Ablation Procedures
An extension of the diagnostic EP Study 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 EP Study, to record from and stimulatethe 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 EP Study and also often requiresa 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.
Catheter Ablation for Atrial Fibrillation - Current Indications
The Arrhythmia Service at St. Luke's-Roosevelt Hospital participated in a live webcast of a catheter ablation, a new treatment for atrial fibrillation. To view the webcast, click here: Go To Webcast
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 many AF patients may be suitable ablation candidates.
It has recently been learned that many 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 its 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.
Elimination of the triggers can lead reduction or elimination of AF. This is
a startling advance that has generated a great amount of optimism for a catheter-based approach of treatment of AF.
Catheter ablation techniques have been designed and successfully applied to a variety of patients with AF targeting the pulmonary vein musculature. These muscle sleeves have discrete and limited connections to the atria, which may be vulnerable to catheter ablation. A mapping catheter and an ablation catheter are passed into the left atrium using a transseptal puncture. The discrete connections of the pulmonary vein to the left atrium are mapped and precisely identified. These connections are then ablated using radiofrequency energy. The pulmonary vein is then progressively disconnected with the ultimate result of complete isolation of the pulmonary vein musculature from the left atrium. Each pulmonary vein is entered and serially ablated until all pulmonary veins are completely electrically disconnected. This can be achieved in about 99% of targeted veins. The pulmonary veins continue to serve as conduits of oxygenated blood to the left atrium.
If the pulmonary veins are the critical trigger for an individual's episodes of AF, the expectation would be an excellent response with elimination of AF events. This very desirable result can occur in up to 90% of patients, who will then require no further antiarrhythmic therapy. Some additional patients may respond to antiarrhythmic drugs that were previous ineffective, or have substantial reduction in AF events. About 10% of patients have no response, presumably due to alternate triggers or tissue in the right or left atria; these can also be targeted at subsequent procedures if desired.
The procedure has a small risk of about 2%. Fortunately, serious complications are infrequent. The specific complication of pulmonary vein stenosis has been limited to about 1% of cases given advances in energy delivery and targeting.
This is a revolutionary advance in AF therapy. For the first time, a catheter technique has successfully and reproducibly controlled AF in a substantial number of patients who have had had this procedure. Ideal candidates include patients who have paroxysmal AF without major structural heart disease. Selected patients with persistent AF may be also be candidates. If AF is chronic, alternative treatment modalities should be considered.
Remarkable progress has been made in the understanding of how AF develops, and the therapeutic options available to produce a desirable response. Catheter ablation is an effective tool.
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 bybystanders 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 tellthe 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.
Biventricular Devices for Treatment of Congestive Heart Failure
Congestive heart failure is a progressive condition in which the heart's function gradually deteriorates resulting in diminished cardiac performance and pumping ability. Ultimately, blood flow to vital and nonvital organs is reduced, leading to a variety of symptoms including shortness of breath, lack of energy, swelling, etc. Patients with heart failure often require repeated hospitalizations for treatment and adjustment of medications. Medications have been the primary mode of therapy for heart failure and have made important inroads in the high risk of death that many heart failure patients face. However, patients with extreme forms of heart failure often remain highly symptomatic despite maximum medical therapy, and face grave risk
Another one of the manifestations of heart failure is a delay in the electrical activation of the heart. Anywhere between one quarts and one half of all heart failure patients have this electrical abnormality, often called bundle branch block or intraventricular conduction delay, on the electrocardiogram. If you have heart failure, your physician can readily tell you if you have this common abnormality. If present, electrical delay will adversely affect heart function resulting in a variety of problems relating to pumping action of the heart and the ability of the heart to fill adequately. An abnormal electrocardiogram in the setting of heart failure also increases the risk of death.
Recently, major advances have been made in technology that can overcome the problems created by the electrical abnormalities described above. Specifically, a therapeutic intervention termed "cardiac resynchronization" will reverse many or all of these abnormalities. Cardiac resynchronization is accomplished by a procedure called biventricular pacing. With this procedure, a standard two-wire pacemaker is placed in the right-sided cardiac chambers, and an additional wire is threaded through the vein that travels on the back of the heart to overly the left-sided pumping chamber. By stimulating the right and left-sided chambers simultaneously, the heart is "resynchronized". When this is accomplished, the vast majority of patients have improved cardiac function and reversal of all the clinical consequences created by bundle branch block. The procedure can be successfully performed in 85-95% of patients with a risk of about 2-4%.
Controlled clinical trials have been completed and published. These clearly indicate an improvement in overall heart failure outcome for patients treated with biventricular pacing devices, such that symptoms are improved, exercise capacity are increased, and hospitalization rates are reduced. Whether this form of pacing results in an improved overall outcome is still uncertain and is the subject of ongoing clinical trials.
Many patients with heart failure also face a risk of potentially fatal abnormalities of the heart rhythm, or cardiac arrest. When this occurs, unless a patient is rapidly resuscitated, sudden death may result. Standard treatment for a patient who it at high risk of this event or who has survived such an event, is the implantable cardiac defibrillator (reviewed elsewhere on this website). Biventricular pacing systems can be combined with the implantable defibrillator in appropriate patients to accomplish the dual desirable endpoints of improving heart failure and preventing sudden death.
For patients who have an unsuccessful implantation procedure of a biventricular pacing system, alternatives have recently become available. These include the very innovative approach of robotic implantation of the left-sided lead directly on the heart surface. Using robotic techniques, a very small incision is made in the chest wall and the robotic arm places leads directly on the heart surface, the incision is closed and the lead is connected to the pacing system. This procedure can be accomplished in virtually all patients who have previously had a pacemaker attempt.
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Ablation