What is Sinoatrial Nodal Reentrant Tachycardia?
The sinoatrial node (or SA node for short) is a part of your heart that’s shaped like a crescent and is found just beneath the outer layer of the heart. In an average adult, it’s about 13.5 millimeters long and connected to both the vagus nerves and sympathetic nerves, which help control heart rate. The SA node gets its blood supply from a small artery known as the sinoatrial nodal artery. In about 60% of people, this small artery branches off from the right coronary artery. In the other 40%, it comes from the left circumflex coronary artery. The SA node plays a crucial role in the heart’s electrical system and sets the heart’s normal rhythm.
Sinoatrial nodal reentrant tachycardia is an uncommon type of heart rhythm disorder (or ‘paroxysmal supraventricular tachycardia’). If you have this condition, you might observe the following signs on your heart rhythm test, or electrocardiogram:
* A heart rate usually between 100 to 150 beats per minute
* A certain pattern of electrical waves (known as P waves) that’s similar to accelerated heart rate
* A premature contraction of the heart’s upper chambers (atria) often seen at the start or end of the rapid heart rate
* Sudden start and stop of the rapid heart rate
The American College of Cardiology, the American Heart Association Task Force, and the Heart Rhythm Society provide guidelines for doctors and they define sinoatrial nodal reentrant tachycardia as an fast heart rate caused by a tiny circular electrical pathway within the SA node.
What Causes Sinoatrial Nodal Reentrant Tachycardia?
The specifics of how sinoatrial nodal reentrant tachycardia works are still a bit unclear, and there are three possibilities that have been discussed. Sinoatrial nodal reentrant tachycardia is a type of fast heart rhythm.
The first possibility is that the cycle which is causing the rapid heart rhythm is happening primarily within the sinoatrial node. The sinoatrial node is an area of the heart that sends out electrical signals that regulate your heartbeats, so its role in this is crucial.
The second theory is that the cycle involves the sinoatrial node playing the role of a refractory center. This means the node is the central area where the electrical activity recovers after sending out a signal, and from there another signal is sent out, causing the fast heartbeat.
The third theory is that the rapid heart rhythm involves both the sinoatrial node and the perinodal tissue, the tissues surrounding the node.
Most of the evidence suggests that the cycle causing the fast heart rhythm usually happens either within the sinoatrial node alone, or in both the sinoatrial node and the surrounding tissue. The theory where the sinoatrial node acts as a refractory center doesn’t have much evidence supporting it.
Risk Factors and Frequency for Sinoatrial Nodal Reentrant Tachycardia
SANRT, a type of fast heartbeat, is not very common and is infrequently accompanied by symptoms. While it’s more common in adults and children with heart issues, only 2% to 17% of patients with sporadic, fast heartbeats have been found to have SANRT. It’s challenging to know exactly how many people have SANRT both in America and worldwide because people with this condition usually don’t have symptoms and thereby don’t seek specialized heart examinations. Further complicating things, SANRT often looks like a different type of fast heartbeat (sinus tachycardia) on heart readings, so it can often slip under the radar.
- SANRT is a fast heartbeat that’s quite rare and normally doesn’t come with symptoms.
- It’s seen more in adults and children with heart problems.
- Studies have found that between 2% and 17% of patients with sporadic fast heartbeats have SANRT.
- Determining the exact number of people with SANRT is difficult since people with this condition often don’t show symptoms and don’t undergo specialized heart examinations.
- Moreover, since SANRT looks like sinus tachycardia on heart readings, it often gets missed or mistaken for another condition.
Signs and Symptoms of Sinoatrial Nodal Reentrant Tachycardia
SANRT, an abbreviation for Sinoatrial Nodal Reentry Tachycardia, is a cardiac condition that typically doesn’t present with any symptoms. However, in certain rare cases, affected individuals can experience a series of discomforting effects. These may include:
- Intermittent palpitations
- Dizziness
- Shortness of breath
- Neck pain or discomfort
- Chest pain or discomfort
- Anxiety
- Frequent urination (caused by increased secretion of a hormone called the atrial natriuretic factor)
Individuals with SANRT and preexisting heart conditions like coronary artery disease or heart failure may also present more severe symptoms like a heart attack or sudden cardiac exacerbation respectively. Heart rate in these cases usually falls in the 100-150 bpm range.
