Paroxysmal Supraventricular Tachycardia Diagnosis And Treatment

Introduction

Tachycardia refers to an increased heart rate beyond the normal limit. Tachycardia in adults is defined as having a heart rate above 100 beats per minute. However, diagnosing tachycardia depends on certain factors such as age and physical condition.¹ The heart is responsible for pumping oxygen-rich blood throughout the body in order to stay alive. The amount of blood pumped and how rapidly it is pumped is based on the needs of various tissues and muscles during certain activities.² The heart consists of the cardiac conduction system, a special electrical system that regulates the heart rate and rhythm.³

Contraction of the heart involves the following steps:

1. The signal begins at the sinoatrial node (SA node), which is the pacemaker of the heart. The SA node is located at the upper wall of the right atrium and kickstarts the electrical activity.
2. The signal then travels down through the atria, causing blood to be pumped into the ventricles.
3. The signal then reaches the atrioventricular node (AV node), another group of pacemaker cells between the atrium and the ventricles. Conduction of the initial electrical signal is terminated here, allowing the ventricles to fill with blood.
4. The AV node then initiates another signal that travels through the ventricular wall, causing them to contract so that blood is pumped out from the ventricles through large arteries.
5. The ventricle relaxes and the whole process repeats in the SA node.

There are generally 3 subtypes of tachycardia:⁴

• Sinus tachycardia – an increased heart rate due to certain triggers such as pain, emotions or illness which resolves after the trigger is eliminated.
• Supraventricular tachycardia (SVT) – SVT occurs in the atria, which are the upper chambers of the heart.
• Ventricular tachycardia – occurs in the ventricles, which are the lower chambers of the heart.

Paroxysmal Supraventricular Tachycardia (PSVT) is a type of SVT. In PSVT, it has an abrupt onset and termination. They occur in other heart issues except the ventricles, usually the atria. PSVT generally affects younger people and may occur during heavy exercise. 

Diagnosis 

SVT can present with a variety of symptoms such as:

• Palpitations (often described as a fluttering sensation in the chest)
• Chest discomfort/pain
• Sweating
• Breathlessness
• Dizziness

These symptoms have a sudden onset and some patients can identify these triggers. However, certain symptoms require more attention as it may indicate unstable tachycardias. Symptoms including altered mental status, hypotension and severe chest pain should prompt medical attention to be sought immediately.⁵ Diagnosing SVTs involves finding out the cause. Causes of SVT may be down to several reasons, ranging from infections to cardiac-related issues. Firstly, vitals are taken and a physical examination is done to ensure the patient is stable before proceeding. In arrhythmias, the main diagnostic tool for investigation is an electrocardiogram (ECG). A typical ECG of a patient who is suffering from SVT shows a rapid heart rate (>100 bpm), a narrow QRS complex (<120 ms), and a regular or irregular heart rhythm depending on the type of arrhythmia.⁶  

If the findings are inconclusive, a Holter ECG can be considered to record the heart’s electrical activity over some time (24-48 hours). Once it is confirmed, laboratory tests can be done. These include a complete blood count (to look for signs of infections), a thyroid function test (to check for thyroid disorders) and electrolytes. A heart scan can also be ordered (usually Transthoracic Echogram) to investigate any structural heart abnormalities or signs of heart failure.⁷ 

Treatment

The treatment of PSVT depends on 2 factors:

• The condition of the patient and 
• The type of rhythm present.⁸

Patients who are considered hemodynamically unstable, that is, with a high heart rate and low blood pressure, should have their ECG evaluated to check if they are in sinus rhythm. If they are not in sinus rhythm, a cardioversion should be done immediately to prompt the heart back into sinus rhythm. Once sinus rhythm is achieved, the underlying cause should be investigated.

In stable patients, vagal manoeuvres are usually done to slow the heart rate down. These manoeuvres aim to lower the heart rate via vagal nerve stimulation, in turn slowing down the AV node and terminating the arrhythmia. Medications can also be used to help with SVT.⁹ Medications such as antiarrhythmics, beta blockers and calcium channel blockers are proven successful in terminating SVT. 

If a patient is suspected of having a pre-excitation syndrome or where pharmacological treatments have failed a catheter ablation may be considered. A catheter ablation is a drug-free alternative and involves passing catheters into the heart via blood vessels.¹⁰ The heart muscle with the abnormal rhythm is identified and removed in this process. It is a successful procedure whereby a majority of patients are resolved from their conditions.

Acute and long term management 

As mentioned, SVTs can occur abruptly and individuals should be aware of how to manage an acute attack. When an acute episode occurs, SVTs tend to stop on their own after some time and in these cases treatment is not needed. However, it can also be stopped by various methods such as drinking cold water, submerging your face in cold water or holding your breath.¹¹ If the episode persists, or if they do not resolve after some time. Consider seeking medical treatment immediately. In cases where the individual is driving, it is advisable to stop driving and inform relevant authorities if they are experiencing symptoms while driving. 

Long-term management of SVT focuses on preventing future attacks, managing the symptoms and monitoring disease progression. SVTs can be caused by certain triggers. If these triggers are identified, precautions can be taken to avoid these triggers. Medications are also known to help to reduce these attacks from occurring. Therefore, medication adherence is important to minimise the frequency of these attacks. Those who suffer from SVTs are usually seen by the cardiologist. Cardiologists are doctors who specialise in the heart and are responsible for diagnosis and managing heart-related conditions. Patients who are affected should follow up with their cardiologist regularly to monitor their situation and can start any intervention if necessary as early as possible, drastically improving prognosis. 

Prognosis and complications 

Generally, PSVT is not life-threatening. However, it can be unpleasant and may deteriorate the quality of life of an individual. With proper treatment and management, those who suffer from PSVT tend to have a good outcome. However, the outcome is dependent on factors such as age, health conditions and treatment adherence. Thus, the patient must take their medications and follow up with their doctors regularly. Despite not being life-threatening, unmanaged PSVT can lead to certain complications such as stroke, heart attack or even a heart block which might need a pacemaker.¹² Without treatment, these complications can be fatal.

Summary

Paroxysmal supraventricular tachycardia is a type of supraventricular tachycardia that commonly occurs in younger individuals. PSVT happens and resolves abruptly and is typically non-life threatening but it may cause discomfort in some individuals. PSVT usually occurs due to certain triggers and is typically diagnosed via an ECG. However, additional testing can be done to find out the causes of these attacks as well as monitor disease progression. Management is based on avoiding certain triggers and regulating the heart rate. Certain medications can help to keep PSVT in control. Despite this, a regular follow-up with doctors is crucial to make sure that the condition is well managed as untreated PSVT can lead to serious complications. Catheter ablation is also a great method to manage PSVT but it is more invasive compared to other methods. Although not life-threatening, PSVT can still affect the quality of life. Hence, it is still essential that we put more focus on researching new methods to manage to improve the quality of life of affected individuals.