Atrial Tachycardia

What is Atrial Tachycardia?

Atrial Tachycardia (AT) is a form of supraventricular tachycardia (SVT) which is characterized by fast heart beats, more than 100 to almost 300 per minute. The term Tachycardia signifies heartbeat beyond normal pace. Atrial Tachycardia refers to faster heartbeat due to signal sent from atrium. In this form of SVT, the electrical impulse is received from a different location of atrial tissue instead of SA or sino-atrial node.

In normal conditions, the SA node (a small tissue mass) is situated close to the right atrium and sends the impulse. A false cardiac rate is caused due to this alternate origin of the impulse. Hence, premature atrial contractions cause atrial tachycardia to occur.

Atrial Tachycardia Incidence

AT is a rare condition, comprising around 5 to 15% of the SVT cases. It seems to be common in children diagnosed with congenital heart ailments, although it may strike individuals of any age groups. MAT is more infrequent, with an occurrence rate of 0.05 to 0.32% of the hospitalized patients. Elderly patients having several other diseases may be at risk.

Atrial Tachycardia vs. Ventricular Tachycardia

With the contraction of the right atrium, the ventricle receives deoxygenated blood and transports it into the lungs through the pulmonary artery. Similarly, the left atrium and ventricle function by absorbing oxygenated blood and releasing into the body. The disturbance in the rhythm of the heart may originate in the atria, where the focus is located in any one of the two chambers, leading to AT. On the other hand, Ventricular tachycardia is caused by signals coming from ventricles which do not allow its maximum contraction for efficiently pumping blood to the body.

Classification of Atrial Tachycardia

AT can be classified into two groups, namely:

Focal Atrial Tachycardia

It occurs from one site of the atrium – left or right. This is different from Atrial flutter and Atrial fibrillation, which occur in several sites or circuits of bigger dimensions. The condition arises suddenly and subsides within a specific time.

Reentrant Atrial Tachycardia

It is common in patients diagnosed with structured heart ailments. It mainly occurs after performing surgery as a result of scars developing in atria or due to incisions in the atria.

Atrial Tachycardia Vs Atrial Flutter

Atrial flutter is caused when electrical impulse flows around large tissue areas like the whole of the right or left atrium. It is associated with Macroreentrant atrial tachycardia and generates atrial rate around 240 to 300 every minute.

Atrial Fibrillation Tachycardia

Atrial fibrillation is even more common than sinus tachycardia and presents as a chaotic arrhythmia in the atrium. Atrial Fibrillation results in the small rapid movement of the atrium instead of contracting as happens during atrial flutter. Atrial fibrillation is also common in some patients, with Atrial flutter. Presence of both often creates difficulty in administering treatment to a patient.

What is Paroxysmal Atrial Tachycardia?

This is a type of acute atrial tachycardia which commences and ends all of a sudden. It is also termed as Bouveret-Hoffmann syndrome and paroxysmal supraventricular tachycardia (PSVT). Heart rate noted during this period generally varies from 160 to 200 beats, every minute. It is more common in newborns and young individuals. Paroxysmal atrial tachycardia with block may result due to digitalis poisoning, especially in critically ill heart patients. This type of arrhythmia usually ceases with the administration of potassium.

Multifocal Atrial Tachycardia

Usually common in aged people, Multifocal Atrial Tachycardia (MAT) is characterized by rapid heartbeat, which sets in when intense or several electrical impulses are sent from the atria located in the upper part of the heart to the ventricles which forms the lower part.  It is often symptomatic but this is highly subjective.

Ectopic Atrial Tachycardia

This form of arrhythmia is rare but prevalent in infants. It is marked by increased heart beat in a certain period of time thereby gradually returning back to normal rhythm. The baby suffers three premature contraction of the atrium altogether. It might occur in adults too and the response to treatment can be different for them. Ectopic atrial tachycardia symptoms generally include a change in the rate of heartbeat.

Causes of Atrial Tachycardia

AT has been found to occur in healthy patients, alongside those with heart ailments. It is not known why this afflicts only some part of the population. Know about some of the causes of this condition:

• There is a fair chance of its occurrence following the treatment of atrial fibrillation with cardiac ablation. Other causes related to the heart are weak or injured heart muscles, defective heart from birth and problems in the valve.
• Electrolytes are essential to facilitate functions in the heart. Imbalance caused in these minerals can be caused due to vomiting, dehydration or diarrhea. In these conditions, calcium may soar high and magnesium and potassium may decrease, causing AT. Dehydration can be caused due to excess intake of alcohol, nicotine, drugs or caffeine.
• Medication like digoxin, which is administered to address heart diseases, can lead to AT. Even surgeries like coronary artery bypass grafting and heart valve replacement may double the risk of AT in patients.
• MAT is predominantly caused by underlying diseases, often critical ones. They are more prone to digitalis poisoning.
• Underlying medical conditions like hyperthyroidism, chronic lung conditions and pulmonary edema are equally responsible for causing AT.
• Considering the risk factors and causes responsible for AT, it must be concluded that gaps caused in the ablation lines might be responsible to certain extent.

