Vasculitis of Vasa Vasorum and Aneurysm Formation in Kawasaki Disease: Predilection for Coronary Arteries Lesions

Backgrounds. The mechanism causing coronary artery lesions in Kawasaki disease (KD) has not yet been fully clarified. Objective. We hypothesized that the main coronary artery (MCA) segment perfused by the vasa vasorum (VV) arose from the atrial and ventricular branches of peripheral coronary arteries in the myocardium (Type 1 VV externa) is more prone to aneurysm formation than that perfused by Type 2 VV originated from the ostium. Methods and Results. We reviewed the coronary angiography and two-dimensional echocardiogram (2DE) data of KD patients in our hospital and measured the distances from the left coronary ostium to the proximal point of the aneurysm in the left MCA (D1) and to the MCA bifurcation (D2). We found that the ratio of the distances (D1/D2) was negatively correlated with the patients’ age of KD onset, indicating that longitudinal extension of the left MCA aneurysms coincided with the development of Type 1 VV externa. We performed a literature review of KD cases with extracardiac aneurysms and found that 15 patients also had giant aneurysms in the MCA. Also, 8 of 9 extracardiac aneurysm cases whose clear 2DE images were available in the reports, the giant MCA aneurysms seemed to have developed at positions immediately adjacent to the ostium. We assume that the giant coronary aneurysms might be a consequence of the coincidence of aneurysms in the MCA segments perfused by Type 1 and 2 VV externas and reflect a severe inflammation where Type 2 VV externa which is less susceptible to blood flow reduction than Type 1 VV externa is affected. Conclusions. Vasculitis in VV externa with the unique structure originating from and distributing most richly across coronary arteries might induce a vicious circle of hypoperfusion of VV externa and reduced coronary blood flow.