An electrophysiology (EP) study is performed to diagnose an abnormal rhythm problem. Special EP catheters (flexible, insulated wires with metal electrode tips) are inserted into the heart in order to study the cardiac electrical system. The cardiac electrical system is important because it controls the heart rhythm, and abnormalities in the electrical system are responsible for most heart arrhythmias.
Sometimes, a problem with the conduction system causes the heart to beat too fast, too slow, or to have an erratic or irregular beat and Radiofrequency Ablation (RAF) is done to correct an abnormal or irregular heart beat.
The Hearts Electrical System
The heart's rhythmic contractions depend on its electrical system that conducts electrical impulses throughout the heart.
The sinus node, a group of specialised cells in the right atrium, is the place where the electrical impulse normally begins. The sinus node functions as the heart’s “natural pacemaker,” setting the pace for the heartbeat. The electrical impulse spreads throughout the atria, causing the muscle in the atrial walls to contract and squeeze blood into the ventricles. From the atria, the electrical impulse reaches the atrioventricular node, (AV node) that is located between the atria and the ventricles. This node acts like a “relay station,” slowing down each electrical impulse before allowing it to pass on to the ventricles. The impulse then travels throughout the ventricles through a system of specialised muscle fibers. The impulse stimulates the ventricular muscle, causing it to contract and pump blood.
Abnormal Rapid Heart Rhythms
An abnormal heart rhythm or arrhythmia, is the change in either the speed or pattern of the heartbeat. During an arrhythmia, the heart may beat too slowly (Bradycardia), too rapidly (Tachycardia) or irregularly. The following is a brief description of several common rhythm problems that may be treated with Radiofrequency Ablation.
AV nodal re-entrant tachycardia (AVNRT)
In this condition, two pathways exists in the AV node. If an electrical impulse enters only one of the pathway, it may double back through the unused second pathway and start travelling in a circular pattern. This may contract the heart to contract with each cycle, and may result in a very rapid, irregular heartbeat.
Ventricular Tachycardia (VT)
Ventricular tachycardias arise from the major pumping chambers at the bottom of the heart. VT is a more serious rhythm problem because it often occurs in a setting of previous heart damage (e.g. a heart attack) and may be best managed with an implanted defibrillator.
Sometimes with VT, the heart is otherwise healthy and the abnormal rhythm arises from an abnormal trigger point. This trigger can often be localised and successfully ablated.
Atrial Flutter
In Atrial Flutter, there is a single short circuit that conducts electrical impulses rapidly around the inlet valve of the right ventricle.
Usually every second beat is conducted from this abnormal circuit to the ventricles resulting in a heart rate of around 150 beats per minute. This rhythm can often be difficult to treat with medication. Similarly to Atrial Fibrillation, there can be risk of blood clots forming in the atria. If the heart rate cannot be controlled, there can be risk of weakened heart muscle pumping function.
Atrial Fibrillation (AF)
In AF, multiple circuits in the atria occur simultaneously, stimulating the heart in an unco-ordinated fashion. As a result the atria quiver quickly and ineffectively.
The loss of co-ordinated beat may allow the blood to stagnate and form blood clots. The AV node which acts as a gate, allow only some of these impulses to travel down the electrical system to stimulate the ventricles.
Wolff-Parkinson-White Syndrome (WPW)
In WPW, an abnormal "bridge" of tissue connects the atria and the ventricles. This extra pathway is called an accessory pathway and makes it possible for electrical impulses to travel from the atria to the ventricles without going through the AV node. In people with WPW, an arrhythmia can get started when an impulse travels down the normal conduction pathway to the ventricles, and then back up through the accessory pathway to the atria.
If the impulse continues to travel in a circular pattern, it may cause the heart to contract with each cycle, and may result in a very rapid heartbeat. Some accessory pathways conduct impulses rapidly and thereby may allow very rapid and serious rhythms to occur.
The Electrophysiology (EP) Study
As mentioned earlier, EP study portion of the procedure is done to diagnose your heart rhythm problem. Basically, the EP study is performed by doing two things:
1) Recording Electrical Signals.
Electrode catheters sense electrical activity in various areas of the heart and measure how fast electrical impulses travel.
2) Pacing the Heart.
Electrode catheters can also be used to deliver tiny electrical impulses to pace the heart. By doing so cardiologists try to induce (bring on) certain abnormal heart rhythms, so that they can be observed under controlled conditions.
In order to bring on an arrhythmia, medications may be given through the IV line to speed up the heart. The EP study helps determine the location of the heart’s abnormal electrical activity. For example, in people with WPW, several electrode catheters are inserted into the heart, to help define the exact location of the accessory pathway. This technique is called “mapping”. The location and type of rhythm problem you have will help confirm if catheter ablation is an appropriate treatment option for your condition.
Catheter Ablation
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 formation of a tiny scar that cannot transmit electrical impulses. As a result, the abnormal electrical pathway is no longer capable of producing arrhythmias. If the AV node behaves abnormally by transmitting impulses to the ventricle too quickly, such as during atrial fibrillation, 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.
Why is Catheter Ablation Important?
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 of the much lower risk. Catheter Ablation is relatively low-risk procedure with relatively high success rates. When successful, catheter ablation should permanently cure the problem you have been experiencing.
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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