Symptoms of Atrial Tachycardia

The symptoms may not be universally same. Sometimes, AT is found to be asymptomatic in certain individuals except slight awareness about palpitation. Some of these symptoms can be listed:

• Pressure or pain in the chest
• Fatigue
• Fainting/dizziness
• Sudden shortness in breath or increased breathlessness
• Frequent urination
• Pounding or fluttering in the chest

Atrial Tachycardia Diagnosis

In case of the occurrence of arrhythmia, some of these tests are generally performed on the patient:

Blood Tests

Laboratory studies are required to rule out the causes like anemia, hyperthyroidism and other metabolic problems. Serum chemistry, arterial blood gas level and hemoglobin levels are tested.

ECG (Electrocardiogram)

This diagnostic tool is essential to record the electrical activity of the heart. Electrical impulses are jotted on a paper via the machine, which helps in determining the design of the flow of electrical current through the heart along with Arrhythmia.

Holter Monitor

This is an effective way of recording ECG, while a patient is doing his daily chores. It is portable and can be worn all the time. It can detect arrhythmia that is not conspicuous via ECG.

Event recorder

If symptoms are infrequent, a loop recorder or event recorder can be worn for a few days for correct diagnosis of AT.

MSI (Magnetic Source Imaging)

When weak magnetic fields are caused by heart, it is detected by this device.

Electrophysiology Study (EP)

This is an effective detection tool as well as treatment procedure to a certain extent. It offers detailed report alongside scope for treatment during the study.

Exercise Stress Test

This is often done to test the mechanism of AT.

Echocardiography

This is yet another diagnostic mode for measuring size of the left atrial, assess and detecting structural heart disease. It also evaluates functions of the left ventricle, pulmonary arterial pressure and pericardial pathology.

Treatment for Atrial Tachycardia

As a primary treatment plan, AV nodal blocking agents including calcium channel blockers and beta-blockers can be used. Aims of the treatment include controlling the heart rate, establishing normal rhythm in symptomatic AT bouts and the same during asymptomatic period of AT. During pregnancy, the medication (which was earlier used for treating AT) is usually changed to avoid side effects. Some of the basic treatments applied with the occurrence of AT has been enumerated below:

Cardioversion

It is the adopted treatment when drugs to control the rhythm fails and the patient cannot bear it. But, certain considerations are made before it is performed. It might be well-received by certain ATs like MAT and automatic AT.

Antiarrhythmic therapy

This therapy, along with drugs for stopping the recurrence of bouts of AT, can be used on patients. These drugs are not safe as they might lead to other forms of heart arrhythmias.

Electophysiology (EP) study

It is a treatment modality for patients who do not opt for medication. Disturbance in the rhythm of the beats can be addressed with EP, in which radiofrequency energy is administered into the specific site with the aid of inter-cardiac electrode catheters in the lab.

Treatment for Multifocal Atrial Tachycardia

The most important aspect of MAT treatment is providing supportive measures. Whether or not Antiarrhythmic therapy is useful in this regard is not yet clearly understood. Since AT mainly arises due to a secondary cause, it is a bit difficult to ascertain the treatment. However, Magnesium, Metoprolol and Verapamil are some of the considered remedies for reducing the rate. Relief can also be provided by administering patients with oxygen.

Treatment for Paroxysmal Atrial Tachycardia

During the episode of PAT, some of these may be performed:

Picture 2 – Atrial Tachycardia Image

• Holding the breath by covering the mouth and nose and then releasing.
• Massaging the carotid sinus. This can relieve the symptoms to a certain extent.
• In case of the failure of these techniques, adenosine or verapamil injections can be administered for quick relief.
• Cardioversion, which is considered to be the last resort.

Atrial Tachycardia Prognosis

AT might prove to be fatal for patients suffering from congenital heart disorders. This is because they require palliative cardiac surgery like Fontan procedure. In those having normally structured hearts, a low death rate can be noticed. On the other end, MAT significantly improves when the underlying diseases get better with treatment. AT has never been linked with risks like stroke. By altering lifestyle, a lot of positive outcome can be attained. Episodes of AT can be managed by adopting certain life-style changes. Prolonged AT can be bad as it can weaken the ventricular muscle and induce congestive heart failure.

Atrial Tachycardia Life Expectancy

An AT patient may have a normal life span as there are no reports of shortened life due to this disorder.