Left atrial fat with cardiac MR
Journal of Cardiovascular Magnetic Resonance volume 11, Article number: P128 (2009)
It has been proposed that the ganglionated plexi (GP) residing in the fat pads surrounding the left atrium (LA) may be involved in the genesis of atrial fibrillation (AF) . Appropriate ablation of these targets may be a treatment of AF . The gross anatomy of the GPs embedded in peri-atrial fat has been described and classified into five regions : the superior right atrial GP, the superior left atrial GP, the posterior right atrial GP, the posteromedial left atrial GP, and posterolateral left atrial GP. Cardiac MR (CMR) is unique among non-invasive imaging modalities, providing excellent depiction of fat, and can contribute by identifying these fat pads.
Six healthy adult subjects (age = 24 +/- 4, 3 M) underwent CMR with two high spatial resolution 3D free-breathing sequences. Scan parameters in common for both sequences were: 3D gradient echo, axial, navigator-gated and ECG-gating to diastole, TR/TE/θ = 5.3/2.5/20°, 32 views per segment, 16 Nz, 1.3 × 1.3 × 5 mm spatial resolution. The first sequence used an inversion pulse with a TI of 400 ms, to null blood and myocardium, while fat is bright (Figure 1A). The second sequence used a T2-prep (20 ms), and fat-suppression to visualize the pulmonary veins (PVs) and the LA only (Figure 1B). No exogenous contrast was used. These two free-breathing sequences can be fused, with color or non-color highlighting, to demonstrate fat in the context of anatomy (Figure 1C).
Figure 2 shows representative slices (from inferior to superior) from two healthy subjects, with arrows pointing to typical locations of fat. All subjects had fat in proximity to locations of the posterolateral left atrial GP, posterior right atrial GP, and superior right atrial GP, 4/6 subjects had fat around the superior left atrial GP, and 5/6 subjects had fat around the posteromedial left atrial GP.
Discussion and conclusion
This preliminary CMR study shows the ubiquity of fat around the LA and adjacent to the PV ostia, concentrated in previously described locations. Other CMR methods for detecting fat – from simple 2D balanced SSFP slices to 3-point Dixon techniques may also be useful. The ability to detect regional fat distribution may contribute to planning for ablation in AF patients.
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Peters, D.C., Goldfarb, J.W., Nezafat, R. et al. Left atrial fat with cardiac MR. J Cardiovasc Magn Reson 11 (Suppl 1), P128 (2009). https://doi.org/10.1186/1532-429X-11-S1-P128