VT Ablation in Abnormal Hearts
What is Catheter Ablation?
Catheter ablation is a minimally invasive, keyhole technique used to treat a variety of heart rhythm disorders. It is performed in a special operating theatre called a cardiac catheterization laboratory, or cath lab for short. A catheter is a fine wire that can be threaded through a blood vessel via a keyhole opening in the skin and placed in the heart. Usually, a blood vessel at the top of the right thigh in the groin area is used for access to the heart.
Depending on the complexity of the arrhythmia, up to 4 catheters may be used during the procedure. Each catheter has electrodes on its end that can monitor the heart’s internal electrical activity, akin to performing an internal ECG of the heart. An ablation catheter can be used to deliver radiofrequency energy to the problem area in the heart. Radiofrequency energy is a low power, high frequency energy that is delivered to a tiny region of heart tissue near the tip of the catheter, thus cauterizing or ablating the tissue.
Radiofrequency energy has been used for decades by surgeons to cut tissue and to stop bleeding. For the treatment of heart rhythm disorders, radio-frequency energy at a much lower power is used to ablate tissue within the heart that is responsible for initiating or perpetuating your arrhythmia.
VT ablation strongly indicated in patients with structural heart disease and recurrent ICD shocks for VT despite appropriate medical therapy. It is also indicated in patients with symptomatic or sustained VT despite appropriate medical therapy. It is useful where therapy with medications is not effective, not tolerated, or not preferred.
This is normally an elective procedure. You will receive a letter from the hospital bookings clerk or doctor’s secretary outlining the date, time, and other details of your hospital admission for the procedure. A nurse may call you to confirm your personal and medical details. You may need to attend a blood collection service for a blood test approximately 1 week prior to your procedure. If so, a blood test request slip will be provided.In some cases, a CT or MRI scan of your heart will be arranged prior to your procedure.
You will receive specific instructions about any medications changes that are necessary prior to your procedure. If you are unsure about the instructions, please do contact the clinic for clarification. You will be required to fast for at least six hours before your ablation. If your procedure is in the morning or early afternoon, do not eat or drink after midnight, except for a sip of water to help you swallow your pills. If your procedure is in the mid to late afternoon, you may have a light, early breakfast.
You will normally be admitted on the day of your procedure. Pre-operative checks will be performed and your groin area will be shaved before transfer to the cath lab. The cath lab has a movable patient bed, an X-ray machine, ECG monitors, and other equipment.
ECG electrodes and patches will be attached to your chest and back. These will feel cool on your skin. An anaesthetist will insert a fine intravenous tube usually into the back of your hand before administering a sedative. A second tube will be placed into the artery of your wrist to monitor blood pressure. The entire ablation procedure will usually be performed under general anaesthesia.
After you are asleep, intravenous lines will be placed in a vein at the top of the right thigh in the groin area through which catheters will be passed and positioned in the heart using X-ray or a computerized 3D mapping system for guidance. Sometimes, access to the left heart via an artery in the right groin area is also required. The catheters are used to perform electrophysiologic testing of the heart, with attempts to induce the culprit arrhythmia.
VT in structural heart disease is normally due to one or more re-entrant short circuits involving regions of scar tissue found in the ventricles. Ablation of this form of VT is therefore also referred to as re-entrant or scar-related VT ablation. Once the culprit arrhythmiais identified, an ablation catheter is used to target the VT circuit for ablation, and any other regions in the heart that may support further VT circuits.
In many cases, the ablation catheter may need to be positioned across a thin membrane within the heart that separates the left and right heart. A transoesophageal ultrasound scan (TOE) may be required to guide this process. Under general anaesthesia, the TOE probe is passed down the throat into the gullet which lies just behind the heart to provide clear pictures of the heart while access to the left heart is established. The TOE probe is removed before you wake up and may cause a self-limiting sore throat that resolves over several days.
If problem area lies close to the heart’s own blood supply, it may be necessary to perform a coronary angiogram to ensure that there is an adequate distance separating the ablation catheter tip and the critical arteries. This involves the injection of dye into the heart’s coronary arteries to define their anatomy on X-ray.
A scar-related VT ablation procedure typically lasts 3-4 h, although it may last longer depending on several factors including the number of different VT circuits present and the severity of the underlying structural heart disease.
VT ablation in structural heart disease is a complex procedure with an up to 5% risk of serious complications.
- Nerve injury and vascular damage requiring transfusion or surgical repair is very rare.
- There is a very small risk of heart attack, stroke, and cardiac bleeding.
- The need for emergency open heart surgery and death are exceedingly rare.
- There is a risk of inducing a dangerous heart rhythm that may cause dizziness and may require a small electric shock to restore normal rhythm.
If there is a chance you are pregnant, please notify the doctor performing the procedure.
After the procedure you will wake up in the recovery ward before being transferred to a normal hospital ward. There will be a compression clamp at the access site in the right groin which will remain in place for around 2-4 h. You must lie flat for at least 6 hours after the procedure. During this time, it is important to keep your legs straight and your head relaxed on the pillow. You may also have a urinary catheter in place. If so, it will be removed later that evening or the next morning.
It is usual to stay in hospital for 1 to 2 nights after the procedure. If you required a transoesophageal echocardiogram, it is common to have a sore throat and some mild chest discomfort. You may also have some discomfort and bruising in the groin. Symptoms will typically improve over several days. You should avoid exercise, driving, and heavy lifting for 5 days after the procedure. Please arrange to take 1 week off work for your recovery.
You will need to arrange for a family member or friend to pick you up from the hospital following discharge. A follow-up appointment will be arranged 8 to 12 weeks post procedure or earlier if necessary.
- Wound care. The access site at the top of the right thigh in the groin area may take several days to heal. Observe the area every day and keep it dry and clean. Avoiding applying soap and talcum powder to the site. A pea-sized lump and a minimal amount of bruising is normal and may last for up to 2 weeks. If there is increasing pain, active bleeding, or an expanding mass in the groin, please make immediate contact with the clinic, or proceed immediately to your local emergency service for assessment.
- Rest and recovery. To facilitate healing of the access site, it is best to take a week off work, particularly if your job involves physical activity. Avoid exercise, driving, abdominal straining, and heavy lifting for 5 days. Rest and gentle walking at home is permitted. After 5 days, slowly return to normal activities. After 1 week, there should be no limitations on your usual activities.
- Contact details. Prior to your first follow-up appointment, it is best to contact the treating team for any procedure-related concerns as they will be most familiar with the details of the procedure. For public patients, contact the Alfred Heart Centre on 03 9076 3263. For private patients, contact the Heart Rhythm Clinic on 03 8560 0535. If the clinic is closed or the treating doctor or nurse not available, please proceed to your GP or local emergency service for evaluation.
The success rate of VT ablation depends very much on the cause and the severity of the underlying structural heart disease, as well as the number of VT circuits present.
A VT ablation is completely successful if all clinical VTs are eliminated and no additional VT circuits can be induced at the conclusion of the procedure. A VT ablation is partially successful if at least 1 clinical VT is eliminated with additional VTs remaining inducible at the conclusion of the procedure.
Generally speaking, complete success can be achieved in up to 50% of cases and partial success in a further 25%. A partially successful procedure is often all that is required to control symptoms. Repeat procedures are sometimes required to address VT recurrence following ablation.