Subscribe in a reader

Tuesday, January 20, 2009

Procedures for treating and preventing atrial fibrillation

After successful cardioversion many patients (up to 75%) may experience recurrence of AF within 12 months. Therefore, many patients will need long-term treatment with medications to prevent a recurrence of AF; however, medication(s) are effective only 50%-75% of the time in preventing recurrence. Moreover, many patients cannot tolerate the side effects of long-term medication. For these reasons, several procedures have been developed to treat and prevent recurrence of AF; they include:
Ablation of the AV node with implantation of a pacemaker
Implantation of a pacemaker
Implantation of an atrial defibrillator
Maze procedure
Isolation of the pulmonary vein
Ablation of the AV node with implantation of a pacemaker. Ablation of the AV node is a procedure that destroys the AV node so that the atrial electrical discharges cannot pass through the AV node to activate the ventricles. The procedure usually is performed in a cardiac catheterization unit or an electrophysiology unit of a hospital.
1) Procedure. For ablation of the AV node, patients are given a local anesthetic to minimize pain and are mildly sedated with intravenous medications. Using x-ray guidance, a wire (catheter) is inserted through a vein in the groin to reach the heart. Electrical recordings from inside the heart help to locate the AV node. The AV node is destroyed (ablated) using heat delivered by the catheter. After successful ablation of the AV node, electrical discharges from the atria can no longer reach the ventricles. Destruction of the AV node (whether by catheter ablation or by disease that occurs with age) can lead to an excessively slow rate of ventricular contractions (slow heart rate). Therefore, a pacemaker is implanted in order to provide the heart with a minimum safe heart rate.
2) Benefits of ablation of the AV node. The benefits of ablation of the AV node and implantation of a pacemaker include:
resumption of a regular heart rate (even though a pacemaker may be determining the heart rate)
relief from palpitations, fainting, dizziness, and shortness of breath
ability to stop medications and avoid their potentially serious side effects
3) Risks of ablation of the AV node. Potential complications of ablation of the AV node and permanent implantation of a pacemaker include bleeding, infection, heart attack, stroke, introduction of air into the space between the lung and chest wall, and death. Still, this technique has helped many patients with severe symptoms to live normally.
4) Candidates for ablation of the AV node. Candidates for ablation of the AV node are patients with AF who respond poorly to both chemical and electrical cardioversion. These patients experience repeated relapses of AF, often with rapid rates of ventricular contractions despite medications. Ablation also may be an option for patients who develop serious side effects from the medications that are used for treating and preventing AF.
5) Limitations of ablation of the AV node. Ablation of the AV node only controls the rate with which the ventricles beat. It does not convert AF to normal rhythm. Therefore, blood clots still can form in the atria and patients are still at risk of strokes. Thus, there is a need for long-term anticoagulation in addition to the permanent pacemaker.
Pacemakers. Permanent pacemakers are battery-operated devices that generate electrical discharges that cause the heart to beat more rapidly when the heart is beating too slowly. Recent studies suggest that some patients with recurrent paroxysmal AF can benefit from the implantation of a permanent pacemaker. Although the reasons for this benefit are unknown, regular electrical pulses from the pacemakers may prevent the recurrence of AF. Furthermore, newer pacemakers that can stimulate two different sites within the atria (dual site atrial pacing) may be even more effective than standard pacemakers in preventing AF. Nevertheless, permanent pacemaker implantation cannot be considered as standard non-medication treatment for AF.
Implantable atrial defibrillators. Implantable atrial defibrillators can detect and convert AF back to a normal rhythm by using high-energy shocks. By detecting AF and terminating it quickly, doctors hope that these devices will prevent recurrences of AF over the long term.
Atrial defibrillators are surgically implanted within the chest under local anesthesia. These devices deliver high-energy shocks to the heart that are somewhat painful. Atrial defibrillators are not useful in patients with chronic sustained AF and are suitable only for patients with infrequent episodic attacks of AF.
Maze procedure. Many doctors believe that the atria cannot fibrillate if they are sectioned into small pieces so that the conduction of the electrical current through the atria is interrupted. During the Maze procedure, numerous incisions are made in the atria to control the irregular heartbeat and restore a regular rhythm to the heart.
1) Procedure. The Maze procedure is most commonly performed via open-heart surgery. Some electrophysiologists (doctors specially trained to treat abnormalities of rhythm) are now attempting to perform the Maze procedure using catheters inside the heart that are passed through a vein in the groin without open-heart surgery. Unfortunately, the success rate using the catheter is below 50% and complications (such as strokes) may occur.
2) Effectiveness of the Maze procedure. The Maze procedure done surgically (using open heart surgery) has been reported to correct AF in 90-99% of patients. Only 15-20% of the patients need a pacemaker after surgery, and there is only a 30% chance of requiring long-term medications to maintain a normal rhythm.
3) Risks of the Maze procedure. The surgical maze procedure involves open-heart surgery and the pumping of blood by an external bypass pump while the surgery is performed, much like patients undergoing cardiac bypass surgery. The complications are not insignificant and include stroke, bleeding, infection, and death. Therefore, doctors usually do not recommend a surgical Maze procedure for the treatment of AF unless the patient is undergoing open-heart surgery for another condition (such as for coronary artery bypass or replacement or repair of a diseased heart valve).

No comments:

Post a Comment