Supraventricular Tachycardia (SVT)

Supraventricular tachycardia (SVT):

Supraventricular tachycardia (SVT) is a type of abnormal heart rhythm characterized by a rapid heart rate originating above the ventricles. In SVT, the heart rate typically exceeds 100 beats per minute and may reach 150-250 beats per minute. Episodes of SVT can occur spontaneously or may be triggered by certain factors, such as stress, caffeine, alcohol, or medications.

What are symptoms of SVT?

Common symptoms associated with supraventricular tachycardia (SVT) may manifest as palpitations (a feeling of a racing or pounding heart), rapid heartbeat, lightheadedness, shortness of breath, chest discomfort, and in severe cases, fainting. It’s important to note that some individuals may not be aware of their arrhythmia or experience noticeable symptoms.

After an episode of SVT, even after the heart rhythm returns to normal, it can take some time for the heart rate to stabilize. This recovery period may vary from person to person. It is not uncommon for individuals to feel tired or drained, as if their energy has been depleted, following an SVT episode.

Is SVT dangerous?

In the vast majority of cases, supraventricular tachycardia (SVT) is not regarded as a life-threatening condition. It is generally not expected to result in sudden death, heart attack, heart damage, or a reduction in life expectancy. However, it is important to note that there are exceptions to this general rule, and treatment approaches may vary depending on individual circumstances.

The management of SVT is tailored to each individual, taking into account factors such as the frequency and severity of episodes, symptoms experienced, and the impact on overall health and well-being. Treatment options may include lifestyle modifications, medication therapy, or procedural interventions like catheter ablation.

Types of SVT:

Although AF and Flutter are supraventricular in origin, the term SVT is generally associated with one of the following three conditions:

• 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
• Atrial tachycardia

AV nodal re-entry tachycardia:

AVNRT, short for atrioventricular nodal re-entrant tachycardia, is the most commonly encountered type of supraventricular tachycardia (SVT). The atria and ventricles are connected by the atrioventricular (AV) node, usually through a fast-conducting pathway referred to as the fast pathway.

This fast pathway plays a crucial role in facilitating normal and efficient communication between the upper and lower chambers of the heart. However, some individuals possess an additional backup connection known as the slow pathway, which is not typically required for normal heart function and communication.

In the case of AVNRT, an anomaly arises within the region of the AV node, resulting in a short circuit. This short circuit occurs when the slow pathway and the fast pathway resulting in a rapid continuous circuit that is transmitted to the ventricles, forcing it to pump rapidly.

The heart rate during AVNRT tends to be exceedingly rapid, sometimes exceeding 200 beats per minute (bpm). While it can manifest at any age, it is often identified in younger individuals and can occur sporadically without any prior indication. AVNRT is generally not considered 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.

Atrioventricular reciprocating tachycardia (AVRT):

This type of SVT is the second most prevalent. Normally, there is a single electrical pathway called the Bundle of His that connects the upper and lower chambers of the heart. However, some individuals are born with an additional pathway known as an “accessory pathway” that links the atria and ventricles. When appropriately stimulated, individuals with an accessory pathway can enter an abnormal circular rhythm that involves both the AV node and this extra connection.

In many instances, this extra pathway remains concealed and can only transmit signals from the ventricles back to the atria. This condition is referred to as a concealed accessory pathway. Determining the presence of a concealed accessory pathway requires the use of catheters during electrophysiological testing within the heart. In some people, the extra pathway can transmit signals from the top to the bottom chambers as well. This condition is known as Wolff-Parkinson-White (WPW) syndrome, and individuals with this syndrome exhibit preexcitation on a 12-lead ECG.

In individuals with WPW or preexcitation on an ECG, there is a rare possibility of sudden death, which typically prompts concern and further investigation. However, in completely asymptomatic individuals, a thorough discussion is necessary to assess the benefits 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.

Atrial tachycardia:

Atrial tachycardia is characterized by rapid beating of a cluster of cells within the atria, deviating from the regular activity dictated by the sinoatrial node. The origin and cause of this abnormal focus are currently unknown. Although atrial tachycardia is generally deemed not dangerous, treatment alternatives such as medications or ablation may be pursued. It seems that a correlation exists between atrial tachycardia and atrial fibrillation (AF) in certain individuals.

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:

Medications are usually the initial treatment for the majority of cases. They prove to be highly effective in many individuals. However, for those who experience ongoing episodes despite medication usage, have difficulties tolerating prescribed medications, or prefer to avoid long-term medication use, procedural options can be considered. In certain cases, particularly with atrial tachycardia, the use of a pacemaker may be necessary to safely and effectively administer medications.

There are various medications available, and combinations of medications may be prescribed based on your specific condition. Most medications used to address abnormal rhythms require regular monitoring by your general medical practitioner. They can be used either as a “pill-in-pocket” approach for immediate use during episodes or taken regularly as part of a maintenance regimen.

What is pill-in-pocket approach?

The concept of the “pill-in-the-pocket” approach involves the utilisation of specific prescribed medications, typically beta blockers, calcium channel blockers, flecainide, or sotalol. This approach is employed when patients with a history of SVT experience recent onset episodes of suspected or confirmed SVT. Normally, the initiation of this approach is determined by a cardiologist or electrophysiologist. Its objective is to terminate the suspected SVT episode without requiring the patient to visit the emergency department or be admitted to the hospital.

The “pill-in-the-pocket” medication is typically taken if a suspected SVT episode does not respond to the Valsalva manoeuvre and persists for more than 10-15 minutes. It is important to note that medications may take a few hours to take effect. If you are feeling severely unwell during your episode or if it lasts for an extended period, it is advisable to seek immediate medical attention. It is crucial not to drive in such circumstances.

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.