Focal scar and diffuse myocardial fibrosis are independent imaging markers in repaired tetralogy of Fallot

Figure 1. T1 measurements on the LV and RV. Identical regions of interest were drawn on native (A) and post-contrast (B) T1 maps. LV T1 was computed by averaging two regions drawn within the mid-wall layer on basal and mid-ventricular maps (red contours in A and B). RV T1 was computed by averaging a minimum of four regions drawn on basal and mid-ventricular maps (blue contours in A and B), RV measurements being only performed in areas with wall thickness >2.8 mm (two pixels). For both LV and RV regions, care was taken not to include areas exhibiting scar on LGE images (yellow arrows in C). Pre- and post-contrast T1 measurements were also performed within the blood pool (yellow contours in A and B) to enable the computation of ECV.10

Figure 2. Quantification of scar area from high-resolution LGE images in patients with rTOF. On LGE images acquired during free breathing at high spatial resolution (A), endo- and epicardial contours were drawn (B) to segment the biventricular myocardium (C). The histogram of signal intensities in the myocardium was analysed (D), the scar threshold being set 3 SD above the mean intensity of the normal myocardium. This resulted in automated segmentation of scars within the myocardium (yellow region in E). Scar distribution was displayed on volume rendering reconstructions (F), and projected on an endocardial surface mesh (G) to automatically compute scar area.

Figure 3. Examples of scar distributions on high-resolution LGE images in patients with rTOF. LGE data from six patients are shown (A through F). Trans-axial LGE images are shown in the left column, yellow and green arrows indicating RVOT and septal scars, respectively. In the right column, the corresponding scar distributions are displayed in RVOT and septal views (left and right images, respectively). (A) A 27-year-old man with RVOT scar (transannular patch) of average size (8 cm2), and large septal scar (11 cm2). (B) A 29-year-old man with large RVOT and septal scars (24 and 12 cm2, respectively). (C) A 26-year-old woman with small scars on RVOT and septum (3 and 4 cm2, respectively). (D) A 33-year-old man with infundibulectomy without patch (RVOT scar 4 cm2) and septal scar of average size (5 cm2). (E) A 25-year-old man with large RVOT scar (20 cm2) and large septal scar (10 cm2). (F) A 40-year-old woman with small RVOT scar (5 cm2) and large septal scar (9 cm2).

Figure 4. Relationship between left and right ventricular native T1 measurements.

Figure 5. Relationship between CMR tissue characteristics and right ventricular dilatation and systolic dysfunction in rTOF.

Figure 6. Association of LV native T1 with NYHA functional class and maximum exercise capacity in patients with rTOF.

Figure 7. Scar area, LV native T1, and RVEF values in patients with vs. without history of ventricular arrhythmia.