Adenosine for SVT (Supraventricular Tachycardia): Side Effects & Warnings

Key Takeaways

Adenosine is an injectable solution used to treat paroxysmal supraventricular tachycardia (PSVT), a type of arrhythmia that causes the heart to beat faster than normal, while the heart rhythm can be normal or abnormal.
Adenosine expands blood vessels and increases blood flow to the heart muscle during cardiac stress testing. Adenosine also reduces heart rate in people with paroxysmal supraventricular tachycardia (PSVT).
People with certain types of heart problems should not get an intravenous adenosine injection. Side effects of adenosine can include rapid flush on the face, shortness of breath, and chest discomfort.

Paroxysmal supraventricular tachycardia (PSVT) is a type of arrhythmia causing an abnormally fast heart rate that happens as the result of problems with the heart’s electrical system. Keep in mind that while the heart rate is elevated during SVT, the heart rhythm can be either normal or abnormal.

When a person goes into SVT, the heartbeats can be anywhere between 100 and 300 beats per minute. The good news is SVT is not dangerous for a lot of people as their hearts continue to pump normally to perfuse (supply blood) the rest of the body.

Adenosine (brand names: Adenocard, Adenoscan) is a prescription drug that has both diagnostic and therapeutic uses. It has coronary vasodilation effects (it expands blood vessels and increases blood flow to the heart muscle) and is used during cardiac stress testing. Doctors also administer adenosine intravenously to reduce heart rate in people with paroxysmal supraventricular tachycardia (PSVT). Please continue reading to learn more about the warnings and adverse effects of adenosine.

How do doctors treat paroxysmal supraventricular tachycardia?

Treatment for paroxysmal supraventricular tachycardia consists of vagal maneuvers such as the Valsalva maneuver (you can learn to do this at home) to temporarily slow down your heart rate during an episode of PSVT. If you have frequent episodes of PSVT, your healthcare provider may recommend other treatments such as carotid sinus massage, catheter ablation procedures, implantable devices such as a permanent pacemaker, electrical cardioversion, and antiarrhythmic medications to prevent irregular heart rhythms. Adenosine, verapamil, and diltiazem are the drugs of choice for treating PSVT. They are given intravenously in a hospital setting.

Outside of the hospital, calcium-channel blockers (CCBs), beta-blockers (BBs), and antiarrhythmic medications are available as oral tablets to take daily to control abnormal rate and rhythm.

How does adenosine help in treating supraventricular tachycardia?

Endogenous adenosine (adenosine monophosphate and adenosine triphosphate) is a naturally occurring substance that plays a role in metabolism. The main effects of adenosine on the cardiovascular system include slowing of the heart rhythm, widening of the coronary arteries, and lowering blood pressure.

When adenosine is used as a medication to treat PSVT, it binds to adenosine receptors that are found throughout the body, but most notably in the cardiac atrioventricular (AV) nodal tissue. The AV node is a structure in the heart that electrically connects the atria (upper heart chambers) and ventricles (lower heart chambers).

Adenosine administration slows conduction and interrupts reentry pathways in the atrioventricular node (AV node), thus restoring normal sinus rhythm in patients with paroxysmal supraventricular tachycardia (PSVT), including PSVT associated with a condition called Wolff-Parkinson-White syndrome.

Certain substances, such as caffeine and theophylline (a medication used to treat bronchospastic lung diseases such as asthma or chronic obstructive pulmonary disease COPD), are adenosine receptor antagonists. They block or inhibit adenosine’s vasoactive effects.

What should I know about adenosine administration?

Adenosine is a prescription medication that comes as an injectable solution. It is given by intravenous injection (into a vein) in a hospital setting. When clinically advisable, in the absence of cardiovascular instability, healthcare providers usually try vagal maneuvers, such as the Valsalva maneuver, before adenosine administration to try and convert PSVT to a normal sinus rhythm.

Short-term management of supraventricular tachycardia (SVT) consists of intravenous adenosine or calcium channel blockers. Long-term pharmacologic therapy for patients with refractory (recurring) supraventricular tachycardia depends on the type of arrhythmia, the frequency and duration of the episodes, the person’s symptoms, and associated risk factors.

Adenosine does not convert other types of abnormal heart rhythms, such as atrial fibrillation, atrial flutter, or sustained ventricular tachycardia, to normal sinus rhythm.

Who should not get adenosine?

People with certain types of heart problems should not get an intravenous adenosine injection, such as those with a second or third-degree AV block or sinus node disease, such as symptomatic bradycardia or sick sinus syndrome (other than people with a functioning artificial pacemaker). Also, anyone with a known hypersensitivity (previous allergic reaction) to adenosine should not receive this medicine again.

What are the side effects of adenosine?

