Intracardiac Echo (ICE) Guided Atrial Fibrillation Ablation

The use of intracardiac echocardiography (ICE) in atrial fibrillation ablations is quite common (and recommended by the Heart Rhythm Society) for obtaining access to the left atrium via transseptal punctures.  The video tutorial below demonstrates the use of radial ICE (9MHz, UltraICE, Boston Scientific Corporation) to gain access to the left atrium.  {I must acknowledge my mentor Dr. Dave Schwartzman, University of Pittsburgh Medical Center, spent several months/years laboriously explaining left atrial anatomy and the electroanatomic correlations of left atrial anatomy; None of the ICE images would be possible without his guidance.}

An 11F Mullins sheath with heparinized saline flush is introduced via the left femoral vein and the ICE catheter is placed into to the sheath and positioned along the interatrial septum.  Next, an 8F mullins sheath is placed into the right femoral vein; a Brockenbrough transseptal needle is used to cross the septum and enter the left atrium.  You can see tenting of the interatrial septum and then advancement of the 8F mullins sheath into the left atrium (over the Brockenbrough transseptal needle).  This process is repeated leaving two transseptal 8F Mullins sheaths for left atrial access; one access is for intra left atrial ICE and the other access for the ablation catheter.

At this point in time, an 8.5 F SRO sheath holding an irrigated tip ablation catheter (Thermocool, Biosense-Webster) and a steerable sheath (St. Jude Agilis) holding a radial ICE catheter are positioned in the left atrium.  The following figure depicts a wide shot of the left pulmonary antrum showing the left superior (LSPV) and inferior pulmonary vein (LIPV) entrances (‘Figure of 8’ appearing region on left side of image) the mitral valve (leaflets opening and closing), and the left atrial appendage (LAA contracting to the right of left superior pulmonary vein).

In the next video, the ICE catheter is positioned in body of LA superior to mitral orifice. Watch as the ICE is moved into vestibule of LAA and subsequently into the LAA proper. Note how thin the LAA walls are.

At this point, the ICE catheter is positioned into the left pulmonary venous antrum where we begin to see the ostial entrances of LSPV and LIPV.  The left antrum looks like a “peanut” shape with the waist representing the beginnings of the carina that separates the LSPV and LIPV.  Once the ICE catheter is in this position, subtle manipulation of the steerable sheath can direct our ICE catheter into the pulmonary veins.

Now we can begin the ablation of the left pulmonary vestibule.  The video below depicts ablation of the posterior aspect of Left Pulmonary Vestibule. Note the appearance of “bubbles;” this is saline irrigation during ablation.  The figure following the video shows the approximate position of the ablation lesion on the CT of the left pulmonary vestibule.

Once the primary encircling lesion around the left pulmonary venous atrium is completed, we can then turn our attention to assessing entrance/exit block of the pulmonary venous region subtended by this lesion.  The following video shows the ICE catheter in the LSPV, the ablation catheter is placed along the inferior aspect of the vein, and an esophageal probe can be seen at 11 o’clock.  Direct visualization of the esophagus allows us the titrate power and duration of ablative lesions to minimize risk of esophageal damage.  Of note, not only does the position of the esophagus change from the preoperative CT scan but movement of the esophageal probe can affect changes in esophageal/atrial positions during the case.

The goal at this time in the ablation is to assess pulmonary vein (PV) potentials and ablate any potentials getting into the PV from the LA around/through breaks in the primary encircling lesion (entrance block).  This is performed down to the first branch of the pulmonary vein with care not to make any encircling full encircling lesion within the PV (to prevent PV stenosis from occurring).  Once PV potentials are eliminated down to the first branch of PV, unipolar pacing is then performed (with indifferent electrode placed in the inferior vena cava) to assess exit block.  Any point that unipolar pacing captures the LA is ablated to obtain complete exit block.

The next video shows moving from LSPV into the LIPV.

The following video shows the ICE catheter approaching  the first branch of the LIPV at 11 o’clock.  At this point, we have established entrance block to the LIPV and will work back out of the LIPV to establish exit block using unipolar pacing.

Isolation of the right pulmonary venous antrum begins with reorienting the ICE catheter by clockwise rotation of the steerable sheath around the posterior left atrium and into view of the right pulmonary veins as shown in picture below.  This view typically looks like Edward Munch’s The Scream with the SVC and main PA representing the eyes and the right pulmonary venous antrum the mouth.

With the ICE catheter in position at the right pulmonary venous antrum, we can then begin a primary encircling lesion of this antrum.  Once the entire antrum is encircled by the primary line, the right superior (RSPV) and right inferior (RIPV) are then evaluated for entrance and exit block.  The next video shows the ICE catheter entering the RSPV. Towards the end of the video you can see the ablation catheter directed into the superior aspect of the RSPV.  Of note, in this view one can see how Bachman’s bundle can come across the septum and run over the RSPV on its way to the LSPV.  Additionally, the phrenic nerve often runs near the septal aspect of the RSPV at 9 o’clock so pacing in this area is mandatory prior to ablation to avoid diaphragmatic paralysis.

This final video shows the ICE catheter moving from the RSPV into the RIPV.  Again, the pulmonary veins are evaluated (down to the first branch) for any PV potentials.  Once entrance block is demonstrated, unipolar pacing is performed (via the mapping/ablation catheter) and areas of conduction are ablated to achieve exit block.

The final ablation lesion set is shown below with approximate primary line trajectories shown on the comparative CT scan of the right (RPV) and left (LPV) pulmonary venous antra.

The entire procedure usually takes 6-8 hours including preoperative transesophageal echo to assess for left atrial appendage thrombus, all vascular access, induction of general anesthesia (including high frequency jet ventilation), and full ablation time with 15-30min of fluoroscopy and 4-6 hours of continuous ICE imaging.


Leave a Reply