For those patients who have preexisting heart disease, there can be symptoms like chest pain, symptoms of heart failure like wheezing and swelling in the legs, and increased breathing rate. In very rare occurrences, patients may faint due to a fast heartbeat causing less blood to fill the heart chambers, which then results in decreased brain blood flow. Additionally, blood pressure can be low due to less blood filling in the heart chambers. This may be a significant discovery during a patient’s physical examination.
Testing for Sinoatrial Nodal Reentrant Tachycardia
If you visit a doctor with symptoms that suggest you might have sinoatrial nodal reentrant tachycardia (SANRT, a condition where your heart beats abnormally fast), they will primarily examine your medical history and perform a physical examination. This includes checking your vital signs, such as breathing rate, blood pressure, body temperature, and heart rate. They will also likely perform a special test known as an electrocardiogram (ECG) to monitor the electrical activity of your heart.
The doctor will also check for other potential heart conditions that might be contributing to your symptoms, such as clogged heart arteries (known as coronary artery disease) or heart failure.
During the assessment, it’s crucial to determine whether your body is coping well with the fast heart rate. Key aspects they may look at include your blood pressure, how alert you are and your breathing rate.
It might also be necessary to perform tests to measure the function of your thyroid (a gland that produces hormones controlling metabolism) and lungs, along with standard blood tests. Because SANRT often occurs alongside other heart conditions, your doctor might also order an echocardiogram. This is a type of scan that uses sound waves to create a detailed image of your heart, helping your doctor see any abnormalities in its structure.
Treatment Options for Sinoatrial Nodal Reentrant Tachycardia
Most people with a specific type of abnormal heart rhythm known as SANRT usually don’t require medical treatment because a heart rate of 100 to 150 beats per minute typically doesn’t cause any symptoms. However, in rare cases, people who have frequent SANRT episodes might have symptoms and need medical management. Treatment may also be useful in preventing long-term complications like tachycardia-induced cardiomyopathy. This is a condition that can weaken your heart’s ability to pump blood effectively due to a fast heart rate over a prolonged period.
If a person with SANRT needs medical attention, doctors will first assess whether the person is hemodynamically stable. Hemodynamic instability means that the heart isn’t pumping enough blood to the body, leading to symptoms like fast heart rate, low blood pressure, chest pain, changes in mental state, difficulty breathing, or even shock. If a patient is unstable, immediate medical intervention is needed to bring the heart rate back to normal, often through a procedure called electrical cardioversion. This procedure uses electricity to reset the heart’s rhythm.
If the patient is stable, a technique known as carotid massage or other similar methods may be used first to try and return the heart rhythm to normal. If these methods are ineffective or inappropriate, a medication called adenosine can be given intravenously, as long as the patient doesn’t have any conditions that would make use of adenosine unsafe.
Currently, because SANRT is rare and doesn’t often cause complications, there isn’t a large amount of research regarding drug treatment for people with this condition. For ongoing management of recurrent SANRT, a procedure called radiofrequency catheter ablation is usually recommended over long-term medication use, due to its higher success rates and fewer long-term side effects. However, in certain cases where continuous medication is necessary, medications such as verapamil, digoxin, or amiodarone can be used.
What else can Sinoatrial Nodal Reentrant Tachycardia be?
Here are different types of fast heart rates or tachycardias:
- Junctional ectopic tachycardia
- Nonparoxysmal junctional tachycardia
- Atrial flutter with variable block
- Atrial fibrillation
- Intraatrial reentrant tachycardia
- Atrial tachycardia
- Multifocal atrial tachycardia (MAT)
- Sinus tachycardia
- Inappropriate sinus tachycardia
- Atrial flutter
- Atrioventricular nodal reentrant tachycardia
- Atrioventricular reciprocating (reentrant) tachycardia
