Patients

We included 21 patients with the convalescent phase of KD who underwent follow-up coronary angiography and OCT between January 2012 and December 2016 at Wakayama Medical University Hospital. The diagnosis of KD was based on the established diagnostic criteria described in the guideline.5 Briefly, the patients had an aneurysm (inner diameter of the coronary artery was ≥4 mm or the Z score.6 was ≥2.5) in a coronary arterial branch on echocardiography at 1 month after the onset of KD. Additionally, the patients were diagnosed with a CAA using cardiac catheterization within the acute phase (median of 2 months) after onset. To follow the disease course based on the guidelines for observing KD,7,8 coronary angiography (CAG) was repeatedly performed. In a follow-up CAG, the OCT imaging was limited to patients weighing ≥30 kg for the reason of safety.

CAG

To perform CAG, a 6 Fr sheath was used in the right radial artery, and 5 Fr catheters for CAG were advanced to the bilateral coronary ostia. Bilateral selective CAG was performed.

OCT imaging

To perform OCT imaging, a 6 Fr guiding catheter was advanced to the ostium of each coronary artery. A guidewire was then advanced, and a C7 Dragonfly Intravascular Imaging Catheter (0.036-inch outer diameter; St. Jude Medical, St. Paul, MN) was inserted into the target coronary artery and pulled back. OCT images were recorded on a C7-XR OCT Intravascular Imaging System (St. Jude Medical).

Classification of the coronary artery

Coronary arteries were classified into three groups as follows. In the CAA group, the coronary aneurysm (the inner diameter of the coronary artery was ≥4 mm or the Z score was ≥2.5) had formed in the acute phase and remained on the latest CAG in the convalescent phase. In the regressed group, a coronary aneurysm had formed in the acute phase, but was regressed in the convalescent phase and showed no abnormal findings on the latest CAG. In the no CAA group, no CAAs were documented.

Measurement of intimal thickness of the coronary arteries

In OCT, images of three layers with high, low, and high signals were acquired in a concentric pattern outward from the vascular lumen. The high- and low-signal regions on the near side of the vascular lumen showed the intima and media, respectively, and the outside high-signal region was the adventitia. In each image, the intimal thickness was measured in four directions (top, bottom, left, and right) using image analysis software (ImageJ v.1.50i, U.S. National Institutes of Health, Bethesda, MD) and the average value was calculated.

Definition and evaluation of VV

Signal-poor tubuloluminal structures in the adventitia or intima with continuity in at least two cross sections in the long axial direction were defined as VV as described by a previous study by Taruya et al.9 The number of VV was automatically counted by ImageJ v.1.50i. These measurements are based on the method used by Taruya et al.9 and Nishimiya et al.10 to assess VV using ImageJ. Regarding the position of VV, the longitudinal distribution in the adventitia and intima was defined as the adventitial VV and internal VV, respectively.

Three-dimensional rendering of images

To visualize the VV, three-dimensional (3D)-rendered images were reconstructed with OsiriX (Pixmeo SARL, Bernex, Switzerland), as described by Taruya et al.9.

Statistical analysis

Calculations were performed using JMP Pro v.14 (SAS Institute Japan, Tokyo, Japan). Categorical variables were compared by Fisher’s exact test, and continuous variables were compared by the Steel–Dwass test. The number of VV and intimal thicknesses were evaluated by single regression analysis. A p value < 0.05 was regarded as significant in all analyses.