Intra-Cardiac Echo (ICE)

Intracardiac echocardiography (ICE) is about as effective as transesophageal echocardiography (TEE) at assessing thromboembolic risk prior to cardioversion in patients with atrial fibrillation undergoing invasive electrophysiologic (EP) procedures, according to investigators who presented a prospective comparison of the two imaging techniques at the Heart Rhythm Society 2007 Scientific Sessions [1].

TEE is commonly used to detect or rule out potentially embolic intra-atrial thrombus or to spontaneous echo contrast (SEC), a sign that suggests impending thrombus, in patients with atrial fibrillation about to undergo cardioversion who haven't been given a protracted preventive course of warfarin, explained Dr Sanjeev Saksena (Robert Wood Johnson School of Medicine, New Brunswick, NJ) when reporting the trial, called Intracardiac Echocardiography-Guided Cardioversion Helps Interventional Procedures (ICE-CHIP).

ICE has been used for the same purposes, but until now, Saksena told heartwire, neither it nor TEE has been subjected to the scrutiny of a prospective, randomized trial. ICE-CHIP, he said, "is the first multicenter trial ever executed with ICE and TEE in this population."

The ICE devices used in ICE-CHIP were from EP MedSystems, which funded the trial. Saksena reports consulting for, holding ownership interest in, and receiving royalties from the company. The TEE systems were from a variety of manufacturers, he said.

The 95 patients in ICE-CHIP, treated at one center in the Netherlands and at five US sites, underwent TEE within two days prior to right-heart catheterization or EP studies; ICE was then performed during the procedures, which included diagnostic EP evaluation in 31%, right-atrial ablation in 7%, and left atrial ablation in 85%. Images of the left atrium (LA), left atrial appendage (LAA), septum, and aorta obtained using both techniques were evaluated in a double-blind fashion at a core laboratory. There were no observed adverse events associated with either technique.

Both forms of echocardiography were highly sensitive for the presence of SEC, Saksena reported, but ICE more readily imaged LA thrombi and atrial-septal aneurysms despite shortfalls in imaging the LAA, where TEE was more effective at disclosing thrombus, according to Saksena's report. The two methods were highly concordant in visualizing the septum, he said, but ICE may require color-flow Doppler imaging to disclose patent foramen ovale (PFO).

Diagnostic concordance (%) of ICE and TEE in patients with atrial fibrillation undergoing invasive procedures

Parameter	Concordance (%)
LA SEC	65
LAA SEC	60
LA thrombus	97
LAA thrombus	92
Good or satisfactory septal image quality	90
PFO	100
ASD	100
ASA	96

CE=intracardiac echocardiography; TEE=transesophageal echocardiography, LA=left atrial; LAA=left atrial appendage; SEC=spontaneous echo contrast; PFO=patent foramen ovale; ASD=atrial-septal defect; ASA=atrial-septal aneurysm

"The predictive value of a negative ICE study is high for TEE findings that are associated with low risk of systemic embolism," Saksena said. "However, the positive predictive value of ICE is more modest, and ICE and TEE procedures may provide complementary imaging and prompt more detailed imaging in these patients."

He continued, "ICE can be used during cardiac catheterization and EP procedures for left atrial appendage and left atrial and septal imaging without significant safety concerns and may obviate the need for TEE in these situations." The intracardiac imaging method, in contrast to TEE, can also be used expeditiously when atrial fibrillation arises during procedures, he said. "You need an imaging modality to know whether you can cardiovert that patient immediately."

To heartwire, Saksena said that ICE can benefit patients by potentially obviating TEE, which is a separate procedure and involves general anesthesia and additional personnel with the appropriate specialized expertise. As a catheter-based technique, he observed, ICE can be performed by the operator of the invasive procedure.

ICE-CHIP was supported by a grant from EP MedSystems. Saksena reports receiving consulting fees, honoraria, or research grants from Aryx, Biosense Webster, Biotronik, EP MedSystems, GE Healthcare, Medtronic, Sanofi-Aventis, and St Jude and reports holding equity interest or stock ownership in or receiving royalties from Boston Scientific, EP MedSystems, and St Jude.

1. Saksena S, Sra JS, Jordaens L, et al. Intracardiac Echocardiography-Guided Cardioversion Helps Interventional Procedures (ICE-CHIP) trial. Heart Rhythm Society 2007 Scientific Sessions; May 11, 2007; Denver, CO. Late Breaking Clinical Trials II.