Ebstein Anomaly

Published on 24/02/2015 by admin

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CHAPTER 48 Ebstein Anomaly

The incidence of congenital heart disease ranges between 2.2 and 8.8/1000 live births.1 Cyanotic lesions account for a low percentage of these defects, but result in a significant proportion of congenital heart morbidity and mortality, particularly if left untreated. Characterization of the pulmonary blood flow (PBF) and cardiac chamber morphology remains a fundamental step in evaluating suspected cyanotic congenital heart disease. This chapter will review cyanotic congenital heart disease with cardiomegaly and decreased PBF, specifically focusing on Ebstein anomaly.

EVALUATING THE CYANOTIC PATIENT

Clinical cyanosis is defined as tissue-threatening hypoxemia. If not promptly recognized and the cause is not correctly diagnosed and effectively treated, multisystem end-organ dysfunction will occur. Clinical workup and initial management will depend on prenatal diagnosis, obstetric course, comorbid symptoms, physical examination, and preliminary diagnostic imaging.

Initial diagnostic imaging in most algorithms begins with chest radiography. Single- and two-projection chest radiographs afford fundamental cyanotic cardiac disease evaluation, including heart size and contour, degree of pulmonary vascularity, and aortic arch sidedness. If the heart is enlarged, analysis should address which chambers may be dilated. In parallel, the airway, lung parenchyma, pleura, and thoracic skeleton are analyzed for alternative or comorbid noncardiovascular causes.

Recognition of cardiomegaly with decreased pulmonary vascularity on the chest radiograph signals that there is significant pulmonary inflow obstruction associated with intracardiac right-to-left shunting of venous deoxygenated blood away from the lungs and into the systemic circulation. Flow obstruction may occur at the tricuspid valve, infundibulum, pulmonary valve, or a combination thereof, whereas the shunting may occur at the atrial or ventricular septal levels. Specific anatomic pathologies include Ebstein anomaly, pulmonary atresia with ventricular septal defect, a severe variant of tetralogy of Fallot, isolated critical pulmonary stenosis, and pulmonary atresia with intact ventricular septum.

For anatomic obstructive lesions, the ductus arteriosus is often patent, providing retrograde flow into the pulmonary circulation. Bronchial arteries and other aortopulmonary collaterals (APCs) may also provide systemic perfusion into the pulmonary circulation. The degree of decreased PBF and size and involvement of the ventricular and atrial chambers will depend on the level of obstruction, level of shunting, collateral flow, right ventricular pressures, and tricuspid valve competence.

When further diagnostic imaging is required to evaluate cyanotic structural congenital heart lesions, decisions should reflect the cardiac imaging goals, presence of comorbid synchronous disorders in other body systems, and the patient’s sedation, anesthesia risk, and radiosensitivity. Options include echocardiography, right and left heart catheterization with angiography, right heart catheterization with or without angiography, magnetic resonance imaging (MRI), and magnetic resonance angiography (MRA), and computed tomography angiography (CTA).

Echocardiography is ideal as the next step for most algorithms. It is portable, relatively inexpensive, and does not expose patients to ionizing radiation or iodinated contrast medium. Real-time two-dimensional, multiprojectional, transthoracic echocardiography with standard gray-scale and color Doppler techniques readily evaluates the cardiac chambers, interatrial and interventricular septa, valves, systemic and pulmonary venous connections, central pulmonary arteries, and thoracic aorta (including arch sidedness). In select applications, such as with valvular disease, three-dimensional echocardiography can offer greater structural detail. Concurrent with the structural analysis, flow, function, and hemodynamics are all assessed. Echocardiography, however, is operator-dependent, may have limited sonographic windows, and cannot evaluate peripheral thoracic vascular anatomy.

In the diagnostic algorithm at many centers, catheterization with angiography follows echocardiography. The objective is not primarily to confirm the anatomy, but rather to obtain flow and pressure dynamics directly. However, this approach is invasive, exposes the patient to ionizing radiation, uses iodinated contrast medium and, in the current workflow, is not cost-effective. Radiation dose can be reduced and contrast medium obviated if the procedure is limited to a right heart catheterization without angiography.

MRI, MRA, and CTA are alternative noninvasive modalities to catheterization and may provide comprehensive evaluation of cardiac and pulmonary morphology and function, which is key to diagnosing the cyanotic patient with decreased pulmonary vascularity (Figs. 48-1 and 48-2). Both can generate cardiac chamber volume and qualitative and quantitative functional data. Image postprocessing can readily be facilitated for data sets from both modalities.

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