Ablation Procedures

An extension of the diagnostic EPS is the catheter ablation. In a similar way, catheters are placed intravenously and advanced to several positions within the right heart. These catheters can be used, as with the EPS, to record from and stimulate the heart. These catheters can be manipulated throughout the heart in an attempt to identify the precise location from which an arrhythmia originates. Since most arrhythmias require a specific and usually small area of the heart in order to begin or continue, localization of these key, but vulnerable sites, could lead to eradication of the arrhythmia.

If these sites are identified, a catheter is moved to this area of the heart. The tip of a specially designed catheter placed in this position can be used to deliver high frequency, or radiofrequency, energy. This energy will heat up the adjacent .tissue to the point of coagulation. The amount of tissue heated, however, is quite small. But if it includes the critical area for arrhythmia formation, this tissue can be permanently made nonfunctional and thus incapable of causing an arrhythmia.

This procedure lasts somewhat longer than the typical EPS and also often requires a one night hospital stay.

The anticipated results of the procedure depend somewhat on the nature of the arrhythmia targeted. For the most common arrhythmias, the procedural success rate in experienced laboratories is in the range of 90-99%. The risks of the procedure are generally small and often only related to intravenous puncture. Serious cardiac complications are uncommon, but can occur.

 
Implantable devices

Some of the most serious arrhythmias that patients can experience are the rapid and prolonged arrhythmias that come from the pumping chambers. This usually occurs when these chambers have been previously damaged and scarred, such as the aftermath of a heart attack. During these arrhythmias, there is frequently a fall in blood pressure and even unconsciousness. Unless terminated, some can lead to fatal consequences. These arrhythmias require prompt termination which can be most readily accomplished by the administration of an electrical shock passed across the chest. Outside the hospital, this is accomplished by an ambulance team who places paddles on the chest and delivers the shock. This concept is also applied with an implantable device. The premise is that this device, being permanently available to monitor a patient's rhythm, can automatically and in a short period of time, deliver lifesaving electrical energy directly to the heart muscle. Patients who are deemed high risk for the development of these dangerous arrhythmias will often be treated with an implanted device so that they are permanently protected without need for intervention by bystanders or emergency personnel.

These devices are called implantable cardioverter defibrillators (ICD). These are implanted much the way permanent pacemakers are. Using a large vein that passes underneath the collar bone, a wire or lead can be passed intravenously into the right side of the heart. This wire can record the electrical signals from within the heart and tell the device when the heart has gone into a rapid, dangerous arrhythmias. This lead is connected to the device which is then buried under the skin beneath the collar bone. When this device detects a dangerous arrhythmia, it can deliver enough electrical energy through the lead into the heart that the heart will resume its normal electrical activity. The entire process of detection and termination of this potentially fatal arrhythmia can last only a few seconds. Because this period of time is so brief, the patient usually comes to no harm. This device can be highly effective and often life saving in patients who may otherwise succumb to dangerous electrical conditions.

Catheter Ablation for Atrial Fibrillation - Current Indications

Catheter ablation has been successfully applied to virtually all supraventricular arrhythmias with great success. Atrial fibrillation (AF) has been the one exception, owing to its greater complexity of mechanism and involvement of large portions of both atria. However, recent results suggest that there is at least a subset of AF patients who may be suitable ablation candidates.

It has recently been learned that some forms of AF may be triggered or maintained by a single focus of automatic firing. In most patients, these sites have been mapped to the pulmonary veins. These venous structures have sleeves of atrial tissue extending from the left atrium for variable distances into the main branch or tributaries. This musculature is capable of generating ectopic complexes, or repetitive activity at very rapid rates. In susceptible patients, this may lead to AF, either paroxysmal or persistent.

Mapping these foci followed by catheter ablation using radiofrequency energy can eliminate these triggers. Elimination of the triggers can lead to reduction or elimination of AF. This is a startling advance that has generated a great amount of optimism for a catheter-based approach for treatment of AF.

It is not certain how many AF patients can be treated in this manner. Ideal candidates are those who have frequent and paroxysmal AF, high density atrial ectopy (isolated and repetitive forms) and minimal or no structural heart disease. However, many other candidates exist with variable levels of atrial ectopy and degrees of structural heart disease.

The catheter ablation procedure usually requires mapping ectopic complexes or the initiation of AF. These procedures typically involve multiple mapping catheters, including left atrial catheters placed via transseptal puncture.

If a patient is successfully mapped and ablated, response rates have been excellent. This may lead to elimination of AF episodes and no further need for medical therapy. However, not all patients are suitable candidates, and some require mapping data before this conclusion can be reached.

The risks of the procedure are similar to those of other catheter ablation procedures. A specific risk relates to the development of pulmonary vein stenosis and pulmonary hypertension. Several technical maneuvers, however, can limit this potential complication.

Remarkable progress has been made in the understanding of how AF develops, and the therapeutic options available to produce a desirable response. Catheter ablation may be an effective tool.


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