Gery F. Tomassoni MD, FACC, FHRS
A 66-year-old woman with a past medical history of hypertension, diabetes, and symptomatic paroxysmal atrial fibrillation (AF) was transferred for radiofrequency catheter ablation (RFCA) of the pulmonary veins. The patient had failed multiple antiarrhythmic medications and was extremely symptomatic during the AF episodes, which were increasing in frequency and duration. A previous attempt at RFCA failed due to difficulty in gaining transseptal access to the left atrium. Intracardiac echocardiography (ICE) was not used during the procedure. Laboratory evaluation was unremarkable including thyroid function tests. A 12-lead ECG confirmed AF during her symptoms. Baseline 12-lead ECG in normal sinus rhythm and an echocardiogram were normal.
EVOLUTION AND UTILITY OF ICE
• The use of ICE in the electrophysiology (EP) laboratory has increased dramatically in the past 15 years as more and more patients are undergoing left-sided procedures.
• As procedures are becoming increasingly more complex, several limitations have become apparent when using fluoroscopy as the primary imaging tool, including poor visualization of soft tissue structures and significant radiation exposure to both the patient and physician.
• As a result, ultrasound imaging techniques that are characterized by real-time high quality soft tissue imaging are now readily available.
• ICE in the EP lab allows:
direct visualization of all relevant anatomical structures and their relationship to catheters during the procedure.
assessment of unusual anatomical septal and left (LA) variations.
guiding site-specific transseptal puncture (TSP) along the septum.
functional analysis such as flow measurements and early monitoring for complications.
ICE CATHETERS AND GUIDANCE FOR TRANSSEPTAL ACCESS IN EP LAB
• ICE uses high-frequency ultrasound for cardiac imaging. Most commercially available ICE catheters provide sector-based imaging using a phased-array transducer.1
• Phased-array ICE:
allows for a greater frequency range and a greater depth of field resulting in higher imaging resolution.2
has the ability to acquire Doppler and color flow imaging.2
uses a catheter with a deflectable tip that is easy to steer and maneuver.
• TSP was first described in 1960, predominantly for the diagnostic evaluation of valvular heart disease.3 With the emergence of therapeutic procedures for structural heart disease and RFCA, there has been a revival in the use of transseptal catheterization. Despite high success rates and overall low complication rates, complications of fluoroscopic-guided transseptal catheterization still exist and include the following:
pericardial effusion with or without cardiac tamponade
cardiac and aortic perforation
thrombus formation on the transseptal sheath
• Since the fossa ovalis (FO) is easily recognizable on ICE, this imaging modality is well established at facilitating safe TSP.
• In addition, ICE allows for direct imaging of the structures important for assuring an optimal puncture site including the FO, the posterior left atrial wall, and the aorta.5
• Finally, ICE has been shown to be extremely useful in many cardiac interventional procedures that require transseptal access, including RFCA (AF, SVT, and VT), percutaneous LAA occlusion, ASD device closure, and mitral valvuloplasty.6
MANAGEMENT AND PATHOPHYSIOLOGY
• After the patient arrived to the EP lab, typical venous access was obtained from both the femoral and internal jugular veins.
• A phased-array ICE transducer was advanced from the left femoral vein to the level of the right atrium (RA). The FO was visualized demonstrating a double layered or membrane interatrial septum (Figure 3-1).
FIGURE 3-1 ICE image from RA demonstrating the variation of a double layered or membrane interatrial septum.
• Prior to transseptal access, intravenous heparin was initiated to maintain an ACT >350 seconds.
• After the dilator, 8 Fr transseptal sheath, and Brockenbrough needle (BRK-1) was advanced into the SVC, the assembly was retracted until the tip was engaged in the FO. The angle of the sheath and dilator was directed in a posterior manner for easier access to the posteriorly directed pulmonary veins. Mechanical pressure applied at the FO was performed causing “tenting” (Figure 3-2).
FIGURE 3-2 RA ICE image showing “tenting” of both interatrial septums. During TSP, ICE imaging allows direct visualization of the transseptal sheath and dilator apparatus as it enters the interatrial septum during retraction from the SVC. When the dilator tip engages the FO, “tenting” of the FO is seen.
• The needle tip was then advanced across both septum, and the location was confirmed with pressure monitoring and bubbles seen in the LA by ICE. A second TSP was performed in a similar fashion.
• RFCA and isolation of the pulmonary veins was done successfully without complications.
INTERATRIAL SEPTAL VARIATIONS
• Many different interatrial septal variations exist that can have a significant impact on TSP.7 In addition to the double septum (see Figure 3-1), the variations include:
an FO with a thickened septum
an FO with a thickened, enlarged superior limbus
patent FO with a tunnel
a large intra-atrial aneurysm
a fenestrated septum with multiple defects (Figure 3-3)
FIGURE 3-3 ICE images depicting multiple interatrial septal variations. Normal septum with an average diameter and thickness (A), both a small diameter and thickened FO (B), a small diameter normal thickness FO with a thickened, enlarged superior limbus (C), patent FO with tunnel (D1, D2), a large intra-atrial aneurysm (E), and a fenestrated septum with multiple defects demonstrated with Doppler color flow (F). The patent FO with tunnel is depicted with asterisks (D1) and doppler color flow (D2).
• Each septal variation has its own unique set of challenges making TSP extremely difficult. The use of ICE is invaluable in these circumstances. Not only does it confirm the appropriate location and angle of the TSP, but it also allows for recognition of immediate complications (Figure 3-4).
FIGURE 3-4 ICE images of potential complications from transseptal catheterization and RFCA. Early detection of a pericardial effusion (arrow) (A), thrombus formation (arrow) on transseptal sheath (B), and LIPV (arrow) stenosis (C). In addition, ICE can help prevent esophageal damage by identifying its location (arrow) behind the LA prior to RFCA (D).
• This case demonstrated the utility of ICE allowing visualization of a double membrane and ultimately safe passageway to the LA so that PV isolation could be successfully performed.
ADDITIONAL BENEFITS OF ICE
• While performing RFCA of AF, the goal of TSP is to cross the FO at lower end of the septum and posteriorly for easier access to pulmonary veins, especially the right inferior vein.
• An anterior TSP higher along the septum can be helpful for procedures such as insertion of LAA occlusive devices and ablation of left ventricle VT.
• ICE can guide the location of TSP in patients with structural heart disease and previous cardiac procedures such as ASD closure devices (Figure 3-5).
FIGURE 3-5 An ICE image showing the presence of an ASD device (red arrow). The white arrow depicts a safe location for TSP below or inferior to the ASD.
• Repeat left-sided procedures after previous TSP and patients with valvular surgery can have excessive interatrial scarring, making TSP nearly impossible. New tools such as radiofrequency-assisted TSP and needle-tipped guidewires have been specially designed for such an issue.8,9
• ICE-guided ablation can monitor thrombus formation on sheaths, endocardial lesion sites, and coagulum formation on ablation electrodes.5
• ICE has been used effectively to guide antral isolation for atrial fibrillation as opposed to ostial isolation.5
• ICE can also identify the location of the esophagus during the ablative procedure in an attempt to avoid esophageal ulceration or fistula formation10 (see Figure 3-4).
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9. Wieczorek WM, Hoeltgen R, Akin E, et al. Use of a novel needle wire in patients undergoing transseptal puncture associated with severe septal tenting. J Interv Card Electrophysiol. 2010;27(1):9-13.
10. Cummings JE, Schweikert RA, Saliba WI, et al. Assessment of temperature, proximity, and course of the esophagus during radiofrequency ablation within the left atrium. Circulation. 2005;112:459-464.