Andersons pediatric cardiology 1576

sickle-shaped deformity in the red cells The pathophysiologic consequences of this are vasoocclusive phenomena and chronic hemolysis Organs affected by this process are the kidneys, lungs, liver, spleen, central nervous system, and bones There are a host of potential cardiovascular signs and symptoms in patients with sickle cell anemia Cardiac output is increased, with an increase in stroke volume The most common symptoms are exertional dyspnea and palpitations Physical examination reveals signs of a hyperdynamic circulation Peripheral pulses are full, and the apex beat is prominent and displaced laterally Heart sounds are loud The second heart sound is widely split, and the pulmonary component is often increased Ejection systolic murmurs are usually present A third heart sound may be heard, but its presence does not imply cardiac failure Signs of CHF are rare Peripheral edema, pulmonary rales, and hepatomegaly may be secondary to venous stasis, pulmonary disease, and cholestasis, respectively, and this can confuse the issue The ECG is nonspecific Signs of left ventricular hypertrophy are usually present First-degree atrioventricular block and ST-segment and T-wave changes are common Right ventricular hypertrophy is rare but might indicate secondary pulmonary vasoocclusive disease and is more frequent in older patients Cardiac enlargement and increased pulmonary vascular markings resembling those seen with a left-to-right shunt are the most frequent radiographic signs Pulmonary infiltrates produced by infarction and infection may also be present Echocardiographic examination reveals left atrial and ventricular dilation as a result of the volume overload of chronic anemia Left ventricular contraction is often hyperdynamic Mild mitral and tricuspid valvar regurgitation are also seen commonly.362 CHF is more common in adults than in children Myocardial dysfunction with an abnormal response to exercise has been demonstrated in children, particularly if they suffer from pulmonary hypertension.363 Approximately one-third have pulmonary hypertension, and this risk probably increases with age.364 The pulmonary hypertension is multifactorial, resulting from the effects of chronic vasoocclusive disease, increased left ventricular filling pressures due to the leftsided chamber enlargement, and probably other as yet undefined effects of vascular dysfunction The presence of pulmonary hypertension greatly increases long-term risk.365 Additionally, the risk of sudden death during acute pulmonary vasoocclusive crises is increased in the presence of pulmonary hypertension, probably secondary to acute increases in pulmonary vascular resistance related to the crisis.366 Left ventricular dilation has been shown to normalize following the transfusion of packed red cells, further supporting the notion that cardiac abnormalities are related to chronic anemia and not specific to sickle cell anemia per se, although microvascular myocardial damage may be a manifestation of subclinical myocardial damage as part of the sickling process.367 Of course chronic transfusion can lead to the deposition of iron, resulting in ventricular diastolic dysfunction, and it is unclear whether chelation therapy is effective at preventing this complication.368 Repair of congenital cardiac malformations is complicated by the presence of sickle cell disease, as cardiopulmonary bypass and hypothermic circulatory arrest can precipitate vasoocclusive crises Most recommend a partial or complete exchange transfusion prior to the initiation of surgery, with optimization of blood gases, rates of flow, and volumes These practices are also often employed even in patients with sickle cell trait Despite this common practice, there are reports of successful cardiac surgery using cardiopulmonary bypass without the use of exchange transfusion.369 Anorexia Nervosa Anorexia nervosa is a life-threatening disorder in which affected individuals attempt to lose weight through starvation, the use of laxatives, and exercise It affects females more often than males and typically begins in adolescence Patients have a distorted body image and fear of weight gain, maintaining a weight less than five-sixths of their ideal weight Although this disorder affects all bodily systems, it carries a high mortality in part due to its effects on the cardiovascular system Common findings include sinus bradycardia, reduced volumes, and diminished ventricular mass and cardiac output.370,371 Despite these changes, left ventricular contractility usually remains normal,372 although cardiomyopathy has been reported.373 QT prolongation is often seen on the ECG and may be due to or exacerbated by hypokalemia associated with the dietary derangements This also may explain some cases of sudden death.374 The precise etiology of reduction in left ventricular mass, volume, and output remains to be elucidated It may be due to atrophy secondary to malnutrition or to the effects of chronic loss of preload Refeeding can normalize many of the cardiac derangements including sinus bradycardia, QT prolongation, and left ventricular changes.375,376 Nonetheless, refeeding by itself can lead to severe cardiopulmonary compromise and must be carried out judiciously.377 Summary The heart is susceptible to many congenital and acquired, endogenous and exogenous, insults that may modify its performance Careful cardiac evaluation should form part of the assessment of these often multisystem disorders Conversely, unexplained abnormalities of cardiac function are rarely truly “idiopathic,” and such findings should lead to careful evaluation for the presence of a unifying underlying disorder This is important as, increasingly, specific therapies are available that may reverse or attenuate progression of the disease and associated cardiac problems