Supraventricular tachycardia (SVT)
Supraventricular tachycardia (SVT):
Supraventricular tachycardia (SVT) is any rapid abnormal heart rhythm that involves the upper chambers of the heart (above the ventricle – hence the term ‘supraventricular tachycardia’).
SVT often results in sudden unexpected rapid heart rhythm. In many cases it is close to 200bpm. These episodes are often random without a trigger but can be associated with dehydration, stress, anxiety, sudden movements such as bending over.
What are symptoms of SVT?
Palpitations is the usual symptom. Other symptoms include dizziness, shortness of breath, chest discomfort, feeling of anxiety. The heart rate could take sone time to return normal even after the episode stops and people often feel tired or washed out.
Is SVT dangerous?
SVT is generally not considered to be dangerous in the vast majority. It is not expected to cause sudden death, heart attack, damage your heart or reduce your life expectancy. There are exceptions to this rule and treatment is tailored to individuals.
Types of SVT:
Although AF and Flutter are supraventricular in origin, the term SVT is generally associated with one of the following three conditions:
- Atrial tachycardia
- Atrioventricular nodal re-entrant tachycardia (AVNRT) – It is so common that people often refer to this condition as SVT
- Atrioventricular reciprocating tachycardia. This can sometimes be referred to as Wolff-Parkinson-White (WPW) syndrome in selected cases
1. Atrial tachycardia
Atrial tachycardia occurs when a group of cells in the atria decide to beat very fast instead of following the normal sinoatrial node activity. It is not known when or why such an extra focus develops. Atrial tachycardia is not considered dangerous buy can be frequent.
Treatment options Include medications and an ablation. There appears to be a link between atrial tachycardia and AF in some people.
2. AV nodal re-entry tachycardia:
This is the most common type of SVT. The top and bottom chambers are connected electrically by the AV node. In AVNRT, the abnormality is a short circuit within the area of the AV node. A second fibre within the area called the slow pathway results in a short-circuit between the fast normal fibre and the slow spare fibre.
The heart rate is often very fast at about 170-210 bpm, but slower and faster rates could occur. It is often diagnosed in younger people and can occur sporadically without warning.
Generally, it is not considered to be dangerous. Treatment options Include valsalva manoeuvre {weblink https://www.webmd.com/heart-disease/atrial-fibrillation/valsalva-maneuver}, medications as needed or regularly and an ablation.
3. Atrioventricular reciprocating tachycardia (AVRT):
This is the next most common type of SVT. Normally there is one wire connecting the top and bottom chambers in the middle of the heart called the Bundle of HIS. Some people are born with a separate extra wire called an “accessory pathway” connecting the atria and ventricles. With the right stimulus, people with an accessory pathway can go into an abnormal circular rhythm utilising the AV node and this extra connection.
In many cases, the extra connection is usually hidden and can only transmit signals back from ventricles to atria. This is called a concealed accessory pathway. This cannot be determined until we have catheters in the heart at the time of electrophysiological testing. In some people, this extra connection can transmit the signals from the top to bottom as well. This is called Wolff-Parkinson-White syndrome and people with this condition are said to have preexcitation on 12 lead ECG. In people with WPW / preexcitation on ECG, there is a rare chance of sudden death which usually prompts further investigation. In completely asymptomatic individuals, a detailed discussion is required about the merits of investigation and intervention.
Treatment options Include Valsalva manoeuvre {weblink https://www.webmd.com/heart-disease/atrial-fibrillation/valsalva-maneuver}, medications as needed or regularly and an ablation.
People can choose not to have any treatment for SVT if they are not severely symptomatic
What is the long-term prognosis with SVT?
Vast majority of the people with SVT are expected to lead a normal healthy life if SVT can be managed adequately with treatment – medications or ablation.
What are the treatment options available for SVT?
Conservative management:
If you have a good understanding of your SVT, have good control when they do occur without severe symptoms, you can choose not to have any treatment. Management recommendations, especially to do with AVRT, continues to evolve. Recommendations can vary.
Medications:
The primary and mainstay of treatment in majority of cases is medications. In some people, this is very effective. In people who have ongoing episodes despite mediations or have intolerances to prescribed medications or wish not to be on long term medications, procedural options can be considered. In some people, a pacemaker is required to use medications effectively / safely. There are several medications and combinations of medications you could be prescribed. Most medications used to target abnormal rhythms require regular monitoring with your general medical practitioner. Medications can be used as “pill-in-pocket” or regularly.
What is pill-in-pocket approach?
The “pill-in-the-pocket” approach refers to use of a prescribed medication, (usually beta blockers, calcium channel blockers, flecainide or sotalol), following recent onset of episodes of suspected or confirmed SVT in patients with history of SVT. It is generally initiated by the cardiologist / electrophysiologist. The idea is to terminate the suspected episode of SVT without having to present to emergency department or hospital. Generally, it is to be taken if suspected SVT episode does not respond to Valsalva manoeuvre and lasts more than 10-15 mins. Medications can take upto a few hours to work. If you are feeling very unwell with your episode or have a prolonged episode, seek medical attention. Do not drive.
Procedural options:
A Catheter ablation is a common and minimally invasive procedure where the abnormal circuit is identified and ablated to prevent recurrence. Effectiveness can vary between different types of SVT but is generally >90-95% with 1 or 2 procedures. AVNRT is expected to respond very well to ablation with 98% efficacy.
Catheter ablation is an effective way to manage SVT. Age and comorbidities influence the management options.
What are the risks of having an SVT ablation?
They include but are not limited to the following.
Common risks and complications (more than 5%) include:
- Bruising bleeding at the puncture site. Bruising can extend beyond the puncture site and can take a few weeks to improve in some cases.
Uncommon risks and complications (0.5- 5%) include:
- Major bleeding related to the groin puncture site or injury to an artery in the groin. This (rarely) may need surgery and or blood transfusion.
Rare risks and complications (less than 0.5%) include:
- A stroke. This may cause long term disability (0.1%)
- Requirement for a pacemaker following the procedure (0.2%)
- Injury to the food pipe related to the ultrasound used during the procedure.
- Injury to the urinary tract if a urinary catheter is required for the procedure.
- Blood clot in the leg (DVT) causing pain and swelling. In rare cases part of the clot may break off and go to the lungs called pulmonary embolus.
- Death because of this procedure is rare
