Procedures

VT occurs most commonly in patients with weakened heart muscle (cardiomyopathy) or when scar tissue develops in the heart. In patients with coronary artery disease (blockage of blood vessels on the surface of the heart), this scar is the result of a prior heart attack (myocardial infarction) when the muscle dies as a result of a blockage in blood flow. Scars or fibrosis can interfere with the normal electrical impulse in the heart, leading to a short-circuiting of the rhythm, called re-entry. VT can also occur in patients with normal hearts by a different mechanism whereby the electric conduction is overly excitable, like a muscle twitch.

Sudden cardiac death causes about 450,000 fatalities each year in the United States alone. It is most commonly caused by VT deteriorating into ventricular fibrillation (VF), which is fatal within a few minutes if not defibrillated (shocked) back to a normal rhythm. Defibrillation may be accomplished by an automated external defibrillator or an implantable cardioverter-defibrillator (ICD).

It is important to distinguish VT and VF, which are electric problems of the heart, from a heart attack, which is due to the sudden blockage of an artery. Heart attacks are treated with clot-busting drugs, balloon angioplasty, or stents. Sometimes, VT and VF are seen in that setting and are treated with electric shocks and drugs. The treatment of abnormal rhythms is discussed below.

There are 3 treatment options for VT in patients with structural heart disease, although many patients require a combination: an ICD, antiarrhythmic medications, or catheter ablation. Many patients at risk for VT with structurally normal hearts are at risk of sudden cardiac death and as such are treated with an ICD. This is the most effective method of restoring a potentially life-threatening rhythm such as VT or VF back to a normal rhythm. However, an ICD does nothing to prevent the heart from going into VT. The ICD is a “safety net” and is like having an ambulance crew accompany you 24 hours a day.

Antiarrhythmic medications that modify the conduction of the electric impulse of the heart can be effective in suppressing VT. These medications can reduce the risk of recurrence by 75% but have potential side effects that include proarrhythmia, or worsening of the heart rhythm. For this reason, initiation of antiarrhythmic agents often requires close monitoring. Amiodarone, the most effective drug, has many side effects, which can involve toxicity to the vital organs like the liver, thyroid, lungs, eyes, and skin. Because of the discomfort associated with frequent ICD shocks and the side effects of antiarrhythmic drugs, catheter ablation is an important additional treatment option for many patients already using these therapies. The third treatment option is catheter ablation.

Since radiofrequency catheter ablation was first described 20 years ago, it has played an increasing role in the treatment of ventricular arrhythmias. Initially used in the treatment of patients with multiple ICD shocks for VT (VT storm), it is now used more frequently and earlier in the management of VT, particularly in centres with a high volume of patients and experience. Catheter ablation is an excellent choice for patients when medications are not effective, tolerated, or preferred.

The aim of this procedure is to target the origin of the VT by placing a long, thin wire or catheter into the heart chambers through the veins of the leg. When areas that are critical to the VT circuit are identified, radiofrequency energy is applied to a small area (4 – 5 mm in diameter) to destroy the abnormal tissue. The number of burns required to treat the VT varies among patients. In patients with scar tissue in the heart, ablations may be performed within the scar and around its perimeter to cauterize or ablate the abnormal electric circuit responsible for the VT.

You will need to stop taking any medication that you have been prescribed for your abnormal heart rhythm 5 days prior to your procedure, and any anticoagulants (blood thinning) medications 24 hrs before your procedure – this will be discussed with you prior to your admission. If this has not been discussed with you, or if you are unsure, please call the Rhythm and Cardiac Specialists.

You will be required to fast for at least six hours before the study. If your procedure is in the afternoon, you may have a light early breakfast.

The hospital will notify you the day before your procedure of your admission time and fasting times. The clinics nurse will phone you one week prior to discuss medications and answer any questions you may have leading up to your procedure.

You will be transferred to the Electrophysiology Laboratory (EP lab) from your ward. Usually before leaving your ward your groin will be shaved.

The EP lab has a patient table, X-Ray tube, ECG monitors and various equipment. The staff in the lab will be dressed in hospital theatre clothes and during the procedure will be wearing hats and masks.

