Discussion

We present a case of Kawasaki with giant coronary artery aneurysm and concomitant active myocarditis, which is in keeping with non-ischaemic active myocardial injury. Employing cardiac magnitude resonance showed the comprehensive effects of Kawasaki disease in the heart, from coronary aneurysms to myocardial injury. Our patient was referred for cardiac magnitude resonance in the sub-acute phase of the disease in the presence of normal erythrocyte sedimentation rate and C-reactive protein levels and after intravenous immunoglobulin and infliximab administration. The cardiac magnitude resonance showed ongoing active myocarditis and myocardial injury. However, ischaemic myocardial injury is the most prevalent type of fibrosis in the late phase of Kawasaki disease patients.

In Kawasaki disease, acute systemic inflammatory process results in disruption of the medial and internal elastic layer of the major coronary vessel, causing vasculopathy and aneurysm formation. As a result of simultaneous stagnant coronary blood flow and active inflammation, myo-intimal proliferation and/or layering thrombosis can happen in the vessel lumen, leading to ischaemic cardiomyopathy. ^{Reference Dietz, Tacke and Kuipers1}

According to echocardiographic studies, induced myocarditis is universal in all patients in the acute phase causing transient left ventricular dysfunction in more than 50% of the patients. It usually occurs around the coronary arteries due to inflammatory cell shedding from perivasculitis and shows almost complete recovery after timely intravenous immunoglobulin administration. ^{Reference Dionne2} Rarely, severe myocarditis can show degenerative changes and lead to cardiomyopathy. Pathological findings in patients with Kawasaki disease are mostly related to oedema and inflammation. Myocardial cell necrosis is unusual as opposed to viral myocarditis. ^{Reference Pilania, Jindal, Bhattarai, Naganur and Singh3}

It has been shown that myocardial fibrosis following Kawasaki disease is primarily consistent with myocardial infarction from coronary artery aneurysm, leading to ischaemic cardiomyopathy with subendocardial late gadolinium enhancement patterns in the coronary territories. However, myocardial fibrosis may develop secondary to Kawasaki disease-induced myocarditis affecting the patient’s long-term outcome, the likelihood of mortality, sudden cardiac death, and arrhythmias. These patients are prone to developing cardiomyopathy over time. ^{Reference Dusenbery, Newburger, Colan, Gauvreau, Baker and Powel4}

According to the American Heart Association (AHA) scientific statement for treatment and management of Kawasaki disease, patients with definite Kawasaki disease should receive high dose aspirin (80 mg/kh/d) accompanied with intravenous immunoglobulin 2 gr/kg in the acute phase. In patients with limited response to intravenous immunoglobulin, support with other anti-inflammatory agents, for instance, infliximab, is recommended to reduce resistance to treatment and improve outcomes. For management of patients with giant coronary aneurysms (absolute dimension >= 8mm), therapy with low dose aspirin and warfarin is recommended, and prednisolone for its anti-inflammatory effects. ^{Reference McCrindle, Rowley and Newburger5}

Cardiac magnitude resonance is a valuable modality for evaluating Kawasaki disease activity and cardiomyopathies in active and chronic phases of Kawasaki disease in both diagnostic and prognostic pathways.