Abstract 12533: First Noninvasive Visualization of Sinoatrial Node Fibrosis via High-Resolution 3D Gadolinium Enhanced MRI of Intact Human Hearts
Introduction: The normal adult human sinoatrial node (SAN) structure consists of 35-55% fibrotic tissue, which provides mechanical and electrical protection for the primary pacemaker of the heart. The level of fibrosis and its spatial density can significantly increase in disease conditions, leading to SAN dysfunction. We hypothesize that gadolinium enhanced MRI (GE MRI) can be used to identify and locate 3D SAN structure in the human heart.
Methods: Explanted human hearts (n=5, 19-65 y.o., 507±135 g) were coronary-perfused and the SAN was functionally identified with an intramural optical mapping approach. After mapping, the preparations were formalin fixed and incubated in 0.2% gadolinium based contrast agent to perform GE MRI (9.4T Bruker BioSpin Spectrometer) with a spatial resolution of 78-175μm3. The entire SAN pacemaker structure was then sectioned at 5μm thickness and stained with Masson’s trichrome.
Results: Percent fibrosis vs total tissue area was measured from 2D GE MRI sections by applying a fibrosis enhancement mask, which was based on signal intensity threshold differences of connective and muscular tissue and validated with 2D histology sections from the same locations (Figure). GE MRI vs histology percent fibrosis measurements of SAN (60±6% vs 63±1%), CT (16±6% vs 18±4%), RAFW (13±6% vs 14±2%) and septum (29±22% vs 28±7%) were strongly correlated (r = 0.87, p < 0.01). GE MRI allowed for the complete delineation of the 3D SAN structure (averaged SAN size 16.6±2.8 x 3.9±0.7 x 2.2±0.6 mm3) by distinguishing significant increased fibrosis in SAN compared to surrounding atrial tissue.
Conclusions: Our integrative study for the first time demonstrated the application of GE MRI to resolve the intact 3D structure of the human SAN and estimate its fibrotic spatial density and distribution. Analysis of SAN fibrosis content with GE MRI supports further work to develop in vivo SAN fibrosis imaging in patients and help predict the need for pacemaker implantation.
Author Disclosures: T.A. Csepe: None. J. Zhao: None. B.J. Hansen: None. N. Li: None. Y. Wang: None. A. Bratasz: None. K.A. Powell: None. R.D. Higgins: None. A. Kilic: None. S.V. Raman: None. O.P. Simonetti: None. P.J. Mohler: None. P.M. Janssen: None. V.V. Fedorov: None.
- © 2015 by American Heart Association, Inc.