Many ECG monitoring electrodes will be attached to your chest area and patches to your chest and back. These patches may momentarily feel cool on your skin.

A nurse or doctor will insert an intravenous line usually into the back of your hand. This is needed as a reliable way to give you medications during the study without further injections. You will also be given further sedation if and as required. You will also have a blood-pressure cuff attached to your arm that will automatically inflate at various times throughout the procedure.

An anaesthetist will be present, and your procedure will be performed under general anaesthesia. However, patients with Idiopathic VT only require sedation and local anaesthesia. This will be discussed with you before the procedure.

The catheters are positioned in your heart using X-Ray guidance. Once the catheters are in place, your heart will be stimulated and usually your abnormal heart rhythm will be induced. We will use a three-dimensional computer mapping system to guide the ablation procedure. This will help us move the catheters in your heart without the need for X-rays and help us create an electrical map of the VT circuits. When the VT circuits have been identified and the abnormal tissue localized, the radiofrequency ablation will be applied to this spot. This may cause a transient warm discomfort in the chest. Radiofrequency ablation procedures are lengthy, and the average duration is approximately 3 to 4 hours.

The catheters are inserted through intravenous ports, or sheaths, placed in the veins in the groin and sometimes through a vein on the side of the neck. To access the left ventricle, a needle may be used to create a small puncture in the wall between the right and left sides of the heart under ultrasound guidance (called transseptal catheterization). Alternatively, a catheter can be inserted into the heart through an artery in the groin (similar to heart catheterization procedures). The ablation catheter is moved around the ventricle, and a virtual 3-dimensional image of the heart is created with a computer mapping system that acts like a navigation system. The location of the catheter is determined by use of fluoroscopy (x-ray) and this mapping system. Typically, the procedure lasts from 3 to 6 hours.

Afterwards, the catheters are removed, but the sheaths are left in until the blood thinner wears off. Typically, this requires the patient to lie still for several hours to prevent bleeding from the puncture sites. Slight discomfort and bruising in the groin area can occur, and some patients experience self-limited mild chest pain resulting from inflammation caused by the ablation lesions. When the procedure is successful, antiarrhythmic medications may be stopped at the discretion of the physician.

A blood test must be taken to determine when the blood thinners have worn off. Once the blood test is within range the sheaths will then be removed. During this time, it is important to keep your legs straight and your head relaxed on the pillow.

You will be required to stay in the hospital overnight and your heart rhythm will be monitored during this time.

The groin area may feel sore and bruised for several weeks after the procedure. You should avoid strenuous physical activity and sports for 2 weeks after the procedure until this has settled. Most people take approximately 1 week off work.

The risk of any major complication for VT ablation in patients with structural heart disease (Ischemic and Non-ischaemic Cardiomyopathy) is approximately 6-8%. The risk of major complications for VT ablation in patients with normal hearts (Idiopathic VT) is ~3%.

Major risks of VT ablation in structural heart disease include but are not limited to:

• The peri-procedural risk of death during a VT ablation in patients with structural heart disease has been reported as low as 0.4% and up to 3%.
• The risk of major vascular complications (arteriovenous fistula, pseudo aneurysm, dissection) requiring surgery is 4% and minor vascular complications (hematoma in the leg) is 7%. Vascular complications are the most common major complication encountered during a VT ablation.
• The risk of stroke or transient ischemic attack is 1-2% .
• The risk of damage to the heart wall causing bleeding in the sac around the heart (cardiac tamponade) requiring drainage with another catheter or urgent cardiac surgery is 1% to 2%.
• Damage to a major artery (aorta) or heart valve (These complications may require urgent vascular or open heart surgery to correct).
• In patients with VT arising from the septum or near the fibres of the normal conducting system, there is a risk of heart block requiring permanent pacing.
• Acute exacerbation of heart failure can occur after VT ablation due to either fluid infused via the ablation catheter or “stunning effects” of the ablation itself.
• Deep vein thrombosis (DVT) at the site of vascular access can occur after the procedure but is minimized with routine prophylactic blood thinning medications in the postoperative period.