Porth's Essentials of Pathophysiology, 4e

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Disorders of Cardiac Function

C h a p t e r 1 9

Japan, the disease affects children of many races, occurs worldwide, and is increasing in frequency. The disease is characterized by a vasculitis that begins in the small vessels (i.e., arterioles, venules, and capillaries) and progresses to involve some of the larger arteries, such as the coronaries. The exact etiology and pathogenesis of the disease remain unknown, but it is thought to be of immunologic origin. 94,95 Immunologic abnormalities, including increased activation of helper T cells and increased levels of immune mediators and antibodies that destroy endothelial cells, have been detected during the acute phase of the disease. It has been hypothesized that some unknown antigen, pos- sibly a common infectious agent, triggers the immune response in a genetically predisposed child. Manifestations and Clinical Course The course of the disease is triphasic and includes an acute febrile phase that lasts approximately 7 to 14 days, a subacute phase that follows the acute phase and lasts from days 10 through 24, and a convalescent phase that follows the subacute stage and continues until the signs of the acute-phase inflammatory response have subsided and the signs of the illness have disappeared. 34,35,67–69 The acute phase begins with an abrupt onset of fever, followed by bilateral conjunctivitis, usually without exu- dates; erythema of the oral and pharyngeal mucosa with “strawberry tongue” and dry, fissured lips; redness and swelling of the hands and feet; rash of various forms; and enlarged cervical lymph nodes. The fever typically is high, reaching 40°C (104°F) or more; has an erratic spik- ing pattern; is unresponsive to antibiotics; and persists for 5 or more days. 94 The conjunctivitis begins shortly after the onset of fever, persists throughout the febrile course of the disease, and may last as long as 3 to 5 weeks. The subacute phase begins with abatement of the fever and lasts until all signs of the disease have disap- peared. During the subacute phase, desquamation (i.e., peeling) of the skin of the fingers and toe tips begins and progresses to involve the entire surface of the palms and soles. Patchy peeling of skin areas other than the hands and feet may occur in some children. The convalescent stage persists from the complete resolution of symptoms until all signs of inflammation have disappeared. This usually takes approximately 8 weeks. In addition to the major manifestations that occur during the acute stage of the illness, there are several associated, less specific characteristics of the disease, including arthritis, urethritis and pyuria, gastrointes- tinal manifestations (e.g., diarrhea, abdominal pain), and hepatitis. Arthritis is more common in girls and may occur early in the illness along with the fever and other acute manifestations of the disease or during the 2nd or 3rd week, generally affecting the hands, knees, ankles, or toes. 96,97 Central nervous system involvement occurs in almost all children and is characterized by pro- nounced irritability and lability of mood. Cardiac involvement is the most important mani- festation of Kawasaki disease. Coronary artery abnor- malities develop in approximately 20% of children,

manifested by coronary artery dilation and aneurysm formation as seen on 2D echocardiography. 96,97 The manifestations of coronary artery involvement include signs and symptoms of myocardial ischemia or, rarely, overt myocardial infarction or rupture of a coronary aneurysm. Pericarditis, myocarditis, endocarditis, heart failure, and arrhythmias also may develop. Diagnosis andTreatment No specific diagnostic test for Kawasaki disease is avail- able; therefore, the diagnosis is made on clinical grounds following published guidelines. 98 The guidelines specify fever persisting at least 5 days or more without another source in association with at least four principal fea- tures, including oral changes that may include erythema or cracking of the lips, strawberry tongue, and erythema of the oral mucosa; bilateral, nonexudative conjuncti- vitis; rash of various forms (maculopapular, erythema multiforme, or scarlatiniform) with accentuation in the groin region; erythema and swelling of the hands or feet with desquamation of fingers and toes 1 to 3 weeks after onset of illness; and cervical lymphadenopathy, often unilateral, with at least one node that is 1.5 cm in size. 98 Chest radiographs, ECG tests, and 2D echocardiogra- phy are used to detect coronary artery involvement and follow its progress. Coronary angiography may be used to determine the extent of coronary artery involvement. Intravenous gamma globulin and aspirin are consid- ered the best therapies for prevention of coronary artery abnormalities in children with Kawasaki disease. During the acute phase of the illness, aspirin usually is given in larger doses (80 to 100 mg/kg/day divided in four doses) for its anti-inflammatory and antipyretic effects. After the fever is controlled, the aspirin dose is lowered (3 to 5 mg/kg/day, single dose), and the drug is given for 6 to 8 weeks for its anti–platelet-aggregating effects. 95,98 Recommendations for cardiac follow-up evaluation (i.e., stress testing and sometimes coronary angiogra- phy) are based on the level of coronary artery changes. Anticoagulant therapy may be recommended for chil- dren with multiple or large coronary aneurysms. Some restrictions in activities such as competitive sports may be advised for children with significant coronary artery abnormalities. 95

SUMMARY CONCEPTS

■■ Congenital heart defects arise during fetal heart development, which occurs during weeks 3 through 8 after conception, and reflect the stage of development at the time the causative event occurred. Several factors contribute to the development of congenital heart defects, including genetic and chromosomal influences, viruses, and environmental agents such as drugs and radiation.

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