Pulmonary Vein Isolation Offers Potential Cure for Atrial Fibrillation (AF)
New information about the mechanism of atrial fibrillation has led to the development of ablation techniques including pulmonary vein isolation (PVI) and other related ablation procedures. PVI is based on the observation that early beats originating from within the pulmonary veins are usually the site that initiates AF. Patients who have frequent premature beats and resulting episodes of AF can be helped by isolating one or more of the pulmonary veins.
How does circumferential pulmonary vein ablation work?
PV ablation procedures involve the use of special catheters inserted into the left atrium. Catheters are inserted into veins in the groin and neck and are guided into the right atrium. A thin piece of heart tissue called the septum divides the left and right sides of the heart. In order to get into the left atrium, the doctor uses a needle to guide the catheters through the septum using a special technique called “transeptal catheterization”. The catheters are then used to map the abnormal electrical impulses and to deliver the energy (ablation) to prevent the impulses from spreading throughout the upper chambers. Radiofrequency energy is utilized to accomplish the ablation. Energy is delivered to the area of the left atrium surrounding the pulmonary veins to create regions that block impulses from the region of the pulmonary veins, thus preventing AF from occurring. All of the pulmonary veins are encircled with this technique.
There are usually four pulmonary veins in most people, but the anatomy varies from person to person. The pulmonary veins are important blood vessels that transport oxygen-rich blood from the lungs to the heart. Contrast medium (“dye”) is injected into the heart to help visualize their size and other anatomical features. Intracardiac ultrasound may be used to visualize the anatomy of the left atrium and the pulmonary veins. The pulmonary vein region in the left atrium is encircled with ablation applications without entering the pulmonary veins. Other related atrial structures (superior vena cava, coronary sinus os, ligament of Marshall) may also be ablated if they have abnormal impulses that induce AF. In addition, an atrial flutter ablation may be performed at the same time in select patients. This involves ablation in the lower right atrium. Because patients may come to the hospital in AF or experience AF during the procedure, a cardioversion may be required.
The procedure is performed under sedation and takes from 2-3 hours to complete. Usually patients only spend one night in the hospital. Patient preparation includes pre-procedure anticoagulation for at least 4 weeks to avoid a pre-existing blood clot being encountered during the procedure. Heparin and other blood-thinning agents are given during portions of the procedure to prevent a clot from forming near the tissue being ablated. Patients receive a series of low molecular weight heparin (Lovenoxi) injections for three days pre-procedure and 2 days post-procedure. Antiarrhythmic medications and warfarin (Coumadin) are continued for at least 1-2 months post-procedure due to the common occurrence of “post-procedure” AF which appears to represent a phenomenon associated with the heart’s healing process. Most patients resume their usual activities within 3-5 days. (Click here for detailed information about the UAB patient experience.)
The risk of potentially serious or life-threatening complications associated with PVI are believed to be about 1-2%. The most common risks include: groin problems, stroke, perforation of the heart with bleeding into the sack around the heart, and stenosis (narrowing) of the pulmonary veins.
Presently, much research is being conducted in the techniques of catheter ablation of AF. The indications for wide area encircling ablation around the pulmonary veins have evolved to include all types of AF.
PICTURES: catheter in PV, PV electrograms
What about the success rate?
After the procedure is performed once or twice, it is about 85% effective in preventing recurrence of paroxysmal AF in the first year of follow up (normal rhythm without medications). The technique is often effective for more advanced AF (persistent or permanent) though the chances of cure are lower (approximately 60%). Other patients may experience fewer or less intense episodes of AF or medications that didn’t work before may control the AF post-procedure. Some patients may not have any noticeable improvement. Because the procedure is still somewhat new, limited data are available regarding long-term effectiveness.
Who is a candidate for circumferential catheter ablation?
The procedure has been most successful in patients with intermittent (paroxysmal) AF than in those who have permanent AF. Almost all patients have been treated unsuccessfully with antiarrhythmic drugs or do not wish to take long-term antiarrhythmic and anticoagulation medications. Ideal candidates are patients without significant structural heart disease that have remained symptomatic despite a trial of antiarrhythmic medication. Patients should have enough symptoms from their AF to justify the risks of the procedure. To make sure the procedure is appropriate for you, your UAB physician will conduct an extensive evaluation- usually in the clinic setting. This includes a through review of your records, medical history, and physical examination. Additional diagnostic tests or records may be needed in order to make a final determination. A tentatively assigned procedure date will be confirmed after your consultation with your UAB physician.