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Atrial Fibrillation Drivers Resolved With Integrated Imaging
Study Questions:
Can the integration of contrast-enhanced cardiac magnetic resonance imaging (MRI) improve the accuracy of detection of atrial fibrillation (AF) drivers using the Focal Impulse and Rotor Mapping (FIRM) system?
Methods:
Sustained AF was induced in 11 coronary-perfused explanted hearts obtained from transplant recipients. Near-infrared optical mapping, along with endocardial and epicardial mapping with custom FIRMap catheters was performed. The maps were integrated with MRIs that displayed regions of fibrosis.
Results:
The optical mapping identified 1-2 spatially stable intramural re-entrant AF drivers per heart (total of 14), along with a total of six focal drivers. The drivers identified by optical mapping were validated by demonstrating that focal ablation of these drivers resulted in AF termination. Fourteen of the 20 drivers were correctly identified by epicardial/endocardial FIRM. Using FIRM, a mean of 1.1 false-positive rotors/heart was identified. The degree of fibrosis by MRI was significantly lower in the regions of false-positive rotors than in the regions of actual rotors (14.9% vs. 23.2%).
Conclusions:
The identification of stable AF drivers can be enhanced by the integration of high-resolution endocardial and epicardial mapping with analysis of fibrosis by MRI.
Perspective:
This important study provides strong evidence that a small number of stable drivers is present during AF in the human heart. However, these hearts were ex vivo, denervated, missing some atrial tissue, and not subject to the stretch and wall tension present in vivo. In addition, it is not known how many other driver sites might emerge at unablated regions of the atrium in the clinical setting, resulting in recurrent AF. Even with these limitations, the study provides important insights into the mechanisms of human AF and explains why intramural re-entrant AF drivers may not be correctly identified by high-density endocardial/epicardial mapping.
Clinical Topics: Arrhythmias and Clinical EP, Noninvasive Imaging, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Magnetic Resonance Imaging
Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Diagnostic Imaging, Electrophysiology, Endocardium, Epicardial Mapping, Fibrosis, Heart Atria, Magnetic Resonance Imaging
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