Ultrastructure of the myocardium in acute febrile mucocutaneous lymph node syndrome

Coronary microvascular dysfunction in childhood: An emerging pathological entity and its clinical implications

Coronary microvascular dysfunction (CMD) encompasses a spectrum of structural and functional alterations in coronary microvasculature resulting in impaired coronary blood flow and consequent myocardial ischemia without obstruction in epicardial coronary artery. The pathogenesis of CMD is complex involving both functional and structural alteration in the coronary microcirculation. In adults, CMD is predominantly discussed in context with anginal chest pain or existing ischemic heart disease and its risk factors. The presence of CMD suggests increased risk of adverse cardiovascular events independent of coronary atherosclerosis. Coronary microvascular dysfunction is also known in children but is rarely recognized due to paucity of concommitent coronary artery disease. Thus, its clinical presentation, underlying mechanism of impaired microcirculation, and prognostic significance are poorly understood. In this review article, we will overview variable CMD reported in children and delineate its emerging clinical significance.

Increased production of vascular endothelial growth factor-d and lymphangiogenesis in acute Kawasaki disease

BACKGROUND

Kawasaki disease (KD) is characterized by systemic vasculitis with tissue edema. During the healing process of inflammation, lymphangiogenesis is essential for reducing tissue edema. One potential responsible candidate for the induction of lymphangiogenesis in the healing process of acute KD is vascular endothelial growth factor-D (VEGF-D).

METHODS AND RESULTS

Sequential changes in serum VEGF-D levels in patients with acute KD (n = 47) using an enzyme-linked immunosorbent assay were investigated. Cross-sectional areas of lymphatic vessels and VEGF-D protein expression were evaluated immunohistochemically in cardiac tissues of patients (n = 6) who died of KD. Regulation of VEGF-D messenger RNA (mRNA) expression in cultured fibroblasts was assessed using quantitative real-time polymerase chain reaction. Serum VEGF-D levels increased after intravenous immunoglobulin therapy in patients with acute KD (P < 0.001). In addition, they were significantly lower in patients with coronary artery lesions (CAL) than in those without CAL (P < 0.05). The cross-sectional areas of lymphatic vessels in cardiac tissues were enlarged in patients with acute KD. VEGF-D protein was detected on the endothelium of the enlarged lymphatic vessels. In vitro, tumor necrosis factor- significantly down-regulated VEGF-D mRNA expression in cultured fibroblasts (P = 0.004).

CONCLUSIONS

This study indicates that the production of VEGF-D increases and is related to lymphangiogenesis in patients with acute KD. In addition, low VEGF-D production appears to be associated with the development of CAL.

Ultrastructural characteristics of myocardial and coronary microvascular lesions in Kawasaki disease

Kawasaki disease (KD) is an acute febrile mucocutaneous lymph node syndrome with multisystemic vasculitis affecting mainly infants and children. Although several studies on cardiovascular lesions in KD have been done at the light microscopic level, the ultrastructural characteristics and incidences of these lesions have not been well defined. In order to investigate the myocardial and coronary microvascular sequelae in KD, we performed an ultrastructural study on endomyocardial biopsy specimens obtained during follow-up from 54 patients who had typical clinical manifestations of KD, of whom 47 had associated coronary aneurysms as demonstrated by coronary arteriography (CAG) or two-dimensional echocardiography in the acute or healed stage. The average age of onset was 2.2 years old and the duration of illness was from 2 months to 23 years. Follow-up CAG showed that the coronary aneurysms persisted in 33 of the 47 patients (8 with associated stenosis) and resolved in the remaining 14 patients. Ultrastructurally, the myocardial changes revealed hypertrophy, various degrees of degeneration, proliferation and abnormality of mitochondria, infiltration of a small number of lymphocytes, and fibrosis. The coronary microvascular lesion was characterized by microvascular dilatation, endothelial cell injury, platelet aggregation with thrombosis, and stenotic lumen with thickened walls in the small arterioles. It persisted after convalescent stage even up to 23 years and closely correlated with the myocardial sequelae. Moreover, significantly increased incidences of myocardial and coronary microvascular lesions were found in patients with coronary artery lesion. These findings suggest the coronary microvascular lesion as a possible underlying factor of persistent sequelae in KD.

