High Frequency Jet Ventilation in AF Ablation
Condition: Atrial Fibrillation
MeSH terms: Atrial Fibrillation
Study type: Interventional

Summary: 
      Atrial fibrillation (AF) is a cardiac condition that results in patients experiencing an
      irregular heart beat resulting in symptoms including palpitations and breathlessness. It is
      known that in most cases, AF is caused by abnormal electrical activity from the top of the
      left side of the heart (left atrium) which overrides the heart natural pacemaker in the right
      atrium. Treatment options include tablets which suppress this abnormal electrical activity,
      but in some patients these are not sufficient and a procedure is carried out where the areas
      of abnormal electrical activity are disconnected or 'ablated' to prevent AF from occurring.
      This treatment is well established and performed worldwide, often under general anaesthetic
      (GA). The heart and lungs sit close together in the chest, and when the lungs are inflated
      and deflated during the procedure, the heart also moves. This movement is then transmitted to
      the special wires or 'catheters' that are placed inside the heart to deliver the ablation
      treatment. Instability during the treatment can result in ineffective areas of ablation which
      may later contribute to reduced success of the procedure. Previous research has shown that by
      reducing the movement of the heart under anaesthesia using alternative techniques can improve
      catheter stability and improve procedural results. Once such technique is called high
      frequency jet ventilation (HFJV) which allows the lungs to filled with air using fast and
      shallow breaths resulting in normal blood oxygen levels with little movement in the heart.
      This technique has been shown to be safe and effective for this procedure but a direct
      comparison with conventional ventilation has not been done. The investigators wish to test
      this and determine if using HFJV improves outcomes during the procedure (i.e. can
      investigators do the treatment faster and more effectively) and if this translates to better
      outcomes long term.
    

Detailed description: 
      Catheter ablation for the treatment of the symptoms of fibrillation is now a well-established
      technique. The technique is complex and commonly undertaken under general anaesthesia.
      Catheters are introduced into the circulation from the veins at the top of the leg and
      advanced to the right side of the heart. Using x-ray and ultrasound guidance, the catheters
      are passed to the left atrium by puncturing the muscle that divides left and right atria
      (septum). A model of the left atrium is created and this used to guide the movement of an
      ablation catheter across the tissue and create ablation lesions that lead to electrical
      isolation of target sites.

      Under general anaesthesia, the lungs are inflated and deflated via the ventilator circuit.
      The expansion of the lungs results in movement of the heart with each respiratory cycle. This
      leads to catheter instability as the tissue is moved towards and away from a catheter
      positioned in the left atrium. This movement is particularly marked at the back of the left
      atrium. This instability can lead to real time variation in the delivery of energy which can
      result in ineffective lesions. These will then translate acutely to incomplete isolation and
      the need for further ablation (thereby increasing procedure time) and later into reconnection
      of tissue which can result in repeated procedures being needed to achieve an effective
      outcome. Each procedure carries risk of minor and major complications therefore measures to
      improve first time success are critical.

      Current research supports the use of steerable catheter sheaths (tubes through which the
      catheters travel to the atria) and 3 dimensional mapping in improving ablation parameters.
      Data also exists demonstrating significant variation in catheter contact despite these
      measures. In order to improve catheter stability further, changes to the mode of ventilation
      has been studied. Small studies have shown that by stopping cardiac movement altogether by
      transiently stopping ventilation (apnoea) catheter stability is improved and ablation is more
      effective. However, intermittent apnoea is not an effective method of ventilation in long
      cases. An alternative is high frequency jet ventilation. This is where the lungs are
      ventilated with low volume, high speed and high pressure breaths. This technique is well
      established and has safety data in upper airway surgery and liver radiology procedures where
      movement of airways and diaphragm needs to be minimized. In view of this, this technique has
      been studied in AF ablation and has been shown to improve catheter stability and energy
      delivery with no increase in complications related to the mode of ventilation. However,
      existing studies have focused mainly in paroxysmal AF patients (where less ablation is
      needed) and conducted in a non randomized trial design.

      The investigators wish to research the use of HFJV in patients undergoing ablation for
      persistent AF in a prospective and randomised trial to answer the primary and secondary
      questions shown below.
    

Intervention name(s): High frequency jet ventilation; Conventional ventilation
Intervention type(s): Device; Device
Intervention description(s): General anaesthesia and ventilation with the Acutronic Monsoon III Jet ventilator system; General anaesthesia and ventilation with a conventional Phillips intermittent positive pressure ventilator system
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: atrial fibrillation; catheter ablation; general anaesthesia