Multimodality Imaging for Atrial Fibrosis Detection in the Era of Precision Medicine

Abstract

In recent years, atrial fibrillation (AF) has increasingly become a focus of attention because it represents the most encountered arrhythmia in clinical practice and a major cause of morbidity and mortality. Issues underlying AF have long been debated; nevertheless, electrical, contractile, and structural remodeling is demonstrated to be the pivotal contributor to arrhythmic substrate. Fibrosis is a hallmark of arrhythmogenic structural remodeling, resulting from an accumulation of fibrillar collagen deposits, as a reparative process to replace degenerating myocardium with concomitant reactive fibrosis, which causes interstitial expansion. Although the precise role of fibrosis in AF initiation and maintenance remains to be fully elucidated, a better definition of its extent and distribution may assist in designing individually tailored ablation approaches and improving procedure outcomes by targeting the fibrotic substrates with an organized strategy employing imaging resources. A deep comprehension of the mechanisms underlying atrial fibrosis could be crucial to setting up improved strategies for preventing AF-promoting structural remodeling. Imaging modalities such as echocardiography, cardiac computed tomography, and cardiac magnetic resonance, combined sometimes with invasive electroanatomical mapping, could provide valuable information for the optimal patients' management if their use is not limited to cardiac anatomy study but extended to characterize abnormal left atrial substrate. Although pulmonary vein isolation is usually efficacious in treating paroxysmal AF, it is not sufficient for many patients with nonparoxysmal arrhythmias, particularly those with longstanding persistent AF. Noninvasive imaging techniques play a pivotal role in the planning of arrhythmic substrates ablation and show a strong correlation with electro-anatomic mapping, whose novel multipolar mapping catheters allow nowadays a more precise comprehension of atrial substrate. This review aims to explore the impact of the various imaging modalities for the detection of atrial fibrosis and their role in the management of AF.

Keywords: Atrial fibrillation; atrial fibrosis; cardiac magnetic resonance; catheter ablation; echocardiography; electroanatomical mapping.

Figure 1

How to detect atrial fibrosis: Invasive and noninvasive imaging methods

Figure 2

Example of normal activation mapping at the left atrium with multipolar mapping catheter. Left Panel: late activation at posterolateral aspect of left atrium (lateral projection; purple spot); Right Panel: right anterior oblique projection showing the earlier left atrium activation at anterior wall (red spot) in the region of Bachmann's bundle

Figure 3

Correlation between echocardiography and electro-anatomic mapping: a long PA-tolerable daily intake interval is associated with extended low voltage area. Panel A: a PA-tolerable daily intake value of 187 ms recorded on the lateral mitral annulus. Panel B: anterior left atrial wall after pulmonary vein isolation (in red) with very large low-voltage areas (in red, green and yellow) in the Bachmann's bundle region and only limited area of normal-voltage myocardium

Figure 4

Panel A: Electro-anatomical mapping showing a large low voltage area (red) at the anterior wall with already isolated pulmonary veins (red); Panel B: the same projection showing a thinning (red regions) at the same sites of low-voltage areas