Endomyocardial biopsy: a review of the literature

A review of the literature relating to endomyocardial biopsy (EMB) is presented. This is considered important at this time since EMB is being utilized with increasing frequency, particularly for the diagnosis of myocarditis. The development of the technique is briefly outlined. Emphasis is placed on the clinical application of EMB in the various primary cardiomyopathies (dilated, hypertrophic, restrictive, and obliterative), the infiltrative secondary cardiomyopathies (amyloidosis, sarcoidosis, hemochromatosis), myocarditis, as well as such conditions as adriamycin cardiotoxicity, cardiac transplant rejection, and Kawasaki disease. More controversial application of EMB in primary mitral valve prolapse (Barlow's syndrome), idiopathic ventricular arrhythmias, and the elucidation of the enigmatic finding of angina with angiographically normal coronary arteries is detailed. Experience with immunological and biochemical investigation of biopsy material, as well as with virus isolation and drug assays in the myocardium, is alluded to. Complications encountered with this procedure are also discussed, and its future role is contemplated.

Kawasaki syndrome in an adult: endomyocardial histology and ventricular function during acute and recovery phases of illness

Kawasaki syndrome, an acute systemic inflammatory illness of unknown origin usually affecting children, may develop into a serious illness complicated by coronary artery aneurysms or myocarditis. This report describes an adult with Kawasaki syndrome studied by right ventricular endomyocardial biopsy and cardiac catheterization during the acute and recovery phases of illness. The initial biopsy specimen showed acute myocarditis and was associated with hemodynamic evidence of biventricular dysfunction, a severely depressed left ventricular ejection fraction and global hypokinesia. With time, there was spontaneous and rapid resolution of the inflammatory cell infiltrate with concurrent return to normal myocardial function. Right ventricular endomyocardial biopsy studies early in the course of the cardiac disease associated with Kawasaki syndrome may correlate with ventricular function and may be useful for monitoring immunosuppressive therapy in patients with this syndrome.

Clinical course of cardiovascular involvement in the mucocutaneous lymph node syndrome. Relation between clinical signs of carditis and development of coronary arterial aneurysm

Seventy-nine patients with mucocutaneous lymph node syndrome were evaluated prospectively by clinical examination, electrocardiography, chest radiography, M mode and two dimensional echocardiography and thallium-201 myocardial scanning. Serial changes were categorized according to the duration of illness: stage I (1 to 10 days), stage II (11 to 20 days), stage III (21 to 30 days), stage IV (31 to 60 days) and stage V (61 days to 40 months). The presence of myocarditis in stages I and II was suggested in 40 of 79 patients (50.6 percent) by electrocardiographic, echocardiographic, radiographic and clinical abnormalities. Myocarditis was accompanied by pericarditis in six patients and by both endocarditis and pericarditis in one patient. These signs of inflammation were resolved by stage III in all but three patients with electrocardiographic abnormalities. In the active stage, large coronary arterial lesions were suspected only because of an abnormal spherical echo-free space in the region of the coronary arteries on two dimensional echocardiograph as well as electrocardiographic evidence of deep Q waves in leads II, III and aVF. One or more coronary aneurysms developed in 11 patients, primarily in stage II; regression of the aneurysm was noted in 5 of these patients during stages III, IV and V. Aneurysm regression demonstrated by angiography did not correlate with echocardiographic changes in aneurysm size in one patient. Moreover, the occurrence of coronary aneurysm did not correlate with the presence of signs of carditis, because the frequency of carditis was the same in patients with and without aneurysm.