Some of the reported side effects of adenosine include facial flushing, headache, sweating, chest pain, chest pressure, palpitations, low blood pressure, shortness of breath, fast breathing, lightheadedness, dizziness, numbness and tingling, burning sensations, blurred vision, heaviness in the arms, neck pain, back pain, nausea, metallic taste in the mouth, throat tightness, and groin pressure. It also relevant to note that a person may feel odd initially after receiving adenosine due to it blocking conduction through the AV node.

How long do adenosine side effects last?

Adenosine has a very short half-life of just 10 seconds (this is the time it takes for the adenosine concentration to reduce to half its initial value). Due to the rapid metabolism of this medicine, the adverse effects of adenosine are usually short-lived and self-limited and resolve quickly, as reported by nuclear stress test candidates (as mentioned, adenosine is a diagnostic agent used during a cardiac stress test).

But sometimes, the side effects of adenosine may persist for 24 hours. If there are prolonged side effects, doctors can treat them depending on the specific effect. As mentioned, methylxanthines like caffeine and theophylline are adenosine receptor antagonists and can block the effects of adenosine.

How does adenosine for SVT make you feel?

Adenosine commonly produces symptoms such as a rapid flush on the face. The facial flushing and other symptoms, such as shortness of breath and chest discomfort reported, are usually of a short duration. Serious adverse reactions are rare.

Is adenosine safe for SVT?

Like most medications, adenosine administration carries some warnings and risks.

Drug interactions

Certain drugs interact with adenosine and can cause moderate interactions or known serious interactions.

Medications that affect the heart, such as quinidine, beta blockers, calcium channel blockers, and angiotensin-converting enzyme (ACE) inhibitors, have been used safely with adenosine during cardiac nuclear stress tests without any known severe interactions. Rarely, cardiac glycosides (digoxin, digitalis) and calcium channel blockers (verapamil) can cause ventricular fibrillation, a type of ventricular arrhythmia, when used in combination with adenosine, due to their additive depressant effects on the AV node and SA node.

Your health care professional may make dosing considerations based on drug interactions. For example, methylxanthines (caffeine, theophylline) can block the effects of adenosine. Therefore, in the presence of these substances, high-dose adenosine may be required for the medicine to be effective.

The antiplatelet drug dipyridamole can enhance the effects of adenosine. Therefore, a smaller dose of adenosine may be needed if someone is on dipyridamole.

The antiseizure drug carbamazepine can increase the degree of heart block caused by other drugs. Adenosine decreases conduction through the AV node, and the use of adenosine and carbamazepine together may lead to higher degrees of heart block.

Use during pregnancy

Given that endogenous adenosine appears throughout the body (it is a naturally occurring substance), this drug is not anticipated to cause maternal or fetal harm. But, studies on the safety and efficacy of adenosine in pregnant women have not been done. Therefore, this drug is only used during pregnancy if absolutely necessary.

Use in pediatric patients

No controlled studies have been done in pediatric patients to establish the safety and efficacy of adenosine for converting paroxysmal supraventricular tachycardia (PSVT) to normal sinus rhythm. However, intravenous adenosine is commonly used to treat PSVT in pediatric patients, including newborns, nursing infants, children, and adolescents.

Use in older adults

No clinical studies have been done to assess the safety and efficacy of adenosine use for PSVT in people aged 65 years and older. In general, this drug is used with caution in older adults since they are more likely to have reduced heart function, AV nodal dysfunction, other coexisting diseases, or be on medications that can affect cardiovascular hemodynamics and lead to complications.

Heart block

Adenosine injection decreases conduction through the atrioventricular node (AV node) and can lead to a short-lived first-, second-, or third-degree heart block, which may require treatment. These effects are usually short-lasting and self-limited. Adenosine is given in a hospital setting where resuscitation measures are available. People who develop high-level heart block after one dose of adenosine are not given additional doses.

Transient or prolonged asystole can occur after adenosine administration and may be fatal in some cases. There are also rare reports of ventricular fibrillation following adenosine administration, requiring resuscitation. The risk of these complications is higher with the concomitant administration of digoxin or digoxin and verapamil.

New arrhythmias

Approximately half of all patients treated with adenosine for PSVT develop new arrhythmias on electrocardiogram at the time of conversion to normal sinus rhythm. These include premature atrial contractions, premature ventricular contractions, atrial fibrillation, sinus tachycardia, sinus bradycardia, skipped beats, and varying degrees of AV nodal block. These abnormal rhythms are generally short-lived, lasting only a few seconds, and resolve without intervention.

Respiratory effects

Administration of adenosine by inhalation can cause bronchoconstriction (narrowing of the airways) in asthmatic patients and lead to worsening symptoms. Adenosine IV infusion has been reported to cause respiratory compromise in people with obstructive lung disease. Adenosine is therefore used with caution in people with lung disease and generally avoided in people with asthma. Your healthcare professional may need to stop adenosine administration if you develop severe respiratory difficulties.

Convulsions

There are some convulsive seizures reported, including tonic-clonic (grand mal) seizures along with loss of consciousness, in postmarketing reports of adenosine for paroxysmal supraventricular tachycardia.

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