Wolff-Parkinson-White (WPW) Syndrome
In the normal heart, the AV node is the only electrical connection between the atria and ventricles. With WPW, the heart has an extra "nerve, pathway or wire" which we call an " accessory pathway" that electrically connects the atrium to the ventricle. It is present from birth but may not detected or cause any problems with tachycardia until later in life. Many WPW patients may not ever experience heart problems from this abnormal nerve and may not even know they have until it is detected by a doctor. This pathway is in the wall of the heart and can be located anywhere on the right, left, front or back walls. Many people have more than one accessory pathway. People with WPW may experience tachycardia attacks because the electrical impulse gets trapped in an electrical circuit that travels in a large circle between the normal AV node and the accessory pathway. This can cause the heart to race up to 150 - 300 beats per minute. The tachycardia attacks start suddenly without warning and there is often no obvious cause. The feeling of the heart pounding in the chest or neck can be associated with lightheadedness, chest pain and sometimes a blackout. Rarely, WPW can cause the heart to race rapidly and dangerously out of control.
Wolf-Parkinson-White
Catheter ablation of WPW syndrome involves destroying the accessory pathway. The EP study determines the number of extra pathways and the location of each. The ablation catheter is then inserted and used to carefully map the heart to precisely locate each pathway. Each time that the catheter locates an extra pathway and is placed next against it, ablation energy is delivered.
This rhythm problem is due to an abnormality of the AV node itself which results in a "short circuit" to develop in the area around the AV node. An electrical signal can get trapped into a small loop in this area, causing the heart to race. The tachycardia may feel very similar to that experienced by those with WPW syndrome simply because a racing heart still feels like a racing heart regardless of the cause.
Catheter ablation is directed at destroying the tissue near the AV node causing the heart racing without causing serious damage to the AV node. To minimize this risk, your doctor will start by burning a safe distance from the AV node and gradually burn tissue progressively closer until he/she sees signs that enough burning has been done or if signs of danger appear. The technique is similar to whittling away at a piece of wood where you shave away part of the wood without weakening it and causing it to break. Unfortunately, the abnormal tissue can be very, very close to the AV node and damage to the AV node occurs in 2-3% of cases depsite all measures taken to avoid it. If this should happen, a pacemaker will be necessary but does not need to be put in immediately (it can be implanted several days later if desired). The success rate for a first attempt is nearly 95% because of the desire to avoid damaging the AV node. If the first catheter ablation procedure does fail to get rid of all the tachycardia, it is possible to undergo a second or even third attempt. Your doctor will speak to you about the merits of trying again and make you aware of any additional risks.
Atrial Flutter
In atrial flutter, the electrical signal gets trapped in a loop running around the right atrium, causing it to beat at 300 beats per minute while the ventricles beat usually at 150 beats per minute. The abnormal tissue causing this rhythm problem is located near the bottom of the right atrium . This area is easy to reach with the ablation catheter but it may be thick and uneven, making it somewhat difficult to burn all the tissue necessary to eliminate the flutter. The success rate for a first attempt is in the order of 80-90%. The most important risk is the possibility of burning a hole in the heart wall in this region (less than 1%).
Atrial Flutter
It is also important to point out that people with atrial flutter can have more than one kind of flutter many have attacks of atrial fibrilllation also. In these cases, eliminating the atrial flutter may not reduce or eliminate atrial fibrillation attacks. The only way to know is the proceed with the atrial flutter ablation and observe what results afterwards. Patients who have continued problems with attacks of atrial fibrillation can be candidates for other types of ablation procedures.
Atrial Fibrillation
Atrial fibrillation (often called "A Fib") is most commonly seen in people who have other heart disease (such as heart valve problems, heart attacks, long-standing high blood pressure) or thyroid disease but can be seen in otherwise healthy people without any medical problems. The atria become scarred and irritable and are not able to pass the electrical impulse smoothly like a ripple traveling across a calm water pond. Instead, the electrical impulse breaks up into many smaller ripples that travel around the atria in a very fast, irregular and disorganized manner much like a stormy ocean surface. This makes the atria beat at between 300-600 beats/minute. A proportion of these impulses travel down the AV node and cause the ventricles to beat quite fast (120-190 beats/min) and very irregularly. The atria beat so fast that blood does not get pumped normally and blood clots tend to form in the atria. Therefore, blood thinners are often prescribed. Atrial fibrillation is often very difficult to control with drugs.
