New ultrasound-based system shows promise mapping atrial fibrillation

Patrick Heck

Initial findings have shown that a new ultrasound-based imaging system with continuous dipole density mapping provides real-time rapid global left atrial reconstruction and compares favourably to segmented computed tomography (CT). The system could potentially allow mapping of atrial fibrillation with high precision to identify areas of interest as potential ablation targets.

Data were presented for the first time by Patrick Heck (Papworth Hospital, Cambridge, UK) at the Heart Rhythm Congress (HRC; 4-7 October, Birmingham, UK).

“Electroanatomic mapping is standard practice in atrial fibrillation ablation procedures. Virtual anatomies are created to locate structures and navigate catheters and voltage is used to map arrhythmias,” said Heck. This study evaluated the difference in ultrasound chamber reconstruction with the AcQMap System (Acutus Medical) as compared to segmented CT scans and mapping clarity using dipole density instead of voltage in 10 patients diagnosed with atrial fibrillation.

AcQMap, explained Heck, is a novel non-contact imaging and mapping system consisting of a basket catheter (48 ultrasound transducers, 48 electrodes) and console.

“The system simultaneously acquires 100,000+ ultrasound points per minute to reconstruct the chamber anatomy and 150,000 intracardiac unipolar voltage samples per second to map cardiac activity. The 3D surface is algorithmically reconstructed from the ultrasound point-set with mesh-density comparable to a segmented CT,” he said. “Inverse and forward algorithms are applied on intracardiac voltage to derive and display electrical activation as dipole density and unipolar voltage maps, respectively, upon the ultrasound-constructed 3D anatomy. Global data are acquired simultaneously and derived continuously from single-beats or single-cycles (for atrial fibrillation) in real-time.”

The data presented at HRC included results from nine patients (56% male), average age 63.7±9.4 years, with average atrial fibrillation duration of 7.0±5.5 years.

Heck commented that during atrial fibrillation, the mean depolarised area for dipole density maps was 24.5cm2, “significantly less than for voltage maps (104.7cm2, p<0.001),” which means that dipole density mapping provided four times higher resolution of atrial activity than voltage maps.

“These data underscore the potential advantage the AcQMap system can provide to electrophysiologists during atrial fibrillation procedures,” said Heck. “The image quality of AcQMap is unparalleled and allows us to visualise heart rhythm like never before. This is an impressive leap forward that opens the possibility to map atrial fibrillation with more precision to identify areas of interest as potential ablation targets.”

Andrew Grace (Papworth Hospital, Cambridge, UK) also presented a poster with these findings at the scientific sessions of the American Heart Association (AHA; 7–11 November, Orlando, USA).

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