Contents

1. What is supraventricular tachycardia (SVT)?

What causes supraventricular tachycardia?

Supraventricular tachycardia (SVT), also known as paroxysmal supraventricular tachycardia, occurs when electrical impulses above the heart’s ventricles (supraventricular) or in the atria or Atrioventricular (AV) node, start to produce an abnormally rapid heart rate.

A normal heart beats 60 to 100 beats per minute (bpm) but when you have SVT, your heart rate may be sustained way above 100 bpm, sometimes up to 180 or 200bpm, for several minutes or hours. You may feel that you have a racing heartbeat, which can be described as palpitations.

Single lead electrocardiogram (ECG) showing rapid regular heart rates from supraventricular tachycardia (SVT), followed by abrupt termination of tachycardia followed by normal rhythm.

Because of the rapid heart rate, heart muscles cannot rest in between their contractions. When the hearts’ chambers cannot contract forcefully, they cannot also fulfil our body’s oxygen demand and as a result, you may feel symptoms such as chest pain, difficulty in breathing, lightheadedness, and dizziness.

In an SVT, symptoms typically start abruptly and end abruptly. Often, even before the onset of symptoms, you may feel a sense that something is about to start, akin to an impending sense of “doom,” which is really your nervous system telling you that the heart is about to start to misbehave.

There are 2 kinds of SVT namely: Atrioventricular Re-Entrant Tachycardia (AVRT) and Atrioventricular Nodal Reentry Tachycardia (AVNRT).

2. TYPES OF SVT

A. Atrioventricular Re-Entrant Tachycardia (AVRT)

Atrioventricular reentrant tachycardia may also be referred to as Atrioventricular Reciprocating Tachycardia or AVRT, is a kind of abnormally rapid heart rhythm that is commonly related to Wolff-Parkinson-White syndrome, a congenital disorder wherein an accessory pathway permits electrical signals from the heart’s ventricles to pass in the atria and cause earlier-than-normal heart contraction, which leads to the appearance of an unusual ECG appearance, termed a delta wave, or short-PR interval. The palpitations commence typically when there is an extra heartbeat (ectopic) beat which conducts down the AV node and backs up the accessory pathway creating a continuous circuit of activation.

B. Atrioventricular Nodal Reentry Tachycardia (AVNRT)

Atrioventricular nodal reentry tachycardia (AVNRT) is the most common kind of SVT, causing an abnormally rapid heart rate, which can reach anywhere from 120 to 220 beats per minute. It is caused by the presence of 2 distinct electrical pathways (rather than the usual single pathway present in most individuals) in the atrioventricular (AV) node that in turn gives way to a reentry circuit within the AV node.

Palpitations often start and end abruptly and repeatedly occur, sometimes with triggers, but often without.

Episodes of AVNRT have a tendency to occur more often in young females, but it can affect both men and women of any age group.

3. Causes of SVT

Some patients who experience SVT recognize triggers like sleeplessness, lack of exercise, changing posture such as bending down or squatting, and psychological stress. For some, there are no clear triggers. Listed below are some triggers for SVT:

• Alcohol consumption
• Chronic lung disease
• Cocaine and methamphetamines use
• Excessive caffeine consumption
• Exercise
• Emotional stress
• Heart disease or heart failure
• Hyperthyroidism
• Use of over-the-counter drugs for colds, or medications for asthma

4. Signs and Symptoms of SVT

Supraventricular tachycardia (SVT) may start and stop abruptly, with stretches of normal heart rates in between. Symptoms may last anywhere from a few minutes to a few hours, and most patients experience some symptoms.

Supraventricular tachycardia becomes a problem when it occurs frequently and is ongoing, particularly if you have another disease including heart failure or other coexisting medical problems, which may make you more susceptible to the effects of rapid heart rates.

Signs and symptoms of supraventricular tachycardia may include:

• Chest pain
• Dizziness or lightheadedness
• Heart palpitations
• Fainting episodes (syncope)
• Pounding sensation in the neck (also known as the “frog” sign)
• Shortness of breath
• Fatigue
• Increased urinary frequency
• Sweating

5. Diagnostic Tests which may be performed for SVT

12-Lead Electrocardiogram (ECG). The ECG strip may reveal a narrow-complex SVT and a classic delta wave definitive for Wolff–Parkinson–White syndrome leading to AVRT.

Holter monitor (Ambulatory ECG monitor). This is a monitor that continuously records your ECG for 24 or 48 hours and even 7 days. You should carry on all normal day-to-day activities whilst wearing this monitor. This can be diagnostic for SVT, and you should note the time and day of occurrence of the typical palpitations, or other symptoms so that your physician can focus in on these times to obtain an ECG and symptom correlation.

