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Electrophysiology - Catheter Ablation

Overview

To ablate means to remove or burn - in this case tiny amounts of tissue from the surface of the heart. Catheter ablation is a procedure that is used to destroy very small amounts of abnormal heart tissue that is responsible for your heart rhythm problems. There are various energy sources doctors can choose to produce lesions to treat heart rhythm problems via catheter ablation. The treatment applications used at Mercy Angiography are radiofrequency (RF) ablation and cryoablation. The use of radiofrequency (RF) waves to burn tissue is a well-established treatment for arrhythmias. The evolution of cryothermal (cold-energy) known as cryoablation, means this is also becoming a frequently used technology.

Although medications are frequently used to treat rapid heart rhythms, they may be ineffective or cause side effects, and in addition must be continued indefinitely. Nowadays surgery to treat arrhythmias has been almost completely superseded by catheter ablation because the risk is much lower. Catheter ablation is a relatively low-risk procedure with relatively high success rates. When successful, catheter ablation should permanently cure the problem you have been experiencing.

What happens during catheter ablation?

The procedure is conducted in an angiography suite (“cath lab”) specifically set up for EP at Mercy Angiography, which is in the Mercy Hospital at 98 Mountain Road, Epsom in Auckland. Your Electrophysiologist will be assisted by highly trained staff including an Anaesthetist, Anaesthetic technician, specialist Nurses and a highly trained Electrophysiology technician. In virtually all cases, catheter ablation is preceded by an Electrophysiology study where your heart's electrical signals are recorded and the location of the heart's abnormal electrical activity is determined.
 
  • During catheter ablation, doctors insert an ablating electrode catheter into the heart. 
  • They position the catheter so that it lies close to the abnormal electrical pathway that is causing the arrhythmia and then pass radio-frequency energy between the catheter tip and a patch on your chest.
  • The tip of the catheter heats up and destroys the small area of heart tissue that contains the abnormal pathway. This causes the formation of a tiny scar that cannot transmit electrical impulses.
  • As a result the abnormal electrical pathway is no longer capable of producing arrhythmias.
​You may feel some discomfort when the energy is applied to the tissue. Tell your doctor if you feel discomfort to enable the team to keep you as comfortable as possible.

If the AV node behaves abnormally by transmitting impulses to the ventricle too quickly, such as during atrial fibrillation (AF), the AV node can be ablated. An artificial pacemaker must then be implanted to keep the heart beating at a normal pace. This is usually done a few weeks before the ablation procedure if this type of procedure is planned.

The procedure can be quite lengthy. Depending on the particular arrhythmia you have and the shape of your heart, a complete procedure may last up to 5 hours. Most procedures last only 1.5 to 3 hours. 
 
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What happens after the procedure?

After your procedure, the catheters are removed and the doctor (or nurse) will apply firm pressure to the insertion site(s) for about 10 minutes to prevent bleeding. If a tube in the artery is required, this may be removed several hours later.

You will be transported to your room in the ward for recovery. When you will be allowed to eat or drink following your procedure depends on your condition.

During recovery back in your room, you will lie flat in bed for 2 to 4 hours, to allow a small seal to form over the puncture site in the blood vessel. During that time, do not bend or lift the leg where the catheters were inserted. To relieve any stiffness, you may move your foot or wiggle your toes.

Your heart rhythm will be monitored during the day and sometimes overnight, to help assess the effectiveness of the ablation. The nurse will check your pulse and blood pressure frequently, and will also keep checking the site where the catheters were inserted. If you feel sudden pain at the site or if you notice bleeding, notify the nurse immediately. 

Generally your doctor will visit you that evening or the next morning, to discuss the results of the procedure. When it is time to go home, have a friend or family member drive you.
 
