What Is Pulmonary Vein Isolation?

Pulmonary vein isolation (PVI)

PVI is a procedure for treating atrial fibrillation, by targeting the pulmonary veins, which bring oxygen-rich blood back into the heart. It is in the pulmonary veins where the electrical signals become abnormal causing atrial fibrillation. To treat this, heart ablation is used by applying very hot or very cold temperatures to form small scars. The scar tissue in the pulmonary veins disturbs the electrical signals.

Did you know?

The first catheter ablation was first performed in 1981 in the USA to treat arrhythmia in tachycardia. However, it wasn't until 1998 that it was used for treating atrial fibrillation.¹

Anatomy of pulmonary veins

Heart anatomy

The heart is formed by 4 chambers: 

• 2 upper chambers; left and right atrium 
• 2 lower chambers; left and right ventricles. 
• It also has 4 valves; tricuspid, pulmonary, mitral and aortic.

The walls of the veins have 3 layers and are a lot thinner and less rigid than the walls of an artery, as they have to withstand less pressure. The pulmonary veins take in oxygen-rich blood from the lungs and carry it to the heart, which then sends it around the body. The heart is known as the pumping powerhouse and changes in the blood supply through the pulmonary veins may cause serious issues because the heart would not be able to receive enough oxygenated blood to send to the body.

How does atrial fibrillation happen?

Atrial fibrillation begins the fast electrical activity, from the arrhythmia in the pulmonary veins. This is maintained by many returning ripples. Because of slow conduction and reduced refraction, it is easy to re-entry. After a period of constant atrial fibrillation, the electrical remodelling happens, easing the maintenance of atrial fibrillation. The changes can be reversible at the beginning if the rhythm comes back to normal, but these can become permanent and change the structure if fibrillation continues.² 

Techniques for pulmonary vein isolation

PVI uses catheter ablation, meaning it delivers ablation therapy (either heat or extreme cold) by long tubes being inserted into the pulmonary veins.¹ 

Catheter ablation 

• Radiofrequency Ablation - Uses heat from radio waves to damage the targeted areas of the heart. It is also the most common option
• Cryoablation - uses extreme cold to temporarily freeze and permanently damage the targeted areas 

Surgical approaches

For more complicated cases, surgery may be required:

• Maze Procedure - surgically creating scar tissue to redirect the electrical impulses²  

How to know if PVI is the right choice for you?

Atrial fibrillation diagnosis criteria

To be diagnosed with atrial fibrillation, you would have an irregular heart with over 100 beats per minute, which would also have to be recorded in the electrocardiogram.³ 

Patient selection for PVI

For patients to have a PVI, they would have to have persistent atrial fibrillation even with the use of 2 antiarrhythmic medications.³ 

Procedure 

Patient preparation

Before the procedure starts, you would be given a sedative or be given a general anaesthetic. The amount given to you would depend on the arrhythmia and your overall health.³

During procedure

After the preparation, the doctor would make two incisions, to insert long and flexible tubes (catheters) through a blood vessel either from the groyne (common) or through the shoulders or neck (less common), and into the heart. 

Depending on the type of ablation, your doctor will inject a dye ( contrast) through the catheter, to show the blood vessels clearly on the X-ray imaging. 

The sensors at the tip of the catheter will then send electrical impulses and also record the heart’s electrical impulses. This is where your doctor would be able to detect the area causing arrhythmia and apply the ablation. This part of the procedure is also called the electrophysiology (EP) study.

The doctor would then move the catheter from the upper right chamber of the heart to the upper left chamber where the pulmonary veins are connected. Extreme cold (cryoablation) or heat (radiofrequency energy) are used to form small scars in the region affected and block the arrhythmia. It is common for all 4 pulmonary veins to be treated during PVI.³ 

Complications and risks 

Common complications

PVI is generally a safe procedure. However, as any procedure, there are a few complications, including:

• Allergic reaction to dye used fluoroscopy
• Infections in the incisions
• Phrenic nerve injury
• Hole in the heart ( 1% risk)
• Vein damage (1% risk)
• Stroke (0.5% risk )
• Damage to the oesophagus (0.25%risk)

Strategies to reduce risk

In most cases you will need to take medication post-surgery, for a few months, including:

• Antiarrhythmic medication - controls the abnormal heart rhythms, until the ablation starts to take effects
• Anticoagulants (blood thinners) - reduce the risk of stroke

Periodic blood tests can reevaluate the dosage of the medications you should be taking.

During the first few follow-up appointments, your doctor may also do several tests to check on the health of the heart:

• Electrocardiogram
• Echocardiogram
• Spiral cardiac CT scan 

Future directions in pulmonary vein isolation

As the years go by, researchers are always striving to investigate new technology and this can be seen for PVI too. A study from 2023, investigated and evaluated different technologies. A newer technology mentioned is pulse field ablation also known as irreversible electroporation. This detects the high voltage field that is needed for damaging the targeted area. A unique feature mentioned is that it is tissue-specific, meaning the electrical field threshold for the area is very low and can also be done in various ways and not just limited to catheters.

Summary

PVI is a technique used for treating atrial fibrillation, using catheters that use either heat or cold to damage the area to recover a normal heartbeat. The procedure may have some complications and risks, such as nerve damage or even stroke even though there are fewer chances, so monitoring after the procedure is essential. Also, in effort to understand more complicated cases of atrial fibrillation, it is important to study other ablations apart from the pulmonary veins. So, researchers try to change the new technologies into being used for clinical practice, as it can improve the quality of the life of the patients.