Background: Myocarditis occurs in acute Kawasaki disease (KD), and case series with endomyocardial biopsy report that KD patients (pts) may have myocardial fibrosis. The new cardiac magnetic resonance (CMR) technique of myocardial T1 measurement is a noninvasive means of measuring diffuse myocardial fibrosis. We sought to assess the prevalence and risk factors for diffuse myocardial fibrosis in KD pts using CMR.
Methods: In this retrospective study, all pts with KD who had a CMR with extracellular volume fraction (ECV) measurement at Boston Children’s Hospital were included. The ECV, a measure of diffuse fibrosis, was calculated in the mid-left ventricle by measuring T1 values for blood pool and myocardium before and after gadolinium with a Look-Locker technique, and adjusting for hematocrit. Myocardium with focal fibrosis as evidenced by late gadolinium enhancement (LGE) was excluded. ECV results were compared to values from control subjects (n=20; median age 16 yrs (range, 11-36)) who had a normal CMR exam, and no history of left heart disease or cardiomyopathy.
Results: Subjects (n=10) had a median age at CMR of 13 yrs (range, 8-36), median age at KD diagnosis of 3 yrs (0.3-11), and median time interval from diagnosis to CMR of 10 yrs (0.3-34). Nine pts had coronary aneurysms and the other 1 had mild left ventricular dysfunction. All 3 pts with a known history of myocardial infarction (MI) had a LGE pattern consistent with MI. LGE with a MI pattern was also seen in 1 additional pt without a history of MI but who had undergone coronary bypass surgery. Overall, ECV was not significantly different in KD pts and controls (0.25 ± 0.03 (range, 0.21-0.30) vs. 0.24 ± 0.03 (range, 0.18-0.28), p=0.29). One pt (10%) had an increased mean ECV (>0.28). ECV was not associated with indexed LV mass, mass/volume ratio, ejection fraction, or LGE.
Conclusions: In this small pilot study of KD pts most of whom had aneurysms, diffuse myocardial fibrosis based on ECV did not differ significantly from that in normal control subjects, although 1 in 10 pts had an ECV above the normal range. Future larger studies should compare ECV in KD pts with and without aneurysms to define the risk of myocardial fibrosis after KD and to guide future recommendations for follow-up and therapy.