 
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At home after your ablation procedure

  • Limit your activity during the first few days. You can move about but do not strain or lift heavy objects.
  • Leave the dressing on the insertion site until the day after the procedure. The nurse will tell you how to take it off and when to take a shower.
  • A bruise or small lump under the skin at the insertion site is common. This generally will disappear within 3 to 4 days.
  • Call your doctor or nurse if the insertion site becomes painful or warm to the touch, the bruising or swelling increases, or you develop a fever over 38 degrees.
  • For a few weeks after your ablation, you may experience occasional skipped heartbeats. You may also feel palpitations lasting about 2 to 3 beats. These symptoms are common and will decrease with time.
  • Call your doctor if you have recurrence of your rapid heart rhythm, or if you experience dizziness, chest pain or shortness of breath.
  • Be sure to check with your doctor or nurse about which medications to continue and which ones to stop.
  • You would normally visit your family doctor after the procedure and visit your specialist within a month of your procedure.
Catheter ablation is a relatively low-risk procedure that may permanently cure the heart rhythm problem you have been experiencing. In many cases, it will allow you to avoid a lifetime of medications and give you the chance to lead a normal life.
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Is catheter ablation safe?

Ablation is an “invasive” procedure that requires the insertion of catheters into the body and therefore involves some risk. This risk is small, and the procedure is considered relatively safe. Some patients may develop bleeding at the insertion site.  Blood collects under the skin, resulting in local swelling or a “bruise” in the groin or arm.

Rarely, the procedure may be associated with more serious complications, including damage to the heart and blood vessels, formation of blood clots, and infection.  Deaths are very rare.

Depending on the location and type of the abnormal pathway being ablated, there is a small chance of damage to the heart’s normal electrical system.  An artificial pacemaker may be needed to keep the heart beating at a normal pace. An artificial pacemaker is a small device that’s placed permanently in the body.  It sends tiny signals that keep the heart beating at the right speed.

Although most patients who undergo ablation do not experience problems, you should be aware of the risk. To learn about your particular risk, you should discuss the matter with your cardiologist.

 
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What is the difference between RF ablation and Cryoablation?

Radiofrequency ablation
RF ablation has an established record of successfully treating a variety of arrhythmias. With RF ablation, precisely focused radiofrequency energy (low-voltage, high-frequency electricity) passes between the catheter tip and the heart tissue, effectively burning small, targeted areas of heart tissue, creating a scar. This damaged tissue is no longer capable of generating or conducting electrical impulses thereby preventing the arrhythmia from being generated.

There are many different RF catheters available that make it possible for the cardiologist to access certain sites inside the heart. Once the RF catheter is in the selected position within the heart, it only takes a minute to make a burn (lesion). Given the procedure may continue for up to 4 hours, this is an important consideration.
 
Currently, RF ablation is the primary treatment for heart-racing problems. Clinical trials found an overall success rate using RF ablation of 90 - 95%, while about 5% of patients required a second try because of recurrence.

Cyroablation
Cryoablation is carried out using hollow catheters (Freezor catheters) and cooled, thermally conductive, circulated fluids. During the procedure, a pressurized refrigerant liquid (nitrous oxide or N2O) travels in an ultra-fine tube to the tip of the catheter. The liquid refrigerant vaporizes as it is sprayed into the tip. As it vaporizes, it absorbs heat from the surrounding tissue, thereby cooling and freezing the target tissue. The warmed refrigerant is vacuumed back and out of the system.

Cryoablation is an effective and safer way of treating younger patients with heart rhythm problems where there might be a risk of damaging the conduction system with RF ablation such as AV node re-entry tachycardia or in all patients with high risk of atrioventricular node (AV node) injury such as para-nodal arrhythmias. 

While cryocatheters stick tightly to the heart muscle and do not move like RF catheters, clinical trials show success rate of treating patients with common types of heart racing to be 85%. While croyablation allows the cardiologist to free tissue to test whether it is responsible for heart racing, as the tissue can be rewarmed to restore its function, with RF ablation, once the tissue is burned, it stays burned. Using cryoablation, the time it takes to make a comparable lesion is several minutes, compared to 60 seconds using RF ablation. There is a higher chance of recurrent arrhythmia - approximately 15% with cryoablation and due to the longer "burn time", the procedures take longer.
 
 
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