Electrophysiology Study. An Intracardiac Electrophysiology Study may be advised by your doctor in order to establish the diagnosis of SVT and assess if you are a candidate for curative catheter ablation. If the diagnosis is clear, your doctor will usually proceed on the same sitting to perform ablation in an attempt to cauterize/burn the area of the heart responsible for the setting of SVT.

This is performed in an Electrophysiology (EP) Lab where there is a patient table and a fluoroscopy (x-ray) machine that is suspended over the table. Using state-of-the-art recording equipment, which records signals from electrodes placed inside your heart through femoral (groin) veins, your doctor will be able to clearly diagnose your condition.

Echocardiogram. This uses sound waves to show how blood flows inside the heart and its vessels. This will help assess the heart pump function, and to look for valvular abnormalities.

6. Supraventricular Tachycardia Treatment, including AVRT and AVRNT

An acute episode of SVT: Tips and Tricks to Stop Palpitations

1. Valsalva manoeuvre – This means that you perform an action to increase pressure, typically by breath-holding – imagine trying to “unblock your ears” whilst descending on an aeroplane, or “pushing hard – or bearing down hard” when constipated. Perform that action for approximately 5 seconds, before “releasing” your breath suddenly. On release, there is a chance that your palpitations will terminate. One practical tip is blowing into the tip of a syringe to try to move to plunger – you will be able to move the plunger, but the action creates a Valsalva manoeuvre.
2. Drinking a big gulp of ice-cold fluids
3. Splashing cold water on your face
4. If you are under 30, consider rubbing on your neck (carotid sinus massage), where rotational firm pressure on your carotid sinus for 10 seconds (typically on the side of the neck at the level of your chin)
5. Gentle pressure on your closed eyes (termed orbital pressure). Try this on each eye for 5 seconds. All you have to do is locate the carotid sinus (found on the side of the neck below our right ear) and apply pressure on the carotid sinus. However, this must be done with caution when the patient is elderly or those with bruits or occlusive carotid artery disease. (It’s best to consult your doctor). Anyone can perform the Valsalva Maneuver, by increasing chest pressure by trying to let your breath out while holding one’s breath or bearing down (as if having a bowel movement.)

If these simple manoeuvres fail to stop your palpitations, you may need to be admitted to accident and emergency, where you may be given one or more of the following options for treatment

1. Drugs to terminate rhythm. The most commonly used drug is adenosine. Your doctor will usually administer this through a drip line (iv) in your vein, and this usually stops palpitations within 30 seconds of being given. Other options include beta-blockers, such as metoprolol, which can be given IV or orally, and calcium blockers, such as verapamil.
2. Direct Current Cardioversion – DCCV. This is a procedure where you are sedated or given general anaesthesia before an electrical current is passed through pads on your chest to stop and restart the heart.

Longer-term treatment strategies for SVT

i) Catheter ablation. This is now strongly recommended for SVTs and is the only treatment that provides a cure, to prevent further SVT episodes from occurring in the future.

This is a keyhole procedure that your cardiac electrophysiologist can usually perform in under 2 hours.

Success rates are >90% to completely abolish your palpitations, with a small complication rate of 3% of groin bruising, and a 1% with of fluid collection around your heart, <0.5% of needing a pacemaker, and <0.1% risk of a life-threatening complication such as a stroke or heart attack.

You are encouraged to strongly consider this approach for SVTs. Useful links providing information on this form of treatment include:

Arrhythmia Alliance.

ii) Drugs such as beta-blockers (bisoprolol, metoprolol) or calcium blockers (verapamil, diltiazem), or flecainide may be prescribed by your doctor to minimize the frequency and duration of recurrent episodes of palpitations. However, your symptoms are unlikely to be fully cured by this approach – but you may be able to minimize symptoms. This may be a useful initial strategy, but if it fails, then you should consider a catheter ablation strategy.

TOP TIPS FOR SVT

1. Obtain documentation of the 12-lead ECG – ask your Ambulance Crew, A&E doctor/nurse, or GP for a copy of the ECG, if this is not possible, take a picture of the ECG (typically a pink sheet with squiggly lines!) on your phone, as this may be the only documentation of your palpitations available. It is crucial you bring this ECG information for your consultation with your consultant electrophysiologist!
2. Alive Cor – This is a mobile medical-grade ECG recording device that you can purchase online for under £100, which links up via wireless technology to most modern mobile phones. Consider purchasing one and learn how to use this, and capture some data on your mobile phone to show your consultant electrophysiologist, who can then more readily make a diagnosis.
3. Learn how to stop it! See link above

7. See Dr Lim

Dr Lim is one of the top rated cardiologist in London – Dr Boon Lim can provide an in-depth assessment of your palpitations, using modern diagnostic tests, in comfortable surroundings.

Contact Dr Boon Lim now to arrange an appointment for SVT Heart Treatment in London, UK.

SVT FAQs