AV nodal ablation

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ayokunle Olubaniyi, M.B,B.S [2]

Synonyms and keywords: AVNA

Overview

Atrioventricular nodal or AV junction ablation is a procedure by which the electrical pathways that connect the atria to the ventricles are modified or interrupted in order to restore a normal cardiac rhythm. This procedure creates a disconnect between the upper chambers (which controls the heart rate and rhythm) and the lower chambers (ventricles). Due to the invasive nature of the procedure and the requirement for a pacemaker implantation, AVNA is mostly as a fallback treatment in patients with atrial fibrillation that is refractory to medications, or have developed side effects to the medications. It is important to note that this procedure is not a cure for the atrial fibrillation, its function is to regulate the ventricular rate. Therefore, patients will still require life-long anticoagulation.

Indications

• Control of ventricular rate in atrial fibrillation
• Recurrent symptomatic atrial tachycardia in which all therapeutic options have failed

Procedure

Process

During this procedure, a special catheter is passed through the femoral vein into the heart under fluoroscopic guidance. Once the catheter is in place, a small amount of radiofrequency energy or heat is applied adjacent to the AV node in order to destroy it or create a scar which permanently blocks the entry of fast impulses from the atrium. After a successful ablation, the ventricles will no longer respond to the impulses from the atria, in other words, they beat independently of each other. The ventricular rate is about 40 beats per minute which may be too slow for adequate perfusion under exercise conditions, therefore, an implantation of a permanent pacemaker is required. The choice of pacemaker depends on the overall clinical status of the patient. This could be a single chamber versus a dual chamber ventricular pacemaker. A single chamber pacemaker may be adequate for a patient with chronic atrial fibrillation while a patient with paroxysmal AF may require a dual chamber pacemaker.

Risks of The Procedure

The procedure is relatively safe, but there are some risks associated with the procedure either during or after the procedure. They are:

• Cardiac tamponade - This occurs in less than 1% of cases. The catheter electrode may perforate the heart causing a collection of blood around the heart. This may require the insertion of a drain to remove the blood.
• Damage to the blood vessels - Occasionally, the blood vessels may be perforated by the catheter electrode.
• Iatrogenic pneumothorax - The lung wall may be punctured resulting into leakage of air into the pleural space. This may require a drain in order to re-inflate the lungs.
• Other risks include but not limited to hemorrhage at the operation site, hemothorax, pulmonary embolism, stroke, but these are extremely rare.

Complications and Prognosis

With the advent of AVNA, some complications have been reported including the development of inappropriate sinus tachycardia which occurs when radiofrequency ablation in the anterior, mid, and posterior regions of the low interatrial septum disrupts the parasympathetic fibers destined to innervate the sinus node. Some episodes of ventricular fibrillation have also been reported. Also, a very rare case of an acquired ventriculo-atrial shunt (between the left ventricle and the right atrium (Gerbode defect) was reported. Some patients with AVNA and right ventricular pacing (pacemaker situated in the right ventricle) experience interventricular dyssynchrony which involves right ventricle contracting before the left ventricle. This condition, which causes a reduction in left ventricular output or result in mortality, may require cardiac resynchronization therapy (CRT).

Despite all this, AVNA has been associated with a reduction in all-cause mortality and cardiovascular mortality in patients with coexisting atrial fibrillation and heart failure when compared with medical therapy. Conversely in another study, AVNA with implantable permanent pacemakers had no significant effect on the long-term survival of patient with atrial fibrillation when compared with drug therapy.