Ventricular Tachycardia (VT) with Abnormal Heart structure
What is VT?
Ventricular Tachycardia occurs when an abnormal electrical short circuit forms in the lower chambers of your heart (ventricle). This will result in an abnormal contraction sequence in the heart at a rate of 120-260 beats a minute.
The controlled contraction of the ventricles is important for the heart to pump blood around your body and brain and to maintain a good blood pressure. VT can impair the ability of the heart to supply blood and may result in palpitations, dizziness and blackouts. VT can degenerate into Ventricular Fibrillation (VF) when the heart rate rises to over 300 beats a minute causing a life-threatening cardiac arrest. Defibrillation (shocking the heart) resets the heart from VT to restore normal rhythm and saves lives.
Ventricular Tachycardia from Khan Academy.
VT commonly occurs in patients with weakened heart muscle. The weak muscle forms when scars develop in the heart. This is usually due to a previous heart attack where some muscle dies as a result of blockage in blood flow. Scars encourage short circuits to form, resulting in VT.
What are the treatment options for VT?
Implanted Defibrillator (AICD). This device delivers a shock to the heart and is the most effective method of treating VT or VF by restoring normal rhythm. The AICD does not improve your symptoms or reduce your risk of going into VT, but treats you if you develop VT or VF and can be life-saving when used in appropriate patients.
Medications. Tablet treatments can be effective in up about 75% of patients. These medications usually prevent abnormal heart rhythms, but also have the potential of worsening your heart rhythm. Therefore, these medications are often started whilst you are in the hospital with close monitoring. Amiodarone is the most effective drug but has many potential side effects including risk of damage to the thyroid, liver, skin and eyes. Your doctor will discuss these risks with you.
Radiofrequency ablation. This is a procedure performed by an Electrophysiologist and is often performed as an additional treatment to both AICD and medications for people with VT. It is usually performed in patients who have experienced multiple AICD shocks or those unable to tolerate adequate medication doses.
How do I prepare for VT ablation?
Please refer to the section on EPS. Depending on suitability, this procedure can be performed under conscious sedation or general anaesthesia.
You will usually need an echocardiogram prior to the procedure to exclude blood clots in your heart.
How is Radiofrequency Ablation performed for VT?
Please refer to the section on EPS on how EPS is performed. Catheters will be placed in your heart to identify and localise the abnormal tissue. Most Electrophysiologist routinely use a 3-dimensional navigational system which works like GPS navigation to guide the ablation procedure. This will help navigate the catheter inside your heart and minimise the need for X-rays. The 3-dimensional mapping also helps to localise the circuits responsible for the VT.
To reach the left ventricle where most of the VT circuits are located, we would either insert the catheter into your groin artery (rather than vein) or cross over to the left atrium using a long needle in a routinely performed procedure called transeptal puncture.
When VT circuits have been identified, radiofrequency ablation will be applied to the circuit. Ablations may be performed within the scar and around its perimeter to treat these VT circuits.
The entire procedure may take 3-4 hours.
What is the success rate for ablation of VT?
Success for this procedure is measured by a reduction in VT frequency rather than by longstanding cure. Success rate ranges between 50-75% at 6-12 months.
What are the risks of VT ablation?
VT ablation is commonly performed in patients with sick hearts. Most patients who undergo VT do not experience any complications but you should be aware of the following risks. In general, it has been estimated that the risk of any complications is between 5-8%. This includes:
- Blood vessel problems: bleeding, bruising, damage to the vessel wall, abnormal connections and blood clots can form in the blood vessel in your groin or higher up near the heart. Usually these settle by themselves, but sometimes medications, injections or small operations are required to fix them.
- Abnormal heart rhythms: these are deliberately provoked during the procedure, but can become unstable requiring an electric “shock” to restore a normal heart rhythm. There is a very small risk of requiring a pacemaker if the normal and necessary electrical system of the heart is damaged. If you already have an implantable defibrillator (AICD), this may be less of a problem.
- Perforation: there is a very small chance of causing a leak of blood around your heart. This usually settles without treatment but can also be dealt with by inserting a drain from the chest wall.
Major and life-threatening complication risks are quoted as 1-2%, which includes:
- Heart attack
- Damage to a major blood vessel (aorta) or heart valve requiring urgent surgery to correct
What happens after VT ablation?
You will be required to lie flat for 2-4 hours. You may have a compression clamp over your groin area during this time. Your nurse will check on you to see if there is bleeding or swelling at the groin site. Most people can start eating and drinking water within 4-6 hours after the procedure. Most patients stay in the hospital for either one or two nights or longer and their heart rhythm may be monitored. Your Electrophysiologist may stop, switch or commence you on new medications after the procedure.
The amount of time you should avoid strenuous physical activity, work or driving will depend on the circumstances of your presentation. Your Electrophysiologist will discuss this with you. Some patients may experience minor chest discomfort several days after the procedure. If this persists, please consult your Electrophysiologist.
Your groin site might be sore for several days. A small bruise at the groin site is normal but if it starts to bleed, you can contact your local doctor or the Electrophysiologist.