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Cryoablation therapy for treatment of Atrial Fibrillation

prof. Usman Jafferprof. Usman Jaffer

Introduction

Atrial fibrillation is a common, for every 1000 people atrial fibrillation is diagnosed in 6.7 people each year in the United Kingdom(1). It is more common with increasing age(1).

Atrial fibrillation is a condition in which the chambers of the heart do not beat in a coordinated way. There are four chambers in the heart. These chambers normally beat together. The two chambers at the top of the heart beat more often in comparison to the two chambers at the bottom of the heart. The result of this mismatch is an irregular heartbeat.


Left side: Normal organised flow of electrical signals in the heart - from the SA node in the Right atrium to the ventricles. Right side: Atrial Fibrillation - the electrical activity begins in a disorganised and uncoordinated way.

Atrial fibrillation can be caused by an issue with the valves between the chambers, this puts extra strain on the chambers and can mean that the top two chambers become thickened. This thickening changes the conduction at the top of the heart, causing atrial fibrillation. Atrial fibrillation can also be caused by other conditions of the heart, this is known as non-valvular atrial fibrillation. In this case, damage to the conduction system in the heart from heart disease results in abnormal rhythm.


What is Cryoablation

Cryoablation is the use of cooling to stop a targeted tissue working. Cryoablation uses a fluid called liquid nitrogen that enables rapid cooling of a tissue. For the treatment of atrial fibrillation, a balloon containing the cooling liquid is passed to the top of the heart to treat the targeted area.

What will happen before my procedure?

There are some tests, or investigations, that are undertaken prior to organising the cryoablation therapy. These include:

-       Visiting a specialist who will talk through your history and perform a  physical examination

-      Electrocardiograms (ECGs) to assess the rhythm and electrical activity of the heart

-      Portable or ambulatory cardiac monitoring: this is when you wear a small recorder attached to three leads that will recorder your heart rate and rhythm whilst you undertake your normal routine

-      Transthoracic echocardiography: this is a scan of the heart using ultrasound, it is done by applying the scanner to the skin of the chest and is non-invasive


What happens on the day of the procedure?

Unless specifically advised to do otherwise, you can be instructed by the following guidance:

-      Fasting: you will need to fast from midnight of the night prior to the procedure, this is to ensure that you remain safe when undergoing sedation or anaesthesia

-      Medications: on the morning of the procedure you will need to stop taking your cardiac medications such as beta-blockers or digoxin, these may be resumed after the procedure with guidance of the operating clinician

-      There is no specific need to change anything else about your daily routine

-      When you arrive, the clinician performing the cryoablation will discuss the benefits, risks, and steps of the procedure

-      You will be attached to basic monitoring equipment for the procedure, this includes leads connected by stickers to the chest and also a sensor on the finger

-      You will also have a small plastic tube inserted into a vein, known as a cannula, in order to give you necessary medicines

The Procedure

Technique

Anaesthesia

Cryoablation can be performed with sedation, meaning you will be awake and conscious throughout the procedure but feel more relaxed and sleepy than normal. Cryoablation can also be performed under a general anaesthetic, meaning you will be completely asleep.

What happens during the procedure?

-      Once in the operating room, you will be lying down for the duration of the procedure


Picture of the setup in an Electrophysiology lab. The patient lies on a table, there is a machine for x rays and TV screens to help guide the doctors.

-      Cryoablation can be performed with sedation, meaning you will be awake and conscious throughout the procedure but feel more relaxed and sleepy than normal

-      Cryoablation can also be performed under a general anaesthetic, meaning you will be completely asleep

-      An ultrasound camera is placed down the food pipe to look at the structure of the heart, this can be very uncomfortable so sedation is used to help.

Illustration of a camera being inserted down the food pipe into the stomach. This camera has an ultrasound probe attached which is used to see the heart from the inside of your stomach.

-      A local anaesthetic will be used to numb the area in which the needle will be inserted, the needle is usually inserted into the right and left groin.

Picture showing a needle being inserted into the main vein in the groin using ultrasound to guide the needle tip.

-      This needle is used to place the procedure wire used to guide the device that will later freeze the heart

-      The wire is passed into the heart for electrical recording and cryoablation

-      The wire is passed from the right side of the heart to the left side of the heart by making a small incision in the wall between the two sides of the heart

-      The electrical activity is frozen around the main pulmonary vein in this part of the heart

Device is passed from the Right to the Left side of the heart (insert). The Cryo-balloon is placed in the pulmonary vein where treatment is given.

-      Your blood will be thinned to reduce the risk of a stroke whilst the wires are in the heart

How long does it take?

The total length of the procedure will be ~120 minutes(2)

What happens after the procedure?

-      Once the procedure is finished you will be admitted for observation to ensure you recover from the procedure well

-      You will be reviewed to ensure that the heart rhythm has been treated and that there is no bleeding around the heart or in the groin area in which the needle was used

- After discharge you will be seen back in the cardiology clinic as an outpatient

How long will I be in hospital?

Typically, you will be able to go home the next day (although some patients can leave on

the same day).

What care will I need at home?

No particular care is required.

Will I need anyone at home with me?

You will need someone to stay with you for 24 hours after the procedure.

What follow up care is needed? 

You will need to be followed up in an electrophysiology clinic. You will likely need to continue your anticoagulation at least until you have discussed it with your electrophysiologist.

When can I start driving again?

Driving

You should avoid driving for two days at least. After this, you can commence driving when you feel ready to do so. There is no need for the medical team to inform the DVLA of this restriction.

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