Atrial Fibrillation
A number of different drugs are used to treat atrial fibrillation. Some drugs are prescribed to try and prevent atrial fibrillation attacks from recurring. Other drugs (beta blockers, calcium blockers, digoxin) are used slow the heart when atriual fibrillation occurs and makes the attacks more tolerable or less uncomfortable but do not prevent attack from recurring. When a person cannot tolerate medications or when drugs are not effective at preventing attacks or reducing symptoms from attacks, catheter ablation may be necessary.
There are several types of ablation that can be performed for atrial fibrillation and each has a slightly different purpose and approach.
1) AV node-His bundle ablation: This type of ablation was the first type ever to be performed and was introduced in 1983. This treatment does not cure someone of AF attacks. Rather, it eliminates symptoms by destroying the AV node-His bundle so that the atrial fibrillation signals cannot cause the ventricles to beat rapidly and irregularly. After the ablation, AF is still present BUT people no longer have any symptoms from the fibrillation. AV node ablation is 99% successful on the first attempt and the risks are very low (<1%).
2) AV node modification: This form of ablation procedure is a variant of AV node-His bundle ablation. Rather than completely destroy the AV node-His bundle, AV node modification attempts to burn only part of the AV node- His bundle so that the number of atrial fibrillation impulses getting through is reduced and the resulting heart rate is reduced by 25-50%. Because signals still get through, there is no need for a pacemaker after a modification procedure. However, a good result is only obtained in 50% of patients in whom this is tried while 25% have only a temporary improvement and the other 25% end up with complete AV node-His bundle ablation and a permanent pacemaker.
3) Focal AF blation: In recent years, new research has found that some patients have atrial fibrillation that is triggered by one or more spots in the atrial chambers. Heart cells in these areas send out rapid electrical pulses and start the atrial fibrillation just like a malfunctioning ignition on a gas barbeque or oven. The most common sites for these abnormal rapidly firing cells is in the pulmonary veins that connect to the left atrium. Pulmonary veins are veins that carry blood back from the lungs to the heart. Every person usually has four pulmonary veins but the most common veins causing atrial fibrillation are the left and right upper veins. In focal atrial fibrillation, these spots are either destroyed by burning them or burning completely around the spots so they are trapped and the impulses coming from these cells are prevented from getting out to the rest of the heart and causing atrial fibrillation. The procedure can be very long (6 hours or more) and the success rate is about 70%. Another 10-20% of people having focal AF ablation are improved by having much fewer or shorter attacks and may be better controlled by antiarrhythmic drugs that previously were not effective.
This procedure is relatively new and is still being improved. We do not yet know which persons with atrial fibrillation have the best chance of success but, at our London Health Sciences Center, good candidates for this procedure are people who: 1) have otherwise normal hearts free of any scarring or damage from other heart disease, 2) have atrial fibrillation attacks that stop on their own (have periods where the heart beat returns to normal in between attacks and 3) few other medical problems. While age is not strictly speaking a criterion, we generally recommend focal ablation only for younger patients because of the increased risk in the elderly. For people of advanced age or who have other medical problems, AV node ablation and permanent pcemaker insertion may be a easier and safer choice.
Ventricular tachycardia (often called VT, for short) is a form of heart racing that starts inside the right or left ventricle. It is most commonly due to damage or scarring of the lower heart chambers, usually as a result of a previous heart attack. However, any disease that damages the heart can cause ventricular tachycardia to occur later in life. The time period between when the heart damage occurs and when ventricular tachycardia first develops can be days, months or up to many years. In someone who has heart disease, ventricular tachycardia is considered a potentially dangerous arrhythmia that requires careful treatment. Rarely, ventricular tachycardia can occur in healthy, young individuals without any history of heart disease(called idiopathic or primary VT). In these people, VT is NOT a dangerous problem but is nonetheless bothersome. With ventricular tachycardia, the heart can race at 130-250 beats per minute. Often, lightheadedness and blackouts can accompany the feeling of palpitations. Chest discomfort and shortness of breath may also be noticed
In patients whose VT is caused by previous damage or scarring of their hearts, catheter ablation is not often a good first choice for treatment. Drug therapy to try and suppress attacks or implantation of an implantable cardioverter defibrillator (ICD for short) is preferred. Ablation therapy may be used in conjunction with the others to help reduce the frequency of attacks.
In VT patients who otherwise have normal hearts, catheter ablation is an alternative to drug therapy and can be curative. However, VT ablation can be more difficult because it may be difficult to turn on the VT at the time of the EP study. If the VT cannot be triggered, it is impossible to map and ablation cannot be done. This can happen in 25-40% of patients. The risks of VT ablation are usually less than 1-3%.
Ventricular Tachycardia
