Lymphatic pathway evaluation in congenital heart disease using 3D whole-heart balanced steady state free precession and T2-weighted cardiovascular magnetic resonance

Abstract

Background: Due to passive blood flow in palliated single ventricle, central venous pressure increases chronically, ultimately impeding lymphatic drainage. Early visualization and treatment of these malformations is essential to reduce morbidity and mortality. Cardiovascular magnetic resonance (CMR) T2-weighted lymphangiography (T2w) is used for lymphatic assessment, but its low signal-to-noise ratio may result in incomplete visualization of thoracic duct pathway. 3D-balanced steady state free precession (3D-bSSFP) is commonly used to assess congenital cardiac disease anatomy. Here, we aimed to improve diagnostic imaging of thoracic duct pathway using 3D-bSSFP.

Methods: Patients underwent CMR during single ventricle or central lymphatic system assessment using T2w and 3D-bSSFP. T2w parameters included 3D-turbo spin echo (TSE), TE/TR = 600/2500 ms, resolution = 1 × 1 × 1.8 mm, respiratory triggering with bellows. 3D-bSSFP parameters included electrocardiogram triggering and diaphragm navigator, 1.6 mm isotropic resolution, TE/TR = 1.8/3.6 ms. Thoracic duct was identified independently in T2w and 3D-bSSFP images, tracked completely from cisterna chyli to its drainage site, and classified based on severity of lymphatic abnormalities.

Results: Forty-eight patients underwent CMR, 46 of whom were included in the study. Forty-five had congenital heart disease with single ventricle physiology. Median age at CMR was 4.3 year (range 0.9-35.1 year, IQR 2.4 year), and median weight was 14.4 kg (range, 7.9-112.9 kg, IQR 5.2 kg). Single ventricle with right dominant ventricle was noted in 31 patients. Thirty-eight patients (84%) were status post bidirectional Glenn and 7 (16%) were status post Fontan anastomosis. Thoracic duct visualization was achieved in 45 patients by T2w and 3D-bSSFP. Complete tracking to drainage site was attained in 11 patients (24%) by T2w vs 25 (54%) by 3D-bSSFP and in 28 (61%) by both. Classification of lymphatics was performed in 31 patients.

Conclusion: Thoracic duct pathway can be visualized by 3D-bSSFP combined with T2w lymphangiography. Cardiac triggering and respiratory navigation likely help retain lymphatic signal in the retrocardiac area by 3D-bSSFP. Visualizing lymphatic system leaks is challenging on 3D-bSSFP images alone, but 3D-bSSFP offers good visualization of duct anatomy and landmark structures to help plan interventions. Together, these sequences can define abnormal lymphatic pathway following single ventricle palliative surgery, thus guiding lymphatic interventional procedures.

Keywords: 3D-balanced SSFP; Cardiac catheterization; Congenital heart disease; Interventional CMR; Lymphatic imaging; Lymphatic intervention; Magnetic resonance imaging; SSFP; Single ventricle; T2-weighted imaging.

Fig. 1

Flowsheet showing the screening, inclusion and assessment of patients

Fig. 2

Four slices through the thoracic duct (blue arrows) shown with the T2 weighted (T2w) scan, 3D-balanced steady state free precession (bSSFP), and overlay used to identify lymphatic pathway on 3D-bSSFP. The red arrow indicates a portion of the thoracic duct that was not visualized with the T2w scan but could be seen with 3D-bSSFP (corresponding Additional file 1)

Fig. 3

a Maximum intensity projection (MIP) of a T2w scan with the entire thoracic duct (blue arrows) visualized. b Curved planar reformat of the same patient (a) showing the thoracic duct with 3D-bSSFP, also visualized in its entirety. c MIP of a T2w lymphatic scan in another patient, with loss of thoracic duct visualization in the upper thorax (red arrow), while (d) 3D-bSSFP showed the complete pathway of the duct

Fig. 4

a A curved planar reformat of a 3D-bSSFP image. The course of the thoracic duct and lymphatic leakage in the thorax (red arrow) are shown. b A T2w image with loss of lymphatic duct visualization around the left lung apex (blue arrow). c 3D-bSSFP image in the axial upper thorax. Thoracic duct traversing from posterior to anterior and eventually draining into the internal jugular vein (blue arrow). d 3D-bSSFP guidance used for quick fluoroscopic-guided retrograde thoracic duct access, leading to a quick, successful lymphatic occlusion procedure in the catheterization lab with low radiation exposure