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] Anahita Deylamsalehi, M.D.[3]

Synonyms and keywords: AVNA, atrioventricular nodal ablation, AV junction ablation

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 control the heart rate and rhythm) and the lower chambers (ventricles). Due to the invasive nature of this procedure and the requirement of pacemaker implantation, AVNA is mostly done 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 atrial fibrillation, its function is to regulate the ventricular rate. Therefore, patients will still require life-long anticoagulation.

Indications and Considerations

• Control of ventricular rate in atrial fibrillation that is non-responsive to drug treatment.
• Recurrent symptomatic atrial tachycardia in which all therapeutic options have failed.
• Based on NICE guideline updated in 2021, the following are indications of AV node ablation:
  • Permanent symptomatic atrial fibrillation
  • Permanent atrial fibrillation with left ventricle dysfunction due to high ventricular rate
• It is recommended to study the necessity for left atrial catheter ablation before AV node ablation or pacemaker insertion, specially in patients with paroxysmal atrial fibrillation or heart failure (due to paroxysmal or persistent atrial fibrillation).

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 (complete AV block) the entry of fast impulses from the atrium.
• After a successful ablation, the ventricles will no longer respond to 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.
• Options 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 atrial fibrillation 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. The following is a list of this possible risks:

• Cardiac tamponade:
  • Occurs in less than 1% of cases. The catheter electrode may perforate the heart causing a collection of blood around the heart.
  • 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.
• Systemic embolism
• Pulmonary valve stenosis
• Left atrial tachycardia
• Other risks include but not limited to hemorrhage at the operation site, hemothorax, pulmonary embolism, stroke/TIA, and femoral artery pseudoaneurysm but these are extremely rare.

Complications and Prognosis

• With the advent of AV nodal ablation (AVNA), some complications have been reported including the development of inappropriate sinus tachycardia which occurs when radiofrequency ablation in the anterior, middle, and posterior regions of the low interatrial septum disrupts the parasympathetic fibers destined to innervate the sinoatrial node.
• Some episodes of ventricular fibrillation have also been reported.
• 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 AV nodal ablation (AVNA) and right ventricular pacing (pacemaker situated in the right ventricle) experience interventricular dyssynchrony which involves the 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, AV nodal ablation (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 patients with atrial fibrillation when compared with drug therapy.
• The current ACC/AHA/ESC guidelines for the management of atrial fibrillation clearly stated that AV nodal ablation AVNA should serve as the last resort when atrial fibrillation can not be controlled pharmacologically or when tachycardia induced cardiomyopathy is suspected, but nowadays in medical practice, this procedure is gradually been faded out due to a number of reasons.
  • First is the issue of the interventricular dyssynchrony which is an adverse effect of the right ventricular pacing.
  • Other reasons are related to the fact that the patient still has atrial fibrillation, and will continue to require anti-coagulation coupled with regular hospital visits, the risk of strokes, and the denial of one's right to take advantage of the future medical advances since the procedure is irreversible. In fact, some centers have limited this procedure to the elderly patients - above 70 years in whom all medical [[treatments] have proven abortive.